Fabrication Of Bifunctional Antibacterial/Bioactive Hybrid Coatings On Biomedical Titanium Alloys

Due to their excellent mechanical properties and good biocompatibility,biomedical titanium(Ti)implants have been widely used in hard tissue repair and regeneration.But associated infection still poses serious threat leading to possible complications.Bacterial infection is a tough tissue in surgery.Even comprehensive disinfection and strict aseptic operation regulations are carried out,the postoperative infections often occur.There are two main reasons for the high incidence of infection:protein layer which absorbed onto the surface of implants accelerate the biofilm colonization and compromised host defenses on the implant surface for the lack of bioactivity.Hence,surface modification could carry out to improve the biological activity of implants and endow them certain functions,such as antibacterial property,by surface engineering methodology.To improve the biological activity of implants,the main solution is the formation of hydroxyapatite(HA)on the surface of implants,but it is easy to fall off because of the weak interface binding.Antibiotic injection is the main route to cure bacterial infection in clinical.And antibiotics have certain specificity to bacteria;it needs long-term injection and cause the generation of bacterial drug resistance.Based on the above problems,Ti and its alloys,which used as the substrates,were modified to improve their antibacterial ability.Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)were used to test the antibacterial ratio of samples.MC3T3-E1 cells were used to test the cytotoxicity.A thin polydopamine(PDA)formed on the Ti substrate by polymerization of dopamine monomer,then after immersing in simulated body fluid for 14 days,HA bioactive layer was deposited on the surface of PDA modified Ti substrate.Nanosilver particles were formed on HA by used the UV light reduction method.Finally,chitosan solution with a concentration of 2 mg/ml was spined onto the substrate to form a slow release layer.According to the SEM,XRD and TEM analysis,PDA promoted the deposition of HA on Ti substrate and the interface bonding strength.SEM,XRD and EDS of Ag doped HA coating showed a relatively uniform distribution of Ag on HA.Though Ag showed a certain effect on the structure of the membrane layer,the film still revealed strong biological activity.ICP test result showed that,with the increase of chitosan coating layer upon layer number,the release of silver ions concentration increased slowly,when layer increased to 7 layers,the 14th day of the release of silver ions concentration to 30%of chitosan coating.The antimicrobial properties of samples were tested by incubation with E.coli and S.aureus.With the increase of silver content,E.coli antibacterial rate of coating reached 93%,S.aureus antibacterial rate of coating reached 78%.With the increase of chitosan coating thickness,the antibacterial rate of the samples decreased,while the cytotoxicity of the samples decreased.Preparation of doped with Ag and nano HA powder of zinc oxide,then with two-dimensional laser platform for laser coating,powder cladding to Ti-6Al-4V surface of titanium alloy.XRD results show that the combination of the coating and the substrate is achieved by the chemical reaction of the interface,which is not easy coating off,and the binding between the powder and the substrate is strong.In the antibacterial experiment,with the increase of the pulse width,the antibacterial rate is gradually increased.MC3T3-E1 showed good proliferation on the surface of the material.And the adhesion of platelets on the surface of the sample is also different from the surface composition of the samples.This study will be on titanium surface through three methods of surface engineering,preparation of antimicrobial activity and biological activity of hybrid coating.