CLAIM OF PRIORITY
The instant application claims the benefit of priority to U.S. provisional applications having Ser. Nos. 60/859,284, filed Nov. 14, 2006, and 60/959,437, filed Jul. 13, 2007, the specifications of both of which are incorporated herein by reference in their entireties. The instant application is also a continuation-in-part of U.S. patent application Ser. No. 11/728,964, filed Mar. 26, 2007, the specification of which is incorporated herein by reference in its entirety.
The technology described herein generally relates to systems for detecting polynucleotides in samples, particularly from biological samples. The technology more particularly relates to microfluidic systems that carry out PCR on nucleotides of interest within microfluidic channels, and detect those nucleotides.
The medical diagnostics industry is a critical element of today's healthcare infrastructure. At present, however, diagnostic analyses no matter how routine have become a bottleneck in patient care. There are several reasons for this. First, many diagnostic analyses can only be done with highly specialist equipment that is both expensive and only operable by trained clinicians. Such equipment is found in only a few locations—often just one in any given urban area. This means that most hospitals are required to send out samples for analyses to these locations, thereby incurring shipping costs and transportation delays, and possibly even sample loss. Second, the equipment in question is typically not available ‘on-demand’ but instead runs in batches, thereby delaying the processing time for many samples because they must wait for a machine to fill up before they can be run.
Understanding that sample flow breaks down into several key steps, it would be desirable to consider ways to automate as many of these as possible. For example, a biological sample, once extracted from a patient, must be put in a form suitable for a processing regime that typically involves using PCR to amplify a vector of interest. Once amplified, the presence of a nucleotide of interest from the sample needs to be determined unambiguously. Sample preparation is a process that is susceptible to automation but is also relatively routinely carried out in almost any location. By contrast, steps such as PCR and nucleotide detection have customarily only been within the compass of specially trained individuals having access to specialist equipment.
There is a need for a method and apparatus of carrying out PCR and detection on prepared biological samples, and preferably with high throughput. In particular there is a need for an easy-to-use device that can deliver a diagnostic result on several samples in a short time.
The discussion of the background to the technology herein is included to explain the context of the technology. This is not to be taken as an admission that any of the material referred to was published, known, or part of the common general knowledge as at the priority date of any of the claims.
Throughout the description and claims of the specification the word “comprise” and variations thereof, such as “comprising” and “comprises”, is not intended to exclude other additives, components, integers or steps.
The present technology addresses systems for detecting polynucleotides in samples, particularly from biological samples. In particular, the technology relates to microfluidic systems that carry out PCR on nucleotides of interest within microfluidic channels, and detect those nucleotides.
The present technology provides for a fluorescent detector, comprising: a LED emitting light of a specified color that excites a probe associated with one or more polynucleotides contained within a microfluidic channel; and a photodiode configured to collect emitted light of the specified color, wherein the photodiode is connected to a pre-amplifier circuit having a time-constant of less than about 1 s.
A diagnostic apparatus, comprising: one or more microfluidic channels configured to amplify one or more polynucleotides; and one or more fluorescence detectors configured to detect presence of the one or more polynucleotides in the one or more channels by detecting fluorescent light emitted from a probe associated with the one or more polynucleotides, wherein the one or more detectors each comprise: a first LED emitting light of a first color; a second LED emitting light of a second color; a first photodiode configured to collect emitted light of the first color; a second photodiode configured to collect emitted light of the second color; and wherein the first and second photodiodes are each connected to a pre-amplifier circuit having a time-constant of less than of about 1 second. In certain embodiments, the time constant is 50-100 ms.
In certain other embodiments, the pre-amplifier circuit further comprises a resistor having a resistance in excess of 0.5 GΩ.
The detector can be configured to detect fluorescence from one or more microfluidic channels in a removable microfluidic cartridge, such as disposed within a receiving bay in the apparatus.
The technology further provides for a diagnostic apparatus, comprising: one or more microfluidic channels configured to amplify one or more polynucleotides; and one or more fluorescence detectors configured to detect presence of the one or more polynucleotides in the one or more channels by detecting fluorescent light emitted from a probe associated with the one or more polynucleotides, wherein the one or more detectors each comprise: a LED emitting light of a specified color that excites the probe; a photodiode configured to collect emitted light of the specified color; and wherein the photodiode is connected to a pre-amplifier circuit having a time-constant of less than about 1 s.
The technology further provides for a diagnostic apparatus, comprising: one or more microfluidic channels configured to amplify one or more polynucleotides; and one or more fluorescence detectors configured to detect presence of the one or more polynucleotides in the one or more channels by detecting fluorescent light emitted from a probe associated with the one or more polynucleotides, wherein the one or more detectors each comprise: a first LED emitting light of a first color; a second LED emitting light of a second color; a first photodiode configured to collect emitted light of the first color; a second photodiode configured to collect emitted light of the second color; and wherein the first and second photodiodes are each connected to a pre-amplifier circuit having a Gain of about 109.
BRIEF DESCRIPTION OF THE DRAWINGS
The details of one or more embodiments of the technology are set forth in the accompanying drawings and further description herein. Other features, objects, and advantages of the technology will be apparent from the description and drawings, and from the claims.
FIG. 1 shows a cross-section of a pipetting head, a detector, and a cartridge in position in a microfluidic apparatus.
FIG. 2 shows a cross-sectional view of an exemplary detector, inverted relative to other views herein;
FIG. 3 shows a cutaway view of an exemplary detector in a read-head;
FIGS. 4A and 4B show perspective and cross-sectional views respectively of a detector in a read-head;
FIG. 5 shows an exterior view of an exemplary multiplexed read-head with an array of detectors therein;
FIG. 6 shows a cutaway view of an exemplary multiplexed read-head, as in FIG. 5;
FIG. 7 shows exemplary pre-amplifier circuitry for a fluorescence detector;
FIG. 8A shows effects of aperturing on fluorescence intensity; FIG. 8B shows a detector in cross section with an exemplary aperture;
FIG. 9A shows an exemplary multi-lane cartridge;
FIG. 9B shows a portion of an exemplary multi-lane cartridge;
FIG. 10 shows a plan of microfluidic circuitry and inlets in an exemplary multi-lane cartridge.
FIG. 11 shows an exemplary microfluidic network in a lane of a multi-lane cartridge;
FIG. 12 shows an exemplary highly-multiplexed microfluidic cartridge;
FIG. 13 shows an exemplary highly-multiplexed microfluidic cartridge;
FIG. 14 shows a radially configured highly multiplexed microfluidic cartridge.
FIG. 15 shows a cross-section of a microfluidic cartridge, when in contact with a heater substrate;
FIGS. 16A and 16B show a plan view of heater circuitry adjacent to a PCR reaction chamber; FIG. 16C shows an overlay of an array of heater elements on an exemplary multi-lane microfluidic cartridge, wherein various microfluidic networks are visible;
FIG. 17 shows an exemplary layout for electronics and software components, as further described herein;
FIG. 18 shows an exemplary apparatus, a microfluidic cartridge, and a read head, as further described herein;
FIG. 19 shows an exploded view of an exemplary apparatus;
FIGS. 20A and 20B show an exemplary apparatus having a detector mounted in a sliding lid;
FIGS. 21A-21C show a force member;
FIGS. 22A-22 D show a force member associated with a detector;
FIG. 23 shows a block diagram of exemplary electronic circuitry in conjunction with a detector as described herein;
FIG. 24 shows a cross-section of a detector;
FIG. 25 shows an interface for exemplary software;
FIG. 26 shows a cross-section of a scanning read-head;
FIG. 27 shows cut-away views of a scanning readhead;
FIGS. 28A and 28B show a microfluidic cartridge aligned to an aperture plate;
FIG. 29 shows a perspective view of a scanning read head; and
FIG. 30 shows cutaway and cross-section views of a read head.
One aspect of the present technology relates to a fluorescence detection system for use with a microfluidic-based diagnostic system. In particular, the detection system described herein is configured to detect presence of a nucleotide amplified by, e.g., a polymerase chain reaction (PCR), in a microfluidic channel. It is to be understood that, unless specifically made clear to the contrary, where the term PCR is used herein, any variant of PCR including but not limited to real-time and quantitative, and any other form of polynucleotide amplification is intended to be encompassed.
As further described herein, a microfluidic channel, within which presence of an analyte is detected by the detection system, is typically a chamber or a reactor, such as a PCR reactor, wherein a sample is subjected to a temperature protocol that causes one or more reactions to occur.
Channels of a microfluidic network in a lane of a microfluidic substrate, such as in a cartridge, typically have at least one sub-millimeter cross-sectional dimension. For example, channels of such a network may have a width and/or a depth of about 1 mm or less (e.g., about 750 microns or less, about 500 microns, or less, about 250 microns or less).
By microfluidic, as used herein, is meant that volumes of sample, and/or reagent, and/or amplified polynucleotide are from about 0.1 μl to about 999 μl, such as from 1-100 μl, or from 2-μl. Similarly, as applied to a cartridge, the term microfluidic means that various components and channels of the cartridge, as further described herein, are configured to accept, and/or retain, and/or facilitate passage of microfluidic volumes of sample, reagent, or amplified polynucleotide.
Furthermore, the detection system can be configured to simultaneously detect presence of several nucleotides, distributed amongst several microfluidic channels. The microfluidic channel or channels may be in, for example, a microfluidic substrate, such as found in a microfluidic cartridge, with which the detector is in communication. In particular, the detection system is configured to detect very weak signals as are characteristic of samples having very small effective amounts of the analyte (e.g., polynucleotide) whose presence is being determined. The detector is typically mounted within an apparatus that controls the progress of the amplification reaction in the one or more microfluidic channels, such as by controlled selective application of localized heat to the one or more channels, wherein the apparatus is also typically able to accept user instructions as input, and to provide the result of detection as an output. Other characteristics of such an apparatus are described further herein.
Embodiments of the optical system described herein are configured to measure fluorescence from a real-time PCR reaction but it would be understood that the principles involved could be transferred to monitoring other reactions on the same or similar scales. The process amplifies a single copy of target DNA into millions or billions of copies depending on the number of PCR cycles performed in the reaction. As most of the real-time PCR reaction systems such as Taqman or Scorpion chemistries involve one to one correspondence between the number of target DNA copies and the number of fluorescent probes, the amount of fluorescence emanating from a reaction volume should be detectable by a sensitive fluorescent detection system, as is described herein. Assuming the PCR reaction is 100% efficient, the sensitivity of the PCR system is proportional to the detection volume seen by the photodetector. However, as DNA molecules will diffuse approximately a millimeter over a time of 14-20 minutes (the typical total time required to perform 45 cycles of PCR according to methods described herein) and the probe molecules may diffuse an even greater distance than DNA (probe molecules are much smaller than template DNA molecules), the detection volume can be slightly smaller than the full reaction volume in order to detect each and every copy of DNA initially present in the reactor at the start of the reaction. The detection volume may thus be 80% of, or as low as 50% of, the reaction volume.
The microfluidic PCR reactor used herein is typically a straight microchannel, 0.3 mm deep and 1.5 mm wide. Depending on the required reaction volume, the length of the reactor can be from 10 mm to 20 mm. The width of the channel can be varied from 100 microns to 3 mm to be able to use the same geometry of PCR heaters to maintain desired temperature uniformity and speed of heating (which depends on effective thermal mass heated by the heaters). The depth of the channel can also be increased to 350 microns or 400 microns without incurring loss of uniformity of temperature.
