Investigating Physicochemical and Biological Properties of Chemical Silver Nanoparticles and Green Silver Nanoparticles Mediated with Morus alba L. Extracts and the Related Antimicrobial Mechanism

Abstract

In order to investigate the physicochemical properties and bioactivities of AgNPs prepared using green and chemical approaches and further explore the related antibacterial mechanism, one kind of chemical AgNPs (C-AgNPs) and three kinds of green AgNPs (G-AgNPs) mediated with aqueous extracts of Morus alba L. were prepared and characterized. All G-AgNPs displayed higher antioxidant activities in DPPH radical scavenging, reducing power and total antioxidant assays than C-AgNPs and extracts. Meanwhile, all G-AgNPs exerted significantly (P < 0.05) enhanced antimicrobial activities against various pathogens compared with C-AgNPs and extracts. Among prepared AgNPs, ML-AgNPs mediated with aqueous extract of Morus alba L. leaves exhibited the most powerful antibacterial effect with the largest inhibition zones (13.11 ± 0.76 mm for S. aureus, 13.27 ± 0.22 mm for E. coli) and the lowest minimum inhibition concentrations against S. aureus (6.125 μg/ml) and E. coli (3.125 μg/ml). ML-AgNPs could inhibit the growths of S. aureus and E. coli in time- and dose-dependent modes, and even could disrupt the bacterial structure integrality resulting in the leakage of intracellular contents. G-AgNPs, especially ML-AgNPs, with remarkable bioactivities could replace C-AgNPs as related agents applied in agriculture and medicine.