US20060051396A1

US20060051396A1 - Biofunctional coatings

Info

Publication number: US20060051396A1
Application number: US11/153,143
Authority: US
Inventors: Paul Hamilton; Mark Grinstaff; Daniel Kenan; Dale Christensen
Original assignee: Affinergy Inc
Current assignee: Affinergy Inc
Priority date: 2004-06-16
Filing date: 2005-06-15
Publication date: 2006-03-09
Also published as: US20100136211A1; ES2342551T3; EP2255832A3; US20100331518A1; US8022183B2; EP2255832A2; US7994277B2; US20100317828A1; DE602005020320D1; WO2006098744A3; US20100317829A1; EP1793875B9; ATE462451T1; US7572766B2; US20100331519A1; US7795383B2; US20090326199A1; WO2006007368A3; US20110263499A1; EP1793875A2

Abstract

The present invention provides compositions and methods for an improved coating for medical devices. The coating is an interfacial biomaterial (“IFBM”) which comprises at least one binding module that binds to the surface of a device (“surface-binding module”) and at least one binding module that performs another function (“affector module”) and which acts to inhibit biofilm formation.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/580,019, filed Jun. 16, 2004; U.S. Provisional Application No. 60/651,338, filed Feb. 9, 2005; and U.S. Provisional Application No. 60/651,747, filed Feb. 10, 2005, each of which is hereby incorporated by reference herein.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The research underlying this invention was supported in part with funds from: NIH grants no. RO1 CA77042 and R21 CA81088; NIH grant no. R01 AI051360-01A1; and NSF DMR-0239769 Career Award. The United States Government may have an interest in the subject matter of this invention.

FIELD OF THE INVENTION

The present invention provides materials and methods for coating surfaces with a coating that reduces adsorption by, and/or biochemically interacts with, biological cells, viruses and/or macromolecules. Generally, the present invention finds use in providing improved medical implants, catheters, and similar items.