- Fluorescence Detection System, Including Lenses and Filters, and Multiple Parallel Detection for a Multi-Lane Cartridge
FIG. 1 shows a schematic cross-sectional view of a part of an apparatus as described herein, showing input of sample into a microfluidic cartridge 200 via a pipette 10 (such as a disposable pipette) and an inlet 202 in the cartridge. Suitable cartridges 200 are further described herein but it is to be understood that the detection system can also be configured to detect analytes in microfluidic channels found in situ in the apparatus. Such channels may therefore be fixed in the apparatus and reusable, for example by flushing through after each use, instead of being associated with a removable and disposable item such as a cartridge. Inlet 202 is preferably configured to receive a pipette or the bottom end of a PCR tube and thereby accept sample for analysis with minimum waste, and with minimum introduction of air. Although not apparent from FIG. 1, several pipettes 10 may operate in parallel with one another to introduce multiple samples into cartridge 200. Cartridge 200 is disposed on top of and in contact with a heater substrate 400. A detector, as further described herein, comprises a read head 300 and a cover 310. Read head 300 is positioned above cartridge 200, and a cover for optics 310 restricts the amount of ambient light that can be detected by the read head.
The detection system herein is configured to monitor fluorescence coming from one or more species involved in a biochemical reaction. The system can be, for example, an optical detector having a light source that selectively emits light in an absorption band of a fluorescent dye, and a light detector that selectively detects light in an emission band of the fluorescent dye, wherein the fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof, as further described elsewhere herein. Alternatively, the optical detector can include a bandpass-filtered diode that selectively emits light in the absorption band of the fluorescent dye and a bandpass filtered photodiode that selectively detects light in the emission band of the fluorescent dye. For example, the optical detector can be configured to independently detect a plurality of fluorescent dyes having different fluorescent emission spectra, wherein each fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof. For example, the optical detector can be configured to independently detect a plurality of fluorescent dyes at a plurality of different locations of, for example, a microfluidic substrate, wherein each fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof. The detector further has potential for 2, 3 or 4 color detection and is controlled by software, preferably custom software, configured to sample information from the detector.
The detection system described herein is capable of detecting a fluorescence signal from nanoliter scale PCR reactions. Advantageously, the detector is formed from inexpensive components, having no moving parts. The detector can be configured to couple to a microfluidic cartridge as further described herein, and can also be part of a pressure application system, such as a sliding lid on an apparatus in which the detector is situated, that keeps the cartridge in place.
FIGS. 2-4B depict an embodiment of a highly sensitive fluorescence detection system that includes light emitting diodes (LED's), photodiodes, and filters/lenses for monitoring, in real-time, one or more fluorescent signals emanating from the microfluidic channel. The embodiment in FIGS. 2-4B displays a two-color detection system having a modular design that couples with a single microfluidic channel found, for example, in a microfluidic cartridge. It would be understood by one skilled in the art that the description herein could also be adapted to create a detector that just detects a single color of light. FIGS. 4A and 4B show elements of optical detector elements 1220 including light sources 1232 (for example, light emitting diodes), lenses 1234, light detectors 1236 (for example, photodiodes) and filters 1238. The detector comprises two LED's (blue and red, respectively) and two photodiodes. The two LED's are configured to transmit a beam of focused light on to a particular region of the cartridge. The two photodiodes are configured to receive light that is emitted from the region of the cartridge. One photodiode is configured to detect emitted red light, and the other photodiode is configured to detect emitted blue light. Thus, in this embodiment, two colors can be detected simultaneously from a single location. Such a detection system can be configured to receive light from multiple microfluidic channels by being mounted on an assembly that permits it to slide over and across the multiple channels. The filters can be, for example, bandpass filters, the filters at the light sources corresponding to the absorption band of one or more fluorogenic probes and the filters at the detectors corresponding to the emission band of the fluorogenic probes.
FIGS. 5 and 6 show an exemplary read-head comprising a multiplexed 2 color detection system that is configured to mate with a multi-lane microfluidic cartridge. FIG. 5 shows a view of the exterior of a multiplexed read-head. FIG. 6 is an exploded view that shows how various detectors are configured within an exemplary multiplexed read head, and in communication with an electronic circuit board.
- Detection Sensitivity, Time Constant and Gain
Each of the detection systems multiplexed in the assembly of FIGS. 5 and 6 is similar in construction to the embodiment of FIGS. 2-4B. The module in FIGS. 5 and 6 is configured to detect fluorescence from each of 12 microfluidic channels, as found in, for example, the respective lanes of a 12-lane microfluidic cartridge. Such a module therefore comprises 24 independently controllable detectors, arranged as 12 pairs of identical detection elements. Each pair of elements is then capable of dual-color detection of a predetermined set of fluorescent probes. It would be understood by one of ordinary skill in the art that other numbers of pairs of detectors are consistent with the apparatus described herein. For example, 4, 6, 8, 10, 16, 20, 24, 25, 30, 32, 36, 40, and 48 pairs are also consistent and can be configured according to methods and criteria understood by one of ordinary skill in the art.
A typical circuit that includes a detector as described herein includes, in series, a preamplifier, a buffer/inverter, a filter, and a digitizer. Sensitivity is important so that high gain is very desirable. In one embodiment of the preamplifier, a very large, for example 100 GΩ, resistor is placed in parallel with the diode. Other values of a resistor would be consistent with the technology herein: such values typically fall in the range 0.5-100 GΩ, such as 1-50 GΩ, or 2-10 GΩ. An exemplary pre-amplifier circuit configured in this way is shown in FIG. 7. Symbols in the figure have their standard meanings in electronic circuit diagrams.
The FIG. 7 shows a current-to-voltage converter/pre-amplifier circuit suitable for use with the detection system. D11 is the photodetector that collects the fluorescent light coming from the microfluidic channel and converts it into an electric current. The accompanying circuitry is used to convert these fluorescent currents into voltages suitable for measurement and output as a final measure of the fluorescence.
A resistor-capacitor circuit in FIG. 7 contains capacitor C45 and resistor R25. Together, the values of capacitance of C45 and resistance of R25 are chosen so as to impact the time constant τc (equal to the product of R25 and C45) of the circuit as well as gain of the detection circuit. The higher the time constant, the more sluggish is the response of the system to incident light. It typically takes the duration of a few time constants for the photodetector to completely charge to its maximum current or to discharge to zero from its saturation value. It is important for the photo current to decay to zero between measurements, however. As the PCR systems described herein are intended to afford rapid detection measurements, the product R25C45 should therefore be made as low as possible. However, the gain of the pre-amplifier whose circuitry is shown is directly proportional to the (fluorescent-activated) current generated in the photodetector and the resistance R25. As the fluorescence signal from the microfluidic channel device is very faint (due to low liquid volume as well as small path lengths of excitation), it is thus important to maximize the value of R25. In some embodiments, R25 is as high as 100 Giga-Ohms (for example, in the range 10-100 GΩ), effectively behaving as an open-circuit. With such values, the time-constant can take on a value of approximately 50-100 ms by using a low-value capacitor for C45. For example, the lowest possible available standard off-the-shelf capacitor has a value of 1 pF (1 picoFarad). A time-constant in the range 50-100 ms ensures that the photocurrent decays to zero in approximately 0.5 s (approx. 6 cycles) and therefore that approximately 2 samplings can be made per second. Other time constants are consistent with effective use of the technology herein, such as in the range 10 ms-1 s, or in the range 50 ms-500 ms, or in the range 100-200 ms. The actual time constant suitable for a given application will vary according to circumstance and choice of capacitor and resistor values. Additionally, the gain achieved by the pre-amplifier circuit herein may be in the range of 107-5×109, for example may be 1×109.
As the resistance value for R25 is very high (˜100 GΩ), the manner of assembly of this resistor on the optics board is important for the overall efficiency of the circuit. Effective cleaning of the circuit during assembly and before use is important to achieve an optimal time-constant and gain for the optics circuit.
- Sensitivity and Aperturing
It is also important to test each photo-diode that is used, because many do not perform according to specification.
The LED light passes through a filter before passing through the sample in the micro-fluidic channel (as described herein, typically 300 g deep). This is a very small optical path-length for the light in the sample. The generated fluorescence then also goes through a second filter, and into a photo-detector. Ultimately, then, the detector must be capable of detecting very little fluorescence. Various aspects of the detector configuration can improve sensitivity, however.
The illumination optics can be designed so that the excitation light falling on the PCR reactor is incident along an area that is similar to the shape of the reactor. As the reactor is typically long and narrow, the illumination spot should be long and narrow, i.e., extended, as well. The length of the spot can be adjusted by altering a number of factors, including: the diameter of the bore where the LED is placed (the tube that holds the filter and lens has an aperturing effect); the distance of the LED from the PCR reactor; and the use of proper lens at the right distance in between. As the width of the beam incident on the reactor is determined by the bore of the optical element (approximately 6 mm in diameter), it is typical to use an aperture (a slit having a width approximately equal to the width of the reactor, and a length equal to the length of the detection volume) to make an optimal illumination spot. A typical spot, then, is commensurate with the dimensions of a PCR reaction chamber, for example 1.5 mm wide by 7 mm long. FIG. 8A shows the illumination spot across 12 PCR reactors for the two different colors used. A typical aperture is made of anodized aluminum and has very low autofluoresence in the wavelengths of interest. FIG. 8B illustrates a cross-section of a detector, showing an exemplary location for an aperture 802.
The optimal spot size and intensity is importantly dependent on the ability to maintain the correct position of the LED's with respect to the center of the optical axis. Special alignment procedures and checks can be utilized to optimize this. The different illuminations can also be normalized with respect to each other by adjusting the power current through each of the LED's or adjusting the fluorescence collection time (the duration for which the photodetector is on before measuring the voltage) for each detection spot. It is also important to align the detectors with the axis of the micro-channels.
The aperturing is also important for successful fluorescence detection because as the cross-sectional area of the incident beam increases in size, so the background fluorescence increases, and the fluorescence attributable only to the molecules of interest (PCR probes) gets masked. Thus, as the beam area increases, the use of an aperture increases the proportion of collected fluorescence that originates only from the PCR reactor. Note that the aperture used in the detector herein not only helps collect fluorescence only from the reaction volume but it correspondingly adjusts the excitation light to mostly excite the reaction volume. The excitation and emission aperture is, of course, the same.
- Use of Detection System to Measure/Detect Fluid in PCR Chamber
Based on a typical geometry of the optical exctiation and emission system and aperturing, show spot sizes as small as 0.5 mm by 0.5 mm and as long as 8 mm×1.5 mm have been found to be effective. By using a long detector (having an active area 6 mm by 1 mm) and proper lensing, the aperture design can extend the detection spot to as long as 15-20 mm, while maintaining a width of 1-2 mm using an aperture. Correspondingly, the background fluorescence decreases as the spot size is decreased, thereby increasing the detection sensitivity.
