Latent reactive polymers with biologically active moieties

FIELD OF THE INVENTION

0001In one aspect, this invention relates to a method of coating a biomaterial surface.

BACKGROUND OF THE INVENTION

0002Biomaterials have long been used to fabricate biomedical devices for use in both <i>in vitro</i> and <i>in vivo</i> applications.. A variety of biomaterials can be used for the fabrication of such devices, including ceramics, metals, polymers, and combinations thereof. Historically, such biomaterials were considered suitable for use in fabricating biomedical devices if they provided a suitable combination of such basic properties as inertness, low toxicity, and the ability to be fabricated into desired devices (<nplcit id="ncit0001" npl-type="s"><text>Hanker, J.S and B.L. Giammara, Science 242:885-892, 1988</text></nplcit>)

0003As the result of more recent advances, devices can now be provided with surfaces having various desirable characteristics, e.g., in order to better interface with surrounding tissue or solutions. For instance, approaches have been developed to promote the attachment of specific cells or molecules to device surfaces. A device surface, for instance, can be provided with a bioactive group that is capable of attracting and/or attaching to various molecules or cells. Examples of such bioactive groups include antigens for binding to antibodies, ligands for binding to cell surface receptors, and enzyme substrates for binding to enzymes.

0004Such bioactive groups have been provided on the surfaces of biomaterials in a variety of ways. In one approach, biomaterials can be fabricated from molecules that themselves present the desired bioactive groups on the surfaces of devices after fabrication However, desirable bioactive groups are typically hydrophilic and cannot be incorporated into most metals or hydrophobic polymeric biomaterials at effective concentrations without disrupting the structural integrity of such biomaterials.

0005An alternative approach involves adding bioactive groups to the surfaces of biomaterials, e.g., after they have been fabricated into medical devices. Such bioactive groups can occasionally be added by absorption. However, groups that have been added by adsorption cannot typically be retained on surfaces at high levels or for long periods of time.

0006The retention of such bioactive groups on a surface can be improved by covalent bonding ofthose groups to the surface. For instance, <patcit id="pcit0001" dnum="US4722906A"><text>US Patent Nos. 4,722,906</text></patcit>, <patcit id="pcit0002" dnum="US4979959A"><text>4,979,959</text></patcit>, <patcit id="pcit0003" dnum="US4973493A"><text>4,973,493 </text></patcit>and <patcit id="pcit0004" dnum="US5263992A"><text>5,263,992</text></patcit> relate to devices having biocompatible agents covalently bound via a photoreactive group and a chemical linking moiety to the biomaterial surface. <patcit id="pcit0005" dnum="US5258041A"><text>US Patent Nos. 5,258,041</text></patcit> and <patcit id="pcit0006" dnum="US5217492A"><text>5,217,492</text></patcit> relate to the attachment of biomolecules to a surface through the use of long chain chemical spacers. <patcit id="pcit0007" dnum="US5002582A"><text>US Patent Nos. 5,002,582</text></patcit> and <patcit id="pcit0008" dnum="US5263992A"><text>5,263,992</text></patcit> relate to the preparation and use of polymeric surfaces, wherein polymeric agents providing desirable properties are covalently bound via a photoreactive moiety to the surface. In particular, the polymers themselves exhibit the desired characteristics, and in the preferred embodiment, are substantially free of other (e.g., bioactive) groups.

0007Others have used photochemistry to modify the surfaces of biomedical devices, e.g., to coat vascular grafts. (See, e.g, <nplcit id="ncit0002" npl-type="s"><text>Kito, H., et al., ASAIO Journal 39:M506-M511, 1993</text></nplcit>. See also <nplcit id="ncit0003" npl-type="s"><text>Clapper, D.L, et al, Trans. Soc.Biomat, 16:42, 1993</text></nplcit>).

0008Cholakis and Sefton synthesized a polymer having a polyvinyl alcohol (PVA) backbone and heparin bioactive groups The polymer was coupled to polyethylene tubing via nonlatent reactive chemistry, and the resultant surface was evaluated for thromboresistance in a series of <i>in vitro</i> and <i>in vivo</i> assays. For whatever reason, the heparin in the polymer prepared by Cholakis and Sefton did not provide effective activity (<nplcit id="ncit0004" npl-type="s"><text>Cholakis, C.H. and M V. Sefton, J. Biomed Mater. Res, 23:399-415, 1989</text></nplcit> See also <nplcit id="ncit0005" npl-type="s"><text>Cholakis, C.H., et al., J. Biomed. Mater. Res, 23:417-441, 1989</text></nplcit>)

0009Finally, Kinoshita et. al. disclose the use of reactive chemistry to generate polyacrylic acid backbones on porous polyethylene, with collagen molecules being subsequently coupled to carboxyl moieties on the polyacrylic acid backbones (See <nplcit id="ncit0006" npl-type="s"><text>Kinoshita, Y, et al., Biomaterials 14:209-215,1993</text></nplcit>).

0010Generally, the resultant coating in the above-captioned situations is provided in the form of bioactive groups covalently coupled to biomaterial surfaces by means of short linear spacers This approach works well with large moleculer weight bioactive groups, such as collagen and fibronectin, where the use of short spacers is desired and the size of the bioactive group is quite large compared to that of the spacer itself

0011The approaches described above, however, with the possible exception of Kinoshita et al., are not optimal for coating small molecular weight bioactive groups. Kinoshita does appear to coat small molecular weight molecules, although it describes a laborious multistep process that can detrimentally affect both yield and reproducibility.

0012Small molecular weight bioactive groups are typically provided in the form of either small regions derived from much larger molecules (e.g., cell attachment peptides derived from fibronectin) or as small molecules that normally diffuse freely to produce their effects (e.g., antibiotics or growth factors). It appears that short spacers can unduly limit the freedom of movement of such small bioactive groups, and in turn, impair their activity when immobilized What are clearly needed are methods for providing improved concentrations ofbioactive groups, and particularly small molecular weight groups, to a biomaterial surface in a manner that permits improved freedom of movement of the bioactive groups.

SUMMARY OF THE INVENTION

0013The present invention discloses a method for providing a coated surface, such as the surface of a biomaterial, or biomedical device fabricated from such a biomaterial. The coated surface, having molecules of the polybifunctional reagent attached thereto in order to provide the device with desirable properties or attributes. The present invention is specifically defined in claim 1.

0014The photoreactive moieties can be activated in order to attach the polybifunctional reagent to a surface providing abstractable hydrogen atoms in such a manner that the pendent bioactive group(s) retain their desired bioactive function. The "two step" method of the invention involves a first step of immobilizing a polymeric backbone via photochemical means, and a second step of attaching (e.g., thermochemically) one or more bioactive groups to the immobilized backbone.

0015Polybifunctional reagents which per se are not part of the invention are used to coat the surfaces of existing biomaterials and/or to generate new biomatetials, e.g., by the formation of bulk materials. In either case, they can improve the surface properties of a biomedical device by providing covalently bound bioactive groups at the device surface. Preferred bioactive groups, in turn, act by either noncovalently binding to, or acting upon, specific complimentary portions of molecules or cells that come into contact with such groups.

0016Preferred bioactive groups function by promoting the attachment of specific molecules or cells to the smfacc. Preferred bioactive groups include, but are not limited to, proteins, peptides, carbohydrates, nucleic acids and other molecules that are capable of binding noncovalently to specific and complimentary portions of molecules or cells. Examples of such specific binding include cell surface receptors binding to ligands, antigens binding to antibodies, and enzyme substrates binding to enzymes. Preferably, the polymeric backbone comprises a synthetic polymeric backbone selected from the group consisting of addition type polymers, such as the vinyl polymers. More preferably, the photogroups each comprise a reversibly photoactivatable ketone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0017As used herein, the following terms and words will have the following ascribed meanings: <ul id="ul0001" list-style="none" compact="compact"><li>"biomaterial" will refer to a material that is substantially insoluble in aqueous systems and that provides one or more surfaces for contact with fluids containing biological molecules, e.g., <i>in vivo</i> or <i>in vitro</i> aqueous systems containing tissues, cells, or biomolecules;</li><li>"device" will refer to a functional object fabricated from a biomaterial;</li><li>"coating", when used as a noun, will refer to one or more polymer layers on a biomaterial surface, and in particular, to one or more layers immobilized on a biomaterial surface by the activation of a polybifunctional reagent;</li><li>"polybifunctional reagent", when used in the context of the presently claimed reagent, will refer to a molecule comprising a polymer backbone, to which are covalently bonded one or more photoreactive moieties and two or more bioactive groups;</li><li>"a photoreactive moiety" will refer to a chemical group that responds to a specific applied external energy source in order to undergo active specie generation, resulting in covalent bonding to an adjacent molecule or biomaterial surface;</li><li>"bioactive group" will refer to a molecule having a desired specific biological activity, such as a binding or enzymatic (catalytic) activity;</li><li>"polymer backbone" will refer to a natural polymer or a synthetic polymer, e.g., resulting from addition or condensation polymerization;</li><li>Preferred reagents of the invention comprise a synthetic polymer which serves as a backbone, one or more pendent photoreactive moieties which can be activated to provide covalent bonding to surfaces or adjacent polymer molecules, and two or more pendent low molecular weight biologically active moieties (bioactive groups).</li></ul>