BACKGROUND OF THE INVENTION

The fouling of polymer surfaces by biological materials is a common problem that can compromise safety and hygiene as well as appearance. Often the fouling involves formation of a “biofilm.” Particularly serious problems result when fouling occurs in the context of medicine or medical care. In the context of medical care, for example, every year over 5 million patients in United States hospitals are implanted with a “central line catheter.” In these catheterizations, a polyurethane or polyvinylchloride hose is implanted into the patient's chest while the other end of the hose remains exposed to the hospital room environment and therefore to a variety of pathogens, including drug-resistant pathogens (McGee & Gould (2003) N. Engl. J. Med. 348: 1123-1133). Frequently, this catheterization results in the life-threatening complication of system-wide infection of the blood. Research suggests that up to 90% of such cases originate in films of bacteria that adhere to catheter walls (Donlan (2001) Emerg. Infect. Dis. 7: 277-281).
Pathogenic bacterial biofilms form on both outer and inner walls of catheters and may be detected on catheter surfaces within twenty four hours of catheter insertion. Bacteria in these biofilms are thickly embedded in a mostly polysaccharide substance known simply as “matrix” which protects the bacteria from administered antibiotics as well as the immune system. These biofilms also provide an environment in which bacteria can exchange drug-resistance genes. The selective pressures on bacteria in these environments give rise to bacteria which are resistant not only to commonly-used antibiotics but also to drugs which are treatments of “last resort.”
Other types of catheters that are frequently used include urinary catheters, which are typically used with incontinent elderly patients and are typically made of silicone and latex. Unfortunately, virtually all patients who have urinary catheters in place for 28 days or more develop urinary tract infections (Donlan (2001) Emerg. Infect. Dis. 7: 277-281). Nearly all hospital-acquired systemic infections that are not associated with central line catheters are associated with urinary catheters (Maki & Tambyah (2001) Emerg. Infect. Dis. 7: 342-347). Treatment of urinary catheter-associated infections alone costs an estimated $1.8 billion annually (Platt et al. (1982) N. Engl. J. Med. 307: 637-642).
Polymer surfaces can also be “fouled” and their usefulness negated by the adherence of non-bacterial cells and/or protein. For example, receptacles that are used for collecting and storing blood for use in transfusion can be “fouled” and destroy the blood stored in them unless they deter the natural tendency of various blood components to clot and to adhere to surfaces. Similarly, receptacles that are used for storing proteins of interest are often made from synthetic polymers such as, for example, plastic tubes, syringes, etc. Once proteins begin to adhere to a receptacle wall, the process often continues until no protein remains in solution. Thus, these receptacles should ideally prevent adhesion of the proteins to the receptacle surface in order to preserve the quality of the proteins stored in them.
Similar problems currently exist with orthopedic implants. The long-term effectiveness of an implanted medical device is extremely dependent upon the appropriate integration of the implant with the patient's tissues. Nowhere is this more true than in the field of orthopedics, particularly for procedures such as total knee arthroplasty and total hip arthroplasty. According to the National Center for Health Statistics, currently there are over 150,000 new hip replacements and 300,000 knee replacements performed in the U.S. each year. These numbers are expected to continue to increase as the baby boom generation ages. With orthopedic implants, failure usually results in surgical removal of the faulty implant and replacement with a new implant, a process known as revision. The revision rate for total joint replacements remains a significant burden to the health care economies of Western countries and varies between 10-20% depending upon the country. See, e.g., Malchau et al. (2002) “Prognosis of total hip replacement: Update of results and risk-ratio analysis for revision and re-revision from the Swedish National Hip Arthroplasty Registry, 1979-2000,” 69th Annual Meeting of the American Academy of Orthopaedic Surgeons, Scientific Exhibition; Fitzpatrick et al. (1998) Health Technol. Assess. 2: 1-64; Mahomed et al. (2003) J. Bone Joint Surg. Am. 85-A: 27-32).
In the United States, Medicare data for patients aged 65 years and older suggests that revision procedures occur at a yearly rate of about 18% relative to the number of primary surgeries (Mahomed et al. (2003) J Bone Joint Surg. Am. 85-A: 27-32). Main causes of implant failure include host inflammation responses and infection due to the formation of bacterial biofilms on the surface of the implants. This has led to an increase in the failure of orthopedic implants. In a study by Charnley and Cupic ((1973) Clin. Orthop. 95: 9-25), it was reported that 4-6% of total hip arthroplasty revision surgeries were due to infection, typically as a result of the formation of bacterial biofilms on the surface of the implants. Once present, these infections are extremely difficult to treat and may lead to removal and replacement of the implant, amputation, or even death. In contrast, the same study revealed that only 1-2% of the revision surgeries were performed due to mechanical loosening of the implant. With the use of prophylactic antimicrobial agents and improved operating room techniques, the rates of deep infection in total hip arthroplasty has dropped to approximately 1% over the last 20 years (Tang et al. (2003) J. Arthroplasty 18: 714-718; Gaine et al. (2000) J. Bone Joint Surg. Br. 82: 561-565; An and Friedman (1998) J. Invest. Surg. 11: 139-146). However, with over 450,000 new hip and knee arthroplasty surgeries each year, infections may affect 4000 to 5000 patients.
Furthermore, studies have shown that infections are very common at the site of pin insertion (Parameswaran et al. (2003) J. Orthop. Trauma 17: 503-507), and infection associated with external fixators may be as high as 85% (Sims and Saleh (1996) Prof. Nurse 11: 261-264). Because metal pins and wires are being used more often in the treatment of orthopedic trauma, primarily for external fixation of bone fractures (Davis (2003) Nurs. Times. 99: 46-48), any device improvements that decreased the rate of infections from joint prostheses or other metallic implants could have a significant impact on the quality of orthopedic healthcare.
The biofilm “life cycle” from the adhesion of bacteria to a surface to the maturation of a biofilm and subsequent release of cells has been the focus of many recent basic research studies. Using a variety of molecular genetic techniques, genes required for biofilm formation and maturation have been identified in a broad range of Gram-positive and Gram-negative microbes. While similar themes have been elucidated among microbes in terms of biofilm development (i.e., a role for surface adhesion and quorum sensing), no universal “biofilm genes” have yet been identified that are conserved among the many opportunistic pathogens.
Biofilm formation is-regulated via the exchange of chemical signals between cells in a process called quorum sensing. Staphylococci bacteria, which are a common cause of nosocomial infections related to biofilm formation on implanted catheters, use two peptide-based quorum sensing systems. The first system is composed of the autoinducer RNA-III activating protein (RAP) and its target receptor TRAP (target of RNA-III activating protein). When the concentration of RAP reaches a threshold concentration, it induces the phosphorylation of TRAP, which in turn leads to increased cell adhesion and the activation of the second quorum sensing system, agr. The agr system controls toxin production (Balaban et al. (2001) J Biol Chem 276: 2658-67). S. aureus virulence can be inhibited by the heptapeptide YSPWTNF, which is called RIP (RNA-III inhibiting peptide). RIP is a competitive inhibitor of RAP binding to TRAP, and thus inhibits TRAP phosphorylation, leading to reduced expression of the agr system, which leads in turn to suppression of the virulence phenotype (Gov et al. (2001) Peptides 22: 1609-1620; Vieira-da-Motta et al. (2001) Peptides 22: 1621-1627). Among Gram-negative bacteria, quorum sensing is accomplished using N-acyl-homoserine lactone signaling molecules (AHLs), LuxI-type signal synthetases and LuxR-type signal receptors. The AHL-dependent sensing system mediates the regulation of a number of genes, including those involved in biofilm formation and production of virulence factors (Eberl (1999) Syst. Appl. Microbiol. 22(4): 493-506).
