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Most high load-bearing implants are metallic alloys which contain toxic chemical components that might be released due to the corrosive environment of body fluids and load-bearing activity. Surface modification techniques do not guarantee biocompatibility. Hence, the bioactive surface of implants can be modified by coating the surface with a suitable material that addresses the needs of the patient. The choice and application process of the coatings should be determined based on the workability of the material and its physiochemical properties, such as the procedures involved and performance in avoiding removal of any desirable material properties that are helpful in the tissue regeneration process. Tailor-made coating materials prove very promising, as they might improve permanent implantations, make them more affordable and reduce the need for surgical revisions. The scope of the featured properties, such as addition of accelerated tissue regeneration, antibacterial properties and controlled release and removal of debris from the biological system to the metal implants makes coatings an ideal choice for surface modification of implants. This report reviews several options available for forming a biologically active layer over metallic surfaces that will interact with and produce desirable effects on host tissues.

Hydroxyapatite [HAP] and Tricalcium phosphate [ß-TCP] are a class of calcium phosphate related ceramic materials that are widely used in tissue regeneration and biomedical applications owing to their excellent bioactivity and biocompatibility. In this investigation, nanocrystalline pure HAP was prepared via sol-gel method by incorporating snail shell as calcium precursor with different phosphorus sources such as triethyl phosphate /phosphite (without using any additives like pH maintaining solutions or gelling agents). Nano crystalline HAP and biphasic calcium phosphate (HAP + ß TCP) were prepared from triethyl phosphate and triethyl phosphite precursors respectively. The prepared material was further characterized by powder XRD, IR, Raman spectroscopy and Thermo gravimetrical analysis to confirm the phase purity, functional groups and thermal stability. SEM coupled with EDAX was also used to examine the size, shape of particles and elemental composition of Ca to P ratio in the material. Different phosphorus based HAP has shown rod and spherical shaped surface morphology which was further confirmed by TEM analysis. MTT assay was performed using NIH-3T3 fibroblast cell lines which indicated that the viability was not affected in various concentrations of pure nano crystalline HAP (12.5-100 µg/ml). This study confirms the improved Downloaded by [New York University] at 02:56 28 July 2015 2 biocompatibility of biowaste converted HAP which would have implications in biomedical applications.

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Metallic materials having good mechanical properties, high corrosion resistance, and good compatibility with biological materials are used as orthopedic devices. Type 316L stainless steel is the most widely used material for implant fabrication in India for orthopedic applications owing to their good corrosion resistance, hot and cold workability, excellent mechanical properties, and availability at low cost. However, it faces corrosion-related problems in physiological environment and thus releases toxic metal ions into the tissues surrounding the implants. Hence, hydroxyapatite (HAP) coatings over the metal implant have been developed as an alternative method to improve the surface conditions of the base metal. In the present investigation, the development of a sol-gel-derived hydroxyapatite coating on 316L SS is being explored. The corrosion resistance behavior of the coating was assessed through electrochemical studies involving cyclic polarization experiments and impedance analysis in Ringer's solution. The results have indicated that the sol-gel-derived HAP coatings exhibited excellent resistance to localized attack on pristine 316L SS.