Nanocomposite hydrogels with temperature-accelerated antioxidant activity for ocular applications

Abstract

Oxidative stress is a major contributor to ocular surface disorders, yet current antioxidant delivery systems remain limited by poor nanoparticle stability, loss of optical clarity, and a lack of physiological responsiveness. Here, we report a thermoresponsive nanocomposite hydrogel that integrates poly(N-isopropylacrylamide) (pNIPAM) with silver/copper bimetallic nanoparticles (Ag/Cu@Cu) to address these challenges within a unified material platform. The pNIPAM matrix stabilized the nanoparticles, preventing aggregation and maintaining optical transmittance above the functional threshold (>70%) at loadings up to 25% (v/v), enabling fabrication of optically transparent hydrogel formats suitable for ocular applications, including contact lenses. Encapsulation also improved redox stability, supporting sustained antioxidant activity relative to bare nanoparticles. Temperature-dependent kinetic analysis showed that the rate constants increased by a substantial margin across the tested temperature range (25–35 °C), whereas all conditions converged to near-complete DPPH depletion by approximately 120 min. This behavior is consistent with thermally induced contraction of the pNIPAM network, which increases substrate accessibility to the catalytic nanoparticle surfaces. Together, these results establish pNIPAM–Ag/Cu@Cu nanocomposite hydrogels as a promising, quantitatively validated platform for developing optically transparent, stimulus-responsive antioxidant materials for ocular applications.