0018<u>Backbone</u>. The polymer backbone can be either synthetic or naturally occurring, and is preferably a synthetic polymer selected from the group consisting of oligomers, homopolymers, and copolymers resulting from addition or condensation polymerization. Naturally occurring polymers, such as polysaccharides and polypeptides, can be used as well Preferred backbones are biologically inert, in that they do not provide a biological function that is inconsistent with, or detrimental to, their use in the manner described

0019Such polymer backbones can include acrylics such as those polymerized from hydroxyethyl acrylate, hydroxyethyl methacrylate, glyceryl acrylate, glyceryl methacrylate, acrylic acid, methacrylic acid, acrylamide and methaacylamide; vinyls such as polyvinyl pyrrolidone and polyvinyl alcohol; nylons such as polycaprolactam; derivatives of polylauryl lactam, polyhexamethylene adipamide and polyhexamethylene dodecanediamide, and polyurethanes; polyethers such as polyethylene oxide, polypropylene oxide, and polybutylene oxide; and biodegradable polymers such as polylactic acid, polyglycolic acid, polydioxanone, polyanhydrides, and polyorthoesters.

0020The polymeric backbone is chosen to provide a backbone capable of bearing one or more photoreactive moieties and two or more bioactive groups. The polymeric backbone is also selected to provide a spacer between the surface and the various photoreactive moieties and bioactive groups. In this manner, the reagent can be bonded to a surface or to an adjacent reagent molecule, to provide the bioactive groups with sufficient freedom of movement to demonstrate optimal activity. The polymer backbones are preferably water soluble, with polyacrylamide and polyvinylpyrrolidone being particularly preferred polymers.

0021<u>Photoreactive moieties.</u> Polybifunctional reagents that are used in the method of the invention carry one or more pendent latent reactive (preferably photoreactive) moieties covalently bonded to the polymer backbone. Photoreactive moieties are defined herein, and preferred moieties are sufficiently stable to be stored under conditions in which they retain such properties (See, e.g., <patcit id="pcit0009" dnum="US5002582A"><text>U.S. Patent No. 5,002,582</text></patcit>). Latent reactive moieties can be chosen that are responsive to various portions of the electromagnetic spectrum, with those responsive to ultraviolet and visible portions of the spectrum (referred to herein as "photoreactive") being particularly preferred.

0022Photoreactive moieties respond to specific applied external stimuli to undergo active specie generation with resultant covalent boding to an adjacent chemical structure, e.g., as provided by the same or a different molecule. Photoreactive moieties are those groups of atoms in a molecule that retain their covalent bonds unchanged under conditions of storage but that, upon activation by an external energy source, form covalent bonds with other molecules.

0023The photoreactive moieties generate active species such as free radicals and particularly nitrenes, carbenes, and excited states of ketones upon absorption of external electric, electromagnetic or kinetic (thermal) energy. Photoreactive moieties may be chosen to be responsive to various portions of the electromagnetic spectrum, and photoreactive moieties that are responsive to e.g., ultraviolet and visible portions of the spectrum are preferred and are referred to herein occasionally as "photochemical" moiety

0024Photoreactive aryl ketones are particularly preferred, such as acetophenone, benzophenone, anthraquinone, anthrone, and anthrone-like heterocycles (i.e., heterocyclic analogues of anthrone such as those having N, O, or S in the 10-position), or their substituted (c.g., ring substituted) derivatives. The functional groups of such ketones are preferred since they are readily capable of undergoing the activation/inactivation/reactivation cycle described herein. Benzophenone is a particularly preferred photoreactive moiety, since it is capable of photochemical excitation with the initial formation of an excited singlet state that undergoes intersystem crossing to the triplet state. The excited triplet state can insert into carbon-hydrogen bonds by abstraction of a hydrogen atom (from a support surface, for example), thus creating a radical pair. Subsequent collapse of the radical pair leads to formation of a new carbon-carbon bond. If a reactive bond (e.g., carbon-hydrogen) is not available for bonding, the ultraviolet light-induced excitation of the benzophenone group is reversible and the molecule returns to ground state energy level upon removal of the energy source. Photoactivatable aryl ketones such as benzophenone and acetophenone are of particular importance inasmuch as these groups are subject to multiple reactivation in water and hence provide increased coating efficiency. Hence, photoreactive aryl ketones are particularly preferred

0025The azides constitute a preferred class of latent reactive moieties and include arylazides (C₆R₅N₃) such as phenyl azide and particularly 4-fluoro-3-nitrophenyl azide, acyl azides (-CO-N₃) such as benzoyl azide and p-methylbenzoyl azide, azido formates (-O-CO-N₃) such as ethyl azidoformate, phenyl azidoformate, sulfonyl azides (-SO₂-N₃) such as benzenesulfonyl azide, and phosphoryl azides (RO)₂PON₃ such as diphenyl phosphoryl azide and diethyl phosphoryl azide. Diazo compounds constitute another class of photoreactive moieties and include diazoalkanes (-CHN₂) such as diazomethane and diphenyldiazomethane, diazoketones (-CO-CHN₂) such as diazoacetophenone and 1-trifluoromethyl-1-diazo-2-pentanone, diazoacetates (-O-CO-CHN₂) such as t-butyl diazoacetate and phenyl diazoacetate, and beta-keto-alpha-diazoacetates (-CO-CN₂-CO-O-) such as t-butyl alpha diazoacetoacetate. Other photoreactive moieties include the aliphatic azo compounds such as azobisisobutyronitrile, the diazirines (-CHN₂) such as 3-trifluoromethyl-3-phenyldiazirine, the ketenes (-CH=C=O) such as ketene and diphenylketene.

0026Upon activation of the photoreactive moieties, the coating adhesion molecules are covalently bound to each other and/or to the material surface by covalent bonds through residues of the photoreactive groups. Exemplary photoreactive groups, and their residues upon activation, are shown as follows. <tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="3" colsep="0"><colspec colnum="1" colname="col1" colwidth="48mm" /><colspec colnum="2" colname="col2" colwidth="28mm" /><colspec colnum="3" colname="col3" colwidth="28mm" /><thead><row><entry valign="top">Photoreactive Group</entry><entry namest="col2" nameend="col3" align="left" valign="top">Residue Functionality</entry></row></thead><tbody><row rowsep="0"><entry>aryl azides</entry><entry>amine</entry><entry>R-NH-R'</entry></row><row rowsep="0"><entry>acyl azides</entry><entry>amide</entry><entry>R-CO-NH-R'</entry></row><row rowsep="0"><entry>azidoformates</entry><entry>carbamate</entry><entry>R-O-CO-NH-R'</entry></row><row rowsep="0"><entry>sulfonyl azides</entry><entry>sulfonamide</entry><entry>R-SO₃-NH-R'</entry></row><row rowsep="0"><entry>phosphoryl azides</entry><entry>phosphoramide</entry><entry>(RO)₂PO-NH-R'</entry></row><row rowsep="0"><entry>diazoalkanes</entry><entry namest="col2" nameend="col3" align="left">new C-C bond</entry></row><row rowsep="0"><entry>diazoketones</entry><entry namest="col2" nameend="col3" align="left">new C-C bond and ketone</entry></row><row rowsep="0"><entry>diazoacetates</entry><entry namest="col2" nameend="col3" align="left">new C-C bond and ester</entry></row><row rowsep="0"><entry>beta-keto-alpha-diazoacetates</entry><entry namest="col2" nameend="col3" align="left">new C-C bond and beta-ketoester</entry></row><row rowsep="0"><entry>aliphatic azo</entry><entry namest="col2" nameend="col3" align="left">new C-C bond</entry></row><row rowsep="0"><entry>diazirines</entry><entry namest="col2" nameend="col3" align="left">new C-C bond</entry></row><row rowsep="0"><entry>ketenes</entry><entry namest="col2" nameend="col3" align="left">new C-C bond</entry></row><row rowsep="0"><entry>photoactivated ketones</entry><entry namest="col2" nameend="col3" align="left">new C-C bond and alcohol</entry></row></tbody></tgroup></table></tables>

0027<u>Bioactive Groups.</u> Low molecular weight bioactive groups as used in the method of the present invention are typically those that are intended to enhance or alter the function or performance of a particular biomedical device in a physiological environment In a particularly preferred embodiment, the bioactive group is selected from the group consisting of cell attachment factors, growth factors, antithrombotic factors, binding receptors, ligands, enzymes, antibiotics, and nucleic acids. In the method of the invention two or more pendent bioactive groups are used

0028Desirable cell attachment factors include attachment peptides (defined below), as well as large proteins or glycoproteins (typically 100-1000 kilodaltons in size) which in their native state can be firmly bound to a substrate or to an adjacent cell bind to a specific cell surface receptor, and mechanically attach a cell to the substrate or to an adjacent cell, Naturally occurring attachment factors are primarily large molecular weight proteins, with molecular weights above 100,000 daltons.

