Green Biosynthesis and characterization of organic Fructus mori-composite silver nanoparticles: Enhanced antioxidant and antibacterial activities

The bacterial resistance to antibiotics is becoming a major challenge worldwide. The novel antimicrobial silver nanomaterial without bacterial resistance has the hope of becoming a suitable substitute for antibiotics. However, it is necessary to produce nanosilver with appropriate size and better antimicrobial performance through a green and simple synthesis process. In the present study, Fructus mori -composite silver nanoparticles (M-AgNPs) were greenly biosynthesized using mulberry fruits ( Fructus mori ). Ultraviolet-visible (Uy -vis) spectroscopy and Xray diffraction (XRD) indicated the formation of M-AgNPs with face centered cubic structure. Fourier transform infrared (FTIR) spectroscopy confirmed reducing and capping effects of mulberry fruits ' organic matter (polyphenols, flavonoids, etc.) on M-AgNPs. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) revealed that M-AgNPs were spherical and equably distributed, with a size of about 28 nm and an excellent stability. The antioxidant activity of M-AgNPs was evaluated by 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) assay, and the highest DPPH clearance rate was 84.69 +/- 3.68 %. M-AgNPs wrapped by biomolecules exhibited stronger antibacterial activity than chemically synthesized commercial nanosilver. MAgNPs ' diameters of inhibition zone against P. aeruginosa , E. coli and S. aureus were 13.9 +/- 0.4, 12.2 +/- 0.3 and 12.8 +/- 0.7 mm, respectively. The minimal inhibitory concentrations of M-AgNPs against E. coli and S. aureus were 4 mu g/mL and 16 mu g/mL, respectively, and the minimal bactericidal concentrations were 4 mu g/mL and 32 mu g/ mL, respectively. M-AgNPs showed time-dependent damage to the cell morphology of pathogens. Such biosynthesized organic silver nanoparticles have good prospects for biomedical applications.