Preparation And Characterization Of Ag/HA Composite Coations By Sol-gel Dip Coating And Electrochemical Deposition On Porous Titanium Surfaces

Titanium and its alloys have excellent mechanical strength, good corrosion resistance, and biocompatibility:being widely used for producing implants and biomedical devices, such as hip joint prosthesis, knee joint prosthesis, and dental implants. One factor that should be taken into account is the mismatch of Young's modulus between bulk Ti-based metals (90-110 GPa) and bone (0.3-30 GPa), which could induce severe stress shielding and eventually result in bone resorption. Porous Ti implants could avoid this problem since its Young's modulus could be tailored by adjusting the porosity and could match with that of natural bone closer than that of bulk Ti. Moreover, porous structures can introduce strong bond strength between the bone and implants because the bone would easily grow into the porous scaffold and form a inter-locking structure.In this paper. Ti power was chosed to paste on Polyurethane (PU) foams to form an unit, which was then sintered at 400℃to remove the PU. After that, it was sintered at 1300℃for 2 h in vacuum environment. Though such kind of method, we could finally obtain porous titanium substrates with good mechanical strength and high porosity.Among plenty of preparation methods of Ag/HA composite coatings, most of them are line-of sight techniques, such as Plasma Spraying,Magnetron Sputtering, which cannot produce uniform coatings on the inner pore surfaces of the porous Ti. In the mean time, these methods require complicated equipments and consequently lead to high cost of production. However, sol-gel dip-coating and pulsed electrochemical deposition (PED) methods could easily solve this problem. In this sol-gel dip-coating method, porous titanium was dipped into the silver-containing HA gel and withdrawed at a stable speed. Then sintering at 600℃and well crystallized Ag/HA composite coatings were obtained. In the pulsed electrochemical deposition method, electrolyte was mainly consist of Ca2+(5.0 mmol/1), PO43-(3.0 mmol/l); deposition time,2 h; pusled potential,—2 V. Concentration of silver ion could be changed by adding different amount of AgNO3 into above electrolyte.Through SEM, XRD and EDS characterization, it could be easily foud that both of these two methods could prepare uniform Ag/HA composite coatings on the inner and outer face of porous titanium substrates. The coating thickness of sol-gel method is around 30μm which is thicker than that of PED.In the antibacterial test, coatings fabricated by both of these two methods expressed powerful antibacterial ability (>95%). The osteoblast culture results indicated that Ag/HA1.6 composite coatings, from sol-gel dip-coating method, appear significant influence on cell proliferate and differentiate. However,EAg/HA0.8 and EAg/HA1.6, from PED method, did not show any side effect on osteoblast.