While research into the use of quorum sensing antagonists as a means of controlling biofilm formation appears promising, it has not yet been reduced to practice (Ehrlich (2004) ASM News 70(3): 127-133). Efforts to reduce the incidence of infection due to biofilms on medical devices, including implants and catheters, have focused on two approaches. The first is the development of antibacterial compounds that retain efficacy on bacteria in biofilms (Shih and Huang (2002) J. Antimicrob. Chemother. 49: 309-314). Unfortunately, it is not yet understood how bacteria within a biofilm become resistant to antibiotics, which makes development of antibiotics with efficacy for treatment of biofilms virtually unattainable. Due to the difficulties of this approach, the main strategy that has been used to combat this problem is to modify the surface or composition of the article to prevent biofilm formation.
Surface modification technologies that have been tested for use with medical devices include diffusion, laser and plasma processing, chemical grafting, and bombardment with high-energy particles. These treatments have traditionally been used to alter the physical or mechanical properties of materials but are not proving to be effective in reducing infection rates (Katz (1997) Medical Device & Diagnostic Industry Magazine, April 1997). More recently, new treatments designed to reduce infection rates have been investigated, including hydrogel encapsulation and impregnation of the catheter or other article surface with antimicrobial agents (Raad and Hanna (1999) Support. Care Cancer 7: 386-390; DiTizio et al. (1998) Biomaterials 19: 1877-1884; Maki et al. (1997) Ann. Intern. Med. 127: 257-266). This approach seeks to kill the bacteria prior to, or shortly after, adhesion to the surface of the article. Representative examples of patents involving articles that have been coated or impregnated with anti-microbial drugs include U.S. Pat. No. 5,520,664 (“Catheter Having a Long-Lasting Antimicrobial Surface Treatment”), U.S. Pat. No. 5,709,672 (“Silastic and Polymer-Based Catheters with Improved Antimicrobial/Antifungal Properties”), U.S. Pat. No. 6,361,526 (“Antimicrobial Tympanostomy Tubes”), U.S. Pat. No. 6,261,271 (“Anti-infective and antithrombogenic medical articles and method for their preparation”), U.S. Pat. No. 5,902,283 (“Antimicrobial impregnated catheters and other medical implants”) U.S. Pat. No. 5,624,704 (“Antimicrobial impregnated catheters and other medical implants and method for impregnating catheters and other medical implants with an antimicrobial agent”) and U.S. Pat. No. 5,709,672 (“Silastic and Polymer-Based Catheters with Improved Antimicrobial/Antifungal Properties”).
Some recent studies and review articles have suggested that impregnating catheters with antibiotics may help prevent colonization by killing organisms when they come in close proximity to the surface, before they can establish a biofilm. There are, however, several other limitations to that approach. For example, although chlorhexidine-impregnated catheters showed limited efficacy in preventing infections, they are also believed to cause hypersensitivity reactions (Knight et al. (2001) Intern. Med. J. 31: 436-437). Furthermore, impregnating catheters with antibiotics may be counter-productive because as the concentration of antibiotics released from the catheter inevitably falls, bacteria are exposed to sublethal levels of antibiotics, a condition that promotes the development of antibiotic resistance (Rachid et al. (2000) J. Bacteriol. 182: 6824-6826; Rachid et al. (2000) Antimicrob. Agents Chemother. 44: 3357-3363; Rupp and Hamer (1998) J. Antimicrob. Chemother. 41: 155-161). Moreover, several studies have demonstrated that sublethal levels of antibiotics actually stimulate biofilm formation by Staphylococcus strains, one of the key organisms involved in implant infections.
Another alternative for preventing biofilm formation is the development of a coating that prevents adherence of bacterial cells to the catheter surface. Such coatings could be used alone or in combination with antibacterial impregnation of the catheter to further prevent biofilm formation. The most commonly used coatings to prevent biological fouling on surfaces-include those generated using plasma treatment, biotin-avidin conjugation strategies, phospholipids, self-assembled monolayers on transition metal coatings, and chemically grafted poly(ethylene glycol) (Kingshott et al. (1999) Anal. Biochem. 273(2): 156-62; Ratner (1993) J. Biomed. Mater. Res. 27: 837-50).
Of these approaches, coating a surface with poly (ethylene glycol) has met with some success for preventing cell and protein adhesion (Dalsin et al. (2003) J. Am. Chem. Soc. 125(14): 4253-8). However, chemically grafting this macromolecule to a surface often requires special preparation of the surface and multi-step chemical procedures (Golander et al. (1992) J. Biomater. Sci. Polym. Ed. 4(1): 25-30). Investigators who have derivatized a percentage of PLL side chains with poly (ethylene glycol) (“PEG”) report both that the polymer so modified retains affinity for surfaces and that surfaces coated with it inhibit adhesion by proteins (Tosatti et al. (2003) Biomaterials 24: 4949; Huang et al. (2001) Langmuir 17(2): 489) as well as bacteria (Harris et al. (2004) Biomaterials 25: 4135; Wagner et al. (2004) Biomaterials 25: 2247). In addition, Hubbell et al. have described a method to suppress the interaction, adsorption or attachment of proteins or cells to a biomaterial surface through a polymer coating comprised of a polyionic backbone with poly(ethylene glycol) (PEG) or poly(ethylene oxide) (PEO) side chains (U.S. Patent Application No. 20020128234). Still another non-covalent means of associating PEG with metal surfaces includes linkage to mussel adhesive protein (Dalsin et al. (2003) J. Am. Chem. Soc. 125: 4253-8). For negatively charged metal oxides (TiO₂, Ta₂O₅, Nb2O₅, SiO₂), an alternative method for coating the surface is the use of polycationic polymers such as poly-L-lysine. This type of polymer spontaneously adsorbs to metal oxides based on the interaction of the positively charged amino groups on the polymer with the negatively metal oxide surface (Huang et al. (2001) Langmuir 17(2): 489). Unfortunately, these current methods of coating surfaces also often require special preparation of the surface and multi-step chemical procedures.
Another disadvantage of current methods to coat medical device surfaces is that, in general, the conditions necessary for attachment of the coating threaten to modify the relatively labile chemical groups or macromolecular folds that are typical of bioactive agents such as antimicrobial compounds. The extra steps and costs necessary to preserve the function of bioactive agents in a surface coating often render the project cost-prohibitive. In principle, each new material and each new agent that is identified for use as a coating presents a different chemical engineering challenge that will require an unknown investment of time, money, personnel and infrastructure in order to obtain a final product.
Thus, existing methods to modify medical devices to prevent protein adsorption, cell adhesion, or biofilm formation suffer from various shortcomings: surface modification is often unreliable, incomplete, and requires specialized equipment; impregnating with traditional antibiotics can lead to increases in antibiotic resistance among bacteria and is often ineffective against bacteria in biofilms; and many of the surface coatings require multiple steps and are prohibitively expensive. Thus, the need remains in the art for a stable coating that can be applied simply, quickly, and in a cost-effective manner to the surface of a medical device.

