| Titanium and its alloys are being widely used in many orthopedic and bioimplant applications, and are preferred load-bearing implants materials, due to its perfect mechanic properties. The titanium oxide that forms on Ti surface makes it be biocompatible. But there are two disadvantages of Ti, poor osteoconductivity and low corrosion resistance. Various surface modifications are used to adjust the properties of Ti surface to the specific needs of the biomedical applications. Hydroxyapatite(Ca10(PO4)6(OH)2, HA) has been widely used as a coating material in biomedical implants, due to its similarity of chemical composition and high biocompatibility with inorganic constituents in natural bone tissue. TiO2 nanotube array was fabricated in an F--containing electrolyte by anodization to promote the nucleation of HA and improve the bond strength of HA coating and substrate. In this paper, HA coatings on as anodized TiO2 nanotube layer were prepared by electrochemical deposition method. Mg and gelatin functionalized GO were added into HA coating for improving the bioactivity. In order to gain antibacterial property, Ag and CS were also incorporated into coating. The morphology and composition of TiO2 nanotube, HA, MgHA, GelGOHA, AgHA and CSAgHA composite coatings were studied by XRD, FTIR,SEM, EDS and XPS. The mechanic properties, corrosion resistance and biocompatibility of the obtained coatings were also investigated.The TiO2 nanotube was prepared on Ti surface by anodization. The results showed that a uniform aligned TiO2 nanotube layer with a diameter of 100 nm was established, the phase structure transformed to the anatase after the heatment at 350°C for 2h. With the TiO2 nanotube layer being formed, the corrosion resistance of Ti was improved. HA coating was prepared on TiO2 nanotube layer by electrochemical deposition method, the typical needle-like HA was observed, and HA coating enhanced the biocompatibility of Ti and be beneficial to the adhesion of osteoblast cells. Besides, the preparation method of HA/TiO2 composite coating was also applicable to Ti screw.Electrochemical deposition was applied to study the production of magnesiumdoped HAp(MgHAp) coatings onto pure titanium with anodized titanium oxide(TiO2) nanotubes as intermediate layer. Results indicated that Mg was uniformly distributed in the coatings, and each coating was found to be 21 ± 1.7 μm thick. With Mg2+ incorporation, Ca2+ was substituted by Mg2+ in the MgHAp coating, thereby reducing apatite crystallinity and weekly increasing bond strength. Bioactivity and corrosion resistance of the coatings was improved in simulated body fluid and polarization tests, respectively. MC3T3-E1 osteoblast cell culture tests indicated that the magnesiumsubstituted coatings had good biocompatibility and no adverse effect.Graphene oxide functionalized gelatin was first time employed as reinforcement fillers in hydroxyapatite coatings by electrochemical deposition process on TiO2 nanotube arrays, the GelGOHA/TiO2 composite coatings was successfully prepared. FTIR and XPS analysis confirmed the presence of GelGO in coatings. The net-like porous surface was observed by FESEM and the thickness of GelGOHA coating was 24.2 ± 1.5 μm, thicker than HA coatings, indicating GelGO induced the formation of HA. With GelGO incorporation, the bond strength between GelGOHA coatings and Ti substrate was approximately 18.5MPa due to the enhanced toughness of coatings. With the dense netlike morphology, composite coatings showed better corrosion resistance. Moreover, MC3T3-E1 cell test confirmed that the bioactivity and biocompatibility of HA coatings were improved with the incorporation of GelGO.Hydroxyapatite doped with Ag+ ions(AgHA) was synthesized via electrochemical deposition method on anodized titanium. XRD analysis suggested that Ag+ is incorporated into HA lattice. A part of the Ca2+ site was replaced by Ag+, which caused the lattice distortion. The XPS narrow scan spectra of Ag was applied to study the chemical state of Ag, and the result showed the main chemical state of Ag is Ag ions. With the Ag+ doped, the coating appeared to be loose and porous structure with the thickness of 17.7 ± 1.5 μm, suggesting that Ag+ inhibited the deposition of HA. Moreover, the bond strength between the coating and substrate was decreased to 15.9 ± 0.56 MPa. Bioactivity and electrochemical studies were performed for the AgHA-coated TiO2 in a simulated body fluid, where significant good bioactivity and corrosion resistance were exhibited. The antibacterial and osteoblast cell adhesion tests in vitro revealed that the AgHA coating with 2.03 wt% silver had significant antibacterial and osteogenic properties with MC3T3-E1 cells. Thus, the AgHA coating was regarded as a promising candidate for protecting coating orthopedic implants from infection.A bio-composite coating containing chitosan, silver and hydroxyapatite was developed on anodized titanium substrate by electrochemical deposition method at 50°C. The FESEM results showed that the prepared coatings has compact and dense morphology with a thickness of 6.2 ± 0.7μm, indicating that the CS and Ag could inhibit the formation of HA. XRD and XPS analysis suggested that Ag was successfully incorporated into HA, and replaced a part of Ca in HA lattice which resulted in the lattice distortion. FTIR analysis confirmed that the main composition of coatings was HA, and the NH2 absorption band in CS was observed, which confirmed the presence of CS. The polarization curves tests in SBF revealed the corrosion resistance of HA coating was improved with the incorporation of CS and Ag. Releasing of Ag in SBF was also investigated. The results showed the antibacterial property of the prepared CSAgHA composite coatings was expected because of long-term sustainable release of Ag. Testing prepared coatings with E. coli and S. aureus strains exhibited antibacterial activity due to a synergistic effect of silver and chitosan. The prepared coatings were also found to be non-toxic to MC3T3-E1 cells. Thus, these results suggesting that the CSAgHAp biocomposite coatings have the potential in preventing bacterial infection of implants. |
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