# Au Nanoparticle Synthesis in the Presence of Thiolated Hyaluronic Acid

## TL;DR

This paper explores using thiolated hyaluronic acid to synthesize gold nanoparticles with tunable properties for biomedical applications.

## Contribution

The study introduces a novel method for directly synthesizing and stabilizing gold nanoparticles using thiolated hyaluronic acid.

## Key findings

- The morphology and size of AuNPs varied with the HA-SH-to-HAuCl4 ratio, producing particles from 6–7 nm to ≥146 nm.
- XPS confirmed the formation of metallic gold and Au−S bonds, while NMR showed partial oxidation of thiol groups to sulfonic acid.
- Lower HAuCl4 concentrations led to higher colloidal stability, with zeta potentials reaching up to −41.5 mV.

## Abstract

Gold nanoparticles (AuNPs) are of significant interest due to their unique properties and applications in biomedicine. While hyaluronic acid (HA) has been used to modify pre-formed AuNPs, its thiolated derivative (HA−SH) has been less explored for the direct synthesis and stabilization of AuNPs. This study investigates the use of thiolated hyaluronic acid as a key component in the synthesis of AuNPs. A series of HA-AuNPs (HA-AuNP1-4) were synthesized by reacting HA-SH with HAuCl4 at different mass ratios. The resulting nanoparticles were characterized using UV-Vis spectroscopy, scanning/transmission electron microscopy (SEM/STEM), X-ray photoelectron spectroscopy (XPS), photon cross-correlation spectroscopy (PCCS), and zeta potential measurements. The chemical transformations of the thiol ligand were studied using NMR spectroscopy. The morphologies and sizes of AuNPs depended on the HA-SH-to-HAuCl4 ratio, ranging from icosahedral and triangular particles (≥146 nm) to quasi-spherical particles with a bimodal distribution (6–7 nm and 45–60 nm). XPS confirmed the presence of metallic gold (Au0) and a Au−S bond, while NMR and XPS revealed the partial oxidation of thiol groups to sulfonic acid. Zeta potential measurements showed that lower HAuCl4 concentrations resulted in higher negative charge (up to −41.5 mV), enhancing colloidal stability. This work demonstrates a versatile approach to the synthesis of hyaluronic acid-based gold nanomaterials with tunable properties for potential biomedical applications.