SUMMARY OF THE INVENTION

The present invention provides materials and compositions for an improved coating for surfaces of medical devices, including implants and catheters. The coating is an interfacial biomaterial (“IFBM”) which comprises at least one binding module that specifically binds to a surface (“surface-binding module”) and at least one binding module that performs another function (“affector module”). The affector module can: inhibit binding to the polymer surface by an organism, cell, or protein (“adhesion-resistance module”); modify the behavior of cells and/or organisms which bind to it (“behavior modification module”); and/or bind to a moiety which is a compound or molecule of interest (“moiety-binding module”). The modules are connected by a linker. In some embodiments, the affector module inhibits biofilm formation. The compositions and methods of the invention improve the performance of medical devices, for example, by preventing unwanted adsorption and/or growth of bacterial cells on the surface of the device.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides compositions for an improved coating for medical devices and methods of coating medical devices using those compositions. The term “medical device” as used herein refers to any article used as an implant in the body of a patient (including both human and non-human patients), any article used as a conduit (e.g., a catheter) related to medical treatment or for biological materials, or any container used as a storage device for biological materials, for example, for proteins or solutions containing cells. Medical devices may be made of any material, including metal and/or polymers. The coating of the invention is an interfacial biomaterial (“IFBM”) which comprises at least one binding module that specifically binds to a surface of a medical device (“surface-binding module”) and at least one binding module that performs another function (“affector module”). The binding modules are connected by a linker. The affector module acts to inhibit formation of a biofilm by any suitable mechanism. For example, the affector module may inhibit formation of a biofilm by inhibiting binding of an organism, cell, or compound (e.g., a protein) to the surface of the medical device (“adhesion-resistance module”). Alternatively, the affector module inhibit formation of a biofilm by modifying the behavior of cells and/or organisms which come into contact with it or bind to it (“behavior modification module”); and/or it may function to specifically bind to a moiety which is a compound or molecule of interest (“moiety-binding module”). Any affector module is suitable for use in an IFBM of the invention so long as an IFBM comprising it acts to inhibit formation of a biofilm. Affector modules may have more than one function; thus, for example, a single affector module may have both adhesion-resistance function and behavior modification function. Any affector module may be used in an IFBM of the invention so long as it accomplishes the objective of the invention to inhibit biofilm formation. In some embodiments, at least one binding module (i.e., surface-binding module or affector module) is a peptide or comprises a peptide. Exemplary binding modules are set forth in SEQ ID NOs: 1-10, 39-43, 95-96, and 97-558.
The compositions and methods of the invention improve the performance of medical devices including those made from polymeric materials. The term “polymer” or “polymeric material” as used herein refers to any of numerous natural and synthetic compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively simple molecule. Generally, wherever the surface of a medical device is to interface with biochemical solutions or biological tissue, such a surface is susceptible to microbial growth, attachment, and biofilm formation. In medical devices that are inserted into a patient's body, said microbial organisms include non-pathogenic microbes that are ordinarily present in non-sterile areas as well as pathogenic microbes that are present as a result of extant disease or due to accidental introduction during the insertion of the device. The IFBM coatings of the invention are useful for improving the performance of medical devices such as, for example, implants, catheters, and endotracheal tubes. In some embodiments, these coatings prevent unwanted adsorption of and/or growth of bacterial cells to the surface of the device.
The surface-binding module of the IFBM of the invention is selected to specifically bind to the material of which the surface of the medical device is made. Typically, this binding is non-covalent. The affector module of the IFBM of the invention is chosen so as to confer to an IFBM-coated surface a desired property such as, for example, resistance to adhesion of bacteria. The IFBMs of the invention comprise at least one surface-binding module and at least one affector module which are connected by a linker. A linker may be chosen for particular properties, such as a specific susceptibility to modification and/or to allow affector modules flexibility of orientation at a distance from the binding modules so linked. In some embodiments, the linker itself may also have activities similar to those of the binding module or affector module; that is, the linker may act to enhance binding to a particular surface or to have anti-adhesive properties such as inhibiting cell attachment, etc. For example, an IFBM comprising a poly (ethylene glycol) (“PEG”) linker to join the surface-binding module to the affector module may help to prevent non-specific protein and/or cell adherence to the surface of the medical device coated with that IFBM.
In some embodiments, the affector module inhibits biofilm formation. In some embodiments, an affector module inhibits biofilm formation due to its anti-adhesive properties; that is, the affector module is a molecule or moiety that does not bind to biomolecules and/or biomolecular constituents of cells. In some embodiments, an affector module inhibits biofilm formation by damaging cells so that they do not adhere to the surface or by affecting a regulatory mechanism of cells that is involved in biofilm formation. Any combination of affector modules may be linked to any combination of surface-binding modules to create an IFBM of the invention so long as the IFBM comprises at least one affector module and at least one surface-binding module.
A surface-binding module is a peptide that binds to the surface of a medical device. A surface-binding module may bind to any material which is used to make a medical device, including a metal, a metal oxide, a non-metal oxide, a ceramic, a polymer, such as, for example, a synthetic polymer such as a polyurethane, a rubber, a plastic, an acrylic, a silicone, and combinations thereof. Suitable materials are known in the art. Binding modules (i.e., surface-binding modules and/or affector modules) can be peptides, antibodies or antibody fragments, polynucleotides, oligonucleotides, complexes comprising any of these, or various molecules and/or compounds. Binding modules which are peptides may comprise sequences disclosed in this application or known in the art, such as the peptides described in pending U.S. patent application Ser. No. 10/300,694, filed Nov. 20, 2002 and published on Oct. 2, 2003 as publication number 20030185870. Binding modules can also be identified using the methods described in pending U.S. patent application Ser. No. 10/300,694 and/or other methods known in the art. In some embodiments, binding modules may be identified by screening phage display libraries for affinity to materials such as titanium, stainless steel, cobalt-chrome alloy, polyurethane, polyethylene, acrylic, latex or silicone. Exemplary binding modules which are peptides which exhibit specific binding to particular materials are set forth in SEQ ID NOs: 1-10 (showing specific binding to titanium), 39-43 (showing specific binding to stainless steel), 95-96 (showing specific binding to Teflon), and 97-558. By “binds specifically” or “specific binding” is intended that a binding module binds to a selected surface, material, or composition. In some embodiments, a binding module that binds specifically to a particular surface, material or composition binds at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 300%, 400%, 500%, or a higher percentage more than the binding module binds to an appropriate control such as, for example, a different material or surface, or a protein typically used for such comparisons such as bovine serum albumin.
