Synthesis and functional assessment of gelatin-stabilized silver nanoparticles: a study on their ionic stability, free radical scavenging, and broad-spectrum antibacterial activity

Over the past few decades, there has been much interest in developing biocompatible, multifunctional nanoparticles for medicinal uses. In this study, gelatin-stabilized silver nanoparticles, Gel-AgNP, were synthesized using a green chemical reduction method and thoroughly characterized using UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Dynamic Light Scattering, and energy-dispersive X-ray spectroscopy. The ionic stability of the produced nano-particles was tested in the presence of sodium chloride to determine their colloidal nature under physiological environments. Furthermore, the antioxidant activity of Gel-AgNP was tested using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H₂O₂). The agar disk diffusion method wasused to assess their antibacterial activity against bacterial strains. The Gel-AgNP showed a surface plasmon resonance around 440 nm. Dynamic Light Scattering (DLS) analysis revealed a hydrodynamic diameter of 107.9 nm, a polydispersity index of 0.27, and a zeta potential of +11.03 mV. Ionic stability revealed an increment in size from 107 to 237 nm as NaCl concentration was increased from 25 to 150 mM.. Gel-AgNP demonstrated strong antioxidant capacity with IC₅₀ values of 132 µg/mL for DPPH and 133 µg/mL for H₂O₂, after comparison with 550 and 210 µg/mL for gelatin alone. The disk diffusion assay revealed inhibition zones of 5-10 mm for <i>E. coli</i>, 2-7 mm for E. feacalis. 20 µg/mL doses possessed moderate sensitivity in <i>P. aeruginosa</i>, whereas <i>S. aureus</i> was inhibited only at 20 µg/mL. These findings lend credence to the Gel-AgNP potential in biological applications, particularly in producing antioxidant-rich antibacterial nanocomposites.