- Microfluidic Cartridge
The fluorescence detector is sensitive enough to be able to collect fluorescence light from a PCR chamber of a microfluidic substrate. The detector can also be used to detect the presence of liquid in the chamber, a measurement that provides a determination of whether or not to carry out a PCR cycle for that chamber. For example, in a multi-sample cartridge, not all chambers will have been loaded with sample; for those that are not, it would be unnecessary to apply a heating protocol thereto. One way to determine presence or absence of a liquid is as follows. A background reading is taken prior to filling the chamber with liquid. Another reading is taken after microfluidic operations have been performed that should result in filling the PCR chamber with liquid. The presence of liquid alters the fluorescence reading from the chamber. A programmable threshold value can be used to tune an algorithm programmed into a processor that controls operation of the apparatus as further described herein (for example, the second reading has to exceed the first reading by 20%). If the two readings do not differ beyond the programmed margin, the liquid is deemed to not have entered the chamber, and a PCR cycle is not initiated for that chamber. Instead, a warning is issued to a user.
Where the microfluidic channels that contain analytes detected by the detection system are situated in a microfluidic cartridge, the cartridge typically has attributes as follows. The microfluidic cartridge is designed so that it receives thermal energy from one or more heating elements present in the heater unit described elsewhere herein when it is in thermal communication therewith. The heater unit may be part of an apparatus, configured to receive the cartridge, and comprising other features such as control circuitry, user interface, and detector, as well as still other features. An exemplary such apparatus is further described herein; additional embodiments of such a apparatus are found in U.S. patent application Ser. No. ______, entitled “Microfluidic System for Amplifying and Testing Polynucleotides in Parallel”, and filed on even date herewith, the specification of which is incorporated herein by reference.
By cartridge is meant a unit that may be disposable, or reusable in whole or in part, and that is configured to be used in conjunction with some other apparatus that has been suitably and complementarily configured to receive and operate on (such as deliver energy to via a heater module as described herein) the cartridge.
One aspect of the present technology relates to a detector that is configured to selectively detect analytes in a microfluidic cartridge having two or more sample lanes arranged so that analyses can be carried out in two or more of the lanes in parallel, for example simultaneously, and wherein each lane is independently associated with a given sample.
A sample lane, as found in a microfluidic cartridge, is an independently controllable set of elements by which a sample can be analyzed, for example by carrying out PCR on a sample in which the presence or absence of one or more polynucleotides is to be determined, according to methods described in, e.g., U.S. patent application Ser. No. ______, entitled “Microfluidic Cartridge and Method of Making Same”, and filed on even date herewith. A sample lane comprises at least a sample inlet, and a microfluidic network having one or more microfluidic components, as further described herein.
In various embodiments, a sample lane of a microfluidic cartridge can include a sample inlet port or valve, and a microfluidic network that comprises, in fluidic communication one or more components selected from the group consisting of: at least one thermally actuated valve, a bubble removal vent, at least one gate, at least one thermally actuated pump, a downstream thermally actuated valve, mixing channels, one or more positioning elements, and a PCR reaction zone. The detector described herein can be configured to detect light emitted from any one of the foregoing microfluidic components, but is typically configured to detect light from a reaction chamber.
In various embodiments, the microfluidic network can be configured to couple heat from an external heat source, such as provided by a heater unit described elsewhere herein, to a sample mixture comprising PCR reagent and neutralized polynucleotide sample under thermal cycling conditions suitable for creating PCR amplicons from the neutralized polynucleotide sample.
- Exemplary Microfluidic Cartridges
A multi-lane cartridge is typically configured to accept a number of samples in series or in parallel, in particular embodiments 12 samples and in other embodiments 24, or 48 samples, wherein the samples include at least a first sample and a second sample, wherein the first sample and the second sample each contain one or more polynucleotides in a form suitable for amplification. The polynucleotides in question may be the same as, or different from one another, in different samples and hence in different lanes of the cartridge. The cartridge typically processes each sample by increasing the concentration of a polynucleotide to be determined and/or by reducing the concentration of inhibitors relative to the concentration of polynucleotide to be determined.
FIG. 9A shows a perspective view of a portion of an exemplary microfluidic cartridge 200 according to the present technology. FIG. 9B shows a close-up view of a portion of the cartridge 200 of FIG. 9A illustrating various representative components. The cartridge 200 may be referred to as a multi-lane PCR cartridge with dedicated sample inlets 202. For example sample inlet 202 is configured to accept a liquid transfer member (not shown) such as a syringe, a pipette, or a PCR tube containing a PCR ready sample. More than one inlet 202 is shown in FIGS. 9A, 9B, wherein one inlet operates in conjunction with a single sample lane. Various components of microfluidic circuitry in each lane are also visible. For example, microvalves 204, and 206, and vents 208, are parts of microfluidic circuitry in a given lane. Microfluidic circuitry is typically disposed within a microfluidic substrate found in one or more layers of the cartridge. Also shown is an ultrafast PCR reactor 210, which, as further described herein, is a microfluidic channel in a given sample lane that is long enough to permit PCR to amplify polynucleotides present in a sample. Above each PCR reactor 210 is a window 212 that permits detection of fluorescence from a fluorescent substance in PCR reactor 210 when a detector is situated above window 212. It is to be understood that other configurations of windows are possible including, but not limited to, a single window that straddles each PCR reactor across the width of cartridge 200.
A multi-sample cartridge comprises at least a first microfluidic network and a second microfluidic network, adjacent to one another, wherein each of the first microfluidic network and the second microfluidic network is as elsewhere described herein, and wherein the first microfluidic network accepts the first sample, and wherein the second microfluidic network accepts the second sample.
In some embodiments, the multi-sample cartridge has a size substantially the same as that of a 96-well plate as is customarily used in the art. Advantageously, then, the cartridge may be used with plate handlers used elsewhere in the art.
The sample inlets of adjacent sample lanes in a multi-sample cartridge are reasonably spaced apart from one another to prevent any contamination of one sample inlet from another sample when a user introduces a sample into any one cartridge. In an embodiment, the sample inlets are configured so as to prevent subsequent inadvertent introduction of sample into a given lane after a sample has already been introduced into that lane. Thus, the elements of the detector described herein are engineered to be compatible with the overall cartridge size and the separation between the respective lanes.
In other embodiments, the multi-sample cartridge is designed so that a spacing between the centroids of sample inlets is 9 mm, which is an industry-recognized standard. This means that, in certain embodiments the center-to-center distance between inlet holes in the cartridge that accept samples from PCR tubes, as further described herein, is 9 mm. The inlet holes are manufactured conical in shape with an appropriate conical angle so that industry-standard pipette tips (2 μl, 20 μl, 200 μl, volumes, etc.) fit snugly. The apparatus herein may be adapted to suit other, later-arising, industry standards not otherwise described herein.
FIG. 10 shows a plan view of an exemplary microfluidic cartridge having 12 lanes. The inlet ports have a 6 mm spacing, so that, when used in conjunction with an automated sample loader having 4 heads, spaced equidistantly at 18 mm apart, the inlets can be loaded in three batches of 4 inlets: e.g., inlets 1, 4, 7, and 10 together, followed by 2, 5, 8, and 1, then finally 3, 6, 9, and 12, wherein the 12 inlets are numbered consecutively from one side of the cartridge to the other.
In use, cartridge 200 is typically thermally associated with an array of heat sources configured to operate the components (e.g., valves, gates, actuators, and processing region 210) of the device. Particular components of exemplary microfluidic networks are further described in U.S. patent application Ser. No. ______, entitled “Microfluidic Cartridge and Method of Making Same” and filed on even date herewith.
FIG. 11 shows a plan view of a representative microfluidic circuit found in one lane of a multi-lane cartridge such as shown in FIG. 10. Other configurations of microfluidic network would be consistent with the function of the cartridges and apparatus described herein. In sequence, sample is introduced through liquid inlet 202, flows into a bubble removal vent channel 208 (which permits adventitious air bubbles introduced into the sample during entry, to escape), and continues along a channel 216. Throughout the operation of cartridge 200 the fluid is manipulated as a microdroplet (not shown in FIG. 5), and the various microfluidic components are actuated or controlled by application of heat from the heater unit further described herein. Valves 204 and 206 are initially open, so that a microdroplet of sample-containing fluid can be pumped into PCR reactor channel 210 from inlet hole 202. Upon initiating of processing, the detector present on top of the PCR reactor checks for the presence of liquid in the PCR channel, and then closes valves 204 and 206 to isolate the PCR reaction mix from the outside. The reactor 210 is a microfluidic channel that is heated through a series of cycles to carry out amplification of nucleotides in the sample, as further described herein. Both valves 204 and 206 are closed prior to thermocycling to prevent any evaporation of liquid, bubble generation, or movement of fluid from the PCR reactor. End vent 214 prevents a user from introducing any excess amount of liquid into the microfluidic cartridge, as well as playing a role of containing any sample from spilling over to unintended parts of the cartridge. A user may input sample volumes as small as an amount to fill from the bubble removal vent to the middle of the microreactor, or up to valve 204 or beyond valve 204. The use of microvalves prevents both loss of liquid or vapor thereby enabling even a partially filled reactor to successfully complete a PCR thermocycling reaction.
The cartridge can further include a heat sealable laminate layer (typically between about 100 and about 125 microns thick) attached to the bottom surface of a microfluidic substrate using, for example, heat bonding. The cartridge can further include a thermal interface material layer (typically about 125 microns thick), attached to the bottom of the heat sealable laminate layer using, for example, pressure sensitive adhesive. This layer can be compressible and have a higher thermal conductivity than common plastics, thereby serving to transfer heat across the membrane more efficiently to the components of the microfluidic network.
The application of pressure to contact the cartridge to the heater unit assists in achieving better thermal contact between the heater and the heat-receivable parts of the cartridge, and also prevents the bottom laminate structure—where present—from expanding, as would happen if the PCR channel was partially filled with liquid so that the entrapped air would be thermally expanded during thermocycling.
Further aspects of a microfluidic cartridge that adapt it to carrying out PCR efficiently are described in U.S. patent application Ser. No. ______, entitled “Microfluidic Cartridge and Method of Making Same” and filed on even date herewith, the specification of which is incorporated herein by reference.
- Highly Multiplexed Cartridge Embodiments
Microfluidic cartridge 200 can be fabricated as desired, for example, according to methods described in U.S. patent application Ser. No. ______, entitled “Microfluidic Cartridge and Method of Making Same” and filed on even date herewith.
Embodiments of the apparatus and cartridge described herein may be constructed that have high-density microfluidic circuitry on a single cartridge that thereby permit processing of multiple samples in parallel, or in sequence, on a single cartridge. Preferred numbers of such multiple samples include 24, 36, 40, 48, 50, 60, 64, 72, 80, 84, 96, and 100, but it would be understood that still other numbers are consistent with the apparatus and cartridge herein, where deemed convenient and practical.
Accordingly, different configurations of lanes, sample inlets, and associated heater networks are contemplated that can facilitate processing such numbers of samples on a single cartridge are within the scope of the instant disclosure. Similarly, alternative configurations of detectors and heating elements for use in conjunction with such a highly multiplexed cartridge are also within the scope of the description herein.
It is also to be understood that the microfluidic cartridges and substrates described herein are not to be limited to rectangular configurations, but can include cartridges having circular, elliptical, triangular, rhombohedral, square, and other shapes. Such shapes may also be adapted to include some irregularity, such as a cut-out, to facilitate placement in a complementary apparatus as further described elsewhere herein.
