Study On Functionalization Of Titanium Alloy By Composite Coating Of Protein Nanocapsule And Polymer Gel

Medical titanium alloy has been widely used as orthopaedic implant devices forits excellent mechanical properties and good biocompatibility. Growth factors, whichalthough have good ability to induce bone regeneration, exist several problems whenthey are used for surface modification on medical titanium such as poor activitymaintainence, low loading capacity, complicated procedures and poor tollerance toGamma irradiation. In this thesis, protein nanocapsules and polymer gel werecombined to modify the surface of titanium alloy. The functionalization of titanium bybioactive proteins and the effect of gamma ray irradiation sterilization on the activityof protein were investigated.The protein nanocapsules were synthesized by free radical polymerization usingglucose oxidase as bioactive protein model, and acrylamide (AAM) and N-(3-aminopropyl) acrylamide (APM) as monomers, methylene acrylamide (Bis) as crosslinkingagent, ammonium persulfate (APS) and the four methyl diethylamine (TEMED) asthe initiator. The obtained nanocapsules were characterized by Scanning electronmicroscopy (SEM), Dynamic light scattering (DLS), Zeta-plus and gel electrophoresis.The results showed that the nanocapsules exhibited as nanospheres with size between20~50nm. The surface ZETA potential is+20mV. The capsulation enhanced thestability of glucose oxidase, and80%of glucose oxidase retained their activities afterthe treatment at60℃for60min, more than85%of glucose oxidase retained theiractivity in15%methanol, ethanol and acetone solution. Moreover, over80%and95%of glucose oxidase maintained their activities after freezing-thawing and freeze-dyingtreatment.To functionalize the surface of titanium, a poly-dopamine layer was formed ontitanium surface by dopamine oxidation polymerization. Then N-(3-amino propyl)acrylamide was introduced through the reaction between its amino groups with thequinone groups of poly-dopamine. Finally, the gel coationg loaded with glucoseoxidase nanocapsules was prepared by means of in situ radical polymerization ofmethacrylate phosphatidyl choline (MPC) and Bis. The surface structure and chemicalcomposition were characterized by Scanning electron microscopy (SEM), electron energy spectrum, Raman spectrum and attenuated total reflection infrared. The loadcapacity and release of glucose oxidase nanocapsules on the surface of titanium werealso studied. The results showed that the amount of glucose oxidase loaded onto thesurface of titanium increased with the increasing of the degree of crosslinking of thegels, the maximal loading amount of glucose oxidase was up to3.81ug. The glucoseoxidase could sustainedly release from the titanium surface. Over50%loaded glucoseoxidase still had activities after gamma ray irradiation sterilization, and no colony wasfound after the soaking and colony.