0029Attachment factors bind to specific cell surface receptors, and mechanically attach cells to the substrate (referred to as "substrate adhesion molecules" herein) or to adjacent cells (referred to as "cell-cell adhesion molecules" herein) [Alberts, B. et al., <u>Molecular Biology of the Cell. 2nd ed.,</u> Garland Publ, Inc., New York (1989)] In addition to promoting cell attachment, each type of attachment factor can promote other cell responses, including cell migration and differentiation. Suitable attachment factors for the present invention include substrate adhesion molecules such as the proteins laminin, fibronectin, collagens, vitronectin, tenascin, fibrinogen, thrombospondin, osteopontin, von Willibrand Factor, and bone sialoprotein. Other suitable attachment factors include cell-cell adhesion molecules ("cadherins") such as N-cadherin and P-cadherin.

0030Attachment factors typically comprise amino acid sequences or functional analogues thereof that possess the biological activity of a specific domain ofa native attachment factor, with the attachment peptide typically being about 3 to about 20 amino acids in length. Native cell attachment factors typically have one or more domains that bind to cell surface receptors and produce the cell attachment, migration, and differentiation activities of the parent molecules. These domains consist of specific amino acid sequences, several of which have been synthesized and reported to promote the attachment, spreading and/or proliferation of cells. These domains and functional analogues of these domains are termed "attachment peptides"

0031Examples of attachment peptides from fibronectin include, but are not limited to, RGD (arg-gly-asp) [<nplcit id="ncit0007" npl-type="s"><text>Kleinman, H.K, et al., Vitamins and Hormones 47:161-186, 1993</text></nplcit>], REDV (arg-glu-asp-val) [<nplcit id="ncit0008" npl-type="s"><text>Hubbell, J.A., et al., Ann. N.Y. Acad. Sci. 665:253-258, 1992</text></nplcit>], and C/H-V (WQPPRARI or trp-gln-pro-pro-arg-ala-arg-ile) [<nplcit id="ncit0009" npl-type="s"><text>Mooradian, D.L., et al., Invest. Ophth. &amp; Vis. Sci. 34:153-164, 1993</text></nplcit>]

0032Examples of attachment peptides from laminin include, but are not limited to, YIGSR (tyr-ile-gly-ser-arg) and SIKVAV (ser-ile-lys-val-ala-val) [<nplcit id="ncit0010" npl-type="s"><text>Kleinman, H.K., et al., Vitamins and Hormones 47:161-186, 1993</text></nplcit>] and F-9 (RYVVLPRPVCFEKGMNYTVR or arg-tyr val-val-leu-pro-arg-pro-val-cys-phe-glu-lys-gly-met-asn-tyr-thr-val-arg) (<nplcit id="ncit0011" npl-type="s"><text>Charonis, A. S., et al, J. Cell Biol. 107:1253-1260, 1988</text></nplcit>].

0033Examples of attachment peptides from type IV collagen include, but are not limited to, HEP-III (GEFYFDLRLKGDK or gly-glu-phe-tyr-phe-asp-leu-arg-leu-lys-gly-asp-lys) [<nplcit id="ncit0012" npl-type="s"><text>Koliakos, G.G, et al., J. Biol. Chem. 264:2323-1989</text></nplcit>]. Desirably, attachment peptides used in the method of the invention have between about 3 and about 30 amino acid residues in their amino acid sequences. Preferably, attachment peptides have not more than about 15 amino acid residues in their amino acid sequences.

0034Other desirable bioactive groups used in the invention include growth factors, such as fibroblastic growth factors, epidermal growth factor, platelet-derived growth factors, transforming growth factors, vascular endothelial growth factor, bone morphogenic proteins and other bone growth factors, neural growth factors, and the like.

0035Yet other desirable bioactive groups used in the invention include antithrombotic agents that inhibit thrombus formation or accumulation on blood contacting devices. Desirable antithrombotic agents include heparin and hirudin (which inhibit clotting cascade proteins such as thrombin) as well as lysine. Other desirable antithrombotic agents include prostaglandins such as PGI₂, PGE₁, and PGD₂, which inhibit platelet adhesion and activation. Still other desirable antithrombotic agents include fibrinolytic enzymes such as streptokinase, urokinase, and plasminogen activator, which degrade fibrin clots. Another desirable bioactive group consists of lysine, which binds specifically to plasminogen, which in turn degrades fibrin clots.

0036Other desirable bioactive groups used in the invention include binding receptors, such as antibodies and antigens. Antibodies present on a biomaterial surface can bind to and remove specific antigens from aqueous media that comes into contact with the immobilized antibodies. Similarly, antigens present on a biomaterial surface can bind to and remove specific antibodies from aqueous media that comes into contact with the immobilized antigens.

0037Other desirable bioactive groups consist of receptors and their corresponding ligands. For example, avidin and streptavidin bind specifically to biotin, with avidin and streptavidin being receptors and biotin being a ligand. Similarly, fibroblastic growth factors and vascular endothelial growth factor bind with high affinity to heparin, and transforming growth factor beta and certain bone morphogenic proteins bind to type IV collagen. Also included are immunoglobulin specific binding proteins derived from bacterial sources, such as protein A and protein G, and synthetic analogues thereof.

0038Yet other desirable bioactive groups used in the invention include enzymes that can bind to and catalyze specific changes in substrate molecules present in aqueous media that comes into contact with the immobilized enzymes. Other desirable bioactive groups consist of nucleic acid sequences (e.g., DNA, RNA, and cDNA), which selectively bind complimentary nucleic acid sequences Surfaces coated with specific nucleic acid sequences are used in diagnostic assays to identify the presence of complimentary nucleic acid sequences in test samples

0039Still other desirable bioactive groups present in the invention include antibiotics that inhibit microbial growth on biomaterial surfaces. Certain desirable antibiotics may inhibit microbial growth by binding to specific components on bacteria A particularly desirable class of antibiotics are the antibiotic peptides which seem to inhibit microbial growth by altering the permeability of the plasma membrane via mechanisms which, at least in part, may not involve specific complimentary ligand-receptor binding [<nplcit id="ncit0013" npl-type="s"><text>Zazloff, M., Curr. Opinion Immunol, 4:3-7, 1992</text></nplcit>].

0040<u>Biomaterials,</u> Preferred biomaterials include those formed of synthetic polymers, including oligomers, homopolymers, and copolymers resulting from either addition or condensation polymerizations. Examples of suitable addition polymers include, but are not limited to, acrylics such as those polymerized from methyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylic acid, methacrylic acid, glyceryl acrylate, glyceryl methacrylate, methacrylamide, and acrylamide; vinyls such as ethylene, propylene, styrene, vinyl chloride, vinyl acetate, vinyl pyrrolidone, and vinylidene difluoride. Examples of condensation polymers include, but are not limited to, nylons such as polycaprolactam, polylauryl lactam, polyhexamethylene adipamide, and polyhexamethylene dodecanediamide, and also polyurethanes, polycarbonates, polyamides, polysulfones, poly(ethylene terephthalate), polylactic acid, polyglycolic acid, polydimethylsiloxanes, and polyetheretherketone.

0041Certain natural materials are also suitable biomaterials, including human tissue such as bone, cartilage, skin and teeth; and other organic materials such as wood, cellulose, compressed carbon, and rubber.

0042Other suitable biomaterials are composed of substances that do not possess abstractable hydrogens to which the photogroups can form covalent bonds. One such class of biomaterials can be made suitable for coating via photochemistry by applying a suitable primer coating which bonds to the biomaterial surface and provides a suitable substrate for binding by the photogroups. A subset of this group includes metals and ceramics which have oxide groups on their surfaces and are made suitable for coupling via photochemistry by adding a primer coating that binds to the oxide groups and provides abstractable hydrogens. The metals include, but are not limited to, titanium, stainless steel, and cobalt chromium. The ceramics include, but are not limited to, silicon nitride, silicon carbide, zirconia, and alumina, as well as glass, silica, and sapphire. One suitable class of primers for metals and ceramics consists of organosilane reagents, which bond to the oxide surface and provide hydrocarbon groups (<nplcit id="ncit0014" npl-type="s"><text>Brzoska, J.B., et al., Langmuir 10:4367-4373, 1994</text></nplcit>). The investigators have also discovered that -SiH groups are suitable alternatives for bonding of photogroups.

0043A second class of biomaterials that require an organic primer are the noble metals, which include gold, silver, copper, and platinum. Functional groups with high affinity to noble metals include -CN, -SH, and -NH₂, and organic reagents with these functional groups are used to apply organic monolayers onto such metals (<nplcit id="ncit0015" npl-type="s"><text>Grabar, K.C., et. al., Anal. Chem, 67:735-743, 1995</text></nplcit>).

