| In response to the problem of bone implantation failure due to poor osseointegration and bacterial infection,the surface and interface properties of the materials are adjusted by immobilizing proteins or other biologically active molecules,thereby improving the biocompatibility of bone implant materials and promoting the osteoblast differentiation,and at the same time solve the problem of high risk of bacterial infection.Poly(aryl ether ketone)(PAEK)is a kind of thermoplastic engineering plastic with great application potential in the medical field due to its good mechanical properties and thermal stability.However,the biological inertness of PAEK limits its use in the field of bone implant materials.Poly(phthalazinone ether nitrile ketone)(PPENK)is a high-performance PAEK engineering plastic.It has mechanical properties that match bones,thermal stability and radiation resistance,and has great application potential in the field of bone implant materials.At the same time,the cyano group with higher reactivity contained in the side chain of PPENK provides more options for its surface chemical modification.Therefore,this article uses surface modification methods to introduce human recombinant bone morphogenetic protein-2(rh BMP-2)and bioactive molecules with antibacterial properties on the surface of PPENK materials to endow the materials with osteogenic and antibacterial properties and solve the problems of poor integrations and antibacterial properties.The main work of this paper is as follows:Firstly,by covalent immobilization and electrostatic adsorption of heparin,rh BMP-2 was introduced on the surface of PPENK material,and endowed the material bone formation properties.The optimal reaction conditions for PPENK hydrolysis were obtained through orthogonal experiments,and the cyano groups on the surface of PPENK were hydrolyzed and modified according to the optimal reaction conditions.X-ray photoelectron spectroscopy(XPS)and enzyme-linked immunohistochemical staining were used to prove that rh BMP-2 was successfully immobilized on the surface of PPENK material.The rh BMP-2 with covalent immobilization was more evenly distributed and had higher immobilized efficiency.In vitro cell compatibility and osteogenic activity were evaluated,the results of the study showed that the introduction of rh BMP-2 promoted the adhesion,proliferation and differentiation,especially the introduction of rh BMP-2 through electrostatic adsorption,the osteogenic differentiation effect was better than covalent immobilization.Secondly,in view of the problem of bacterial infection that may be caused by material implantation,electrostatic adsorption of heparin was used on the surface of PPENK material,and gentamicin and rh BMP-2 were immobilized to prepare drug-loaded coating,which could deliver bioactive molecules around the implant and endow antibacterial and osteogenic properties for materials.Using ethylenediamine andα,ω-diaminopolyethylene glycol as linking agents,respectively,heparin was grafted onto the surface of PPENK,and gentamicin and rh BMP-2 were successively introduced on the surface of PPENK by using the electrostatic adsorption of heparin.and the surface modification of PPENK was successfully carried out.Two kinds of drug-loaded coatings were prepared using PPENK as the carrier to improve the antibacterial and osteogenic properties of the material.XPS,enzyme-linked immunohistochemical staining and quartz crystal microbalance(QCM-D)were used to prove that gentamicin and rh BMP-2 were successfully immobilized to the surface of PPENK material.The effects of the linker ethylenediamine andα,ω-diaminopolyethylene glycol on the release efficiency of gentamicin and rh BMP-2 were compared.The results showed that polyethylene glycol slowed down the release of gentamicin and rh BMP-2.The antibacterial test results showed that gentamicin loading endowed the material with antibacterial properties,and the antibacterial rate was more than 85%.At the same time,polyethylene glycol structure reduced the adhesion of bacteria on the material surface.The cytocompatibility and osteogenic activity were evaluated.The results showed that the loading and release of rh BMP-2 promoted cell proliferation and differentiation on the surface of PPENK material.The introduction of bioactive molecules by electrostatic adsorption can retain the original structure of bioactive molecules and maximize their bioactivity.But there are still some problems in electrostatic adsorption,such as explosion and release.Furthermore,to overcome the overuse of antibiotics such as gentamycin may produce bacterial drug resistance,as well as the possible outbreak of drug release physical adsorption and problems such as side effects and action time short,design and synthesis of cationic antimicrobial peptides,instead of using antibiotics,and use surface click chemistry method to immobilize to PPENK material surface,PPENK material is endowed with antibacterial properties.Three kinds of cationic antibacterial peptides with different structures were synthesized by ring-opening polymerization of amino acid intracyclic anhydride initiated by primary amine,and then chemically immobilized on the surface of PPENK.The structure of the cationic polypeptide was characterized by ~1H NMR and the structure was consistent with that of the design.The characterization data of XPS,QCM-D and Zeta potential proved that the cationic antibacterial polypeptide was successfully immobilized on the surface of PPENK material.Focus on exploring the different structure of the surface grafting cationic antimicrobial peptides influence on antibacterial properties,antibacterial test results show that the surface of PPENK cationic antimicrobial peptides are introduced to improve the antibacterial properties of PPENK material,antibacterial rate can reach more than 95%,polyethylene glycol structure at the same time reduces the dead bacteria on the surface of the material,adhesive,So that the material has a certain antifouling performance,cationic antibacterial polypeptide because of its unique antibacterial mechanism,so that it has a broad spectrum of antibacterial performance.The results of cytocompatibility test showed that PPENK containing cationic antibacterial peptides had no cytotoxicity and had good biocompatibility,which was expected to be applied in antibacterial studies of implants.Finally,rh BMP-2 and cationic antibacterial peptides were immobilized to the surface of PPENK material by chemical bonding to endow PPENK material long-term osteogenic and antibacterial properties.Atomic force microscopy(AFM),XPS and QCM-D data showed that rh BMP-2 and cationic antibacterial peptides were covalently immobilized to the surface of PPENK.The effect of the introduction of rh BMP-2 on the antibacterial performance of covalently immobilized cationic antibacterial polypeptide was investigated.The antibacterial test results showed that covalently immobilized of rh BMP-2 on the surface of PPENK did not affect the antibacterial performance of the material,and the antibacterial rate remained above95%.In vitro cell test results showed that the introduction of rh BMP-2 and cationic antibacterial peptides promoted cell adhesion,proliferation and differentiation on the surface of PPENK materials,especially the introduction of cationic antibacterial peptides containing polyethylene glycol structure did not affect the cytocompatibility of PPENK materials,and promoted the differentiation of osteoblasts to some extent.Using rabbit femoral defect model research on surface modification of PPENK implants in vivo bone induction activity,in vivo implantation test results show that the surface after rh BMP-2 and cationic antimicrobial peptide modified PPENK implants in the body can effectively improve the ability of bone integration,and has antibacterial properties,can also promote the formation of blood vessels around,the binding force between the implant and the surrounding tissue is also significantly improved. |
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