Salt-Mediated Modulation mechanic properties and photothermal response of chitosan/hyaluronic acid hydrogel

Noncovalent chitosan (CS)/hyaluronic acid (HA) hydrogel has been characterized by favorable cytocompatibility, biodegradability and non-toxicity. It bears a close resemblance to human skin and holds promising potential applications in medical engineering. Nevertheless, the CS/HA hydrogels have yet to achieve widespread application due to the relatively weak toughness. In this study, salts were utilized to regulate the mechanical properties of CS/HA hydrogel. The results indicated that copper nitrate was the most effective regulator, which transformed intramolecular hydrogen bonds and electrostatic interactions into intermolecular hydrogen bonds and cation chelations, respectively. The regular domains in the hydrogel were reduced while the crosslink was strengthened. Consequently, the toughness of the hydrogel was increased to 7.8 MJ/m3, 1253-fold that of covalent CS/HA hydrogel. The salt effect was replicated in the other two hydrogels, attesting to its generality. Hence, salt regulation proves to be an effective way to enhance mechanical properties of hydrogel. In addition, the copper nitrate-regulated hydrogel exhibited favorable drug delievring behavior and photothermal response. Under the exposure of near-infrared light, the release rate and amount of the drug loaded in the hydrogel were increased by 40% and 39% respectively within 20 minutes, manifesting a remarkable potential for application as a drug carrier.