Construction Of Nano-scale Composite Structure On Titanium Surface And Its Antibacterial And Biological Activity

Titanium and its alloys have been widely used as orthopedic implant materials because of their good mechanical properties,corrosion resistance and biocompatibility.Although these implants have very high clinical success rates,the lacking of osseointegration and infection around the implant oftentimes lead to the failure of surgery.The implant surface reacts with proteins,bacteria and cells,thereby plays a key role in the success or failure of the implant.In order to improve the success rates of these implants,many research works were carried out on creating idea surfaces through surface modification.However,many research works in this area only considered the ossteointegration properties,ignoring the antibacterial activity of the implant,or vice versa.Ideally,the implant surface should have both antibacterial activities,at the same time,can promote bone-implant integration.In order to resolve the above problems,the functional titanium surfaces were fabricated by the following methods.Firstly,the nanostructure was in-situ produced on the titanium surface by an initial piranha solution pretreatment and the sequent alkali heat treatments.Secondly,Zn²⁺ions were introduced into the nanostructured surface by an ion exchange process,in order to improve the antibacterial and biological activity of the titanium surface.Finally,the carboxymethyl chitosan zinc chelates were fixed on the nanostructured surface by the silanization and covalent grafting methods,which offers its long-term antibacterial and biological activity.The study provided some new ideas and methods for improving the antibacterial and biological activity of biomedical titanium materials,and has scientific significance and medical value.The details are as follows:?1?In-situ fabricating nanostructured titanium surface and its biological activity in vitroThe nanostructured surfaces were in-situ fabricated on the titanium surface by an initial piranha solution pretreatment and the sequent alkali heat treatments.Their physical and chemical properties were characterized by FE-SEM,EDS,XRD and contact angle measurements.The results showed that a porous TiO₂ network structure with an average porous diameter of about200 nm and a wall thickness of 30-50 nm was obtained by the direct alkali heat treated titanium surface.However,thicker and coarser porous surface layer was formed when the titanium surface was treated by an initial piranha solution pretreatment and the sequent alkali heat treatments.In this case,the pore size was about 400 nm.The simulated body fluid immersion experiments indicated that the nanostructure formed by this two-step method enhance the apatite inducing ability.In vitro cell experiments demonstrated that the porous network structure can promote cell adhesion,proliferation and differentiation.It strongly promoted the differentiation and differentiation of MC3T3-E1 cells.?2?Zn²⁺ions incorporated nanostructure and its antibacterial and biological activity in vitroZn²⁺ions incorporated nanostructure was produced by a facile Na⁺ions exchange in titanate formed during the alkali heat treatment process.The results showed that Zn²⁺ions could be successfully introduced into the titanium surface without changing the nanostructured morphology.Zn²⁺ions improved the antibacterial activity and reduced the number of bacteria by approximately 46%on staphylococcus aureus antibacterial experiments.In addition,such nanostructured surface can stimulate the initial adhesion,proliferation,proliferation,ALP activity and extracellular matrix mineralization of MC3T3-E1cells.?3?Nanostructure fixed carboxymethyl chitosan zinc chelate on titanium surface and its antibacterial and biological activity in vitroCarboxymethyl chitosan zinc chelate was fixed by silanization and covalent grafting methods,leading to carboxymethyl chitosan zinc chelate functional nanostructure on the titanium surface.The results showed that the carboxymethyl chitosan zinc chelate was successfully fixed on the titanium surface with zinc content of 3.81%.Antibacterial experiments confirmed that nanostructure fixed carboxymethyl chitosan zinc chelate still showed high antibacterial activity against Staphylococcus aureus after immersed in PBS solution for 14 days.The enhanced cell functions due to such nanostructure benefited to the initial adhesion,proliferation and differentiation of MC3T3-E1cells.?4?Antibacterial and biological activity of the functional titanium implants in vivoThe titanium implatns with nanostructural surfaces were implanted into the femoral condyle of the rabbit.The infection was artificially created by adding Staphylococcus aureus.In vivo antibacterial and biological activity of the functional titanium were preliminarily discussed based on the general observation of the wound,X-ray image observation,X-ray micro-CT and histopathological analysis.The results showed that a large number of bone cells were obtained on the functional titanium surface.No obvious infection signs were observed on the surface of the carboxymethyl chitosan chelate functional titanium surface.