synthesis and characterization of strontium and zinc co-doped nano-hydroxyapatite via hydrothermal method for enhanced bone formation ability

Nano-hydroxyapatite (nha) has gained significant attention as a biomaterial in bone tissue engineering due to its excellent biocompatibility and resemblance to the natural bone mineral component. nha could promote cell adhesion, proliferation, and differentiation of osteoblasts, leading to enhanced bone formation. its nanoscale structure provides a high surface area, facilitating cellular interactions and nutrient diffusion. moreover, nha exhibits remarkable osteoconductivity, and the release of calcium and phosphate ions from nha contributes to osteogenesis. furthermore, nha can be easily incorporated into various scaffolds, coatings, and composites, making it a versatile biomaterial for bone regeneration applications. in recent years, the incorporation of trace elements into nha has been explored, as these elements have been found to possess bone formation abilities. strontium (sr) ions have been found to promote osteogenesis while inhibiting osteoclast activity, which is responsible for bone resorption, leading to enhanced bone formation. zinc (zn) ions play a vital role in bone metabolism and have been shown to enhance osteoblast activity and mineralization, which promotes bone formation and improves the integration of implants with the surrounding tissue. additionally, zinc has antimicrobial properties, inhibiting the growth of various bacteria and reducing the risk of infection. this work presents a detailed synthesis method for 5mol%sr and 5mol%zn-doped nha nanoparticles with ca9sr0.5zn0.5(po4)6(oh)2 formulation using the hydrothermal technique. the hydrothermal process involved the dropwise addition of diammonium hydrogen phosphate to a precursor solution containing calcium nitrate tetrahydrate, strontium nitrate tetrahydrate and zinc nitrate hexahydrate under vigorous stirring. the ph was maintained at 10 by adding ammonia to facilitate the precipitation of the desired nha phase. the resulting suspension was transferred to a teflon-lined stainless-steel autoclave, sealed, and heated up to 180°c for 12h to allow the crystallization and growth of the nano-hydroxyapatite particles. after the hydrothermal reaction, the precipitate was washed with deionized water to remove impurities and unreacted precursors. finally, the washed precipitate was dried at 100 °c to obtain the final sr and zn-doped nha particles. the synthesized nanoparticles were characterized using various techniques to confirm their composition, structure, and morphology. x-ray diffraction (xrd) analysis was performed to determine the crystalline phase and crystallite size of the nanoparticles. the xrd pattern exhibited characteristic peaks corresponding to the nha phase, with a hexagonal crystal structure (jcpds file cards of 00-009-0432). it can be evidenced that the crystallinity is decreased due to doping, attributed to the different ionic radius of zn2+ and sr2+ compared to ca2+. furthermore, the phase composition revealed a decrease in lattice parameters, indicating the substitution of the ca2+ ion with the smaller zn2+ ion. fourier-transform infrared spectroscopy (ftir) was employed to analyze the functional groups present in the synthesized nanoparticles, showing characteristic peaks corresponding to the phosphate and hydroxyl groups of nha. scanning electron microscopy (sem) revealed the formation of rod-like particles with an average particle size around 60nm. energy-dispersive x-ray spectroscopy (eds) exhibited characteristic peaks corresponding to the elemental composition of the doped nanoparticles, indicating the successful incorporation of sr and zn. in conclusion, the hydrothermal method was successfully employed to synthesize sr and zn co-doped nha nanoparticles. the characterized nanoparticles exhibited enhanced bone formation ability, suggesting their potential application in bone tissue engineering.