A nanoscale osteoinductive peptide coating for metal spinal implants

Abstract

The disclosed concept includes a metal or metal alloy implant device, such as a metal or metal alloy spinal implant or interbody device, having a metal oxide surface, a modification applied to said metal oxide surface, such as binding of a copolymer to form a modified surface, and a bioactive peptide additive bonded to the modified surface, wherein presence of the bioactive peptide facilitates and improves osseous integration of the implant device and promotes segmental arthrodesis. In addition, the disclosed concept includes methods of making and implanting the device in the human body.

Description

A NANOSCALE OSTEOINDUCTIVE PEPTIDE COATING FOR METAL SPINAL IMPLANTSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This PCT patent application claims priority to U.S. Provisional Patent Application No. 63 / 703,506 entitled “A NANOSCALE OSTEOINDUCTIVE PEPTIDE COATING FOR METAL SPINAL IMPLANTS” as filed in the United States Patent and Trademark Office, on October 4, 2024, the content of which is incorporated herein in its entirety.Field of the Invention

[0002] The disclosed concept includes a metal or metal alloy implant device, such as a metal spinal implant, e.g., interbody, device, having a metal oxide surface, a modification applied to said surface, such as binding of a copolymer, to form a modified bioactive surface, and a bioactive peptide additive bound to the modified surface, wherein presence of the bioactive peptide facilitates and improves osseous implant integration, facilitates bone growth, and promotes segmental arthrodesis. In addition, the disclosed concept includes methods of making and implanting the device in a human body.Background

[0003] Over the last several decades, the number of spinal fusion surgeries performed worldwide has increased. As surgical indications broadened, many implants have been developed to facilitate the mechanical linkage of one vertebral segment to another. Most spinal implants are designed to induce bony fusion across vertebral segments. These implants act as mechanical scaffolds to enable the regrowth of bone between affected vertebral segments and allow them to fuse together without motion. In the United States, the number of spinal fusion procedures performed from 1998 to 2014 increased by 120% from 200,000 to 440,000? There is evidence to suggest this number may approach one million per year. The rise in spinal fusion procedures aligns with FDA approval of intervertebral fusion devices in 1996; when coupled with autograft or bony substitutes, these devices utilize the extensive surface area of the vertebral body endplate to enhance the fusion process.2In 2014, 48 billion dollars were charged by hospitals for spinal fusion surgery in the United States alone.3The spinal implant market was estimated to be around 12 billion dollar’s in 2022 and was expected to grow at a 5% annual rate over the next 5 year's.The U.S. spinal implant market was estimated to be 13.3 billion dollars in 2023 and is estimated to sustain a compound annual growth rate of 5.4% until 2030. Pseudoarthrosis, defined as a failure to achieve a bony fusion after surgery, has a reported incidence of 5 to 15% even with the use of modem operative techniques.4Although not all pseudarthroses are symptomatic, those that generate pain, disability, or neurologic compromise often require surgical intervention.

[0004] Over the last 10 to 20 years, a variety of minimally invasive approaches designed to maximize implant size, minimize surgical disruption of soft tissue, and promote arthrodesis have been developed including transforaminal, posterolateral, lateral, oblique lateral, and anterior approaches. Each approach has led to new types of implant, e.g., interbody, fusion devices. Regardless of the approach, the goal remains the same, achieve arthrodesis. This approach is particularly valuable when the intervertebral disc has degenerated, a condition that often becomes inevitable with aging.

[0005] The implant material has, like spine surgery itself, evolved with an understanding of the biomechanical principles of spinal stability and the molecular understanding of bony regrowth. The implant should have a Young’s modulus, or stress-to-strain ratio, which most closely resembles that of human bone.5Autologous bone grafts were utilized in early spine surgery, in which bone was harvested from a variety of sites in the patient's body and inserted onto decorticated surfaces of the posterior column, or into the implant space. However, this was quickly abandoned when high rates of donor site pain, prolonged healing, and pseudoarthrosis were observed.6Most spinal implants, e.g., interbody cages, today are comprised of polyetheretherketone (PEEK) or of titanium / titanium alloys, but a variety of other materials have been utilized including stainless steel, ceramic, silicon nitride, cobalt chrome, carbon fiber, nitinol, and tantalum.7

