Green synthesis of zinc oxide nanoparticles by Neem extract as multi-facet therapeutic agents

This study was designed to develop green synthesized zinc oxide nanoparticles (ZnO-NPs) as potential nano-antibiotics against drug resistant microbes along with multifarious biomedical applications. The developed ZnO-NPs with an average size of 19.57 +/- 1.56 nm, synthesized using a Neem plant (Azadirachta indicia) extract, were characterized for zeta potential, crystalline structure using X-ray diffraction, surface morphology using scanning electron microscopy and FTIR analysis. The ZnO-NPs demonstrated a far superior antioxidant and enzyme inhibition activity with a significantly lower IC50 value as compared to a standard reference. Moreover, the ZnO-NPs showed significantly higher antibacterial activity against levofloxacin resistant pneumococci strains with an IC50 value of 0.014 mu M compared to 2.048 mM for that of levofloxacin. An in vivo acute toxicity study in mice showed slight changes in liver functional tests, especially renal functional tests, compared to that of the control group. Complete blood analysis showed no significant changes. Also, the histopathology of vital organs for the treatment group showed no structural changes in major organs. Overall, the results suggested that the present green synthesized Neem based ZnO-NPs could be developed as a therapeutic agent with antioxidant, enzyme inhibition and strong antibacterial potential against antibiotic-resistant bacteria that can be safely administered.