Photocatalytic, Antimicrobial, and Cytotoxic Efficacy of Biogenic Silver Nanoparticles Fabricated by Bacillus amyloliquefaciens

The biomass filtrate of the endophytic bacterial strain Bacillus amyloliquefaciens Fa.2 was utilized for the eco-friendly production of silver nanoparticles (Ag-NPs). The yellowish-brown color's optical properties showed a maximum surface plasmon resonance at 415 nm. The morphological and elemental composition analysis reveals the formation of spherical shapes with sizes of 5-40 nm, and the Ag ion comprises the major component of the produced Ag-NPs. X-ray diffraction confirmed the crystalline structure, whereas dynamic light scattering reveals the high stability of synthesized Ag-NPs with a polydispersity index of 0.413 and a negative zeta potential value. The photocatalytic experiment showed the efficacy of Ag-NPs to degrade methylene blue with maximum percentages of 73.9 +/- 0.5 and 87.4 +/- 0.9% under sunshine and UV irradiation, respectively, compared with 39.8% under dark conditions after 210 min. Additionally, the reusability of Ag-NPs was still more active for the fifth run, with a percentage decrease of 11.6% compared with the first run. Interestingly, the biogenic Ag-NPs showed superior antimicrobial activity against different pathogenic Gram-negative bacteria (MIC = 6.25 mu g mL(-1)), Gram-positive bacteria (MIC = 12.5 mu g mL(-1)), and uni- and multicellular fungi (MIC = 12.5 mu g mL(-1)). Moreover, the biosynthesized Ag-NPs could target cancer cells (Pc3 and Mcf7) at low concentrations compared with normal cell (Vero) lines. The IC50 of normal cells is 383.7 +/- 4.1 mu g mL(-1) compared with IC50 Pc3 (2.5 +/- 3.5 mu g mL(-1)) and McF7 (156.1 +/- 6.8 mu g mL(-1)). Overall, the bacterially synthesized Ag-NPs showed multifunctional features to be used in environmental catalysis and biomedical applications.