[0006] The materials in implant devices, e.g., interbody cages, are inherently biologically inert, which may lead to fibrotic encapsulation, loosening, and subsequent pseudoarthrosis. Improving biocompatibility is crucial for facilitating bone growth across the disc space and into the graft. The device itself is often packed with bone autograft, commercially available cadaveric allograft bone, or newer carrier substances often comprised of absorbable collagen sponges combined with recombinant human proteins that promote the differentiation of mesenchymal stem cells into boneforming cells. Local autograft has been reported to lead to pseudoarthrosis in up to 50% of cases.7'9Recombinant proteins that are utilized include rhBMP-2 (Bone Morphogenic Protein, Infuse,Medtronic), rhBMP-7 (Osteogenic Protein- 1 , Stryker Biotech), and Pl 5 (I-factor, Cerapedics)', rhBMP-7 is no longer marketed in the United States. P15 has been FDA-approved for use in the cervical spine, specifically during anterior cervical discectomy and fusion.10Further, rhBMP-2 is the most studied peptide and has been utilized for spine surgery worldwide. It is FDA-approved for use in single-level anterior approach interbody fusion from L2 to SI. However, it is used extensively “off-label” in the cervical, thoracic, and lumbar spine during a variety of surgeries to better achieve arthrodesis.11It is also FDA-approved for use in oral and maxillofacial reconstruction and for repair of long bone fractures. Given its significant cost (list price USD 5,569.00 for a 12.0 mg large dose, as of 2021), reimbursement by Medicare and insurers has become increasingly difficult. In certain practices, rhBMP-2 is used “off-label” in large deformity fusions involving many vertebrae, or in patients with risk factors predisposing them to pseudoarthrosis such as osteoporosis.

[0007] In addition to the use of functional peptides, the industry has developed an understanding that cage surface topography and microstructure are important for the recruitment of bone-forming cells and the subsequent ingrowth of new bone into the cage and across the disc space. An example is the commercially available, slowly resorbable biphasic calcium phosphate ceramic bone graph with needle-shaped surface topography (MagnetOs, Kuros Biosciences). This material enhances angiogenesis and osteogenesis while favorably modulating macrophage polarization to the M2 phenotype in the post-surgical inflammatory environment.12This product has been demonstrated to be effective in multicenter randomized controlled non-inferiority trials.13

[0008] Implant, e.g., cage, design itself has also changed over time. The most striking example of this principle is the development of 3D-printed porous titanium cages, which have become the predominant choice in thoracolumbar interbody implants offered by nearly all major spinal instrumentation companies. The surfaces of these implants may be roughened and created porous by blasting their surface with aluminum, silica, or biphasic calcium phosphate particles.15This allows for greater levels of bony ingrowth possibly via upregulation of BMP-2 signaling14, and there is evidence to suggest that these cages lead to lower rates of pseudoarthrosis.16 17There has been a majority adoption of 3D-printed porous titanium cages for a wide range of thoracolumbar spinal fusion approaches. As the focus shifts toward minimally invasive spine surgery, surgeons must effectively leverage the biomechanical and biological properties of their implants.

[0009] Early attempts to functionalize titanium implant surfaces often used self-assembled monolayers (SAMs) of silane molecules, which were then modified with bioactivc peptides.18'20Phosphonic acid molecules were introduced for SAM formation on titanium surfaces, providing greater hydrolytic stability under physiological conditions. Additionally, phosphonic acid SAMs require no pre-coating acid treatment or surface conditioning to achieve high surface coverage, in contrast to silane SAMs. These properties are well suited for the coating of medical devices.21

[0010] The use of fixated Bone Morphogenic Proteins (BMP) on the surface of titanium implants is not new. Over the last two decades, much of the work investigating the feasibility and efficacy of BMP coated titanium has been done in the oral and maxillofacial literature. Within this field, research has been focused on coating titanium screws that are utilized in reconstructive procedures; preliminary studies have shown that these coatings enhance bone-implant contact and promote peri-implant bone formation around the titanium implants.22A compelling demonstration of the efficacy of rhBMP-2-coated titanium devices included a method for coating small craniofacial titanium screws with muscle-derived adhesive peptide, rhBMP-2, and Zn2+ions.23The rhBMP-2- conjugated surfaces resulted in increased viability of surface adherent stem cells, increased cell spreading and expression of filamentous cytoskeletal proteins, and increased cell proliferation during a four-day incubation period. Further, the coated devices upregulate expression and increase activity of osteogenic -related proteins such as alkaline phosphatase (ALP) and osteopontin (OPN) at day 14 of in vitro culture with bone marrow mesenchymal stem cells. These cell cultures showed significant increases in Alizarin Red staining for calcium-binding proteins in the cell matrices and ALP staining, as well as increases in osteogenesis-related gene expression, specifically ALP, type 1 collagen, and runt-related transcription factor 2. The findings were extended to in vivo implantation of titanium dental screws, which then demonstrated lower levels of fibrous tissue deposition, inflammatory cell migration, and Ml subtype macrophage polarization. Immunohistochemical evaluation of the bony tissue surrounding the coated implants showed increased levels of anti-inflammatory cytokine IL- 10. The implants were evaluated for cytotoxicity by implantation into the animal heart, liver, spleen, lung, and kidney, with no signs of cytotoxicity observed. Also assessed were calcium deposition and bone ingrowth using quantitative micro-CT imaging, which revealed increased bone ingrowth into the screw threads. Coated implants also demonstrated greater pull-out strength. Collectively, these findings providecompelling evidence that fixed rhBMP-2 interacts with surrounding mesenchymal stem cells in the pcri-implant microenvironment, effectively enhancing arthrodesis and promoting bone growth.

