Safe polyacrylamide-based hydrogels with low monomer content achieved by using liquid metal nanoparticles or MoS2 nanosheets as efficient initiators

Polyacrylamide (PAAm)-based hydrogels, known for their strong mechanical properties, high water retention, and chemical stability, are widely used in drug delivery and tissue engineering. However, their further clinical development has been limited by the potential toxicity associated with residual acrylamide monomers and some polymerization initiators. This study investigates liquid metal (gallium) nanoparticles (GNPs) and MoS 2 as alternative initiators of the traditional ammonium persulfate and N,N,N′,N′ -tetramethylethylenediamine (TEMED). By employing probe sonication or ultraviolet irradiation to generate free radicals, we aimed to enhance radical polymerization efficiency while minimizing unreacted monomer content. Nuclear magnetic resonance spectroscopy and high-performance liquid chromatography analyses confirmed that these strategies effectively minimized residual monomer content. Notably, double-network hydrogels formed by PAAm and amino acids exhibited no cytotoxicity and did not elicit inflammatory responses, demonstrating excellent cytocompatibility. Additionally, beyond their role of initiators, MoS 2 and GNPs functioned as photothermal agents to enable controlled drug release. These findings offer a promising strategy for improving the biocompatibility of PAAm-based hydrogels, supporting their potential in clinical applications for the treatment of different types of diseases. • Gallium nanoparticles and MoS 2 nanosheets act as efficient initiators for polyacrylamide polymerization, as alternative to widely used ammonium persulfate and N , N , N′ , N′ -tetramethylethylenediamine. • All new formulations markedly reduced residual acrylamide monomer content in polyacrylamide hydrogels. • Gallium nanoparticles and MoS 2 nanosheets serve as photothermal agents to enable drug release. • Polyacrylamide-amino acid double-network hydrogels showed no cytotoxicity and no inflammation.