The term “antibody” as used herein with reference to a binding module encompasses single chain antibodies. Thus, an antibody useful as a binding module may be a single chain variable fragment antibody (scFv). A single chain antibody is an antibody comprising a variable heavy and a variable light chain that are joined together, either directly or via a peptide linker, to form a continuous polypeptide. The term “single chain antibody” as used herein encompasses an immunoglobulin protein or a functional portion thereof, including but not limited to a monoclonal antibody, a chimeric antibody, a hybrid antibody, a mutagenized antibody, a humanized antibody, and antibody fragments that comprise an antigen binding site (e.g., Fab and Fv antibody fragments).
In some embodiments, the IFBM comprises an affector module that is an anti-adhesive or that binds to a protein which is an anti-adhesive. In such embodiments, the surface-binding module of the IFBM binds to the surface of the device and the anti-adhesive forms a dense structure that prevents the adsorption of biological cells, viruses and macromolecules onto that surface. Suitable anti-adhesives are “non-interactive” polymer and/or functional groups that resist adhesion to protein and/or to cells. The term “non-interactive” as used herein with regard to coating polymer articles means a polymer that reduces the amount of non-specific adsorption of molecules to a coated surface, such as, for example, inorganic ions, peptides, proteins, saccharides and cells such as mammalian cells, bacteria and fungi. In embodiments using non-interactive polymers, an IFBM may comprise an affector module which is a non-interactive polymer or an IFBM may comprise an affector module which binds to a non-interactive polymer. Suitable non-interactive polymers which have adhesion-resistant function are known in the art and include, for example: albumin, poly(ethylene glycol) (PEG) (see, e.g., Wagner et al. (2004) Biomaterials 25: 2247-2263; Harris et al. (2004) Biomaterials 25: 4135-4148); mixed polyalkylene oxides having a solubility of at least one gram/liter in aqueous solutions such as some poloxamer nonionic surfactants; neutral water-soluble polysaccharides; poly(vinyl alcohol); poly(N-vinyl pyrrolidone); non-cationic polymethacrylates such as poly(methacrylic acid); many neutral polysaccharides, including dextran, Ficoll™, and derivatized celluloses; non-cationic polyacrylates such as poly(acrylic acid); and esters, amides, and hydroxyalkyl amides thereof, and combinations thereof. For example, an IFBM can comprise an affector module that binds human serum albumin, a native protein present in the blood of people and animals which is known to reduce bacterial adherence to coated surfaces (see, e.g., Keogh and Eaton (1994) J. Lab. Clin. Med. 124: 537-545; U.S. Pat. No. 5,073,171; Sato et al. (2002) Biotechnol. Prog. 18: 182-192). IFBMs comprising an affector module which has affinity for albumin can be coated onto polymer surfaces such as catheters or containers for blood, serum or other tissue, or solutions containing bacteria; albumin present in physiological solutions will then bind to the affector module, effectively providing a coating of albumin to the polymer surface, e.g., of the catheter or container.
In other embodiments, the IFBM comprises an affector module that has anti-microbial activity. For example, the affector module can be a peptide which has anti-microbial activity such as, for example, cationic antimicrobial peptides such as a magainin, defensin, bacteriocin, or microcin, all of which are known in the art (see, e.g., Lin et al. (2001) Medical Device Technology, October 2001 issue; Zasloff (2002) Nature 415: 389-395). Lactoferrin is also known to inhibit biofilm formation and is therefore useful as an affector module. While the invention is not limited to a particular mechanism of action of biofilm inhibition, the mechanism of action for many anti-microbial peptides is through disruption of the integrity of the bacterial membrane; most of these peptides do not affect the membranes of plant or animal cells. Because this disruption is mechanical in nature, it is unlikely that bacteria would develop resistance to these peptides (Zasloff (2002) Nature 415: 389-395).
In other embodiments, an affector module has biofilm inhibitor activity due to its interference with a regulatory mechanism of cells that is involved in their establishment of or participation in a biofilm. Suitable biofilm inhibitors for use as an affector module include compounds that are known in the art to interfere with bacterial quorum sensing such as RNA III inhibiting peptide (RIP), RIP analogs, antagonists of TRAP (Target for RNA III Activating Peptide), antagonists of N-acyl-homoserine lactone-based signaling, and furanone analogs.
The IFBMs of the invention can be coated onto a medical device and implanted into the body. The linkers used in such IFBMs can be, for example, a PEG linker which joins the binding module to the affector module and also may prevent non-specific protein and/or cell adherence to the surface of the medical device. When the IFBM-coated medical device is implanted in a patient, the affector module which has affinity for albumin will bind endogenous serum albumin, thereby specifically coating the surface of the medical device with albumin. A medical device coated with such IFBMs may also be coated with albumin by contacting the device with albumin-containing solutions in vitro prior to implantation of the device in a patient (see, e.g., Wagner et al. (2004) Biomaterials 25: 2247-2263; Harris et al. (2004) Biomaterials 25: 4135-4148).
Phage display technology is well-known in the art and can be used to identify additional peptides for use as binding modules in IFBMs of the invention. Using phage display, a library of diverse peptides can be presented to a target substrate, and peptides that specifically bind to the substrate can be selected for use as binding modules. Multiple serial rounds of selection, called “panning,” may be used. As is known in the art, any one of a variety of libraries and panning methods can be employed to identify a binding module that is useful in the methods of the invention. For example, libraries of antibodies or antibody fragments may be used to identify antibodies or fragments that bind to particular cell populations or to viruses (see, e.g., U.S. Pat. Nos. 6,174,708, 6,057,098, 5,922,254, 5,840,479, 5,780,225, 5,702,892, and 5,667,988). Panning methods can include, for example, solution phase screening, solid phase screening, or cell-based screening. Once a candidate binding module is identified, directed or random mutagenesis of the sequence may be used to optimize the binding properties of the binding module. The terms “bacteriophage” and “phage” are synonymous and are used herein interchangeably. The term “bacteriophage” is defined as a bacterial virus containing a nucleic acid core and a protective shell built up by the aggregation of a number of different protein molecules.
A library can comprise a random collection of molecules. Alternatively, a library can comprise a collection of molecules having a bias for a particular sequence, structure, or conformation. See, e.g., U.S. Pat. Nos. 5,264,563 and 5,824,483. Methods for preparing libraries containing diverse populations of various types of molecules are known in the art, and numerous libraries are also commercially available. Methods for preparing phage libraries can be found, for example, in Kay et al. (1996) Phage Display of Peptides and Proteins (San Diego, Academic Press); Barbas (2001) Phage Display: A Laboratory Manual (Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.).
A binding module that is a peptide comprises about 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 50, 60, 70, 80, 90, 100, 200, or up to 300 amino acids. Exemplary binding modules that are peptides are set forth in SEQ ID NOs: 1-10, 39-43, and 95-558. Peptides that are useful as binding modules in IFBMs of the invention may differ from these exemplary peptides so long as the desired property of the binding module is retained. Peptides useful as a binding module can be linear, branched, or cyclic, and can include non-peptidyl moieties. The term “peptide” broadly refers to an amino acid chain that includes naturally occurring amino acids, synthetic amino acids, genetically encoded amino acids, non-genetically encoded amino acids, and combinations thereof. Peptides can include both L-form and D-form amino acids. A peptide of the present invention can be subject to various changes, substitutions, insertions, and deletions where such changes provide for certain advantages in its use. Thus, the term “peptide” encompasses any of a variety of forms of peptide derivatives including, for example, amides, conjugates with proteins, cyclone peptides, polymerized peptides, conservatively substituted variants, analogs, fragments, chemically modified peptides, and peptide mimetics. Any peptide that has desired binding characteristics can be used in the practice of the present invention.