FIG. 12 shows a representative 48-sample cartridge, and having an inlet configuration different from others described and depicted herein. The inlet configuration is exemplary and has been designed to maximize efficiency of space usage on the cartridge. The inlet configuration can be compatible with an automatic pipetting machine that has dispensing heads situated at a 9 mm spacing. For example, such a machine having 4 heads can load 4 inlets at once, in 12 discrete steps, for the cartridge of FIG. 12. Other configurations of inlets though not explicitly described are compatible with the technology described herein.
In an exemplary embodiment, a highly multiplexed cartridge has 48 sample lanes, and permits independent control of each valve in each lane, with 2 banks of thermocycling protocols per lane, as shown in FIG. 13. This permits samples to be loaded into the cartridge at different times, and passed to the PCR reaction chambers independently of one another. Such embodiments permit batch processing of PCR samples, where multiple samples from different lanes are amplified by the same set of heating/cooling cycles. For example, the PCR heaters can be arranged in 2 banks (the heater arrays on the left and right are not in electrical communication with one another), thereby permitting a separate degree of sample control.
FIG. 14 shows an embodiment of a radially-configured highly-multiplexed cartridge, having a number of inlets, microfluidic lanes, and PCR reaction chambers.
The various embodiments shown in FIGS. 12-14 are compatible with liquid dispensers, receiving bays, heater units, and detectors that are configured differently from the other specific examples described herein. For example, such detectors may be configured to detect light from multiple sample lanes simultaneously, or to scan over sample lanes singly or in batches successively.
- PCR Reagent Mixtures
In another preferred embodiment (not shown in the FIGs.), a cartridge and apparatus is configured so that the read-head does not cover the sample inlets, thereby permitting loading of separate samples while other samples are undergoing PCR thermocycling.
PCR reagent mixes, and methods of preparation and use thereof, are generally known in the art. Herein, general aspects of such methods are described, as they can be used with the apparatus and detection system. In various embodiments, the sample for introduction into a lane of the cartridge can include a PCR reagent mixture comprising a polymerase enzyme and a plurality of nucleotides, and at least one probe that selectively emits light detected by the detection system herein.
In various embodiments, preparation of a PCR-ready sample for use with an apparatus and cartridge as described herein can include contacting a neutralized polynucleotide sample with a PCR reagent mixture comprising a polymerase enzyme and a plurality of nucleotides (in some embodiments, the PCR reagent mixture can further include a positive control plasmid and a fluorogenic hybridization probe selective for at least a portion of the plasmid). Other aspects of suitable PCR reagent mixture, for example lyophilized formulations, are described in U.S. patent application Ser. No. ______, entitled “Microfluidic Cartridge and Method of Making Same”, filed on even date herewith.
In various embodiments, the PCR-ready sample can include at least one probe that is selective for a polynucleotide sequence, e.g., the polynucleotide sequence that is characteristic of a pathogen selected from the group consisting of gram positive bacteria, gram negative bacteria, yeast, fungi, protozoa, and viruses. Steps by which such a PCR-ready sample is prepared involve contacting the neutralized polynucleotide sample or a PCR amplicon thereof with the probe. The probe can be a fluorogenic hybridization probe. The fluorogenic hybridization probe can include a polynucleotide sequence coupled to a fluorescent reporter dye and a fluorescence quencher dye.
In various embodiments, the PCR-ready sample further includes a sample buffer.
In various embodiments, the PCR reagent mixture can further include a polymerase enzyme, a positive control plasmid and a fluorogenic hybridization probe selective for at least a portion of the plasmid.
It is envisaged that the detection system herein is operable with any probe suitable for use in detecting a particular polynucleotide. The choice and use of a suitable probe is within the capability of one skilled in the art. In various embodiments, the probe can be selective for a polynucleotide sequence that is characteristic of an organism, for example any organism that employs deoxyribonucleic acid or ribonucleic acid polynucleotides. Thus, the probe can be selective for any organism. Suitable organisms include mammals (including humans), birds, reptiles, amphibians, fish, domesticated animals, wild animals, extinct organisms, bacteria, fungi, viruses, plants, and the like. The probe can also be selective for components of organisms that employ their own polynucleotides, for example mitochondria. In some embodiments, the probe is selective for microorganisms, for example, organisms used in food production (for example, yeasts employed in fermented products, molds or bacteria employed in cheeses, and the like) or pathogens (e.g., of humans, domesticated or wild mammals, domesticated or wild birds, and the like). In some embodiments, the probe is selective for organisms selected from the group consisting of gram positive bacteria, gram negative bacteria, yeast, fungi, protozoa, and viruses.
In various embodiments, the probe can be selective for a polynucleotide sequence that is characteristic of an organism selected from the group consisting of Staphylococcus spp., e.g., S. epidermidis, S. aureus, Methicillin-resistant Staphylococcus aureus (MRSA), Vancomycin-resistant Staphylococcus; Streptococcus(e.g., α, β or γ-hemolytic, Group A, B, C, D or G) such as S. pyogenes, S. agalactiae; E. faecalis, E. durans, and E. faecium (formerly S. faecalis, S. durans, S. faecium); nonenterococcal group D streptococci, e.g., S. bovis and S. equines; Streptococci viridans, e.g., S. mutans, S. sanguis, S. salivarius, S. mitior, A. milleri, S. constellatus, S. intermedius, and S. anginosus; S. iniae; S. pneumoniae; Neisseria, e.g., N. meningitides, N. gonorrhoeae, saprophytic Neisseria sp; Erysipelothrix, e.g., E. rhusiopathiae; Listeria spp., e.g., L. monocytogenes, rarely L. ivanovii and L. seeligeri; Bacillus, e.g., B. anthracis, B. cereus, B. subtilis, B. subtilus niger, B. thuringiensis; Nocardia asteroids; Legionella, e.g., L. pneumonophilia, Pneumocystis, e.g., P. carinii; Enterobacteriaceae such as Salmonella, Shigella, Escherichia (e.g., E. coli, E. coliO157:H7); Klebsiella, Enterobacter, Serratia, Proteus, Morganella, Providencia, Yersinia, and the like, e.g., Salmonella, e.g., S. typhi S. paratyphi A, B (S. schottmuelleri), and C (S. hirschfeldii), S. dublin S. choleraesuis, S. enteritidis, S. typhimurium, S. heidelberg, S. newport, S. infantis, S. agona, S. montevideo, and S. saint-paul; Shigella e.g., subgroups: A, B, C, and D, such as S. flexneri, S. sonnei, S. boydii, S. dysenteriae; Proteus (P. mirabilis, P. vulgaris, and P. myxofaciens), Morganella (M. morganii); Providencia (P. rettgeri, P. alcalifaciens, and P. stuartii); Yersinia, e.g., Y. pestis, Y. enterocolitica; Haemophilus, e.g., H. influenzae, H. parainfluenzae H. aphrophilus, H. ducreyi; Brucella, e.g., B. abortus, B. melitensis, B. suis, B. canis; Francisella, e.g., F. tularensis; Pseudomonas, e.g., P. aeruginosa, P. paucimobilis, P. putida, P. fluorescens, P. acidovorans, Burkholderia (Pseudomonas) pseudomallei, Burkholderia mallei, Burkholderia cepacia and Stenotrophomonas maltophilia; Campylobacter, e.g., C. fetus fetus, C. jejuni, C. pylori (Helicobacter pylori); Vibrio, e.g., V. cholerae, V. parahaemolyticus, V. mimicus, V. alginolyticus, V. hollisae, V. vulnificus, and the nonagglutinable vibrios; Clostridia, e.g., C. perfingens, C. tetani, C. difficile, C. botulinum; Actinomyces, e.g., A. israelii; Bacteroides, e.g., B. fragilis, B. thetaiotaomicron, B. distasonis, B. vulgatus, B. ovatus, B. caccae, and B. merdae; Prevotella, e.g., P. melaminogenica; genus Fusobacterium; Treponema, e.g. T. pallidum subspecies endemicum, T. pallidum subspecies pertenue, T. carateum, and T. pallidum subspecies pallidum; genus Borrelia, e.g., B burgdorferi; genus Leptospira; Streptobacillus, e.g., S. moniliformis; Spirillum, e.g., S. minus; Mycobacterium, e.g., M. tuberculosis, M. bovis, M. africanum, M. avium M. intracellulare, M. kansasii, M. xenopi, M. marinum, M. ulcerans, the M. fortuitum complex (M. fortuitum and M. chelonei), M. leprae, M. asiaticum, M. chelonei subsp. abscessus, M. fallax, M. fortuitum, M. malmoense, M. shimoidei, M. simiae, M. szulgai, M. xenopi; Mycoplasma, e.g., M. hominis, M. orale, M. salivarium, M. fermentans, M. pneumoniae, M. bovis, M. tuberculosis, M. avium, M. leprae; Mycoplasma, e.g., M. genitalium; Ureaplasma, e.g., U. urealyticum; Trichomonas, e.g., T. vaginalis; Cryptococcus, e.g., C. neoformans; Histoplasma, e.g., H. capsulatum; Candida, e.g., C. albicans; Aspergillus sp; Coccidioides, e.g., C. immitis; Blastomyces, e.g. B. dermatitidis; Paracoccidioides, e.g., P. brasiliensis; Penicillium, e.g., P. marneffei; Sporothrix, e.g., S. schenckii; Rhizopus, Rhizomucor, Absidia, and Basidiobolus; diseases caused by Bipolaris, Cladophialophora, Cladosporium, Drechslera, Exophiala, Fonsecaea, Phialophora, Xylohypha, Ochroconis, Rhinocladiella, Scolecobasidium, and Wangiella; Trichosporon, e.g., T. beigelii; Blastoschizomyces, e.g., B. capitatus; Plasmodium, e.g., P. falciparum, P. vivax, P. ovale, and P. malariae; Babesia sp; protozoa of the genus Trypanosoma, e.g., T. cruzi; Leishmania, e.g., L. donovani, L. major L. tropica, L. mexicana, L. braziliensis, L. viannia braziliensis; Toxoplasma, e.g., T. gondii; Amoebas of the genera Naegleria or Acanthamoeba; Entamoeba histolytica; Giardia lamblia; genus Cryptosporidium, e.g., C. parvum; Isospora belli; Cyclospora cayetanensis; Ascaris lumbricoides; Trichuris trichiura; Ancylostoma duodenale or Necator americanus; Strongyloides stercoralis Toxocara, e.g., T. canis, T. cati; Baylisascaris, e.g., B. procyonis; Trichinella, e.g., T. spiralis; Dracunculus, e.g., D. medinensis; genus Filarioidea; Wuchereria bancrofti; Brugia, e.g., B. malayi, or B. timori; Onchocerca volvulus; Loa loa; Dirofilaria immitis; genus Schistosoma, e.g., S. japonicum, S. mansoni, S. mekongi, S. intercalatum, S. haematobium; Paragonimus, e.g., P. Westermani, P. Skriabini; Clonorchis sinensis; Fasciola hepatica; Opisthorchis sp; Fasciolopsis buski; Diphyllobothrium latum; Taenia, e.g., T. saginata, T. solium; Echinococcus, e.g., E. granulosus, E. multilocularis; Picornaviruses, rhinoviruses echoviruses, coxsackieviruses, influenza virus; paramyxoviruses, e.g., types 1, 2, 3, and 4; adnoviruses; Herpesviruses, e.g., HSV-1 and HSV-2; varicella-zoster virus; human T-lymphotrophic virus (type I and type II); Arboviruses and Arenaviruses; Togaviridae, Flaviviridae, Bunyaviridae, Reoviridae; Flavivirus; Hantavirus; Viral encephalitis (alphaviruses [e.g., Venezuelan equine encephalitis, eastern equine encephalitis, western equine encephalitis]); Viral hemorrhagic fevers (filoviruses [e.g., Ebola, Marburg] and arenaviruses [e.g., Lassa, Machupo]); Smallpox (variola); retroviruses e.g., human immunodeficiency viruses 1 and 2; human papillomavirus [HPV] types 6, 11, 16, 18, 31, 33, and 35.