[0011] There is currently no commercially available implant device that combines the osteogenic properties of biological peptide additives with the biomechanical and structural advantages of 3D- printed porous titanium. Such a device could optimize osseous integration at the bone-device interface, potentially reducing rates of graft pseudoarthrosis, implant failure, and subsequent reoperation. With the increasing focus on minimally invasive surgery, the extensive bony decortication and the use of large quantities of allograft, autograft and peptide carriers commonplace in open surgery may not be feasible.

[0012] Accordingly, there is a need in the art to design, develop, fabricate, and implement a metal or metal alloy implant device, such as but not limited to a metal spinal implant, e.g., interbody implant, having a metal oxide surface, a modification applied to said surface, such as binding of a copolymer, to form a modified surface, and a bioactive peptide additive bound to the modified surface, wherein presence of the bioactive peptide facilitates and improves osseous implant integration, promotes segmental arthrodesis and bone growth at the site of surgery.SUMMARY OF THE INVENTION

[0013] In one aspect, the disclosed concept provides a medical implant device including an implant structure formed of a metal or metal alloy, including a nanoscale metal oxide surface; a copolymer bonded to the metal oxide surface to form a modified surface; and a bioactive peptide additive bonded to the modified surface, wherein presence of the bioactive peptide facilitates, and improves osseous implant integration and promotes segmental arthrodesis.

[0014] In certain embodiments, the implant structure is formed by 3D-printing.

[0015] In certain embodiments, the implant structure is formed of titanium or titanium alloy.

[0016] In certain embodiments, the implant structure includes a plurality of pores.

[0017] In certain embodiments, the metal oxide surface includes titanium oxide.

[0018] In certain embodiments, the copolymer comprises vinylphosphonic acid-acrylic acid copolymer.

[0019] In certain embodiments, the copolymer is in the form of a coating or a layer.

[0020] In certain embodiments, the bioactive peptide additive is selected from the group consisting of functional protein rhBMP-2, vascular endothelial growth factor, rhBMP-7, P15, adenosine monophosphate, activated protein kinase, and combinations thereof.

[0021] In certain embodiments, the implant device further includes one or more of an immunomodulatory peptide, molecule, and element.

[0022] In certain embodiments, the implant device further includes an antimicrobial agent attached to a functionalization site of the copolymer to form a functionalized device.

[0023] In certain embodiments, the functionalized device is pedicle screws, iliac bolt, lateral mass screws, cortical screw, laminar wire, intra-facet spacer, anchoring screw, screw head, rod attachment point, titanium rods used to connect pedicle screws, and combinations thereof.

[0024] In certain embodiments, the medical implant device is selected from spine implant devices, orthopedics implant devices, oral reconstruction implant devices, cranial plating systems, and maxillofacial reconstruction implant devices.

[0025] In certain embodiments, the implant device includes an implant designed for anterior, lateral, and posterior surgical approaches to the spine.

[0026] Further, in certain embodiments, the implant device includes an interbody device.

[0027] In certain embodiments, the interbody device includes a porous cage structure mimicking that or cancellous bone.

[0028] In another aspect, the disclosed concept provides a method of preparing a medical device. The method includes forming an implant structure including a metal or metal alloy surface; oxidizing the surface of the implant structure to form a metal oxide surface; binding a copolymer to the metal oxide surface to form a modified surface; and covalently binding a bioactive peptide additive to the modified surface, wherein the bioactive peptide additive is effective for facilitating and improving osseous implant integration, promoting segmental arthrodesis, and promoting bone growth.

[0029] In certain embodiments, the binding of the copolymer includes applying a coating or layer to the metal oxide surface.