Representative non-genetically encoded amino acids include but are not limited to 2-aminoadipic acid; 3-aminoadipic acid; β-aminopropionic acid; 2-aminobutyric acid; 4-aminobutyric acid (piperidinic acid); 6-aminocaproic acid; 2-aminoheptanoic acid; 2-aminoisobutyric acid; 3-aminoisobutyric acid; 2-aminopimelic acid; 2,4-diaminobutyric acid; desmosine; 2,2′-diaminopimelic acid; 2,3-diaminopropionic acid; N-ethylglycine; N-ethylasparagine; hydroxylysine; allo-hydroxylysine; 3-hydroxyproline; 4-hydroxyproline; isodesmosine; allo-isoleucine; N-methylglycine (sarcosine); N-methylisoleucine; N-methylvaline; norvaline; norleucine; and ornithine. Representative derivatized amino acids include, for example, those molecules in which free amino groups have been derivatized to form amine hydrochlorides, p-toluene sulfonyl groups, carbobenzoxy groups, t-butyloxycarbonyl groups, chloroacetyl groups or formyl groups. Free carboxyl groups can be derivatized to form salts, methyl and ethyl esters or other types of esters or hydrazides. Free hydroxyl groups can be derivatized to form O-acyl or O-alkyl derivatives. The imidazole nitrogen of histidine can be derivatized to form N-im-benzylhistidine.
The term “conservatively substituted variant” refers to a peptide having an amino acid residue sequence substantially identical to a sequence of an exemplary peptide in which one or more residues have been conservatively substituted with a functionally similar residue such that the “conservatively substituted variant” will bind to the same binding partner with substantially the same affinity as the parental variant and will prevent binding of the parental variant. In one embodiment, a conservatively substituted variant displays a similar binding specificity when compared to the exemplary reference peptide. The phrase “conservatively substituted variant” also includes peptides wherein a residue is replaced with a chemically derivatized residue.
Examples of conservative substitutions include the substitution of one non-polar (hydrophobic) residue such as isoleucine, valine, leucine or methionine for another; the substitution of one aromatic residue such as tryptophan, tyrosine, or phenylalanine for another; the substitution of one polar (hydrophilic) residue for another such as between arginine and lysine, between glutamine and asparagine, between glycine and serine; the substitution of one basic residue such as lysine, arginine or histidine for another; or the substitution of one acidic residue such as aspartic acid or glutamic acid for another.
Peptides which are useful as binding modules of the present invention also include peptides having one or more substitutions, additions and/or deletions of residues relative to the sequence of an exemplary peptide sequence as disclosed herein, so long as the binding properties of the original exemplary peptide are retained. Thus, binding modules of the invention include peptides that differ from the exemplary sequences disclosed herein by about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 amino acids but that retain the ability of the corresponding exemplary sequence to bind to a particular material or to act as an affector module. A binding module of the invention that differs from an exemplary sequence disclosed herein will retain at least 25%, 50%, 75%, or 100% of the activity of a binding module comprising an entire exemplary sequence disclosed herein as measured using an appropriate assay. That is, binding modules of the invention include peptides that share sequence identity with the exemplary sequences disclosed herein of at least 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or greater sequence identity. Sequence identity may be calculated manually or it may be calculated using a computer implementation of a mathematical algorithm, for example, GAP, BESTFIT, BLAST, FASTA, and TFASTA in the Wisconsin Genetics Software Package of Genetics Computer Group, Version 10 (available from Accelrys, 9685 Scranton Road, San Diego, Calif., 92121, USA). The scoring matrix used in Version 10 of the Wisconsin Genetics Software Package is BLOSUM62 (see Henikoff and Henikoff (1989) Proc. Natl. Acad. Sci. USA 89: 10915). Alignments using these programs can be performed using the default parameters.
A peptide can be modified, for example, by terminal-NH₂acylation (e.g., acetylation, or thioglycolic acid amidation) or by terminal-carboxylamidation (e.g., with ammonia or methylamine). Terminal modifications are useful to reduce susceptibility by proteinase digestion, and to therefore prolong a half-life of peptides in solutions, particularly in biological fluids where proteases can be present. Peptide cyclization is also a useful modification because of the stable structures formed by cyclization and in view of the biological activities observed for such cyclic peptides. Methods for cyclizing peptides are described, for example, by Schneider & Eberle (1993) Peptides. 1992: Proceedings of the Twenty-Second European Peptide Symposium, Sep. 13-19, 1992, Interlaken, Switzerland, Escom, Leiden, The Netherlands.
Optionally, a binding module peptide can comprise one or more amino acids that have been modified to contain one or more halogens, such as fluorine, bromine, or iodine, to facilitate linking to a linker molecule. As used herein, the term “peptide” also encompasses a peptide wherein one or more of the peptide bonds are replaced by pseudopeptide bonds including but not limited to a carba bond (CH₂—CH₂), a depsi bond (CO—O), a hydroxyethylene bond (CHOH—CH₂), a ketomethylene bond (CO—CH₂), a methylene-oxy bond (CH₂—O), a reduced bond (CH₂—NH), a thiomethylene bond (CH₂—S), an N-modified bond (—NRCO—), and a thiopeptide bond (CS—NH). See e.g., Garbay-Jaureguiberry et al. (1992) Int. J. Pept. Protein Res. 39: 523-527; Tung et al. (1992) Pept. Res. 5: 115-118; Urge et al. (1992) Carbohydr. Res. 235: 83-93; Corringer et al. (1993) J. Med. Chem. 36: 166-172; Pavone et al. (1993) Int. J. Pept. Protein Res. 41: 15-20.
In some embodiments, IFBMs of the invention comprise binding modules which comprise peptides that specifically bind to materials used in medical implants, such as peptides having an amino acid sequence as set forth in SEQ ID NOs:1-10, 39-43, and 95-558. While these exemplary peptide sequences are disclosed herein, one of skill will appreciate that the binding properties conferred by those sequences may be attributable to only some of the amino acids comprised by the sequences. Thus, a peptide which comprises only a portion of an exemplary amino acid sequence disclosed herein may have substantially the same binding properties as a peptide comprising the full-length exemplary sequence; thus, also useful as binding modules in IFBMs of the present invention are peptides that comprise only 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 of the amino acids in a particular exemplary sequence provided herein. Such amino acids may be contiguous or non-contiguous so long as the desired property of the binding module is retained as determined by an appropriate assay. Such amino acids may be concentrated at the amino-terminal end of the exemplary peptide (for example, 4 amino acids may be concentrated in the first 4, 5, 6, 7, 8, 9, 10, 11, or 12 amino acids of the peptide) or they may be dispersed throughout the exemplary peptide.
Binding modules of the present invention that are peptides can be synthesized by any of the techniques that are known to those skilled in the art of peptide synthesis. Representative techniques can be found, for example, in Stewart & Young (1969) Solid Phase Peptide Synthesis, (Freeman, San Francisco, Calif.); Merrifield (1969) Adv. Enzymol. Relat. Areas Mol. Biol. 32:221-296; Fields & Noble (1990) Int. J. Pept. Protein Res. 35:161-214; and Bodanszky (1993) Principles of Peptide Synthesis, 2nd Rev. Ed. (Springer-Verlag, Berlin). Representative solid phase synthesis techniques can be found in Andersson et al. (2000) Biopolymers 55: 227-250, references cited therein, and in U.S. Pat. Nos. 6,015,561; 6,015,881; 6,031,071; and 4,244,946. Peptide synthesis in solution is described in Schröder & Lübke (1965) The Peptides (Academic Press, New York, N.Y.). Appropriate protective groups useful for peptide synthesis are described in the above texts and in McOmie (1973) Protective Groups in Organic Chemistry (Plenum Press, London). Peptides, including peptides comprising non-genetically encoded amino acids, can also be produced in a cell-free translation system, such as the system described by Shimizu et al. (2001) Nat. Biotechnol. 19: 751-755. In addition, peptides having a specified amino acid sequence can be purchased from commercial sources (e.g., Biopeptide Co., LLC of San Diego, Calif., and PeptidoGenics of Livermore, Calif.).
