Biological applications and antiviral activity of biosynthesized zinc oxide nanoparticles

Bacillus subtilis was used to biosynthesize zinc oxide nanoparticles (ZnO NPs) that were investigated as antimicrobial, antiviral, and antioxidant agents. ZnO NPs were characterized using transmission electron microscopy (TEM), Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, and UV-visible spectroscopy. The TEM results verified that ZnO NPs had a spherical shape and ranged in size from 10.3 to 32.7 nm. Zeta potential analysis revealed that ZnO NPs had a positive charge (+34.2 mV). In contrast to Pseudomonas aeruginosa (ATCC 27853), the ZnO NPs demonstrated a good antimicrobial activity against the tested bacterial strains including B. subtilis (ATCC 6633), B. cereus (ATCC 14579), Staphylococcus aureus (ATCC 25923), and Escherichia coli (ATCC 25922) as well as a high level of antifungal activity against the tested pathogenic fungal strains Fusarium oxysporum f. sp. lycopersici Fol4287, Aspergillus niger van Tiegh, and Candida albicans ATCC 10231. Moreover, the ZnO NPs showed antiviral activity toward phage vB_Ec_DUEC01. Phage infectivity was clearly reduced in a dose- and time-dependent manner when the bacteriophage was exposed to increased concentrations of ZnO NPs. After 60 minutes at 100 µg/ml, up to 73% inhibition was seen. Interestingly, ZnO NPs demonstrated a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity of 77.4% inhibition.