0044Another class of biomaterials that do not possess abstractable hydrogens are fibrous or porous. The invention polymers form covalently crosslinked polymer networks that fill the pores or form films around individual fibers and are therefore physically entrapped Expanded polytetrafluoroethylene is such a biomaterial.

0045Biomaterials can be used to fabricate a number of devices capable ofbeing coated with bioactive groups using a polybifunctional reagent of the present invention Implant devices are one general class of suitable devices, and include, but are not limited to, vascular devices such as grafts, stents, catheters, valves, artificial hearts, and heart assist devices; orthopedic devices such as joint implants, fracture repair devices, and artificial tendons; dental devices such as dental implants and fracture repair devices; ophthalmic devices such as lenses and glaucoma drain shunts; and other catheters, synthetic prostheses and artificial organs. Other suitable biomedical devices include dialysis tubing and membranes, blood oxygenator tubing and membranes, blood bags, sutures, membranes, cell culture devices, chromatographic support materials, biosensors, and the like

0046<u>Preparation of Reagents.</u> Those skilled in the art, given the present teaching, will appreciate the manner in which reagents of the present invention can be prepared using conventional techniques and materials. In one preferred method, a polymer backbone is prepared by the copolymerization of a base monomer, such as acrylamide or N-vinylpyrrolidone, with monomers having pendent photoreactive and/on thermochemically reactive groups. The polymers prepared by this copolymerization are then derivatized with the bioactive molecule by reaction through the thermochemically reactive groups. An example of such a coupling is the reaction between an N-oxysuccinimide (NOS) ester on the polymeric backbone with an amine group on the bioactive molecule.

0047An alternative preferred method involves the preparation of monomers that contain the desired bioactive group as well as a polymerizable function, such as a vinyl group. Such monomers can then be copolymerized with monomers containing photoreactive groups and with a base monomer such as acrylamide or N-vinylpyrrolidone.

0048A preferred procedure used to synthesize latent reactive peptide polymers involves the synthesis of N-substituted methacrylamide monomers containing each peptide (peptide monomer) and a methacrylamide monomer containing a substituted benzophenone (4-benzoylbenzoic acid, BBA). The peptide monomers were prepared by reacting the sulfhydryl moiety of each peptide with the maleimide moiety of N-[3-(6-maleimidylhexanamido)propyl]methacrylamide (Mal MAm). Then, each peptide monomer was copolymerized with acrylamide and the monomer containing BBA (BBA-APMA) to produce the final latent reactive peptide polymer.

0049Various parameters can be controlled to provide reagents having a desired ratio (whether on a molar or weight basis) of polymeric backbone, photoreactive moeities and bioactive groups. For instance, the backbone itself will typically provide between about 40 and about 400 carbon atoms per photoreactive group, and preferably between about 60 and about 300 carbon atoms.

0050With respect to the bioactive group, the length of the backbone can vary depending on such factors as the size of the bioactive group and the desired coating density. For instance, for relatively small bioactive groups (MW less than 3000) the polymeric backbone will typically be in the range of about 5 to about 200 carbon atoms pet bioactive group, and preferably between about 10 and about 100. For larger bioactive groups, such as those having a molecular weight between about 3000 and about 50,000, the preferred backbone provides, on the average, between about 10 and about 5000 carbon atoms between bioactive group, and preferably between about 50 and 1000 carbon atoms. In each case, those skilled in the art, given the present description, will be able to determine the conditions suitable to provide an optimal combination of bioactive group density and freedom of movement.

0051<u>Coating method</u>. In the method of the invention reagents can be coated onto biomaterial surfaces using techniques (e.g., dipping, spraying, brushing) within the skill of those in the relevant art.

0052<u>Use of devices,</u> Bioactive polymers are used to modify the surfaces of existing biomaterials or to generate new biomaterials. Biomedical devices that contain the resultant biomaterials are used for a variety of <i>in vitro</i> and in vivo applications. For example, biomedical devices possessing cell attachment groups or growth factors as biomoieties promote the attachment and/or growth of cells on <i>in vitro</i> cell culture devices and improve tissue integration with implant devices such as vascular grafts, orthopedic implants, dental implants, cornea lenses, and breast implants. Biomedical devices possessing antithrombotic factors as biomoieties prevent thrombosis on the surfaces of blood contacting devices, such as catheters, heart valves, vascular stents, vascular grafts, stent grafts, artificial hearts, and blood oxygenators.

0053Biomedical devices such as resins or membranes possessing receptors or ligands as biomoieties can be used for affinity purification of a broad range of biomolecules. For example, heparin (which is also an antithrombotic moiety) is used to specifically bind and purify several clotting factors, protease inhibitors, lipoproteins, growth factors, lipolytic enzymes, extracellular matrix proteins and viral coat proteins. Staphylococcal Protein A specifically binds immunoglobulins and has proven to be very useful for purification of antibodies. Streptavidin is a protein that binds specifically to biotin with extremely high affinity. Streptavidin and biotin are a very useful pair of reagents as a secondary binding pair in diagnostic assays. Many times signal amplification, enhanced sensitivity and faster test performance can be achieved by using immobilized streptavidin.

0054Biomedical devices having surface coated antibodies or antigens can be used in diagnostic tests that depend on the specificity ofbinding for sensitive detection of the complimentary antigen or antibody. The antibodies or antigens can be immobilized onto membranes, plastic tubes, microplate wells or solid state biosensor devices. Immobilized antibodies are also important for purification of a variety of biopharmaceutical agents. Proteins produced in bacteria or fungi by genetic engineering techniques can be purified by affinity purification with immobilized antibodies. Blood fractions, such as clotting factor VIII (antihemophiliae factor) are also purified by immobilized antibodies.

0055Biomedical devices having surfaces coated with nucleic acid sequences can be used to selectively bind complimentary nucleic acid sequences. Such devices are used in diagnostic assays to identify the presence of complimentary nucleic acid sequences in test samples. Devices having surface-coated enzymes as biomoieties can be used for a broad range of enzyme reactors, to catalyze either synthetic processes (e.g., making chiral pharmaceuticals) or degradative/conversion processes (e.g., degrading starch and converting glucose to fructose for making high fructose corn syrup).

0056Coated antimicrobial agents can be used to inhibit bacterial growth on the surfaces of devices. Such antimicrobial surfaces can reduce the rate of infections associated with implant devices, including several types of catheters (intravascular, peritoneal, hemodialysis, hydrocephalus, and urological), arteriovenous shunts, heart valves, vascular grafts, tracheotomy tubes, orthopedic and penile implants. Several in <u>vitro</u> devices can also benefit from such surfaces, e.g., by inhibiting biofilm formation. These include contact lens cases, dental unit water lines, plumbing used in food and pharmaceutical industries, food packaging, table tops and other surfaces used for food handling, and air filters.

EXAMPLES

0057The invention will be further described with reference to the following nonlimiting Examples. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. Unless otherwise indicated, all percentages are by weight.

Example 1

Lysine Polymers

A Synthesis of N-α-[6-(maleimido)hexanoyl]lysine.

00586-Maleimidohexanoic acid, 2.24 g (10.6 mmol) (prepared as described in Example 1) was dissolved in 10.76 g (84.8 mmol) ofoxalyl chloride and stirred as a neat solution for 4 hours at room temperature. The excess oxalyl chloride was then removed under reduced pressure and the resulting acid chloride was dissolved in 25 ml of methylene chloride. This solution was added with stirring to a solution of 3.60 g (10.6 mmol) N-ε-t-BOC lysine t-butyl ester hydrochloride (Bachem California) in 25 ml of methylene chloride and 3.21 g (31.7 mmol) of TEA. The resulting mixture was stirred overnight under nitrogen After this time, the mixture was treated with water and the organic layer was separated and dried over sodium sulfate. The solvent was removed and the product was purified on a silica gel flash chromatography column using a 0-5% methanol in chloroform solvent gradient. Pooling of the desired fractions and evaporation of solvent gave 5.20 g of product (98% yield). Analysis on an NMR spectrometer was consistent with the desired product.

0059The protected amino acid derivative, 0.566 g (114 mmol) was dissolved in 5 ml of trifluoroacetic acid with stirring. After stirring four hours at room temperature, the solvent was removed under reduced pressure. The resulting oil was tritruated with ether to remove residual trifluoroacetic acid to give 373 mg of product for a 98% yield. Analysis on an NMR spectrometer was consistent with the desired product.