The linker that joins the binding module to at least one other module to form an IFBM can be any suitable linker. Linkers may be peptides or non-peptides. Suitable linkers are known in the art and can comprise, for example, a polymer, including a synthetic polymer or a natural polymer. In some embodiments, an IFBM is synthesized as a single continuous peptide comprising sequences originally identified as separate binding modules; in such embodiments, the linker is simply one of the bonds in the peptide. Representative synthetic polymers include but are not limited to polyethers (e.g., poly(ethylene glycol) (“PEG”)), polyesters (e.g., polylactic acid (PLA) and polyglycolic acid (PGA)), polyamines, polyamides (e.g., nylon), polymethacrylates (e.g., polymethylmethacrylate; PMMA), polyacrylic acids, polyurethanes, polystyrenes, flexible chelators such as EDTA, EGTA and other synthetic polymers having a molecular weight of about 200 daltons to about 1000 kilodaltons. Representative natural polymers include but are not limited to hyaluronic acid, alginate, chondroitin sulfate, fibrinogen, fibronectin, albumin, collagen, calmodulin EF-hand domains and other natural polymers having a molecular weight of about 200 daltons to about 20,000 kilodaltons. Polymeric linkers can comprise a diblock polymer, a multi-block copolymer, a comb polymer, a star polymer, a dendritic polymer, a hybrid linear-dendritic polymer, or a random copolymer. A linker can also comprise a mercapto(amido)carboxylic acid, an acrylamidocarboxylic acid, an acrlyamido-amidotriethylene glycolic acid, and derivatives thereof. See, for example, U.S. Pat. No. 6,280,760. Linkers are known in the art and include linkers that can be cleaved and linkers that can be made reactive toward other molecular moieties or toward themselves, for cross-linking purposes. Fluorescent linkers are also known in the art.
Methods for linking a linker molecule to a ligand, binding module, or to a non-binding domain will vary according to the reactive groups present on each molecule. Protocols for linking using reactive groups and molecules are known to one of skill in the art. See, e.g., Goldman et al. (1997) Cancer Res. 57: 1447-1451; Cheng (1996) Hum. Gene Therapy 7: 275-282; Neri et al. (1997) Nat. Biotechnol. 19: 958-961; Nabel (1997) Current Protocols in Human Genetics, vol. on CD-ROM (John Wiley & Sons, New York); Park et al. (1997) Adv. Pharmacol. 40: 399-435; Pasqualini et al. (1997) Nat. Biotechnol. 15: 542-546; Bauminger & Wilchek (1980) Meth. Enzymol. 70: 151-159; U.S. Pat. Nos. 6,280,760 and 6,071,890; and European Patent Nos. 0 439 095 and 0 712 621.
The compositions and methods of the invention find particular use in coating any implantable or insertable medical device that is susceptible to microbial growth on and around the surfaces of the device. Implantable medical devices that can be improved with the compositions and methods of the invention include those adapted to remain implanted for a relatively long-term, i.e., for period of from about 30 days to about 12 months or greater, such as, for example, orthopedic implants. However, devices intended to remain implanted for about 30 days or less such as, for example, certain catheters, are also included within the scope of the present invention. “Medical device” as used herein refers to devices used in human patients as well as to devices used in non-human animals.
Examples of medical devices that are conduits and vessels made of polymers or that have polymeric surfaces include but are not limited to: medical conduits for insertion into a human or animal body, such as catheters and endotrachial tubes; vessels such as blood collection tubes, specimen containers and storage jars; vessels and conduits for the storage and transport of biochemical reagents in biomedical research or manufacturing; and tubing and containers for waste, water or combinations thereof. The polymer may be any suitable kind, including for example a synthetic polymer such as a plastic, rubber, a silicone material and combinations thereof. Suitable materials are known in the art and include polyurethane, polyethylene, polyvinylchloride, acrylic and latex. Examples of implantable medical devices include but are not limited to: prosthetic joints, plates, screws, pins, nails, rivets, bone fixation implants and artificial ligaments and tendons. Medical devices may be made of any suitable material, including for example a synthetic polymer, a plastic, a metal (such as titanium, stainless steel, or cobalt-chrome alloy), a metal oxide, a non-metal oxide, a silicone material, a ceramic material, and combinations thereof. Suitable materials are known in the art and include polyurethane, polyethylene, and silicone.
Medical devices that are coated with IFBMs of the invention will exhibit at least one superior property in comparison to an appropriate control, such as a similar medical device that is not coated with at least one IFBM; for example, a medical device coated with IFBMs of the invention will exhibit reduced formation of bacterial biofilms or show resistance to adhesion of protein or cells. Thus, an IFBM is considered to act to inhibit formation of a biofilm if a surface coated with that IFBM exhibits a detectable decrease in the tendency for a biofilm to form on that surface when compared to a suitable control surface or if a surface coated with that IFBM shows a detectable increase in resistance to adhesion of protein or cells when compared to a suitable control surface. An IFBM also acts to inhibit formation of a biofilm if a surface coated with that IFBM becomes coated with a biofilm which exhibits a detectable reduction in any of the characteristics of a biofilm. That is, an IFBM acts to inhibit formation of a biofilm if it decreases the frequency of biofilm formation or if it reduces a characteristic of a biofilm or resists adhesion of protein or cells by at least 5%, 10%, 15%, 20%, 30%, 40%, 50%, 100% when a surface coated with that IFBM is compared to a surface that is uncoated or that is not coated with that IFBM. In this manner, a medical device which is coated with at least one IFBM has a superior property where that medical device has a measurable characteristic which differs in a statistically significant way from the same characteristic of an appropriate control medical device (such as, for example, a medical device that is not coated with at least one IFBM). Thus a property of a medical device which is coated with at least one IFBM will have a property which is superior to a property of an appropriate control medical device by at least 5%, 10%, 15%, 20%, 30%, 40%, 50%, 100%, or more. Such a property may result from the performance of the IFBM or of its component modules. One of skill in the art is familiar with techniques that can be used to compare the performance of coated and uncoated medical devices or materials. For example, such techniques are described in the American Society of Testing and Materials (ASTM) Standard Method E-2196-02, entitled “Standard Test Method for the Quantification of Pseudomonas aeruginosa Biofilm Grown with Shear and Continuous Flow using a Rotating Disk reactor” and E1427-OOel, entitled “Standard Guide for Selecting Test Methods to Determine the Effectiveness of Antimicrobial Agents and Other Chemicals for the Prevention, Inactivation and Removal of Biofilm.” Thus, for example, a medical device which is coated with at least one IFBM will inhibit biofilm formation by at least 5% when compared to a comparable uncoated medical device.
A medical device that is coated with at least one IFBM is coated by any suitable method, for example, by dipping or spraying the IFBM onto the device. The coating may be stabilized, for example, by air drying or by lyophilization. However, these treatments are not exclusive, and other coating and stabilization methods may be employed; one of skill in the art will be able to select the compositions and methods used to fit the needs of the particular device and purpose.
All publications and patent applications mentioned in the specification are indicative of the level of those skilled in the art to which this invention pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claim(s).

