Reline-assisted green and facile synthesis of fluorapatite nanoparticles

A fast, simple and sustainable method based on choline chloride-urea deep eutectic solvent (known as Reline) was employed to synthesize nanosized fluorapatite (FA) particles. Using XRD, FESEM, TEM, EDS, and FTIR, the formation of FA nanoparticles with average crystal size of ~34nm, percent crystallinity of 93%, particle size of ~45nm, and high crystal, elemental, and structural purity was confirmed. The MTT cytotoxicity assay endorsed the non-toxicity of as-synthesized FA nanoparticles. The good biocompatibility, osteogenity and mineralization ability of as-synthesized FA nanoparticles were confirmed by Alizarin red staining, Acridine orange staining and ALP activity tests. After synthesis of the nanoparticles, the Reline solvent was recovered successfully using freeze-drying method with 71% yield of recovery revealing the green, sustainable and economical nature of the developed synthesis method. According to the results, owing to its alkalinity, high ionic strength and 3D bulky configuration, the Reline solvent provides the optimum conditions required for formation of FA with maximum crystallinity and the particle size controlled in the nanometer range. Providing a simple, cost-effective, and green method for synthesis of FA nanoparticles with potential biological applications is the most innovative aspect of this study.