[0030] In certain embodiments, the bioactive peptide includes one or more of a functional protein rhBMP-2, a vascular endothelial growth factor, rhBMP-7, an adenosine monophosphate, an activated protein kinase, or combinations thereof.

[0031] In certain embodiments, the method further includes attaching an antimicrobial agent to a functionalization site of the copolymer.

[0032] In certain embodiments, forming the implant structure includes forming a porous cage structure.

[0033] In certain embodiments, the coating is applied by a dip coating technique.BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG. 1 is a plot illustration that shows the NMR spectra of the synthesized PVPA-30 polymer (VPA-AA copolymer), in accordance with certain embodiments of the inventive concept.

[0035] FIG. 2 shows x-ray photo electron spectra (XPS) plot illustrations for Cis, P2p and Ti2p signals of a blank Ti-disc, a PVPA-30 coated Ti-disc baked at 150°C and coated disc-exposed to water for 24 days demonstrating stability of the coating, in accordance with certain embodiments of the inventive concept.

[0036] FIG. 3 is a plot illustration that shows the percentage of P (%P) and Ti (%Ti) on a composition surface calculated from XPS survey spectra for samples exposed to water or PBS buffer over time, in accordance with certain embodiments of the inventive concept.

[0037] FIG. 4 is an XPS that shows the stability of a coating (lack of a titanium peak at 458 EV) after sterilization with ethylene oxide, in accordance with certain embodiments of the inventive concept.

[0038] FIG. 5 is a plot illustration that shows the FTIR signals of titanium (Ti) discs under three different conditions: Ti-PVPA30 -oven baked with and coated with PVPA-30, EDC NHS Activated Surface -Ti PVPA-30 coated surface and activated surface bound with rhBMP-2, and BMP-2 Conjugated Surface; FTIR signal at 1721 cm-1 corresponds to C=O stretching in carboxylic acid group present on PVPA-30 coated surface; a shift from that to 1741 cm-1 and generation of two neighboring signals at 1820 cm-1 and 1780 cm-1 indicates EDC activation; FTIR signal for BMP-2 immobilized surface arises at 1653 and 1579 cm-1 which are corresponded to C=O stretching in peptide bond (amide I) and N-H bending in peptide bond (amide II) suggests successful protein conjugation, in accordance with certain embodiments of the inventive concept.

[0039] FIGS. 6A-6D show XPS high resolution spectra of C 1 s, N 1 s, and P2p signals acquired at a pass energy of 55cV for 15 min; in FIG. 6A, a peak at 288.55 eV in Cis spectrum corresponds to the presence of carboxylic acid groups (-O-*C=O) on the surface; In FIG. 6B, disappearance of this peak, along with the appearance of new peaks at 287.74 eV and 285.79 eV, indicates the formation of amide bond (-N-*C=O) and C-N bonds, respectively, thereby confirming covalent protein coupling; similarly, as shown in FIGS. 6C, 6D a sharp Nls signal is observed at 399.74 eV in the BMP-2 coated surface (FIG. 6d), corresponding to amide bond nitrogen (-*N-C=O); this signal is absent in the untreated polymer coated Ti disc (FIG. 6C) further validating the successful protein coupling, in accordance with certain embodiments of the inventive concept.DETAILED DESCRIPTION

[0040] According to the disclosed concept, a nanoscale molecular coating covalently bonds a bioactive protein directly to the surface of a metallic medical implant device, which allows the implant device itself (e.g., interbody graft, rod, or pedicle screw) to directly interact with the external milieu of osteoblast precursors / stem cells precisely at the site where bony fusion is intended to occur.

[0041] In the disclosed concept, the medical implant device, e.g., an interbody device, for placement in a human body, is formed of an implant structure made of a metal or metal alloy. The surface of the implant structure is oxidized to form a metal oxide surface, a modification is applied that includes binding a co-polymer to the metal oxide surface to form a modified surface and then binding a bioactive peptide additive to the modified surface, which facilitates and improves osseous implant integration and promotes segmental arthrodesis. Generally, surgical osseous fusion of the spine is a method of treating a variety of pathologic conditions, including but not limited to degenerative disease, trauma, deformity, cancer, and infection.

[0042] Suitable metals or metal alloys for the implant structure include titanium or titanium alloy. Additional metal, metal alloys, or non-metals that could allow for coating include stainless steel, ceramic, silicon nitride, cobalt chrome, carbon fiber, nitinol, and tantalum.

[0043] Suitable oxidation processes to form the metal oxide surface on the implant structure include those well known in the art. In certain embodiments, atomic layer deposition techniques are used to coat the metal or metal alloy implant structure with a nanoscale metal oxide.

