The Surface Construction And Biological Property Study Of Antimicrobial-osteogenic Multi-functional Titanium Implants Based On Fusion Peptides

Among the orthopedic implants,titanium and its alloys have become the most widely used orthopedic implants due to their high biocompatibility,mechanical properties and great corrosion resistance.However,in clinical applications,titanium-based implants often face the problems such as bacterial infection and slow processing of bone integration,which will lead to the loosening and failure of implanting,and seriously threatens the health and life of patients.In order to meet the multiple clinical demands of antibacterial activity and osseointegration,and the contradiction between the two functions,this paper intended to use fusion peptide technology to linearly fuse antimicrobial peptide(AMP)HHC36 and bone forming peptide(BFP1),and to multiple-functionalize the titanium implants.The AMP sequence could be exposed by the chain rotation and other activities.The spacer molecule polyethylene glycols with different lengths were added between the two sequences,to systematically study influence of the length of spacer to the functions of fusion peptides.First,the chemical grafting method on the titanium surface was studied.A layer of titanium-hydroxyl was formed by acid etching,and through its reaction with thiol in the peptides,the fusion peptides could be grafted onto the titanium surface,and this reaction was fast and highly-efficient,and has been saturated in 4 hours.Second,the biological performances in vitro of functionalized implant surfaces were studied.The titanium surfaces engineered by fusion peptides have killed more than 90% of the common bacteria,and have effectively inhibited the formation of biofilm.Meanwhile,the differences of the antimicrobial activity of fusion peptides were studied by the molecular dynamics simulation technique,the relationship of the bacteria accessible surface area(BASA)and antimicrobial activity was revealed.Besides,the BFP1 sequence in the fusion peptides has promoted the adhesion and proliferation of human mesenchymal stem cells(h BMSCs),and has increased the osteogenic differentiation.Further study has shown that the functionalized surfaces have promoted macrophages RAW264.7 polarization towards M2,which was beneficial for the tissue repair.In the last,the in situ bone defect and in situ bone defect-infection in vivo models were performed on New Zealand rabbits to study the bioadaptability of implants functionalized by fusion peptides.The results have shown that the functionalized implants could resist the bacterial infection in vivo,which have killed more than 95% of bacteria,and have reduced the infiltration of inflammation cells.Meanwhile,they have induced the new bone formation around the implants,effectively reduced the fibrosis formation between the interface,and the osseointegration ability has been tripled.In summary,the functionalized titanium implants constructed by fusion peptides in this paper,have resisted the bacterial infection,at the same time have promoted the osseointegration and increased the bioadaptability.The relative research could provide strategies to solve the problems of bacterial infection and implant loosening caused by the biological inertia in the clinical use of titanium implants.