B. Synthesis of a Photoreactive Polyacrylamide Containing e-Amino Lysine Ligands (Lysine Polymer).

0060Acrylamide (0-22 g, 3.10 mmol), BBA-APMA (0.014 g, 0 039 mmol), and N-α-[6-(maleimido)hexanoyl]lysine (0.266 g, 0.784 mmol; prepared as described herein) were dissolved in 7.3 ml of dry DMSO. To initiate the polymerization, 8 mg (0.047 mmol) of AIBN and 4.0 µl of TEMED were added, followed by sparging with nitrogen to remove all oxygen. The mixture was then heated at 55° C for 16 hours followed by evaporation of the DMSO under reduced pressure. The product was dissolved in DI water and dialyzed three days using 6-8K molecular weight cut off (MWCO) tubing against DI water. The resulting solution was lyophilized to give 160 mg of product.

C. Generation of Lysine Polymer Coatings on Polyurethane (PU)

0061PU sheets were cut into 1x1 cm pieces, washed with IPA and air dried. To improve wetting of the lysine polymer solution on PU, the PU pieces were treated with argon plasma at 250 watts, 0.25 torr, for 1 minute. The PU pieces were then immersed in an aqueous solution of lysine polymer (prepared as described herein, 1 mg/ml) for 5 minutes, air dried, and illuminated for 30 seconds The samples were then washed overnight (in three changes of phosphate buffered saline, pH 7.4, which contained 1% Tween 20) to remove unbound lysine polymer. The coated PU pieces were stored in PBS containing 0.02% sodium azide until evaluated. D. Quantitation of Lysine Polymer Coatings.

0062The lysine polymer (prepared as described above) was radiolabelled via reductive methylation and used to quantitate the levels immobilized onto polyurethane. The tritiated lysine polymer was coated onto PU pieces with or without illumination to determine the density of lysine polymer that was immobilized. After the wash procedure, samples were dissolved in Soluene-350 and counted in Hionic fluor (each from Packard Instrument Co., Meriden, CT). The table below shows the immobilized levels (± SEM) expressed in terms of µg/cm² and nmole/cm² of lysine moiety. Each level is the average of 4 replicates. The results show that 1.51 µg/cm² is immobilized after illumination, which is more than sufficient to produce a monolayer coating and is 3.8 times as much polymer as was retained with the adsorbed control. <tables id="tabl0002" num="0002"><table frame="none"><tgroup cols="3" colsep="0"><colspec colnum="1" colname="col1" colwidth="21mm" /><colspec colnum="2" colname="col2" colwidth="47mm" /><colspec colnum="3" colname="col3" colwidth="49mm" /><thead><row><entry valign="top">Treatment</entry><entry align="center" valign="top">Lysine polymer level (µg/cm²)</entry><entry align="center" valign="top">Lysine moiety level (nmole/cm²)</entry></row></thead><tbody><row rowsep="0"><entry>Adsorbed</entry><entry align="center">0.40±0.03</entry><entry>0.359±0.027</entry></row><row rowsep="0"><entry>Illuminated</entry><entry align="center">1.51±0.23</entry><entry>1.36±0.21</entry></row></tbody></tgroup></table></tables>

E. Evaluation of Plasminogen Binding by Lysine Coated Polyurethane.

0063Others have described the covalent coupling of lysine to silane derivatized glass and the resultant lysine derivatized glass was reported to promote plasminogen binding, with the bound lysine exhibiting significant proteolytic activity. Such a surface is expected to demonstrate improved resistance to thrombus formation when placed in contact with blood. The coating chemistry used in the previous study utilized a short spacer and was limited to glass as a surface, whereas the photoreactive lysine polymer can be applied at high densities to a large range of biomaterials.

0064The lysine moiety in the lysine polymer is coupled via the α-amino group to the polymer backbone, and the ε-amino group is free to bind plasminogen. Therefore PU that is coated with the lysine polymer is expected to inhibit thrombus formation by reversibly binding plasminogen from blood, with the bound plasmin demonstrating proteolytic activity that cleaves fibrin and prevents fibrin clot formation on the coated surface.

Example 2

Prostaglandin Polymers

A. Synthesis of a Photoreactive Polyacrylamide Containing Primary Amine Ligands (Amine Polymer)

0065A solution of acrylamide (7.46 g, 105.1 mmoles), APMA-HCl (2.14 g, 11.9 mmoles), and BBA-APMA (0.837 g, 239 mmoles) is prepared in 170 ml of DMSO. To this solution is added AIBN (0.246 g, 1.50 mmoles) and TEMED (0.131 g, 1.13 mmoles). The solution is then deoxygenated by sparging with helium gas for a period of 10 minutes and is sealed and placed in a 55°C oven for 18 hours to complete the polymerization. The polymer solution is diluted with water and dialyzed against deionized water using 12,000-14,000 MWCO dialysis tubing to remove solvent, unreacted monomers, and low molecular weight oligomers. The final product is isolated by lyophilization, and the photogroup load is determined by UV absorbance at 265 nm. The amine content of the polymer is determined using a trinitrobenzenesulfonate (TNBS) method. The photogroup and amine load can be changed by adjusting the quantity of monomers used in the polymerization.

B. Synthesis of a Photoreactive Polyacrylamide Containing Prostaglandin E

1

Ligands (Prostaglandin E

1

Polymer).

0066A solution of prostaglandin E₁ (Sigma Chemical Co.) (30 mg, 0.0846 mmole) in 5 ml of dry 1,4-dioxane is prepared, and NHS (10.7 mg, 0.0931 mmole) and DCC (26.2 mg, 0.127 mmole) are added to the solution. The mixture is stirred overnight at room temperature with formation of the 1,3-dicyclohexylurea (DCU) byproduct The solid is removed by filtration, and the filter cake is rinsed with 1,4-dioxane The solvent is removed under reduced pressure, and the resulting product is stored under dry conditions and used without further purification.

0067The amine polymer (synthesized as described above) is dissolved in DMSO at a concentration of 10 mg/ml, followed by the addition of 1.5 equivalents of the NOS-derivatized prostaglandin E₁ relative to the amine content of the amine polymer solution. Five equivalents of triethylamine are added to help catalyze the reaction. After an overnight reaction, the polymer solution is placed in dialysis against deionized water using 12,000-14,000 MWCO dialysis tubing to remove excess low molecular weight reactants. The product is isolated by lyophilization C. Synthesis of a Photoreactive Polyacrylamide Containing Carbacyclin Ligands (Carbacyclin Polymer).

0068A solution of carbacyclin (Sigma Chemical Co.) (5 mg, 0 0143 mmole) in 2 ml of dry 1,4-dioxane is prepared, and NHS (1.8 mg, 0 0157 mmole) and DCC (4-4 mg, 0.0215 mmole) are added to the solution. The mixture is stirred overnight at room temperature with formation of the DCU byproduct The solid is removed by filtration, and the filter cake is rinsed with 1,4-dioxane. The solvent is removed under reduced pressure, and the resulting product is stored under dry conditions and used without further purification.

0069The amine polymer (synthesized as described above) is dissolved in DMSO at a concentration of 10 mg/ml, followed by the addition of 1.5 equivalents of the NOS-derivatized carbacyclin relative to the amine content of the amine polymer solution. Five equivalents of TEA are added to help catalyze the reaction. After an overnight reaction, the polymer solution is placed in dialysis against deionized water using 12,000-14,000 MWCO dialysis tubing to remove excess low molecular weight reactants. The product is isolated by lyophilization

D. Prostaglandin Polymer Coatings

0070Each prostaglandin polymer (synthesized as described above) is diluted to 5 mg/ml in 50% (v/v) IPA in water and added to biomaterial samples (polyurethane, silicone rubber and polyethylene). Ihe volume of prostaglandin containing polymer solution that is added to each polymer is just sufficient to cover the surface of each biomaterial (about 100 m/cm²) The polymer solution is allowed to dry onto each sample, after which each sample is illuminated for 1-2 minutes.

0071Both prostaglandin E₁ and carbacyclin (which is a stable analog of prostaglandin <b>I₂;</b> PGI₂) are known to inhibit platelet activation and thrombus formation. Therefore the prostaglandin coatings genetated are expected to inhibit platelet activation and thrombus formation on biomaterials.

Example 3

Protein A Polymer

A Synthesis of N-Succinimidyl 6-Methacrylamidohexanoate (MAm-EAC-NOS)

0072The ε-aminocaproic acid (EAC), 2.00 g (15.25 mmol), was added to a dry round bottom flask, followed by the addition of 2.58 g (16.73 mmol) of methacrylic anhydride. The resulting mixture was stirred at room temperature for two hours, followed by trituration with hexane. The hexane was decanted and the product was triturated two additional times to give 3.03 g of the acylated product (yield >99%). Without further purification, the product was dissolved in 50 ml of chloroform, followed by the addition of 1.922 g (16.7 mmol) of NHS and 6.26 g (30 3 mmol) of DCC The mixture was stirred overnight at room temperature with protection from moisture. The resulting solid was removed by filtration and the filter cake was rinsed with chloroform. The solvent was removed under reduced pressure with 5 ppm of the monomethyl ether of hydroquinone (MEHQ) to prevent polymerization. The residue, 4.50 g, was redissolved in 45 ml of dry THF and the solution was used without further purification. B. Synthesis of a Photoreactive Polyacrylamide Containing Protein A Ligands (Protein A Polymer).