In various embodiments, the probe can be selective for a polynucleotide sequence that is characteristic of an organisms selected from the group consisting of Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella oxytoca, Klebsiella pneumoniae, Escherichia coli, Acinetobacter Baumannii, Serratia marcescens, Enterobacter aerogenes, Enterococcus faecium, vancomycin-resistant enterococcus (VRE), Staphylococcus aureus, methecillin-resistant Staphylococcus aureus (MRSA), Streptococcus viridans, Listeria monocytogenes, Enterococcus spp., Streptococcus Group B, Streptococcus Group C, Streptococcus Group G, Streptococcus Group F, Enterococcus faecalis, Streptococcus pneumoniae, Staphylococcus epidermidis, Gardenerella vaginalis, Micrococcus sps., Haemophilus influenzae, Neisseria gonorrhoeee, Moraxella catarrahlis, Salmonella sps., Chlamydia trachomatis, Peptostreptococcus productus, Peptostreptococcus anaerobius, Lactobacillusfermentum, Eubacterium lentum, Candida glabrata, Candida albicans, Chlamydia spp., Camplobacter spp., Salmonella spp., smallpox (variola major), Yersina Pestis, Herpes Simplex Virus I (HSV I), and Herpes Simplex Virus II (HSV II).
In various embodiments, the probe can be selective for a polynucleotide sequence that is characteristic of Group B Streptococcus.
In various embodiments, a method of carrying out PCR on a sample can further include one or more of the following steps: heating the biological sample in a microfluidic channel; pressurizing the biological sample in the microfluidic channel at a pressure differential compared to ambient pressure of between about 20 kilopascals and 200 kilopascals, or in some embodiments between about 70 kilopascals and 110 kilopascals.
In some embodiments, the method for sampling a polynucleotide can include the steps of: placing a microfluidic cartridge containing a PCR-ready sample in a receiving bay of a suitably configured apparatus; carrying out PCR on the sample under thermal cycling conditions suitable for creating PCR amplicons from the neutralized polynucleotide in the sample, the PCR-ready sample comprising a polymerase enzyme, a positive control plasmid, a fluorogenic hybridization probe selective for at least a portion of the plasmid, and a plurality of nucleotides; contacting the neutralized polynucleotide sample or a PCR amplicon thereof with the at least one fluorogenic probe that is selective for a polynucleotide sequence, wherein the probe is selective for a polynucleotide sequence that is characteristic of an organism selected from the group consisting of gram positive bacteria, gram negative bacteria, yeast, fungi, protozoa, and viruses; and detecting the fluorogenic probe, the presence of the organism for which the one fluorogenic probe is selective is determined.
Carrying out PCR on a PCR-ready sample can additionally include: independently contacting each of the neutralized polynucleotide sample and a negative control polynucleotide with the PCR reagent mixture under thermal cycling conditions suitable for independently creating PCR amplicons of the neutralized polynucleotide sample and PCR amplicons of the negative control polynucleotide; and/or contacting the neutralized polynucleotide sample or a PCR amplicon thereof and the negative control polynucleotide or a PCR amplicon thereof with at least one probe that is selective for a polynucleotide sequence.
- Heater Configurations to Ensure Uniform Heating of a Region
In various embodiments, a method of using the apparatus and detection system described herein can further include one or more of the following steps: determining the presence of a polynucleotide sequence in the biological sample, the polynucleotide sequence corresponding to the probe, if the probe is detected in the neutralized polynucleotide sample or a PCR amplicon thereof; determining that the sample was contaminated if the probe is detected in the negative control polynucleotide or a PCR amplicon thereof; and/or in some embodiments, wherein the PCR reagent mixture further comprises a positive control plasmid and a plasmid probe selective for at least a portion of the plasmid, the method further including determining that a PCR amplification has occurred if the plasmid probe is detected.
In general, the microfluidic channels in which the presence or absence of one or more analytes is determined by the detection system described herein are disposed in thermal contact with a dedicated heater unit. For example, the microfluidic cartridges described herein are typically configured to position in a complementary receiving bay in an apparatus that contains a heater unit. The heater unit is configured to deliver heat to specific microfluidic channels, such as specific regions of the cartridge, including but not limited to one or more microfluidic components, at specific times. For example, the heat source is configured so that particular heating elements are situated adjacent to specific components of a microfluidic network. In certain embodiments, the apparatus uniformly controls the heating of a region of a microfluidic network. In an exemplary embodiment, multiple heaters can be configured to simultaneously and uniformly heat a region, such as the PCR reaction chamber, of a microfluidic network.
Generally, the heating of microfluidic components, such as a PCR reaction chamber, is controlled by passing currents through suitably configured microfabricated heaters. Under control of suitable circuitry, the lanes of a multi-lane cartridge can then be controlled independently of one another. This can lead to a greater energy efficiency of the apparatus, because not all heaters are heating at the same time, and a given heater is receiving current for only that fraction of the time when it is required to heat. Control systems and methods of controllably heating various heating elements are further described in U.S. patent application Ser. No. ______, filed Nov. 14, 2007 and entitled “Heater Unit for Microfluidic Diagnostic System”.
FIG. 15 shows a cross-sectional view of an exemplary microfluidic cartridge to show the location of a PCR channel in relation to the heaters when the cartridge is placed in a suitable apparatus. The view in FIG. 15 is also referred to as a sectional-isometric view of the cartridge lying over a heater wafer. A window 903 above the PCR channel in the cartridge is shown in perspective view. PCR channel 901 (for example, 150μ deep×700μ wide), is shown in an upper layer of the cartridge. A laminate layer 905 of the cartridge (for example, 125μ thick) is directly under the PCR channel 901. A further layer of thermal interface laminate 907 on the cartridge (for example, 125μ thick) lies directly under the laminate layer 905. Heaters 909, 911 are situated in a further substrate layer 913 directly under the thermal interface laminate, shown in cross-section. In one embodiment the heaters are photolithographically defined and etched metal layers of gold (typically about 3,000 Å thick).
An exemplary such heater array is shown in FIGS. 16A and 16B. Additional embodiments of heater arrays are described in U.S. patent application Ser. No. ______, entitled “Heater Unit for Microfluidic Diagnostic System” and filed on even date herewith, the specification of which is incorporated herein by reference in its entirety.
Referring to FIGS. 16A and 16B, the PCR reaction chamber 1001, typically having a volume ˜1.6 μl, is configured with a long side and a short side, each with an associated heating element. The apparatus therefore includes four heaters disposed along the sides of, and configured to heat, the PCR reaction chamber, as shown in the exemplary embodiment of FIG. 16A: long top heater 1005, long bottom heater 1003, short left heater 1007, and short right heater 1009. The small gap between long top heater 1005 and long bottom heater 1003 results in a negligible temperature gradient (a difference of less than 1° C. across the width of the PCR channel at any point along the length of the PCR reaction chamber) and therefore an effectively uniform temperature throughout the PCR reaction chamber. The heaters on the short edges of the PCR reactor provide heat to counteract the gradient created by the two long heaters from the center of the reactor to the edge of the reactor. It would be understood by one of ordinary skill in the art that still other configurations of one or more heater(s) situated about a PCR reaction chamber are consistent with the methods and apparatus described herein. For example, a ‘long’ side of the reaction chamber can be configured to be heated by two or more heaters. Specific orientations and configurations of heaters are used to create uniform zones of heating even on substrates having poor thermal conductivity because the poor thermal conductivity of glass, or quartz, or fused silica substrates is utilized to help in the independent operation of various microfluidic components such as valves and independent operation of the various PCR lanes.
The configuration for uniform heating, shown in FIG. 16A for a single PCR reaction chamber, can be applied to a multi-lane PCR cartridge in which multiple independent PCR reactions occur. See, e.g., FIG. 16C.
Alignment of microheaters in the heater module with corresponding heat-requiring microcomponents (such as valves, pumps, gates, reaction chambers, etc). The microheaters can be designed to be slightly bigger than the heat requiring microfluidic components so that even though the cartridge may be off-centered from the heater, the individual components can still function effectively.
- Exemplary Electronics and Software
In other embodiments, as further described in U.S. patent application Ser. No. ______, filed Nov. 14, 2007 and entitled “Heater Unit for Microfluidic Diagnostic System”, the heaters may have an associated temperature sensor, or may themselves function as sensors,
FIG. 17 describes exemplary electronics architecture modules. It would be understood by one of ordinary skill in the art that other configurations of electronics components are consistent with operation of the apparatus as described herein. In the exemplary embodiment, the electronics architecture is distributed across two components of the apparatus: the Analyzer 2100 and a Heater Assembly 2102. The Analyzer contains an Optical Detection Unit 2108, a Control Board 2114, a Backplane 2112, and a LCD Touchscreen 2110. The Control Board includes a Card Engine 2116 further described herein, and Compact Flash memory 2118, as well as other components. The Heater Assembly includes a Heater Board 2104 and a Heater Mux Board 2106, both further described elsewhere, for example, in U.S. patent application Ser. No. ______, filed on even date herewith and entitled “Heater Unit for Microfluidic Diagnostic System”.
In the exemplary embodiment, the Card Engine electronics module 2116 is a commercial, off the shelf “single board computer” containing a processor, memory, and flash memory for operating system storage.
The LCD+Touchscreen electronics module 2110 is a user interface, for example, driven through a 640 pixel by 480 pixel 8 inch LCD and 5-wire touchscreen.
The Compact Flash electronics module 2118 is a 256 megabyte commercial, off the shelf, compact flash module for application and data storage. Other media are alternatively usable, such as USB-drive, smart media card, memory stick, and smart data-card having the same or other storage capacities.
The Backplane electronics module 2112 is a point of connection for the removable heater assembly 2102. Bare PC boards with two connectors are sufficient to provide the necessary level of connectivity.
The Control Board electronics module 2114 supports peripherals to the Card Engine electronics module 2116. In the exemplary embodiment, the peripherals include such devices as a USB host+slave or hub, a USB CDROM interface, serial ports, and ethernet ports. The Control Board 2114 can include a power monitor with a dedicated processor. The Control Board may also include a real time clock. The Control Board may further include a speaker. The Control Board 2114 also includes a CPLD to provide SPI access to all other modules and programming access to all other modules. The Control Board includes a programmable high voltage power supply. The Control Board includes a Serial-Deserializer interface to the LCD+Touchscreen electronics module 2110 and to the Optical Detection Unit electronics module 2108. The Control Board also includes module connectors.