[0044] In certain embodiments, wherein the implant structure is formed of titanium or titanium alloy, the surface is treated to form a titanium oxide surface. A modification, is then applied to the titanium oxide surface by covalently binding a co-polymer such as vinylphosphonic acidacrylic acid copolymer, this copolymer may be activated, for example with 400 mM N-(3- dimethylaminopropyl)-N '-ethylcarbodiimide hydrochloride (EDOHC1) and 400 mM NHydroxysuccinimide (NHS) in MES buffer, followed by covalently binding the bioactive peptide additive such as rhBMP-2 to the modified surface.

[0045] In certain embodiments, an atomic layer deposition technique is used to coat the implant structure with a nanoscale metal oxide, allowing for the attachment of organic coupling molecules to the coated surface.

[0046] The co-polymer that binds to the metal oxide surface is selected from a wide variety of suitable materials known in the art, including but not limited to poly-phosphonic acids, polycarboxylates, poly-sulfonates, and poly(catechol). In certain embodiments, vinyl phosphoric acid-acrylic acid copolymer is covalently bound to the metal oxide surface.

[0047] In certain embodiments, the co-polymer surface modification is in the form of a coating or layer applied to the metal oxide surface to modify or coat the surface.

[0048] The bioactive peptide additive that binds to the modified surface is selected from a wide variety of suitable materials known in the art, including but not limited to, protein rhBMP-2, vascular endothelial growth factor (VEGF), rhBMP-7, adenosine monophosphate, activated protein kinase, or other immunomodulatory cytokines and cell signaling molecules and proteins.

[0049] In certain embodiments, rhBMP-2 covalently binds via its amine groups to vinyl phosphoric acid-acrylic acid copolymer, utilizing the carboxyl functional groups of the copolymer through carbodiimide chemistry. As a result, the rhBMP-2 is effectively fixated to the surface of the medical device to facilitate osseous implant integration and promote segmental arthrodesis through ligand-mediated stimulation of bone marrow derived mesenchymal stem cells.

[0050] In certain embodiments, the functionalization site inherent to the copolymer can be utilized to attach antimicrobial agents, which can enhance resistance to bacterial colonization that leads to infection. Additionally, these substances can be combined in different coating densities, peptide concentrations, combinations and formulations to customize the properties specific to the implant device.

[0051] In certain embodiments, the medical implanted functionalized device is a three- dimensional (3-D) implant structure prepared using 3D printing processes and devices known in the art.

[0052] In certain embodiments, the medical implant device is a porous structure including multiple or a plurality of pores formed using processes or procedures known in the art.

[0053] The metallic medical implant device includes a wide variety of medical devices and structures. Non-limiting examples include implants, e.g., interbody implants, designed for anterior, lateral, and posterior approaches to all areas of the spine, such as, but not limited to, pedicle-screws, lateral mass screws, and anchoring screws. In certain embodiments, the copolymer surface modification, e.g., coating, is also applied to or deposited on metal (e.g., titanium) pedicle screws, lateral mass screws, anchoring screws for anterior cervical discectomy and fusion procedures, and the endplate opposing surfaces of cervical and lumbar artificial disc replacement devices, sub laminar wires, intra-facet spacers to promote osseous integration. The screw heads, rod attachment points, and titanium rods used to connect pedicle screws, typically viewed merely as mechanical linkages, are regarded as critical interfaces for bone-implant interaction when modified or coated according to the inventive concept. Indeed, in most thoracolumbar fusions these areas are often heavy decorticated and packed densely with autograft, allograft, and other osteogenic additives.

[0054] The primary instrumentation used to achieve surgical bony fusion, or arthrodesis, across a vertebral level in the thoracolumbar spine are pedicle screws and rods with or without an interbody fusion device. Additionally, interbody fusion devices are almost exclusively used in the cervical spine to achieve bony fusion through an anterior approach, often with titanium plates and screws.

[0055] In certain embodiments, the metal or metal alloy implant structure according to the inventive concept is an interbody device, e.g., cage device, that is inserted into an intervertebral disc space to restore the height of the disc space and therefore indirectly open the paired neuroforamen, a common point of pathologic nerve compression.

[0056] The inventive concept is not limited to spine surgery and is applicable to modify or coat metal (e.g., titanium or titanium alloy) devices used in orthopedics, oral and maxillofacial reconstruction, or other fields where the attachment of bioactive peptides to the surface of metal(e.g., titanium or titanium alloy) implants provides a benefit, such as but not limited to, tissue and / or bone growth.