0073To prepare the latent reactive NOS polymer, acrylamide (1.0 gm, 14.1 mmole) was dissolved in 15 ml of dry THF. To that solution was added 44 mg (0.149 mmole) of MAm-EAC-NOS (synthesized as described herein) and 158 mg (0.45 mmole) of BBA-APMA (synthesized as described in Example 1). For the initiator, 500 mg (3.04 mmole) of AIBN was added, followed by the addition of 50 µl of TEMED. The solution was bubbled with nitrogen and incubated at 55°C for 18 hours to allow polymerization. The insoluble polymer was collected by filtration, and then dissolved in dry DMSO. The polymer was precipitated by being added dropwise to stirred ethanol, and was then collected by filtration and dried for storage until used. The product yield was 0.906 gm.

0074To couple protein A to the latent reactive NOS polymer, recombinant staphylococcal protein A (from Calbiochem-Novabiochem Corp., San Diego, CA) was dissolved at 10 mg/ml in 0.1 M carbonate buffer, pH 9. The latent reactive NOS polymer was dissolved at 100 mg/ml in 50 mM phosphate buffer, pH 6.8. Then 200 µl (20 mg) of the NOS polymer was added to 1 ml (10 mg) of the protein A solution, and the mixture was incubated overnight at 4° C. Evaluation by standard sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed that more than 80% of the added protein A was incorporated into the resultant protein A polymer. The protein A polymer solution was used to coat biomaterials without further purification C. Generation of Protein A Polymer Coatings on Biomaterials.

0075The protein A polymer was then photocoupled to two types of membranes, polysulfone (PSO) membranes with a pore size of 0 2 mm (HT-200 membranes from Gelman Sciences, Ann Arbor, MI) and regenerated cellulose (RC) membranes with a pore size of 0.45 mm (no SM18606. from Sartorius, Edgewood, NY). Each membrane was in the form ofa disc that was 1 inch in diameter. Prior to addition of the protein A polymer, each membrane was washed first in 1:1 (v/v) isopropanol:0. 1N HCl and then in water.

0076The protein A polymer (estimated concentration of 8.67 mg/ml) was then added to each type of membrane (1 ml of polymer per 4-6 discs) and incubated overnight at 4° C Then the discs were removed from the polymer solution, air dried, and illuminated for 1 minute on each side in a controlled temperature chamber (at 10° C). Illuminzation was produced with a Dymax lamp as described herein.

0077The membranes were then washed to remove unbound protein A polymer. The wash was achieved by placing the coated disks in membrane holders (MAC-25 holder, from Amicon, Beverly, MA), with 2-4 membranes being placed in each holder. The membranes were then sequentially washed with: 1) 10 ml of 0.1 M glycine in 2% acetic acid, 2) 10 ml of 10x PBS, and 3) 30 ml of PBS. The washed membranes were then stored in PBS containing 0.05% sodium azide until used. D. Evaluation of Activity of Protein A Polymer Coatings on Biomaterials.

0078Protein A is a bacterial protein that binds specifically to the F_c region of immunoglobulin G (IgG) molecules. The activity of the protein A coating on each type of membrane was evaluated by assaying for binding by added IgG Uncoated membranes were used as controls. For this assay, 2 ml of rabbit serum was diluted 1:5 in PBS and perfused through the coated membranes at 2-3 ml/min. The membranes were then washed with PBS to remove unbound IgG. The bound IgG was then eluted with 01 M glycine in 2% acetic acid. The amount ofeluted IgG was determined by measuring the absorbance of the eluant at 280 nm and using an extinction coefficient (ε₂₈₀) of 1.4 ml/cm-mg to calculate the mg of eluted IgG. Also the IgG that eluted from each membrane type was evaluated for purity by reduced SDS PAGE analysis. With the biomaterials coated with protein A polymer, the eluted protein was greater than 90% light and heavy chains of IgG. In contrast, the major protein that eluted from uncoated controls was albumin.

0079Three discs of each type (PSO or RC) were placed in a MAC-25 holder and evaluated using this procedure The table below shows the average amounts of IgG that eluted from each membrane type; with each value being the average of 10 determinations (10 cycles) for 3 PSO disks and the average of 3 determinations (3 cycles) for 3 RC disks. <tables id="tabl0003" num="0003"><table frame="none"><tgroup cols="4" colsep="0"><colspec colnum="1" colname="col1" colwidth="36mm" /><colspec colnum="2" colname="col2" colwidth="29mm" /><colspec colnum="3" colname="col3" colwidth="35mm" /><colspec colnum="4" colname="col4" colwidth="55mm" /><thead><row><entry valign="top">Membrane type</entry><entry valign="top">Coating</entry><entry valign="top">IgG eluted) (mg/disc)</entry><entry valign="top">Fold greater IgG on protein A coating</entry></row></thead><tbody><row rowsep="0"><entry>Polysulfone</entry><entry>uncoated control</entry><entry align="char" char=".">0.020</entry><entry align="center" /></row><row rowsep="0"><entry>Polysulfone</entry><entry>protein A polymer</entry><entry align="char" char=".">0.680</entry><entry align="center">34</entry></row><row rowsep="0"><entry>Regenerated cellulose</entry><entry>uncoated control</entry><entry align="char" char=".">0.006</entry><entry align="center" /></row><row rowsep="0"><entry>Regenerated cellulose</entry><entry>protein A polymer</entry><entry align="char" char=".">0.383</entry><entry align="center">64</entry></row></tbody></tgroup></table></tables>

0080These results show that each type of coated membrane binds 34-64 fold more IgG than does its respective uncoated controL Also, protein A in the polymer has a stable conformation and is tenaciously bound, since there is no decrease in IgG elution after 10 cycles of serum addition and IgG elution.

Example 4

IgG Polymers

A Synthesis of a Photoreactive Polyacrylamide Containing N-Oxysuccinimide Ligands (NOS Polymer).

0081Acrylamide, 3.897 g (0.0548 mol), was dissolved in 53 ml of THF, followed by 0.115 g (0.70 mmol) of AIBN, 0.053 ml of IEMED, 0.204 g (0.58 mmol) of BBA-APMA (prepared as described in Example 1), and 0 899 g (2.9 mmol) of N-succinimidyl 6-maleimidohexanoate (prepared as described in Example 3). The solution was deoxygenated with a helium sparge for 4 minutes, followed by an argon sparge for 4 minutes. The sealed vessel was then heated overnight at 55°C to complete the polymerization. The precipitated polymer was isolated by filtration and was washed by stirring for 30 minutes with 100 ml of IHF. The final product was recovered by filtration and dried in a vacuum oven to provide 4.688 g of solid, a 94% yield. B. Synthesis and Immobilization of a Photoreactive Polyacrylamide Containing IgG Ligands.

0082IgG molecules are a class of antibody molecules that bind to specific antigens. Tritiated rabbit anti-glucose oxidase IgG was used so that the tritium label could be used to quantitate the immobilized level of IgG and glucose oxidase binding could be evaluated to assay IgG activity. NOS polymer (50 mg) (prepared as described herein) was added to 100 mg of [³H] IgG (in 100 ml of 0.1 M sodium carbonate at pH 9) and allowed to react overnight at 4°C The IgG polymer was used without further purification

0083Polyester membrane (Accuwick from Pall Corporation) was cut into 6 mm discs, and 4 µl aliquots of the IgG polymer were spotted on each of 19 discs. Three discs were left as controls that were neither illuminated or washed. Eight discs were illuminated for 1 minute and 8 discs were left nonilluminated. The latter 8 illuminated and 8 nonilluminated discs were washed with 25 mM bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane (BIS-TRIS) at pH 7.2 containing 1% lactose, 1% BSA and 0.1% Brij 35.