Claims

1-9. (canceled)

10. A medical device having an interfacial biomaterial coating on a portion of the surface thereof which inhibits formation of a biofilm thereon wherein the interfacial biomaterial comprises a plurality of moieties each moiety comprising:

a) a binding module comprising a peptide of at least 3 amino acids to about 50 amino acids and having a binding affinity for the surface of the medical device to be coated of 1×10⁴M⁻¹;

b) an affector module selected from the group consisting of:

1) a peptide of at least 3 amino acids to about 50 amino acids that acts to inhibit formation of the biofilm adhesion to the medical device by at least 5% compared to the surface of the medical device that is coated;

2) a peptide of at least 3 amino acids to about 50 amino acids having a binding affinity of 1×10⁴M⁻¹for a protein bound thereto that acts to inhibit formation of adhesion to the medical device by at least 5% compared to the surface of the medical device that is coated;

3) a peptide of at least 3 amino acids to about 50 amino acids having a binding affinity of 1×10⁴M⁻¹for a non-protein bound thereto that acts to inhibit formation of adhesion to the medical device by at least 5% compared to the surface of the medical device that is coated;

4) a non-peptide that acts to inhibit formation of adhesion to the medical device by at least 5% compared to the surface of the medical device that is coated;

c) a linker module that links the binding module to the affector module.

11. A device according to claim 10 wherein the medical device is a patient implant.

12. A device according to claim 10 wherein the medical device is a medical conduit.

13. A device according to claim 10 wherein the medical device is a storage device for biological materials.

14. An interfacial biomaterial for coating at least a portion of the surface of a selected medical device which comprises a plurality of moieties each moiety comprising:

b) an affector module selected from the group consisting of:

c) a linker module that links the binding module to the affector module.

15. An interfacial biomaterial according to claim 14 wherein the affector module binds the biofilm inhibitor albumin.

16. An interfacial biomaterial according to claim 14 wherein the affector module inhibits biofilm formation by damaging cells capable of forming a biofilm.

17. An interfacial biomaterial according to claim 16 wherein the affector module is an anti-microbial or where the affector module binds an antimicrobial.

18. An interfacial biomaterial according to claim 14 wherein the affector module affects a regulatory mechanism of cells capable of forming a biofilm where the regulatory mechanism is involved in the cells establishment of or participation in biofilm formation.

19. An interfacial biomaterial according to claim 18 wherein the affector module is a quorum-sensing inhibitor.

20. An interfacial biomaterial according to claim 19 wherein the affector module is RIP.

21. An interfacial biomaterial according to claim 14 wherein the affector module is poly(ethylene glycol).