In the exemplary embodiment, the optical detection unit electronics module 2108 contains a dedicated processor. The optical detection unit 2108 contains a serializer-deserializer interface. The optical detection unit 2108 contains LED drivers. The optical detection unit also contains high gain-low noise photodiode amplifiers. The optical detection unit preferably has power monitoring capability. The optical detection unit is remotely reprogrammable.
The Heater Board electronics module 2104 is preferably a glass heater board. The Heater Board has PCB with bonding pads for glass heater board and high density connectors.
In the exemplary embodiment, the heater mux (‘multiplex’) board electronics module 2106 has 24 high-speed ADC, 24 precision current sources, and 96 optically isolated current drivers for heating. The heater mux board has the ability to time-multiplex heating/measurement. The heater mux board has multiplexer banks to multiplex inputs to ADC, and to multiplex current source outputs. The heater mux board has a FPGA with a soft processor core and SDRAM. The heater mux board has a Power Monitor with a dedicated processor. The Heater Mux Board is preferably remotely reprogrammable.
Certain software can be executed in each electronics module. The Control Board Electronics Module executes, for example, Control Board Power Monitor software. The Card Engine electronics module executes an operating system, graphical user interface (GUI) software, an analyzer module, and an application program interface (api). The Optical Detection Unit electronics module executes an optics software module. The Heater Mux Board electronics module executes dedicated Heater Mux software, and Heater Mux Power Monitor software. Each of the separate instances of software can be modular and under a unified control of, for example, driver software.
The exemplary electronics can use Linux, UNIX, Windows, or MacOS, including any version thereof, as the operating system. The operating system is preferably loaded with drivers for USB, Ethernet, LCD, touchscreen, and removable media devices such as compact flash. Miscellaneous programs for configuring the Ethernet interface, managing USB connections, and updating via CD-ROM can also be included.
In the embodiment of FIG. 17, the analyzer module is the driver for specific hardware. The analyzer module provides access to the Heater Mux Module, the Optical Detection Unit, the Control Board Power Monitor, the Real Time Clock, the High Voltage Power Supply, and the LCD backlight. The analyzer module provides firmware programming access to the Control Board power monitor, the Optical Detection Unit, and the Heater Mux Module.
The API provides uniform access to the analyzer module driver. The API is responsible for error trapping, and interrupt handling. The API is typically programmed to be thread safe.
The GUI software can be based on a commercial, off-the-shelf PEG graphics library. The GUI can use the API to coordinate the self-test of optical detection unit and heater assembly. The GUI starts, stops, and monitors test progress. The GUI can also implement an algorithm to arrive at a diagnosis from fluorescence data. Such an algorithm can rely on numerical analysis principles known in the art. The GUI provides access control to the apparatus has and may have an HIS/LIS interface.
The Control Board Power Monitor software monitors power supplies, current and voltage, and signals error in case of a fault.
The Optics Software performs fluorescence detection which is precisely timed to turn on/off of LED with synchronous digitization of the photodetector outputs. The Optics Software can also monitor power supply voltages. The Optics Software can also have self test ability.
The Heater Mux Module software implements a “protocol player” which executes series of defined “steps” where each “step” can turn on sets of heaters to implement a desired microfluidic action. The Heater Mux Module software also has self test ability. The Heater Mux Module software contains a fuzzy logic temperature control algorithm.
- Overview of an Apparatus for Detecting Fluorescence from an Analyte in a Microfluidic Channel
The Heater Mux Power Monitor software monitors voltage and current levels. The Heater Mux Power Monitor software can participate in self-test, synchronous, monitoring of the current levels while turning on different heaters.
The present technology relates to a cartridge, complementary apparatus, and related methods for amplifying, and carrying out diagnostic analyses on, nucleotides from biological samples. The technology includes a disposable or reusable microfluidic cartridge containing multiple sample lanes capable of processing samples in parallel as further described herein, and a reusable apparatus that is configured to selectively actuate on-cartridge operations, to detect and analyze the products of the PCR amplification in each of the lanes separately, in all simultaneously, or in groups simultaneously, and, optionally, can display the progression of analyses and results thereof on a graphical user interface. Such a reusable apparatus is further described in U.S. patent application Ser. No. ______, entitled “Microfluidic System for Amplifying And Detecting Polynucleotides In Parallel” and filed on Nov. 14, 2007, and which is incorporated herein by reference in its entirety.
FIG. 18 shows a perspective view of an exemplary apparatus 100 consistent with those described herein, as well as various components thereof, such as exemplary cartridge 200 that contains multiple sample lanes, and exemplary read head 300 that contains detection apparatus for reading signals from cartridge 200. The apparatus 100 of FIG. 18 is able to carry out real-time PCR on a number of samples in cartridge 200 simultaneously or serially. Preferably the number of samples is 12 samples, as illustrated with exemplary cartridge 200, though other numbers of samples such as 4, 8, 10, 16, 20, 24, 25, 30, 32, 36, 40, and 48 are within the scope of the present description. In preferred operation of the apparatus, a PCR-ready solution containing the sample, and, optionally, one or more analyte-specific reagents (ASR's) is prepared, as further described elsewhere (see, e.g., U.S. patent application publication 2006-0166233, incorporated herein by reference), prior to introduction into cartridge 200. An exemplary kit for preparing a PCR-ready sample, the kit comprising buffers, lysis pellets, and affinity pellets, has been described elsewhere (see, e.g., U.S. provisional patent application Ser. No. 60/859,284).
In some embodiments, an apparatus includes: a receiving bay configured to selectively receive a microfluidic cartridge as described herein; at least one heat source thermally coupled to the receiving bay; and a processor coupled to the heat source, wherein the heat source is configured to selectively heat individual regions of individual sample lanes in the cartridge, and the processor is configured to control application of heat to the individual sample lanes, separately, in all simultaneously, or in groups simultaneously; at least one detector configured to detect one or more polynucleotides or a probe thereof in a sample in one or more of the individual sample lanes, separately or simultaneously; and a processor coupled to the detector to control the detector and to receive signals from the detector.
The receiving bay is a portion of the apparatus that is configured to selectively receive the microfluidic cartridge. For example, the receiving bay and the microfluidic cartridge can be complementary in shape so that the microfluidic cartridge is selectively received in, e.g., a single orientation. The microfluidic cartridge can have a registration member that fits into a complementary feature of the receiving bay. The registration member can be, for example, a cut-out on an edge of the cartridge, such as a corner that is cut-off, or one or more notches that are made on one or more of the sides in a distinctive pattern that prevents a cartridge from being loaded into the bay in more than one distinct orientation. By selectively receiving the cartridge, the receiving bay can help a user to place the cartridge so that the apparatus can properly operate on the cartridge. The cartridge can be designed to be slightly smaller than the dimensions of the receiving bay by approximately 200-300 microns for easy placement and removal of the cartridge.
The receiving bay can also be configured so that various components of the apparatus that operate on the microfluidic cartridge (heat sources, detectors, force members, and the like) are positioned to properly operate thereon. For example, a contact heat source can be positioned in the receiving bay such that it can be thermally coupled to one or more distinct locations on a microfluidic cartridge that is selectively received in the bay. Alignment of microheaters in the heater module with corresponding heat-requiring microcomponents (such as valves, pumps, gates, reaction chambers, etc). The microheaters can be designed to be slightly bigger than the heat requiring microfluidic components so that even though the cartridge may be off-centered from the heater, the individual components can still function effectively.
The lower surface of the cartridge can have a layer of mechanically compliant heat transfer laminate that can enable thermal contact between the microfluidic substrate and the microheater substrate of the heater module. A minimal pressure of 1 psi can be employed for reliable operation of the thermal valves, gates and pumps present in the microfluidic cartridge.
In various embodiments of the apparatus, the apparatus can further include a sensor coupled to the processor, the sensor configured to sense whether the microfluidic cartridge is selectively received.
The detector can be, for example, an optical detector as further described elsewhere herein. For example, the detector can include a light source that selectively emits light in an absorption band of a fluorescent dye, and a light detector that selectively detects light in an emission band of the fluorescent dye, wherein the fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof. Alternatively, for example, the optical detector can include a bandpass-filtered diode that selectively emits light in the absorption band of the fluorescent dye and a bandpass filtered photodiode that selectively detects light in the emission band of the fluorescent dye; or for example, the optical detector can be configured to independently detect a plurality of fluorescent dyes having different fluorescent emission spectra, wherein each fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof; or for example, the optical detector can be configured to independently detect a plurality of fluorescent dyes at a plurality of different locations on a microfluidic cartridge, wherein each fluorescent dye corresponds to a fluorescent polynucleotide probe or a fragment thereof in a different sample. The detector can also be configured to detect the presence or absence of sample in a PCR reaction chamber in a given sample lane, and to condition initiation of thermocycling upon affirmative detection of presence of the sample.
In various embodiments, the apparatus can further include an analysis port. The analysis port can be configured to allow an external sample analyzer to analyze a sample in the microfluidic cartridge. For example, the analysis port can be a hole or window in the apparatus which can accept an optical detection probe that can analyze a sample or progress of PCR in situ in the microfluidic cartridge. In some embodiments, the analysis port can be configured to direct a sample from the microfluidic cartridge to an external sample analyzer; for example, the analysis port can include a conduit in fluid communication with the microfluidic cartridge that directs a liquid sample containing an amplified polynucleotide to a chromatography apparatus, an optical spectrometer, a mass spectrometer, or the like.
The heat source can be, for example, a heat source such as a resistive heater or network of resistive heaters, and the like.
In preferred embodiments, the at least one heat source can be a contact heat source selected from a resistive heater (or network thereof), a radiator, a fluidic heat exchanger and a Peltier device. The contact heat source can be configured at the receiving bay to be thermally coupled to one or more distinct locations of a microfluidic cartridge received in the receiving bay, whereby the distinct locations are selectively heated. The contact heat source typically includes a plurality of contact heat sources, each configured at the receiving bay to be independently thermally coupled to a different distinct location in a microfluidic cartridge received therein, whereby the distinct locations are independently heated. The contact heat sources can be configured to be in direct physical contact with one or more distinct locations of a microfluidic cartridge received in the bay. In various embodiments, each contact source heater can be configured to heat a distinct location having an average diameter in 2 dimensions from about 1 millimeter (mm) to about 15 mm (typically about 1 mm to about 10 mm), or a distinct location having a surface area of between about 1 mm2 about 225 mm2 (typically between about 1 mm2 and about 100 mm2, or in some embodiments between about 5 mm2 and about 50 mm2). Various configurations of heat sources are further described in U.S. patent application Ser. No. ______, entitled “Heater Unit for Microfluidic Diagnostic System” and filed on even date herewith.
In various embodiments, the heat source is disposed in a heating module that is configured to be removable from the apparatus.
In various embodiments, the apparatus can include a compliant layer at the contact heat source configured to thermally couple the contact heat source with at least a portion of a microfluidic cartridge received in the receiving bay. The compliant layer can have a thickness of between about 0.05 and about 2 millimeters and a Shore hardness of between about 25 and about 100.
In various embodiments, the apparatus can further include one or more force members configured to apply force to at least a portion of a microfluidic cartridge received in the receiving bay. The one or more force members are configured to apply force to thermally couple the at least one heat source to at least a portion of the microfluidic cartridge. The application of force is important to ensure consistent thermal contact between the heater wafer and the PCR reactor and microvalves in the microfluidic cartridge.
