Synthesis Of Hydroxyapatite Nanomaterials Based On Biomineralization And Study On The Antibacterial Effect Of The Materials

Among various nano materials,hydroxyapatite(HAP)has good biocompatibility and bone conductivity.It’s composition is also similar to that of the natural bone.Nano materials based on HAP can be used as bone materials in the field of bone tissue engineering.However,HAP itself does not have antibacterial function,which is not helpful for fighting bacterial infection after surgery.Antibiotics are,therefore,usually used to prevent bacterial infection in orthopedic surgery.However,the large usage of antibiotics easily results in bacterial resistance.Antimicrobial peptide(AMP)has broad-spectrum antibacterial properties,good thermal stability,and is not easy to induce bacterial drug resistance.It is a new antibacterial agent to improve the antibacterial ability of HAP materials.Therefore,this thesis aims to explore the physical and chemical properties of nano-HAP doped with AMP,and their antibacterial properties,so as to develop nano-HAP materials with antibacterial properties.In this study,HAP coating was synthesized based on biomineralization,and different peptides were modified on its surface to induce mineralization.Thus,HAP nano-composite materials with similar structure to the natural bone,controllable physical properties,broadspectrum antibacterial properties were prepared.The detailed studies are as follows:First,we designed and synthesized three peptides based on the antibacterial functional sequence of Human beta-defensin-3 and the mineralized functional sequence of Human cementum protein 1.They are mineralized functional peptide(C7 peptide,amino acid sequence:MLPHHGA),antibacterial functional peptide(H12 peptide,amino acid sequence:GKCSTRGRKCCRRKK)and bifunctional peptide(H12-C7 peptide,amino acid sequence:GKCSTRGRKCCRRKK MLPHHGA).These three peptides were fixed on the synthesized HAP modified substrate to induce mineralization.The effects of peptides on the surface morphology,crystal structure and hydrophilicity of HAP was systematically studied.Finally,E.coli and S.aureus were used as bacterial models to test the antibacterial effect of HAP nanocomposite materials in vitro.The relationship between its crystal structure,physicochemical properties and antibacterial ability was also explored.The study showed that HAP nano-composite materials containing different peptides have been successfully synthesized based on biomineralization.Peptides affect the surface morphology and crystal structure of HAP,and further change its hydrophilicity.For the bacterial experimental,HAP nano-composite materials doped with peptides can effectively reduce the adhesion of E.coli and S.aureus on their surfaces,and performed the function of preventing bacterial infection.At the same time,it was found that the physicochemical properties of HAP were related to its antibacterial ability in vitro.In summary,HAP nano-composite materials doped with peptides were synthesized based on biomineralization.The crystal structure,physicochemical properties and the relationship of structure and antibacterial function were explored.The study here provided theoretical and practical reference for the potential application of the synthesized HAP nano-composite materials in the field of bone tissue engineering.