Investigation of covalent binding of gold nanoparticles to chitosan nanofibers using cellulose and hyaluronate dialdehydes

Abstract

In this study, the reaction mechanisms of gold nanoparticles (AuNPs) synthesis using dialdehyde cellulose (DAC) and dialdehyde hyaluronate (DAH), and their covalent binding to chitosan nanofibers (CHITs), was investigated. The synthesis uses a redox reaction where dialdehyde polysaccharides are oxidized to dicarboxy polysaccharides and the gold salt precursor is reduced to elemental gold. The formation of the AuNPs-CHIT composite involves Schiff base chemistry, where reactive aldehyde groups of the polysaccharide shell around AuNPs react with chitosan's amine groups, forming pH-labile imine groups, which can be subsequently stabilized using reductive amination. FT-IR and XPS analyses were used to confirm the proposed reaction mechanisms. Next, the catalytic activity of AuNPs synthesized using DAC and DAH was evaluated for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride. Rapid conversion rates and high turnover frequency were observed. The morphology and structure of the composites were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). These analyses confirmed the sub-10 nm size of the AuNPs and their uniform distribution on chitosan nanofibers. The findings confirm the proposed reaction mechanisms, showcase the morphology and catalytic activity of the prepared nanoparticles and highlight their potential industrial applications. The versatility of this method also opens avenues for further functionalization and broader applications of AuNPs in biomedical fields such as biosensors and drug delivery systems.