Microwave Synthesis of Gold Nanoparticles in Poly(Ethylene Glycol)-Based Hydrogels for Drug Delivery

Nanocomposite hydrogels incorporating gold nanoparticles (AuNPs) have garnered significant interest in biomedical and materials science thanks to the synergistic advantages resulting from the integration of the two systems. However, their fabrication typically involves multistep procedures that may alter the physicochemical features of the final platform, limiting their reproducibility and translational potential. In this study, we report a facile and fast one-pot synthesis for in situ formation of AuNPs within an agarose-carbomer-poly(ethylene glycol) (AC-PEG) hydrogel, eliminating the need for multistep nanocomposite assembly. The synthesis is carried out through microwave irradiation, leading to fast and homogeneous heating with a short reaction time (3 min). PEG simultaneously acts as Au precursor reducing agent and, jointly with carbomer, a stabilizer of the produced AuNPs against salt-induced aggregation. The role of solution pH and HAuCl 4 concentration is assessed by independently varying the parameters, respectively, in the ranges 6–11 and 0.25–2.27 mM. Postsynthetic NaOH addition, in a concentration between 12 and 15 mM, demonstrates to further improve the sample uniformity and the synthesis outcomes. The produced AuNPs are characterized by narrow UV–vis spectra, sizes around 15–20 nm, better sphere-like shapes, and improved size distributions (PdI ∼ 0.1), compared to the case without NaOH addition. The internal microstructure of AuNPs/AC-PEG nanocomposites is preserved, compared to pristine hydrogel, while AuNPs exhibit concentration-dependent swelling and viscoelastic behavior. Finally, drug release tests under laser irradiation demonstrate the light-responsiveness of the system, resulting in improved cumulative release (∼80%) of a small hydrophobic drug mimetic (FITC) when subjected to 10 min ON-OFF irradiation cycles for 2 h. This facile and rapid method enables the direct formation of plasmonic nanocomposite hydrogels with tunable properties, opening future routes for responsive system fabrication in biomedical and other applications.