Photochemically-assisted synthesis of non-toxic and biocompatible gold nanoparticles

This contribution describes the photochemically-assisted synthesis of aqueous colloidal suspensions of non-toxic and biocompatible spherical gold nanoparticles stabilized by branched polyethylenimine, or else Au-np-PEI. The method consists on 30min of photoexcitation (254nm, 16W) at room temperature of an aqueous diluted solution of chloroauric acid (HAuCl₄) containing PEI. While the UV irradiation forms the [Au⁽³⁺⁾Cl₄^-]* excited species that succesively transforms into zero valent Au, PEI controls the nucleation step of nanoparticles formation. Varying the PEI to Au molar ratio permits one to tune the size of nanoparticles between 100nm to 8nm. The obtained colloidal suspensions display an intense plasmonic absorption band at 520-530nm and positive zeta potentials greater than +20mV. The cells viability for in vitro tests performed with human connective tissues and human breast adenocarcinoma (MCF-7) cell lines is over 80% and 90%, respectively, when they are incubated with Au-np-PEI formulations (25μgmL^-1). The present photochemically-assisted synthesis is advantageous because it is fast and does not require for either hazardous or cytotoxic reductant agents and additional purification procedures.