Nanosize hydroxyapatite (nHAp) doped with varying levels of Fe(3+) (Fe-nHAp of average size 75 nm) was synthesized by hydrothermal and microwave techniques. The samples were characterized for physiochemical properties by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma optical emission spectrometer (ICP-OES), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), mechanical and dielectric properties. The biological properties like hemocompatibility, antibacterial efficacy, in vitro bioactivity and the cell proliferation of the samples were determined. XRD pattern of the samples were of single phase hydroxyapatite. As the content of Fe(3+) increased, the crystallite size as well as crystallinity decreased along with a morphological change from spherulites to rods. The dielectric constants and Vickers hardness were enhanced on Fe(3+) doping. The VSM studies revealed that the saturation magnetization (M(s)) and retentivity (M(r)) were found to increase for Fe-nHAp. nHAp impregnated with an antibiotic as a new system for drug delivery in the treatment of chronic osteomyelitis was also attempted. The in vitro drug release with an antibiotic amoxicillin and anticancer drug 5-fluorouracil showed sustained release for the lowest concentration of Fe(3+), while with an increase in the content; there was a rapid release of the drug. The hemolytic assay of Fe(3+) doped samples revealed high blood compatibility (<5% hemolysis). The antibacterial activities of the antibiotic impregnated materials were tested against a culture of E. coli, S. epidermidis and S. aureus by agar diffusion test. The in vitro bioactivity test using simulated body fluid (SBF) showed better bone bonding ability by the formation of an apatite layer on the doped samples. The growth of the apatite layer on the samples surface has been confirmed by EDS analysis. The proliferative potential of MG63 cells by MTT assay confirmed the noncytotoxicity of the samples.

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The effect of swift heavy ion irradiation on the surface modification and bioactivity of microwave sintered hydroxyapatite (HAp) pellets has been studied. The irradiated surface of the pellets was completely covered by tightly packed rectangular platy crystals. The pellets subjected to 300°C conventional sintering (after microwave sintering) before irradiation showed a plain surface. XRD studies confirmed the surface to be HAp but decrease in crystallinity and crystal size was observed. In vitro bioactivity study had revealed the formation of unique three dimensional macroporous apatite layer on irradiated surfaces. The irradiation with swift heavy oxygen ions enhanced the bioactivity of the HAp bioceramics.

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