Tailoring PEGDA/gelatin hydrogels with silver nanoparticles: Mechanical characterization and bacterial inhibition studies.

Silver nanoparticles (AgNPs) are promising antimicrobial agents for combating bacterial infections in vitro and in vivo. This study explores the mechanical properties of PEGDA/gelatin hybrid hydrogels synthesized with varying Ag concentrations via electron beam irradiation and their bacterial interactions at the single-cell level, in real-time and in situ. Increased AgNPs concentration slightly alters the mechanical properties of these hydrogels, which are engineered to mimic human skin. Infrared microspectroscopy reveals that silver ions interact with PEGDA and gelatin before irradiation, affecting hydrogel homogeneity. SEM-EDX and TEM morphological analyses, together with XPS surface characterization, confirmed the distribution of AgNPs within the hydrogel matrix. In parallel, their nanostructural features revealed that the AgNP concentration influenced particle size distributions. Remarkably, hydrogels containing AgNPs synthesized from 200 ppm AgNO₃ released only 0.35 ppm of silver after 7 days, highlighting their strong ion-retention capacity. Real-time imaging of Escherichia coli demonstrates that hydrogels containing AgNPs disrupt Min protein oscillation, a key regulator of bacterial division, with a bactericidal effect observed within 18 min for hydrogels containing AgNPs synthesized from 200 ppm AgNO3. Antibacterial efficacy correlates with AgNPs concentration in the hydrogels, as confirmed by quantitative and qualitative analyses. Notably, the cytotoxic effects of hydrogels incorporating AgNPs at different concentrations were examined. Among them, H50 demonstrated a negligible influence on cell viability relative to the control group. These findings provide insights into the bactericidal mechanisms of AgNPs, influenced by mechanical and chemical factors.