One-pot green synthesis of nanohybrid structures: gold nanoparticles in poly(γ-glutamic acid) copolymer nanoparticles

Nanohybrids, comprising gold nanoparticles (Au NPs) and polymer NPs have attracted significant attention in recent years due to their excellent physical and chemical properties. In this work, a novel kind of nanohybrids based on Au NPs and biocompatible poly(γ-glutamic acid)-graft-3,4-dihydroxy-L-phenylalanine (γ-PGA-g-DA) NPs was conveniently achieved through a green and facile one-pot strategy. By simply adding HAuCl4·3H2O to the aqueous solution of γ-PGA-g-DA copolymer, the decrease of the pH value induced the self-assembly of γ-PGA-g-DA into NPs, during which Au3+ was adsorbed in the in situ formed NPs and spontaneously reduced to Au NPs by the dopamine moieties of γ-PGA-g-DA, leading to the formation of Au@γ-PGA-g-DA nanohybrids. In the reaction process, γ-PGA-g-DA was used as scaffold and reductant simultaneously, avoiding the use of extra toxic reducing reagents. Interestingly, the particle size and clustering of Au NPs in Au@γ-PGA-g-DA nanohybrids were varied with the loadings of HAuCl4·3H2O. This one-pot preparation process is very simple, fast, and completely based on the principles of green chemistry. Furthermore, the resultant biocompatible Au@γ-PGA-g-DA nanohybrids were used to detect L-tryptophan and exhibited a good analytical performance. The novel Au@γ-PGA-g-DA nanohybrids are a promising system for detecting the amino acids and biological species.