Enhanced dispersion stability of gold nanoparticles with injectable thermoresponsive poly(l-lactide-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(l-lactide-co-ε-caprolactone) hydrogels

• Thermoresponsive PLCL-PEG-PLCL micelles with near-physiological sol-gel behavior. • Two AuNP-loading routes enable controlled nanoparticle distribution in micelles. • AuNPs localization governs the gelation behavior of micelles. • Micelles greatly enhance AuNPs stability against freezing, drying and heating. Amphiphilic block copolymers are widely used to construct thermoresponsive micellar systems with injectable sol-gel transition behavior, making them promising candidates for biomedical applications. In this study, poly(l-lactide-co-ε-caprolactone)-b-poly(ethylene glycol)-b-poly(l-lactide-co-ε-caprolactone) (PLCL-PEG-PLCL) triblock copolymers were employed to fabricate micelles and micelle-AuNP hybrids. AuNPs were incorporated through two distinct strategies, direct aqueous mixing and THF-induced micellization, resulting in different spatial distributions. Spectroscopic and rheological analyses revealed that corona-associated AuNPs hindered micelle association and delayed gelation, whereas core-encapsulated AuNPs preserved the intrinsic thermo-responsive behavior. In addition, micelle formation significantly enhanced the stability of AuNPs under freezing, lyophilization, and heating conditions. These results demonstrate that controlling AuNPs localization within PLCL-PEG-PLCL micelles offers an effective strategy to tune optical response, rheology, and stability, providing a versatile platform for photothermally active injectable hydrogels.