[0057] In certain embodiments of the inventive concept, the metal or metal alloy implant structure is coated with a nanoscale metal oxide that allows for the attachment of organic coupling molecules to the coated surface. The organic coupling molecules are synthesized using a conventional synthesis method including but not limited to, free radical polymerization, and bonded to the nanoscale metal oxide using a conventional coating technique including but not limited to, a dip-coating technique. Optionally, the coupling molecules are covalently bonded directly to the metal device surface. A protein with osteoinductive properties is then covalently bonded to an attached organic linker molecule to create a bioactive medical implant device.

[0058] The inventive concept is applicable to all implant structures, e.g., interbody devices, orthopedic devices which aim to achieve bony fusion and promote bony healing. For example, the inventive concept is applicable to SI fusion devices, Kyphoplasty devices, and disc replacement devices. Furthermore, the inventive concept is applicable to orthopedic, cranial, and maxillofacial hardware for example, cranial and facial plating systems, intramedullary nails and bony fixation devices, joint replacement devices, and dental implants. In addition, the inventive concept provides an ability to deliver osteoinductive implants without autograft harvest and allograft deposition.

[0059] In certain embodiments, a coated spinal implant device includes a covalently bonded peptide capable of directly interacting with the osteogenic precursors at the site of a graft or hardware insertion and inducing a bony fusion.

[0060] In certain embodiments, the inventive concept includes implant devices, such as existing titanium or titanium alloy implants, having a nanoscale titanium oxide surface, e.g., applied by atomic layer deposition techniques, and a copolymer surface modification, e.g., covalent binding of vinylphosphonic acid-acrylic acid (VPA-AA) to the titanium oxide surface, and covalent binding of a bioactive peptide additive to the copolymer modified surface. In certain embodiments, the copolymer surface modification is in the form of a coating. Without intending to be bound by any particular theory, it is believed that the content of vinyl-phosphonic acid (VPA) in VPA-acrylic acid (AA) copolymer plays a role in determining stability of the copolymer. Specifically, increasing the VPA content enhances the degree of dissociation, whileCa2+chelation affinity reaches a maximum at 30% VPA content which is important for bone growth.

[0061] The inventive concept also includes 3D printing and surface modification (e.g., coating) techniques and methods for preparation of the medical implant devices, as well as techniques and methods for implanting the device to provide bony ingrowth and fusion to a human body. In certain embodiments, for use in spine surgery, the surface modification (e.g., coating) techniques and methods are useful for modifying or coating titanium or titanium alloy implant devices designed for anterior, lateral, and posterior approaches to all areas of the spine.

[0062] In addition, the inventive concept optionally includes an immunomodulatory component for optimal osseous integration of the devices by reducing detrimental proinflammatory signaling cascades. In certain embodiments, the functionalization site inherent to the copolymer is utilized to attach antimicrobial agents, having the capability to enhance resistance to bacterial colonization that leads to infection. Furthermore, these substances are combinable in different concentrations and formulations to customize the properties specific to the implants including both antimicrobial and osteogenic properties.

[0063] The inventive concept is applicable to a variety of metal or metal alloy implant, e.g., interbody, devices. In certain embodiments, when used in spine surgery, these coated devices will be implantable from all commonly used approaches to the spine including but not limited to anterior approaches for cervical discectomy and fusion in a minimally invasive, endoscopic, and traditional open fashion posterior approaches and trans oral approaches to the cervical spine, posterior, posterior lateral, lateral extra cavitary, endoscopic, and trans thoracic anterior approaches to the thoracic spine, and endoscopic, anterior, lateral, posterolateral and posterior approaches to the lumbar spine and sacrum.EXAMPLES

[0064] The following experiments were conducted to assess the osteogenic potential of VPA-AA coated and BMP-2 functionalized titanium implants in vitro.Device Coating and AnalysisSynthesis and Characterization of VPA-AA Copolymer Coatings

[0065] It has been demonstrated that the content of vinyl-phosphonic acid (VPA) in VPA-(acrylic acid) AA copolymer plays a critical role in determining stability of the copolymer. Specifically, increasing the VPA content enhanced the degree of dissociation, while Ca2+chelation affinity reached a maximum at 30% VPA content which is important for bone growth. Based on these findings, VPA-AA copolymer with 30 mol% VPA content was synthesized, referred as PVPA-30 hereinafter. There was used 2,2’-azobis(2-methylpropionamidine) dihydrochloride (AAPH) as the initiator of the polymerization and 1 -octanethiol as the chain transfer reagent to control the molar mass of the polymer.