In various embodiments, the apparatus can further include a lid at the receiving bay, the lid being operable to at least partially exclude ambient light from the receiving bay.
The apparatus preferably also includes a processor comprising microprocessor circuitry, in communication with, for example, the input device and a display, that accepts a user's instructions and controls analysis of samples.
In various embodiments, the apparatus can further include at least one input device coupled to the processor, the input device being selected from the group consisting of a keyboard, a touch-sensitive surface, a microphone, and a mouse.
In various embodiments, the apparatus can further include at least one sample identifier coupled to the processor, the sample identifier being selected from an optical scanner such as an optical character reader, a bar code reader, or a radio frequency tag reader. For example, the sample identifier can be a handheld bar code reader.
In various embodiments, the apparatus can further include at least one data storage medium coupled to the processor, the medium selected from a hard disk drive, an optical disk drive, or one or more removable storage media such as a CD-R, CD-RW, USB-drive, or flash memory card.
In various embodiments, the apparatus can further include at least one output coupled to the processor, the output being selected from a display, a printer, and a speaker, the coupling being either directly through a directly dedicated printer cable, or wirelessly, or via a network connection.
The apparatus further optionally comprises a display that communicates information to a user of the system. Such information includes but is not limited to: the current status of the system; progress of PCR thermocycling; and a warning message in case of malfunction of either system or cartridge. The display is preferably used in conjunction with an external input device as elsewhere described herein, through which a user may communicate instructions to apparatus 100. A suitable input device may further comprise a reader of formatted electronic media, such as, but not limited to, a flash memory card, memory stick, USB-stick, CD, or floppy diskette. An input device may further comprise a security feature such as a fingerprint reader, retinal scanner, magnetic strip reader, or bar-code reader, for ensuring that a user of the system is in fact authorized to do so, according to pre-loaded identifying characteristics of authorized users. An input device may additionally—and simultaneously—function as an output device for writing data in connection with sample analysis. For example, if an input device is a reader of formatted electronic media, it may also be a writer of such media. Data that may be written to such media by such a device includes, but is not limited to, environmental information, such as temperature or humidity, pertaining to an analysis, as well as a diagnostic result, and identifying data for the sample in question.
The apparatus may further include a computer network connection that permits extraction of data to a remote location, such as a personal computer, personal digital assistant, or network storage device such as computer server or disk farm. The network connection can be a communications interface selected from the group consisting of: a serial connection, a parallel connection, a wireless network connection, and a wired network connection such as an ethernet or cable connection, wherein the communications interface is in communication with at least the processor. The computer network connection may utilize, e.g., ethernet, firewire, or USB connectivity. The apparatus may further be configured to permit a user to e-mail results of an analysis directly to some other party, such as a healthcare provider, or a diagnostic facility, or a patient.
In various embodiments, there is an associated computer program product includes computer readable instructions thereon for operating the apparatus and for accepting instructions from a user.
Apparatus 100 may optionally comprise one or more stabilizing feet that cause the body of the device to be elevated above a surface on which system 100 is disposed, thereby permitting ventilation underneath system 100, and also providing a user with an improved ability to lift system 100.
Analyzer and Control Circuitry
In another preferred embodiment (not shown in the FIGs. herein), a cartridge and apparatus are configured so that the read-head does not cover the sample inlets, thereby permitting loading of separate samples while other samples are undergoing PCR thermocycling.
An Analyzer unit can contain typical hardware/firmware that can be employed to drive and monitor the operations on the cartridges as well as software to interpret, communicate and store the results. The unit currently weighs about 20 lbs. and is approximately 10″ wide by 16″ deep by 13″ high. Typical components of the Analyzer can include: (a) Control Electronics (DAQ), (b) Heater/Sensor Module, (c) Fluorescent Detection Module, (d) Mechanical Fixtures, (e) Software and (f) User Interface (LCD/Touch screen) (g) Peripherals (CD-ROM, USB/Serial/Ethernet communication ports, barcode scanner, optional keyboard). An exemplary embodiment is shown in FIG. 18.
Control electronics can be spread over four different circuit board assemblies. These include the Main, MUX, LCD, and Detector boards.
MAIN board: Can serve as the hub of the Analyzer control electronics and manages communication and control of the other various electronic sub-assemblies. The main board can also serve as the electrical and communications interface with the external world. An external power supply (12V DC/10A; UL certified) can be used to power the system. The unit can communicate via 5 USB ports, a serial port and an Ethernet port. Finally, the main board can incorporate several diagnostic/safety features to ensure safe and robust operation of the Analyzer.
MUX Board: Upon instruction from the main board, the MUX board can perform all the functions typically used for accurate temperature control of the heaters and can coordinate the collection of fluorescence data from the detector board.
LCD Board: Can contain the typical control elements to light up the LCD panel and interpret the signals from the touch sensitive screen. The LCD/touch screen combination can serve as a mode of interaction with the user via a Graphical User Interface.
- Example 2
Detector Integrated in Force Member
Detector Board: Can house typical control and processing circuitry that can be employed to collect, digitize, filter, and transmit the data from the fluorescence detection modules.
This non-limiting example describes pictorially, various embodiments of a detection system integrated into a force member, in an apparatus for carrying out diagnostics on microfluidic samples. An exploded view is shown in FIG. 19.
FIG. 20A: The lid of the apparatus can be closed, which can block ambient light from the sample bay, and place an optical detector contained in the lid into position with respect to the microfluidic cartridge.
FIG. 20B: The lid of the apparatus can be closed to apply pressure to the cartridge. Application of minimal pressure on the cartridge: after the slider compresses the cartridge, the slider can compress the compliant label of the cartridge. This can cause the bottom of the cartridge to be pressed down against the surface of the heater unit present in the heater module. Springs present in the slider can deliver, for example approximately 50 lb of pressure to generate a minimum pressure, for example 2 psi over the entire cartridge bottom.
Thermal interface: the cartridge bottom can have a layer of mechanically compliant heat transfer laminate that can enable thermal contact between the microfluidic substrate and the microheater substrate of the heater module. A minimal pressure of 1 psi can be employed for reliable operation of the thermal valves, gate and pumps present in the microfluidic cartridge.
Mechanicals and assembly: the Analyzer can have a simple mechanical frame to hold the various modules in alignment. The optics module can be placed in rails for easy opening and placement of cartridges in the Analyzer and error-free alignment of the optics upon closing. The heater/sensor module can be also placed on rails or similar guiding members for easy removal and insertion of the assembly.
Slider: the slider of the Analyzer can house the optical detection system as well as the mechanical assembly that can enables the optics jig to press down on the cartridge when the handle of the slider is turned down onto the analyzer. The optics jig can be suspended from the case of the slider at 4 points. Upon closing the slider and turning the handle of the analyzer down, 4 cams can turn to push down a plate that presses on 4 springs. On compression, the springs can deliver approximately 50 lb on the optical block. See FIGS. 21A-21C.
The bottom surface of the optics block can be made flat to within 100 microns, typically within 25 microns, and this flat surface can press upon the compliant (shore hardness approximately 50-70) label (approximately 1.5 mm thick under no compression) of the cartridge making the pressure more or less uniform over the cartridge. An optional lock-in mechanism can also be incorporated to prevent the slider from being accidentally knocked-off while in use.
FIG. 22A shows a side view of a lever assembly 1200, with lever 1210, gear unit 1212, and force member 1214. Assembly 1200 can be used to close the lid of the apparatus and (through force members 1214) apply force to a microfluidic cartridge 1216 in the sample well 1217. One force member is visible in this cut away view, but any number, for example 4, can be used. The force members can be, for example, a manual spring loaded actuator as shown, an automatic mechanical actuator, a material with sufficient mechanical compliance and stiffness (e.g., a hard elastomeric plug), and the like. The force applied to the microfluidic cartridge 1216 can result in a pressure at the surface of the microfluidic cartridge 1216 of at least about 0.7 psi to about 7 psi (between about 5 and about 50 kilopascals), or in some embodiments about 2 psi (about 14 kilopascals.
FIG. 22B shows a side view of lever assembly 1200, with microfluidic cartridge 1216 in the sample well 1217. A heat source 1219 (for example, a xenon bulb as shown) can function as a radiant heat source directed at a sample inlet reservoir 1218, where the heat can lyse cells in reservoir 1218. A thermally conductive, mechanically compliant layer 1222 can lie at an interface between microfluidic cartridge 1216 and thermal stage 1224. Typically, microfluidic cartridge 1216 and thermal stage 1224 can be planar at their respective interface surfaces, e.g., planar within about 100 microns, or more typically within about 25 microns. Layer 1222 can improve thermal coupling between microfluidic cartridge 1216 and thermal stage 1224. Optical detector elements 1220 can be directed at the top surface of microfluidic cartridge 1216.
- Example 3
Exemplary Optics Assembly
FIGS. 22C and 22D show further cross-sectional views.
In an exemplary embodiment, an assembly comprising a detector on an optical chassis and a force member that can exert pressure is housed in a plastic enclosure (slider) that can be positioned to cover a multi-lane microfluidic cartridge. The slider has a handle that can be easily grasped (between 4″ and 5″ width) by a user and drawn towards the front of the instrument using less than 11 pounds of force. The slider is guided for smooth and easy pushing and pulling with a handle, which also serves as a pressure-locking device. The slider's horizontal position is sensed in both the all-open (fully away from the user) and in the all-forward position, and reported to controlling software. Once properly located over a microfluidic cartridge, the slider will be locked in a “down” pressured position, and the user will be required to apply no more than seven pounds of upward force normal to the handle to release the pressure. Accidental unlocking of the slider mechanism is thereby prevented. The slider and optical chassis pressure assembly registers with a heater cassette module positioned underneath a microfluidic cartridge to within 0.010″. A close fit is important for proper heater/cartridge interface connections.
The slider aligns with the control chip on the heater unit when it is in the full back position. The height is the same as the distance between the read head bottom and the read area on the cartridge. The slider does not come in contact with the control chip but it is positioned such that the center of the control chip is in the focal plane of the optic system (0.005″). The slider assembly does not degrade in performance over a life of 10,000 cycles, where a cycle is defined as: beginning with the slider in the back position, and sliding forward then locking the handle down on a cartridge, unlocking the handle and returning it to the original back position. All optical path parts should be non-reflective (anodized, painted, molded, etc.) and do not lose this feature for 10,000 cycles. The optics unit is unaffected by a light intensity of <=9,000 foot-candles from a source placed 12″ from the instrument at angles where light penetration is most likely to occur. No degradation of performance is measured at the photo-detector after 10,000 cycles.
A single channel is made that houses two LED sources (blue and amber) and two additional channels that will house one photodiode detector each (four total bored holes). The two paired channels (source and detector) are oriented 43° from each other, measured from the optical axis and are in-line with the other paired channels that are at the same 43° orientation. The holes bored in the optical chassis contain filters and lenses with appropriate spacers, the specifications of which are further described herein. The LEDs are held in place to prevent movement as the mechanical alignment is important for good source illumination. The LED's are preferably twisted until the two “hot spots” are aligned with the reading channels on the cartridge. This position must be maintained until the LED's cannot be moved.
