Preparation of Hydrophobic Bovine-Serum-Albumin-capped Gold Nanoclusters and Encapsulation in Polystyrene Nanoparticles

Abstract

Metal-based nanoclusters (NCs) have unique physicochemical properties, and they have been applied to various fields. Gold NCs (Au NCs) show fluorescence ranging from blue to red under ultraviolet (UV) irradiation. Bovine-serum-albumin (BSA)-capped Au NCs (BSA-Au NCs) have specific fluorescence properties, and they are expected to be used for biomedical applications. However, the environment of BSA-Au NCs is hydrophilic because hydrophilic BSA covers the Au NC surface, limiting their applications. To overcome this drawback, we developed hydrophobic BSA-Au NCs (h-BSA-Au NCs) using (formylmethyl)triphenylphosphonium chloride as the hydrophobic agent by reductive amination reaction. Resulting h-BSA-Au NCs were encapsulated in polystyrene nanoparticles (Au PS NPs) by the typical swelling method under mild conditions. The Au PS NPs showed orange fluorescence under UV irradiation. Therefore, Au PS NPs are promising fluorescent materials for biomedical applications.