[0066] PVPA-30 was synthesized via free radical polymerization mechanism, following a previously reported method as follows.34VPA (2 g, 18.5 mmol) was dissolved in deionized water (3 ml) and added to a three-neck round bottom flask equipped with a reflux condenser and a Schlenk tube. The system was purged with nitrogen gas prior to initiating polymerization. The solution was heated at 90° C for 30 minutes. AA (3.11 g, 43.2 mmol in 3 mL of water), AAPH (12.9 mg, 0.048 mmol in 3 mL water), and 1 -octanethiol (13.9 mg, 0.010 mmol in 2 mL water) solutions were added to the reaction flask in equal portions every 30 minutes over a period of 6 hours. Following the final addition, the reaction mixture was stirred for an additional 18 hours at 90° C. The resulting polymer solution was purified by dialysis using cellulose tubing (500 mL of water, change water 10 times) with molecular weight cutoff 12000-14000 g / mol for 48 hours. The purified polymer was then dried under vacuum at 60° C yielding 1.37 g of a white solid. The product was characterized by nuclear magnetic resonance (NMR) spectroscopy dissolving in deuterated water (D2O) at 500MHz. DOSY was performed to measure diffusion coefficient and approximate molecular weight. Gel-permeation chromatography (GPC) was performed to measure the molecular weight distribution of the synthesized PVPA-30 copolymer.

[0067] The synthesized PVPA-30 copolymer was applied to a 5 mm x 5 mm Ti disc surface using a dip-coating technique. The Ti disc was withdrawn at a rate of 30 mm / min from a polymer solution of 30 mg / mL. The coated sample was subsequently baked at 150° C for an hour to ensure stable attachment of VPA segments to the Ti surface.

[0068] To assess long-term stability under physiological conditions, coated Ti discs were soaked in deionized water and phosphate-buffered saline (PBS, pH 7.4) for 16 and 18 days respectively.Surface composition of the coated Ti discs was characterized by XPS before and after the soaking. In addition, the chemical stability of the coating after sterilization was evaluated by subjecting the PVPA-30 coated Ti plates to ethylene oxide (EO) treatment and analyzing the surface composition via XPS. Presence of phosphorus and titanium on the surface was determined by %P and %Ti respectively calculated from survey spectra collected at 100x100 pm2scanned area over 30 mins scanning time using pass energy 180 eV.Conjugation of BMP-2 to VPA-AA Copolymer

[0069] Conjugation of recombinant human BMP-2 protein (hBMP-2) was conducted via carbodiimide chemistry on PVPA-30 polymer coated titanium discs. Oven baked polymer coated discs were treated with the mixture of 400 mM N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC*HC1) and 400 mM NHydroxysuccinimide (NHS) in MES buffer at pH 4.5 for 15 - 20 mins to activate the acidic surface. Activated surfaces were thoroughly washed three times (1 mL each) with MES buffer at pH 4.5 and two times (1 mL each) with PBS buffer at pH 7.4 followed by nitrogen dry. For immobilization of the protein to the surface, activated Ti-discs were exposed to hBMP-2 in MES buffer (lOpg / ml) at pH 4.5 for overnight at ambient temperature without stirring. Successful conjugations were confirmed by performing FTIR and XPS on the conjugated surface.ResultsVPA-AA Synthesis and Coating

[0070] NMR spectroscopy of the synthesized PVPA-30 polymer confirmed the successful synthesis of the VPA-AA copolymer (FIG. 1). The titanium plate was dip-coated with the polymer solution and baked at 150° C. To assess the stability of the polymer upon prolonged exposure to water, high resolution XPS analysis was performed by monitoring the P2p and Ti2p signals at 132.8 eV and 458.4 eV, using a blank uncoated titanium disc as a reference (FIG. 2). XPS survey spectra demonstrated the stability of the coating, evidenced by the absence of the Ti2p peak at 459 eV and the presence of a distinct P2p peak at 133 eV. The atomic percentages of phosphorus (%P) and titanium (%Ti) were calculated for samples exposed to water and PBS (pH 7.4), respectively (FIG. 3). Furthermore, the chemical composition of the polymer-coated surface afterETO sterilization was also confirmed via XPS survey spectra collected maintaining exactly same scanned area and pass energy specification as described above. (FIG. 4).Binding of rhBMP-2 to VPA-AA Coated and Activated Titanium

[0071] FIG. 5 shows the FTIR signals of Ti-discs at three different conditions; oven baked coated with PVPA-30, EDC-NHS activated surface and immobilized with BMP-2 protein. FTIR signal at 1721 cm-1 corresponds to C=O stretching in carboxylic acid group present on PVPA-30 coated surface. A shift from that to 1741 cm-1 and generation of two neighboring signals at 1820 cm-1 and 1780 cm-1 indicates EDC activation. FTIR signal for BMP-2 immobilized surface arises at 1653 and 1579 cm-1 which are corresponded to C=O stretching in peptide bond (amide I) and N- H bending in peptide bond (amide II) suggesting successful protein conjugation.

