METHOD OF PRETREATING METAL with UV light to covalently bond the hydrophilic photo
SURFACES FOR SUBSEQUENT POLYMER crosslinkable polymer system to the surface of the device.
COATING Catheter guidewires are one example of the kind of
medical device typically coated with a biocompatible mate
This application is a division of application Ser. No. 5 rial. In order to facilitate insertion of the guidewire into a
08/097,458 filed Jul. 27, 1993 U.S. Pat. No. 5,388,343. patient and to minimize ttie threat of thromboembolisms. the
metal core must be surrounded by a lubricious hydrophilic
FIELD OF THE INVENTION polymer coating. The coatings of prior art guidewires.
This invention relates generally to a method for preparing however' m ^adequate, for the reasons stated below.
a surface for subsequent attachment of a coating and. in 10 T*16 BioCoat PTM0655 *>* *e Processes disclosed in U.S.
particular, to a method for preparing a metal surface for Pat' Nos' 4,722,906; 4.973.493; 4.979.959; and 5.002.582
subsequent covalent linking to a polymer coating. This have not teen used successfully to coat metal devices such
invention also relates to articles such as medical devices as guidewires with hydrophilic polymers (despite sugges
made according to this method. tions to the Contral7 in mose references) without first
15 preparing or pretreating the surface of the devices, particu
BACKGROUND OF THE INVENTION larly when (he coated metal devices are used in an aqueous The surface of an object may be coated with a polymer to enTMnif f Two possible pretreatments have been proprotect the surface or to provide the surface witl/properties P°fd Under one «««««*• *' g^ewrre is prepared for of the polymer coating. For example, coatings of synthetic subse<luent "f** .^-wrapping a polyethylene polymers and natural biomolecules are applied to medical 2C sl^ve «?"* ** 8TMta"«~ ^ photocrossknkable hydroDevices for a variety of reasons. In the case of catheters and Phlhc P0^ ... is*en "Wj^ ^ and cur* as guidewires. it is desirable to add a coating with a low d.escribf ab°Ve' to ""^f P°*Slble PfTMTM method
coefficient of friction in the presence of water and a low *e SftldTMTM1S. prep^ed for TMbsequen °?atu« by ***?**
. . . c , . ... f ... , . ., the guidewire in a silane undercoat solution, then drying,
tendency to form clots (thromboemboksms) in the presence ~- . ^ •. . L, . j ,..,• • . • \
of blood. 25 The photocrosslinkable hydrophilic polymer system is then
applied to the silane undercoatine.
As discussed in U.S. Pat. No 5,002,582. the disclosure of ^ p]ior ^ ^^ rf * biocompalible „*_
which is incorporated herein by reference, polymer mol- m tQ ^ ... use ^tion methodslhat fall into
ecules may be provided with latent reactive groups .. . . • »«. u. »• u-j
i « u j j * .u u»t. » l »u 11 the same two categories as the photoactive binder
covalently bonded to them such that when the molecules are „ . *.• I u /i^fj
i_ u. • . i. j' ••*.-»!. _r / u 30 approaches mentioned above: (1) wet undercoat pretreat
brought into bonding proximity with a surface (such as on a r ^ ... . ,-,, ... . . ^
,r , . . , t. , . '. . . . ment methods and (2) sohd sleeve undercoat pretreatment
medical device), the latent reactive groups can be energized .. . _ , . , ... :, ,. . .
. f • f. ti • J ,.iTj methods. For example, a wet undercoat method of applying
to form, via free active species generatou. covalent bonds a ... coating to a cath^e; o^
between these molecules and the surface. The latent reactive ... ^^ £ us Pa, *a 5 B5 516 ^
groups generate acdve species such as free radicals, mttenes 35 «oatin ^^ jn ^, fis afl fa a(e
carbenes. and excited states of ketones upon absorption of ^ a ... binding ^^^J^d „ ^^
external eleclromagnetic or kinetic (thermal) energy. ... component T,fe bl^di component is a
The '582 patent describes a number of suitable latent hydrophilic. water-swellable. acid-containing polymer with
reactive groups and some methods of applying polymers and quaternary ammonium cations bonded into the polymer
other coatings to a surface using the latent reactive groups. n layer to one ... application method, a stainless steel
Under one method, a solution containing a latent reactive guidewire is coated first with a primer solution of a 1%
molecule (e.g.. a molecule having a latent reactive group) is polyisocyanate in methylethylketone, then dried for 30
applied to the surface. Thereafter, the desired polymer is minutes. A topcoat of 1% poly(acrylic acid) and 0.5% of
brought into contact with, and is covalently bonded to. the MYRJ 53 (nonionic surfactant) in dimethylformamide is
latent reactive molecule, as to a reactive group different from 45 ±en applied and Mtd for ^^^ 30 ^^5. The resulting
the latent reactive group, to form a photocrosslinkable hydrophilic surface is then dipped first in a benzalkonium
polymer system. The latent reactive groups may then be chloride solution, then dried and dipped in a heparin salt
activated to cause the photocrosslinkable polymer system to ... ,o complete the process,
covalently bond to the surface. y s pat nq 5<129tg90 describes a solid sleeve pretreat.
Under another method disclosed in the '582 patent, the 50 ment method for coating a metal guidewire with a lubricious
surface is first coated with a solution of the molecules coating. The guidewire coating method disclosed in the'890
bearing latent reactive groups. UV light is applied to cause patent interposes a polyurethane sleeve between the hydro
the molecules to covalently bond, through the latent reactive philic coating and the guidewire. The sleeve provides an
groups, to the surface. A solution containing the desired attachment base for the hydrophilic coating, polymer is then applied to the surface, and the polymer 55
bonds covalently to the photoactively treated surface. Fur- SUMMARY OF THE INVENTION
ther details of photoactive and thermally active covalent One drawback of prior art wet undercoat preparation
attachment of polymers may be found in U.S. Pat. Nos. methods of coating metal devices with biocompatible hydro
4.722,906; 4,973,493; and 4.979.959. The disclosures of philic polymers is the time needed to apply and dry the
these patents are incorporated herein by reference. eo undercoat before the application of the hydrophilic polymer
Bio-Metric Systems. Inc., markets a photoactive biocom- itself. Another drawback of prior wet undercoat pretreatment
patible coating technique under the trademark BioCoat. This methods is the difficulty of obtaining an even layer of the
technique first combines a photoactive binder and the wet undercoat. Any irregularities in the thickness of the
desired coating material, such as a hydrophilic polymer, to undercoat will affect the quality of the hydrophilic outer
create a photocrosslinkable polymer system. A solution of 65 coating.
the photocrosslinkable polymer system is then applied to the The use of wet treatment methods is additionally becom
medical device. The coating is dried, and the binder is cured ing increasingly more of an environmental concern. The