One-pot, green synthesis of gold nanoparticles by gelatin and investigation of their biological effects on Osteoblast cells.

It is useful to find new methods to synthesize and, more importantly, to control the size and shape of gold nanoparticles (AuNPs) without using relatively toxic-reducing agents and surfactants. In this work, we present a one-pot, green synthesis of AuNPs taking the advantage of gelatin biopolymer to operate as unique reducing, growth controlling and stabilizing agent in aqueous solution of tetrachloroauric acid (HAuCl4) at temperatures above its melting point (∼35°C). The shape and size of AuNPs were found to be strongly influenced by the gelatin concentration (0.5-5%), while the growth rate of AuNPs is controlled by temperature of synthesis (40-80°C) and viscosity of the biopolymer. A specific class of gelatin-coated AuNPs was selected to investigate its stability in simulated physiological conditions and cellular media and subsequently to evaluate the in vitro biocompatibility and capacity to sustain proliferation and differentiation of Osteoblast cells. Dark-field microscopy and Rayleigh scattering spectra prove a more efficient internalization of gelatin-coated AuNPs as compared with citrate-coated AuNPs, while methylthiazoltetrazolium bromide (MTT) assay demonstrates enhanced cell proliferation. Interestingly, in the presence of gelatin-coated AuNPs, we find out a first sign of Osteoblast cells differentiation with bone nodules formation, as confirmed by alkaline phosphatase (ALP) activity assay.