[0072] To further investigate the covalent bond formation between protein and the surface, XPS study was performed. Survey spectra were collected at 100 A~ 100 pm2area for 30 mins using 140 eV pass energy. The overall nitrogen content of the protein conjugated surface increased from 0% (in the blank polymer coated disc) to 5%. High resolution spectra of Cis, Nls and P2p signals were acquired at a pass energy of 55 eV for 15 mins. As shown in FIG. 6A, a peak at 288.55 eV in Cis spectrum corresponds to the presence of carboxylic acid groups (-O-*C=O) on the surface. In FIG. 6B, disappearance of this peak, along with the appearance of new peaks at 287.74 eV and 285.79 eV, indicates the formation of amide bond (-N-*C=O) and C-N bonds, respectively, thereby confirming covalent protein coupling. Similarly, as shown in FIG. 6C, 6D a sharp Nls signal is observed at 399.74 eV in the BMP-2 coated surface (FIG. 6D), corresponding to amide bond nitrogen (-*N-C=O). 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Claims

We claim:

1. A medical implant device, comprising: an implant structure formed of a metal or metal alloy, comprising: a nanoscale metal oxide surface; a copolymer bonded to the metal oxide surface to form a modified surface; and a bioactive peptide additive bonded to the modified surface, wherein a presence of the bioactive peptide facilitates and improves osseous integration of the implant device and promotes segmental arthrodesis.

2. The implant device of claim 1, wherein the implant structure is formed by 3D-printing.

3. The implant device of claim 1, wherein the implant structure is formed of titanium or titanium alloy.

4. The implant device of claim 1, wherein the implant structure comprises a plurality of pores.

5. The implant device of claim 1, wherein the metal oxide surface comprises titanium oxide.

6. The implant device of claim 1, wherein the copolymer comprises vinylpho sphonic acidacrylic acid copolymer.

7. The implant device of claim 1, wherein the copolymer is in the form of a coating or a layer.

8. The implant device of claim 1, wherein the bioactive peptide additive is selected from the group consisting of functional protein rhBMP-2, vascular endothelial growth factor, rhBMP-7, P15, adenosine monophosphate, activated protein kinase, and combinations thereof.

9. The implant device of claim 1 , further comprising one or more of an immunomodulatory peptide, molecule, and clement.

10. The implant device of claim 1, further comprising an antimicrobial agent attached to a functionalization site of the copolymer.

11. The implant device of claim 1, wherein the device is selected from pedicle screws, iliac bolt, lateral mass screws, cortical screw, laminar wire, intra-facet spacer, anchoring screw, and screw head, rod attachment point, and titanium rods used to connect pedicle screws, and combinations thereof.

12. The implant device of claim 1, wherein the device is selected from spine implant devices, orthopedics implant devices, oral reconstruction implant devices, cranial plating systems, and maxillofacial reconstruction implant devices.

13. The implant device of claim 1, wherein the interbody device is designed for one or more of an anterior, a lateral, or a posterior surgical approach to the spine.

14. The implant device of claim 1, wherein the interbody device comprises a porous cage structure mimicking that or cancellous bone.

15. A method of preparing a medical implant device, comprising: forming an implant structure comprising a metal or metal alloy surface; oxidizing the surface of the implant structure to form a metal oxide surface; binding a copolymer to the metal oxide surface to form a modified surface; and covalently binding a bioactive peptide additive to the modified surface, wherein the bioactive peptide additive is effective for facilitating and improving osseous integration of the implant device, promoting segmental arthrodesis, and promoting bone growth.

16. The method of claim 15, wherein binding of the copolymer comprises applying a coating or a layer to the metal oxide surface.

17. The method of claim 15, wherein the bioactive peptide comprises one or more of a functional protein rhBMP-2, vascular endothelial growth factor, rhBMP-7, adenosine monophosphate, activated protein kinase, or combinations thereof.

18. The method of claim 15, further comprising attaching an antimicrobial agent to a functionalization site of the copolymer.

19. The method of claim 15, wherein forming the implant structure comprises forming a porous cage structure.

20. The method of claim 16, wherein the coating is applied by a dip coating technique.

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