Laser-assisted synthesis of nano-hydroxyapatite and functionalization with bone active molecules for bone regeneration.

ABSTRACT

The main goal of bone tissue engineering research is to replace the allogenic and autologous bone graft substitutes that can promote bone repair. Owing to excellent biocompatibility and osteoconductivity, hydroxyapatite is in extensive research and high demand for both medical and non-medical applications. Although various methods have been developed for the synthesis of hydroxyapatite, in the present study we have shown the use of nanosecond laser energy in the wet precipitation method of nano-hydroxyapatite (nHAP) synthesis without using ammonium solution or any other chemicals for pH maintenance. Here, the present study aimed to fabricate the nanohydroxyapatite using a nanosecond laser. The X-ray diffraction and Fourier transform infrared spectroscopy have confirmed the hydroxyapatite formation under laser irradiation in less time without aging. A transmission electron microscopy confirmed the nano size of synthesized nHAP, which is comparable to conventional nHAP. The length and width of the laser-assisted nHAP were found to be in the range of 50-200 nm and 15-20 nm, respectively, at various laser parameters. The crystallite size obtained by Debye Scherrer formulae was found to be in the range of ∼ 16-36 nm. In addition, laser-assisted nHAP based composite cryogel (nanohydroxyapatite/gelatin/collagen I) was synthesized and impregnated with bioactive molecules (bone morphogenic protein and zoledronic acid) that demonstrated significant osteogenic potential both in vitro in cell experiment and in vivo rat muscle pouch model (abdomen and tibia muscles). Dual-energy X-ray analysis, micro-CT, and histological analysis confirmed ectopic bone regeneration. Micro-CT based histomorphometry showed a higher amount (more than 10-fold) of mineralization for animal groups implanted with composite cryogels loaded with bioactive molecules compared to only composite cryogels groups. Our findings thus demonstrate a controlled and rapid synthetic method for the synthesis of nHAP with various physical, chemical, and biological properties exhibited as comparable to conventionally synthesized nHAP.