Auricularia Auricula Polysaccharide-Mediated Green Synthesis of Highly Stable Au NPs

Polysaccharide-functionalized gold nanoparticles (Au NPs) exhibit a promising application in biomedical fields due to their excellent stability and functional properties. The Au NPs from Auricularia auricula polysaccharide (AAP) were successfully synthesized using a straightforward method. By controlling the mass fraction of AAP, pH, reaction temperature, reaction time, and concentration of gold precursor, the highly dispersed spherical AAP-functionalized Au NPs (AAP-Au NPs) were prepared. The Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicated that the synthesis mechanism of AAP-Au NPs was as follows: the molecular chain of AAP undergoes a glycosidic bond breakage to expose the reduction terminus in the presence of gold precursor, which reduced Au(III) to Au(0), and itself was oxidized to carboxylate compounds for maintaining the stability of AAP-Au NPs. Additionally, based on the electrostatic interactions and steric forces, as-prepared AAP-Au NPs exhibit excellent stability at various pH (5–11), temperature (25–60 °C), 5 mmol/L glutathione, and 0.1 mol/L Na+ and K+ solutions. Furthermore, AAP-Au NPs retained the ability to scavenge DDPH and ABTS radicals, which is expected to expand the application of Au NPs in biomedical fields.