The optical chassis is made of aluminum and is black anodized. The bottom pressure surface of the optical chassis is flat to +0.001″ across the entire surface. The optical chassis is center-balanced such that the center of the optical chassis force is close to the center of the reagent cartridge. The pressure assembly (bottom of the optical chassis) provides uniform pressure of a minimum of 1 psi across all heater sections of the reagent cartridge. The optical assembly can be moved away from the reagent cartridge area for cartridge removal and placement. Appropriate grounding of the optical chassis is preferred to prevent spurious signals to emanate to the optic PCB.
The LED light sources (amber and blue) are incident on a microfluidic cartridge through a band pass filter and a focusing lens. These LED light sources have a minimum output of 2800 millicandles (blue) and 5600 millicandles (Green), and the center wavelengths are 470 (blue) and 575 (amber) nanometers, with a half band width of no more than 75 nanometers.
The LED light excites at least one fluorescent molecule (initially attached to an oligonucleotide probe) in a single chamber on a cartridge, causing it to fluoresce. This fluorescence will normally be efficiently blocked by a closely spaced quencher molecule. DNA amplification via TAQ enzyme will separate the fluorescent and quenching molecules from the oligonucleotide probe, disabling the quenching. DNA amplification will only occur if the probe's target molecule (a DNA sequence) is present in the sample chamber. Fluorescence occurs when a certain wavelength strikes the target molecule. The emitted light is not the same as the incident light. Blue incident light is blocked from the detector by the green only emission filter. Green incident light similarly is blocked from the detector by the yellow emission filter. The fluorescent light is captured and travels via a pathway into a focusing lens, through a filter and onto a very sensitive photodiode. The amount of light detected increases as the amount of the DNA amplification increases. The signal will vary with fluorescent dye used, but background noise should be less than 1 mV peak-to-peak. The photo-detector, which can be permanently mounted to the optical chassis in a fixed position, should be stable for 5 years or 10,000 cycles, and should be sensitive to extremely low light levels, and have a dark value of no more than 60 mV. Additionally, the photo-detector must be commercially available for at least 10 years. The lenses are Plano-convex (6 mm detector, and 12 mm source focal length) with the flat side toward the test cartridge on both lenses. The filters should remain stable over normal operating humidity and temperature ranges.
The filters, e.g., supplied by Omega Optical (Brattleboro, Vt. 05301), are a substrate of optical glass with a surface quality of F/F per Mil-C-48497A. The individual filters have a diameter of 6.0±0.1 mm, a thickness of 6.0±0.1 mm, and the AOI and ½ cone AOI is 0 degrees and ±8 degrees, respectively. The clear aperture is >/=4 mm diameter and the edge treatment is blackened prior to mounting in a black, anodized metal ring.
The FITC exciter filter is supplied by, e.g., Omega Optical (PN 481AF30-RED-EXC). They have a cut-off frequency of 466±4 nm and a cut-on frequency of 496±4 nm. Transmission is >/=65% peak and blocking is: >/=OD8 in theory from 503 to 580 nm, >/=OD5 from 501-650 nm, >/=OD4 avg. over 651-1000 nm, and >/=OD4 UV-439 nm.
The FITC emitter filter is supplied by, e.g., Omega Optical (PN 534AF40-RED-EM). They have a cut-off frequency of 514±2 nm and a cut-on frequency of 554±4 nm. Transmission is >/=70% peak and blocking is: >/=OD8 in theory from 400 to 504 nm, >/=OD5 UV-507 nm, and >/=OD4 avg. 593-765 nm.
The amber exciter filters are supplied by, e.g., Omega Optical (PN 582AF25-RED-EXC). They have a cut-off frequency of 594±5 nm and a cut-on frequency of 569±5 nm. Transmission is >/=70% peak and blocking is: >/=OD8 in theory from 600 to 700 nm, >/=OD5 600-900 nm, and >/=OD4 UV-548 nm.
The amber emitter filters are supplied by, e.g., Omega Optical (PN 627AF30-RED-EM). They have a cut-off frequency of 642±5 nm and a cut-on frequency of 612±5 nm. Transmission is >/=70% peak and blocking is: >/=OD8 in theory from 550 to 600 nm, >/=OD5 UV-605 nm, and >/=OD5 avg. 667-900 nm.
- Example 4
Exemplary Optics Board
The spacers should be inert and temperature stable throughout the entire operating range and should maintain the filters in strict position and alignment. The epoxy used should have optically black and opaque material and dry solid with no tacky residue. Additionally, it should have temperature and moisture stability, exert no pressure on the held components, and should mount the PCB in such a way that it is fixed and stable with no chances of rotation or vertical height changes. 50% of illumination shall fall on the sample plane within an area 0.1″ (2.5 mm) wide by 0.3″ (7.5 mm) along axis of the detection channel. Fluorescence of the control chip should not change more than 0.5% of the measured signal per 0.001″ of height though a region ±0.010 from the nominal height of the control chip.
An exemplary optics board is shown schematically in FIG. 23, and is used to collect and amplify the fluorescent signature of a successful chemical reaction on a micro-fluidic cartridge, and control the intensity of LED's using pulse-width modulation (PWM) to illuminate the cartridge sample over up to four channels, each with two color options. Additionally, it receives instructions and sends results data back over an LVDS (low-voltage differential signaling) SPI (serial peripheral interface). In some embodiments there is a separate instance of this circuitry for each PCR channel that is monitored.
The power board systems include: a +12V input; and +3.3V, +3.6V, +5V, and −5V outputs, configured as follows: the +3.3V output contains a linear regulator, is used to power the LVDS interface, should maintain a +1-5% accuracy, and supply an output current of 0.35 A; the +3.6V output contains a linear regulator, is used to power the MSP430, should maintain a +/−5% accuracy, and supply an output current of 0.35 A; the +5V output contains a linear regulator, is used to power the plus rail for op-amps, should maintain a +/−5% accuracy, and supply an output current of 0.35 A; the −5V output receives its power from the +5V supply, has a mV reference, is used to power the minus rail for op-amps and for the photo-detector bias, should maintain a +/−11% voltage accuracy, and supply an output current of 6.25 mA+/−10%. Additionally, the power board has an 80 ohm source resistance, and the main board software can enable/disable the regulator outputs.
The main board interface uses a single channel of the LVDS standard to communicate between boards. This takes place using SPI signaling over the LVDS interface which is connected to the main SPI port of the control processor. The interface also contains a serial port for in-system programming.
The optical detection system of FIG. 23 comprises a control processor, LED drivers, and a photo-detection system. In the exemplary embodiment, the control processor is a TI MSP430F1611 consisting of a dual SPI (one for main board interface, and one for ADC interface) and extended SRAM for data storage. It has the functions of power monitoring, PWM LED control, and SPI linking to the ADC and main board. The LED drivers contain NPN transistor switches, are connected to the PWM outputs of the control processor, can sink 10 mA @ 12V per LED (80 mA total), and are single channel with 2 LEDs (one of each color) connected to each. The photo-detection system has two channels and consists of a photo-detector, high-sensitivity photo-diode detector, high gain current to voltage converter, unity gain voltage inverting amplifier, and an ADC. Additionally it contains a 16 channel Sigma-delta (only utilizing the first 8 channels) which is connected to the second SPI port of the control processor.
During assembly of the various components on to the PC board, such as may occur on a production line, there are the following considerations. The extremely high impedance of the photo-detection circuit means that a rigorous cleaning procedure must be employed. Such a procedure may include, for example: After surface mount components are installed, the boards are washed on a Weskleen and blow dried upon exiting conveyor. The belt speed can be set at 20-30. The boards are soaked in an alcohol bath for approximately 3 minutes, then their entire top and bottom surfaces are scrubbed using a clean, soft bristle brush. The boards are baked in a 105° F. (40° C.) oven for 30 minutes to dry out all components.
- Example 5
Fluorescence Detection Module
After all the components are installed: the soldered areas of the boards can be hand wash using deionized water and a soft bristle brush. The same soldered areas can be hand washed using alcohol and a soft bristle brush. The boards are allowed to air dry. Once the board is cleaned, the optical circuitry must be conformal coated to keep contaminates out.
A miniaturized, highly sensitive fluorescence detection system (see FIG. 24) can be incorporated for monitoring fluorescence from the biochemical reactions. This optics module can employ light emitting diodes (LED's), photodiodes and filters/lenses for monitoring, in real-time, the fluorescent signal emanating from the microfluidic cartridge. The current example module contains six identical detection elements and each element can be capable of dual-color detection of a pre-determined set of fluorescent probes.
Software: The software can include two broad parts—user interface and device firmware. The user interface software can allow for aspects of interaction with the user such as—entering patient/sample information, monitoring test progress, error warnings, printing test results, uploading of results to databases and updating software. The device firmware can be the low level software that actually runs the test. The firmware can have a generic portion that can be test independent and a portion specific to the test being performed. The test specific portion (“protocol”) can specify the microfluidic operations and their order to accomplish the test.
- Example 6
Scanning Detector Unit
FIG. 25 shows screen captures from the programming interface and real time heat sensor and optical detector monitoring. This real time device performance monitoring is for testing purposes; not visible to the user in the final configuration.
In one embodiment a detector is configured to scan over multiple lanes of a microfluidic substrate such as in a microfluidic cartridge, rather than remain stationary and require a separate detector instance dedicated to each lane. It is also an aspect of this embodiment that multiple detector units are stacked adjacent to one another thereby permitting simultaneous detection from multiple lanes, even as the detector is travelling over the microfluidic substrate. It is a further aspect of this embodiment that each detector unit is a 4-color system, or is a 1-color system, or is a 2-color system.
FIG. 26 shows a cross-section of the detector. The reader includes an optical detection unit that can be pressed against a 24-lane microfluidic cartridge to optically interface with the PCR lanes as well as press the cartridge against a microfluidic heater substrate. The bottom of the optics block has 24 apertures (two rows of 12 apertures) that are similar in dimension to the PCR reactors in the cartridge. The aperture plate is made of low fluorescent material, such as anodized black aluminum and during operation, minimizes the total background fluorescence while maximizing the collection of fluorescent only from the PCR reactor (FIG. 27). The bottom of the aperture plate has two beveled edges that help align two edges of the cartridges appropriately such that the apertures line up with the PCR reactors (FIGS. 28A, 28B).
The optical detection blocks, FIGS. 29 and 30, (total of 8 detection units in this example) are assembled and mounted onto a sliding rail inside the optical box so that the optical units can be scanned over the apertures (FIG. 29). Each unit is able to excite and focus a certain wavelength of light onto the PCR reactor and collect emitted fluorescence of particular wavelength into a photodetector. Each block of the embodiment shown has 2 units and is configured to measure a particular frequency of light from 2 separate locations, such as where a microfluidic substrate is configured with 2 banks (top and bottom) of PCR reactors. By using 4 different colors, one in each of the four parallel detection units, on the top 4 channels and repeating the 4 colors in the bottom channels, the entire scanner can scan up to 4 colors from each of the PCR lanes.
The optics block can be machined out of aluminum and anodized or injection molded using low fluorescence black plastic (FIG. 30). Injection molding can dramatically reduce the cost per unit and also make the assembly of optics easier. The designed units can be stacked back-to-back.
The foregoing description is intended to illustrate various aspects of the present technology. It is not intended that the examples presented herein limit the scope of the present technology. The technology now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the appended claims.