0084To quantitate the immobilized levels of IgG polymer, the 3 control (uncoated, unwashed) discs and 3 each of the illuminated and nonilluminated conditions were dissolved in Soluene (0.5 ml) and counted in 5 mls of Hionic Fluor. The results are reported in the table below. A comparison of the illuminated (washed) to the control (uncoated, unwashed) shows that 75% of the added IgG polymer was retained after illumination. In contrast, with the nonilluminated samples, only 12.5% of the added IgG polymer was retained <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="48mm" /><colspec colnum="2" colname="col2" colwidth="11mm" /><colspec colnum="3" colname="col3" colwidth="15mm" /><colspec colnum="4" colname="col4" colwidth="14mm" /><colspec colnum="5" colname="col5" colwidth="9mm" /><colspec colnum="6" colname="col6" colwidth="23mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="top">Treatment</entry><entry namest="col2" nameend="col4" align="left" valign="top">IgG Amount on discs (ug)</entry><entry namest="col5" nameend="col7" align="left" valign="top">IgG Activity (A₆₅₅)</entry></row><row><entry valign="top" /><entry valign="top">n</entry><entry valign="top">mean</entry><entry valign="top">SEM</entry><entry valign="top">n</entry><entry valign="top">mean</entry><entry valign="top">SEM</entry></row></thead><tbody><row><entry>Control (uncoated, unwashed)</entry><entry>3</entry><entry align="char" char=".">2.08</entry><entry align="char" char=".">0.03</entry><entry>5</entry><entry>not assayed</entry><entry>NA</entry></row><row><entry>Nonilluminated (washed)</entry><entry>3</entry><entry align="char" char=".">0.26</entry><entry align="char" char=".">0.01</entry><entry>5</entry><entry>0.669</entry><entry>0.021</entry></row><row><entry>Eluminated (washed)</entry><entry>3</entry><entry align="char" char=".">1.56</entry><entry align="char" char=".">0.03</entry><entry>5</entry><entry>1.079</entry><entry>0.059</entry></row></tbody></tgroup></table></tables>

0085To quantitate the activity of the immobilized IgG, the remaining 5 illuminated and 5 nonilluminated discs were incubated with glucose oxidase at 0.1 mg/ml in PBS for 1 hour and washed 5 times with TNT (0.05 M Tris(hydroxymethyl)aminomethane, 0.15 M NaCl, 0.05% Tween-20). Each disc was then transferred to wells in a 96 well microtiter plate and assayed by adding 200 µl of 3,3',5,5'-tetramethylbenzidine (TMB) chromogen mixture (100 µl of IMB reagent from Kirkegaard &amp; Perry Laboratories, Inc., 100 µl 0.2 M sodium phosphate pH 5.5,10 mg of glucose and 4 µg of horseradish peroxidase) and allowing the color to develop for 20 minutes. Aliquots (100 µl) were then transferred to a separate microtiter plate and the absorbance was read at 655 nm. A comparison of the illuminated to nonilluminated samples shows that 61% greater activity was expressed by the illuminated samples.

Example 5

Streptavidin Polymer

A. Synthesis of a Photoreactive Polyacrylamide Containing Streptavidin Ligands

0086Streptavidin (from InFerGene Company, Benicia, CA) was coupled to the NOS polymer (prepared as described in Example 6). Streptavidin (15 mg) was dissolved in 1.5 ml of 0.1 M carbonate buffer (pH 90). The NOS polymer was prepared and dissolved in 5 mM acetate buffer (pH 5) to a final concentration of 100 mg/ml. The NOS polymer solution (0.3 ml) was added to the streptavidin solution (1.5 ml), and the mixture was stirred overnight at 4° C. The insulating streptavidin polymer was used without further purification or characterization

B. Generation of Streptavidin Polymer Coatings on Surfaces

0087Solid glass rods (3 mm diameter x 3 cm length) were washed by sonication in 1:1 (v/v) acetone in 0.1N RCl for 30 minutes, rinsed in water, acetone, dried at 100° C for 1 hr., cooled, and stored desiccated until used. Bis(trimethoxysilylethyl)benzene (from United Chemical Technologies, Inc., Bristol, PA) was diluted to 10% (v/v) in acetone. The rods were dipped in the silane reagent for 30 seconds, air dried, dipped in water for 30 seconds, removed and cured at 100° C for 15 minutes, and rinsed with acetone.

0088The organosilane primed glass rods were dipped into a solution of streptavidin polymer for 30 seconds. The glass rods were removed from the solution, allowed to air dry, and illuminated for 30 seconds with a Dymax lamp Adsorption controls were prepared via the same protocol, except that they were not illuminated. Both type of coated rods were washed with PBS containing 0.05% Tween 20 to remove nonadherent streptavidin polymer.

C. Evaluation of Immobilized Streptavidin Polymer

0089Streptavidin is a receptor that binds strongly to biotin as its ligand. The activity of streptavidin polymer coating was evaluated by quantifying the binding of added biotin derivatized horseradish peroxidase (biotin-HRP, obtained from Pierce Chemical Company, Rockford, IL). The glass rods were incubated for one hour in a 9 µg/ml solution of biotin-HRP. The binding of underivatized HRP (added at 9 µµ/ml) was evaluated as a control for nonspecific binding of HRP to the glass rods. The rods were then washed with PBS containing 0.05% Tween 20 to remove nonbound HRP, and the relative activity of bound HRP was evaluated with a TMB peroxidase substrate system (Kirkegaard and Perry Laboratory, Inc, Gaithersburg, MD). HRP catalyzes the oxidation of TMB and produces a color that is quantitated spectrophotometrically at 405 nm. Each result is the average of 3 determinations. <tables id="tabl0005" num="0005"><table frame="all"><tgroup cols="3"><colspec colnum="1" colname="col1" colwidth="47mm" /><colspec colnum="2" colname="col2" colwidth="42mm" /><colspec colnum="3" colname="col3" colwidth="33mm" /><thead><row><entry>Coating on glass</entry><entry>Absorbance of Biotin-HRP</entry><entry>Absorbance of HRP</entry></row></thead><tbody><row><entry valign="bottom">Uncoated control</entry><entry valign="bottom" align="char" char=".">0.067</entry><entry valign="bottom" align="char" char=".">0.085</entry></row><row><entry valign="bottom">Adsorbed streptavidin polymer</entry><entry valign="bottom" align="char" char=".">0.285</entry><entry valign="bottom" align="char" char=".">0.065</entry></row><row><entry valign="bottom">Covalent streptavidin polymer</entry><entry valign="bottom" align="char" char=".">1.005</entry><entry valign="bottom" align="char" char=".">0.056</entry></row></tbody></tgroup></table></tables>

0090The results show the expected trends, with the greatest peroxidase activity being observed on rods that were coated with photoimmobilized streptavidin polymer (covalent streptavidin polymer) and to which had been added biotin-HRP The adsorbed (nonilluminated) streptavidin polymer produced 3.5 fold less peroxidase activity, and the remaining variants which lacked streptavidin and/or biotin exhibited little peroxidase activity.

Example 6

Biotin Polymer

0091The photoreactive amine polymer (80 mg) (synthesized as described in Example 5) is dissolved in 2 ml of DMSO. To the polymer solution is added 40 mg of biotinamidocaproic acid 3-sulfo-N-hydroxysuccinimide ester (Sigma Chemical Co.) and 0.05 ml triethylamine. The solution is mixed for two hours at room temperature, then dialyzed against deionized water to remove any biotin that is not coupled to the polymer.

0092A solution of the biotin polymer (1.0 mg/ml in deionized water) is applied to wells of a polystyrene microtitration plate and incubated for one hour, after which the plate is illuminated for 1-2 minutes. The plate is then washed with deionized water to remove unbound biotin polymer.

0093Biotin is a ligand that binds to streptavidin as its receptor. Polystyrene microtitration plates are coated with biotin polymer and evaluated for activity by assaying the binding of streptavidin. A solution of straptavidin is added to the plates that are coated with biotin polymer and unbound streptavidin is removed by washing with deionized water. The retained streptavidin is quantitated by adding biotin-HRP and evaluating HRP activity.

Example 7

Magainin Polymer

A. Synthesis ofMagainin Peptide Monomer

0094Magainin-2 was used in this Example and was custom synthesized for BSI by Bachem, Inc.. (Iorrance, CA) with a cysteine being added to the carboxyl terminus of the peptide. The resulting sequence of Magainin consisted of GIGKFLHSAKKFGKAFVGEIMNSC As was described in Example 1, the underlined C (<u>C)</u> denotes a nonnative amino acid that was added to allow coupling via the sulfhydryl group.

0095Magainin (2.36 µmole) was dissolved in 0.5 ml of degassed water. Io this solution was added 2.36 µmole of Mal-MAm (dissolved in 20 µl chloroform) and 0.5 ml ethanol. The reaction was stirred for 90 minutes at room temperature, after which the solution was dried under nitrogen and resuspended in 1 ml water. The recovered magainin monomer solution was determined to have 5.5 mg/ml of magainin moiety, as determined by the MicroBCA assay (kit from Pierce Chemical Company, Rockford, IL).

B. Synthesis of Photoreactive Polyacrylamide Containing Magainin Ligand (Magainin Polymers)

0096BBA-APMA was dissolved at a concentration of 10 mg/ml in DMSO, and acrylamide was dissolved at a concentration of 100 mg/ml in water. The magainin monomer (0.48 µmole in 220 µl water) was not purified after being synthesized (as described above) The appropriate molar amounts of BBA-APMA (0.25 µmol in 44 µl of THF) and acrylamide (6.9 µmol in 120 µl of water) were then added to the reaction vial. An additional 300 µl of THF was added, and the mixture was degassed by water aspiration for 15 minutes Ammonium persulfate (6.8 µl of 10% stock solution in water) and TEMED (1.5 µl) were added to catalyze the polymerization. The mixture was degassed again and incubated overnight at room temperature in a sealed dessicator. The resultant magainin polymer was dialyzed against water (using Spectra/Por 50,000 MWCO dialysis tubing; from Spectrum, Houston, TX) at 4° C to remove unincorporated reactants and then lyophilized. Of the 1.2 mg of magainin peptide that was used to synthesize the methacryloyl magainin, 0.35 mg was present in the solubilized magainin polymer.

