Biosynthesis, optimization, and multifunctional biomedical applications of gold nanoparticles mediated by Streptomyces sp. YJD18.

This study employed extracellular secretions from Streptomyces sp. YJD18, isolated from saline-alkali soil, to synthesize gold nanoparticles (AuNPs) using optimized conditions: 60 min boiling, 48 h mycelial suspension, pH 6.25, 1.0 mM chloroauric acid, 1:1 supernatant-to-water ratio, and 9.0 g mycelial wet weight. AuNP formation was confirmed by a yellow-to-ruby red color shift and a 525 nm UV-Vis absorption peak. TEM and SAED revealed irregular, polycrystalline spheres with good dispersity. Zeta potential (-11.6 mV) and DLS (20-30 nm) confirmed uniform surface properties and narrow size distribution. FTIR showed C-H and amide groups did not contribute to AuNP synthesis. The AuNPs exhibited dose-dependent cytotoxicity against cancer (cervical, lung, liver, breast) and normal (kidney, liver) cells, optimal wound healing at 30 μg/mL (58.07% at 48 h), and concentration-dependent DPPH scavenging (IC50: 12,419.00 μg/mL), suggesting biomedical potential.