Green-assisted tool for nanogold synthesis based on alginate as a biological macromolecule

Abstract

Large-scale biomedical applications of nanogold reflect the challenge faced by recent researches in the investigation of green synthesis methodologies, which are mostly complicated and/or expensive processes. The present report offers a totally green method using a quite simple and costless technique for the manufacture of Au nanoparticles based on alginate macromolecules. Hydrogen peroxide was used for the oxidative degradation of alginate at room temperature to produce more accessible fragments, beneficial for the reduction of Au ions to Au⁰ and as a stabilizer for the produced nanogold. The competence of the mentioned procedure was tested by comparison with the alkali/glucose/alginate system, in which glucose and alginate were used as a reducer and stabilizer, respectively. For both the systems, surface plasmon resonance peaks for nanogold were detected and similar absorbance spectra were observed. Using either 30 mmol L⁻¹ H₂O₂ or 1 g L⁻¹ glucose, similar reducing sugar content (0.32 g L⁻¹) resulted from 1 g L⁻¹ alginate. Nanogold manufactured by H₂O₂ exhibited smaller size (3.7 ± 1.1) with narrower size distribution (1.5–8.0 nm) than that produced in the case of glucose. However, enlarged nanogold was observed after storage for 5 months, which still maintained the nano dimension. The produced nanogold via the completely green technique using H₂O₂/alginate could be safely used in biomedical applications.