C. Evaluation of Immobilized Magainin Polymer

0097Magainin is a cationic peptide antibiotic that was originally isolated from the skin of <i>Xenopus laevis.</i> It is active against a broad spectrum of pathogens and acts at the surface of the pathogens. The activity of the magainin polymer was evaluated by a standard solution assay, which determined the minimum inhibitory concentration (MIC) of magainin polymer that was required to prevent the growth of bacteria. The MIC of magainin polymer was 50 µg/ml for both <i>Escherichia coli</i> (ATCC No. 25922) and for <i>Staphylococcus epidermidis</i> (ATCC No. 12228), whereas native monomeric magainin (not incorporated into either a magainin monomer or the magainin polymer) had an MIC or 625-12.5 µg/ml for <i>E. coli</i> and 25 µg/ml for <i>S. epidermidis</i>

0098The magainin polymer is diluted to 250 µg/ml in 50% (v/v) IPA in water and added to biomaterial samples (PU, SR and PE). The volume of magainin polymer solution that is added to each polymer is just sufficient to cover the surface of each biomaterial (about 100 µl/cm²). The polymer solution is allowed to dry onto each sample, after which each sample is illuminated for 12 minutes. The coated samples are washed in 0.1 N HCl followed by PBS.

0099The antimicrobial activity of immobilized magainin polymer is evaluated with a centrifugation assay. Sheets of biomaterials are cut into disks of 1-5 cm diameter, coated with magainin polymer, and placed in individual wells of 24-well culture plates. Bacteria (<i>E. coli and S. epidermiidis</i>) are suspended at 200-400 colony forming units per ml (cfu/ml) in PBS. One ml aliquots of bacterial suspensions are placed in wells that contain magainin-coated biomaterials, and the plates are centrifuged at 3500 xg at 4° C for 20 minutes to sediment the bacteria on the coated biomaterial disks. The disks are then placed in tryptic soy agar (TSA) bacterial culture plates and overlaid with a thin layer of TSA. After overnight incubation at 37° C, the colonies of bacteria growing on the disks are counted The magainin polymer coatings are expected to inhibit bacterial growth and support the growth of fewer colonies of bacteria than uncoated controls.

Example 8

β-Galactosidase Polymer

A Synthesis of a Photoreactive Polyacrylamide Containing β-Galactosidase (β-Galactosidase Polymer)

0100A mixture containing 50 mg/ml of the NOS polymer (prepared as described in Example 6) and 6.4 mg/ml β-galactosidase (from Boehringer Mannheim, Indianapolis, IN) in 0.1 M sodium carbonate, pH 9, was prepared. The mixture was allowed to react at room temperature for 1 hour and stored at 4° C overnight The resultant β-galactosidase polymer solution was used without purification for the generation of crosslinked films.

B. Generation of Crosslinked Films.

0101Films were cast by placing 40 ml aliquots of the β-galactosidase polymer solution (synthesized as described herein) on a Teflon block and allowing each aliquot to dry. The resulting films were illuminated for 0.5 or 4 minutes as described above.

C. Assay for Integrity of the Films.

0102The integrity of the films was assayed by determining whether they would retain their shape after being placed in a solution of PBS. Films illuminated for 0.5 min. dissolved upon exposure to saline; whereas films illuminated for 4 minutes retained their shape. These results are consistent with light activation of the BBA groups producing covalent crosslinking of invention polymer molecules.

0103The crosslinked β-galactosidase polymer was washed 3 times with 1 ml of PBS to remove nonincorporated enzyme. The last wash (02 ml) and the recovered film were each analyzed for enzyme activity using o-nitrophenol-β-D-galactopyranoside (o-NPG) (from Pierce, Rockford, IL) at 1 mg/ml in water using the protocol described in the "<nplcit id="ncit0016" npl-type="b"><text>Worthington Enzyme Manual" (Worthington Biochemical Corp., Freehold, NJ, 1977</text></nplcit>). The last wash showed no β-galactosidase activity while the film gave the yellow nitrophenol product. This result demonstrated that the β-galactosidase moiety was active after the invention polymer was crosslinked to form an insoluble biomaterial.

Example 9

DNA Polymer

0104A model oligodeoxynucleotide (oligoDNA) probe with a sequence from exon 1 of the H-2K^b gene of the major histocompatibility complex was synthesized and used as a capture probe. The sequence of the oligoDNA capture probe was 5'-GTCTGAGTCGGAGCCAGGGCGGCCGCCAAGAGCAGGAGCA-3' and was synthesized with an aliphatic C12 spacer at the 5' end that terminated with a primary amine. The oligoDNA capture probe (80 µg, or 6 nmole) was coupled via the terminal amino group on the C12 spacer to 160 pg NOS polymer described herein in 50 mM phosphate buffer (pH 8.5, 1 mM EDTA, 0.24 ml final volume) at room temperature for 2.5 hours. The resultant DNA polymer was utilized without further purification or characterization.

0105The DNA-polymer was applied to microplate wells (polypropylene plates from Corning Costar Corporation, Cambridge, MA) at 10 pmole (in 0.1 ml solution) per well and incubated for 10-30 minutes. The plates containing DNA polymer solutions were illuminated for 1.5 minutes with a Dymax lamp as described herein except that a filter was used that removes light of wavelengths shorter than 300 nm. A control consisted of oligoDNA capture probe (10 pmole in 0.1 ml 50 mM phosphate buffer, pH 8.5, 1 mM EDTA) that was added to wells, allowed to adsorb for 2.5 hr., and not illuminated. The plates were washed with phosphate buffered saline containing 0.05% Tween 20 in PBS to remove unbound DNA polymer or control oligoDNA capture probe.

0106A detection probe with a sequence complementary to the capture probe described herein was synthesized with a biotin at the 5' end and used to evaluate the activity of the immobilized DNA polymer. The sequence of the detection probe was 5'-CCGTGCACGCTGCTCCTGCUGTTGGCGGCCGCCCTGGCTCCGACTCAGAC-3'. A control detection probe consisting of a noncomplementary sequence from exon 2 of the H-2K^b gene was also synthesized with a biotin moiety at the 5' end.

0107The binding of each detection probe was assayed by subsequently adding a conjugate of streptavidin and horseradish peroxidase (SA-HRP, available from Pierce, Rockford, IL) and measuring the activity of the bound HRP For this assay, the coated plates were blocked with hybridization buffer (0.75 M NaCl, 0.075 M citrate, pH 7.0, 0.1% lauroylsarcosine, 1% casein, and 0.02% sodium dodecyl sulfate) at 55°C for 30 minutes. Complementary and noncomplementary detection probes were added at 50 fmole per 0.1 ml of hybridization buffer per well and incubated for one hour at 55°C. The plates were then washed with 0.3 M NaCl, 0.03 M citrate, pH 7.0 containing 0.1 % SDS for 5 minutes at 55°C SA-HRP was added at 0.5 µg/ml and incubated for 30 minutes at 37°C. The plates were then washed with 0.05% Tween 20 in PBS, followed by addition of peroxidase substrate (TMB Microwell Peroxidase substrate system from Kirkegaard and Perry Laboratories, Gaithersburg, MD) and measurement of absorbance at 655 nm on a microplate reader (mode5l 3550, Bio-Rad Labs, Cambridge, MA). Since the polypropylene plates were opaque, the reacted substrate solutions were transferred to polystyrene plates to read the absorbance. Hybridization Signals (A₆₅₅) from Polypropylene Microwells Coated with Photoimmobilized DNA-polymer or Adsorbed OligoDNA Capture Probe (n=3). <tables id="tabl0006" num="0006"><table frame="none"><tgroup cols="3" colsep="0"><colspec colnum="1" colname="col1" colwidth="52mm" /><colspec colnum="2" colname="col2" colwidth="49mm" /><colspec colnum="3" colname="col3" colwidth="54mm" /><thead><row><entry valign="top" /><entry align="center" valign="top">Complementary detection probe</entry><entry align="center" valign="top">Noncomplementary detection probe</entry></row></thead><tbody><row rowsep="0"><entry>Adsorbed oligoDNA capture probe</entry><entry align="center">0.037±0 005</entry><entry align="center">0.033±0.001</entry></row><row rowsep="0"><entry>Photoimmobilized DNA polymer</entry><entry align="center">1.170±0.079</entry><entry align="center">0.068±0.010</entry></row></tbody></tgroup></table></tables>

0108The results in the above table provide the hybridization signals from polypropylene microwells coated with photoimmobilized DNA-polymer or adsorbed oligoDNA capture probe (n=3). These results demonstrate that the photoimmobilized DNA polymer binds 32-fold more complementary detection probe than does the adsorbed control, and neither coating binds the noncomplementary probe.