Optimization of microwave-assisted green synthesis of zinc oxide nanoparticles using Ocimum americanum and Euphorbia hirta extracts: In vitro evaluation of antioxidant, anti-inflammatory, antibacterial, cytotoxicity, and wound healing properties

Abstract

This investigation optimized the microwave-assisted green synthesis of zinc oxide nanoparticles utilizing Ocimum americanum and Euphorbia hirta extracts for enhanced wound healing applications. The synthetic process employed microwave radiation and natural reductants from plant extracts, offering an environmentally benign, cost-effective, and time-efficient approach. Design expert software was utilized to optimize the synthesis, with the concentration of the zinc sulphate precursor, microwave irradiation time, and plant extract ratio as independent variables, and nanoparticle size as the dependent variable. The optimal conditions (12.8 ​mM zinc sulphate, 12 ​min of irradiation, and a 26:1 plant extract ratio) yielded Zinc oxide nanoparticles characterized by UV, SEM, FTIR, XRD, EDX, and zeta-sizer techniques to assess the nanoparticle formation, morphology, functional groups, crystal structure, elemental composition, and stability. The nanoparticles exhibited strong antioxidant activity (90.23% ​± ​0.82% at 50 ​μg/mL), comparable anti-inflammatory effects to diclofenac sodium (86.13% ± ​1.03% at 50 ​μg/mL), significant concentration-dependent antibacterial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas sp., and effective biofilm inhibition. Time-kill curve assays demonstrated effective bacterial count reduction, while zebrafish embryonic toxicity studies indicated minimal toxicity at lower concentrations (5–20 ​μg/mL) with reduced hatching and survival rates at higher concentrations (40–80 ​μg/mL). Additionally, zinc oxide nanoparticles promoted wound healing in vitro by enhancing fibroblast cell migration and proliferation of mouse fibroblast (3T3-L1) cells. The results elucidate the potential of microwave-assisted green-synthesized zinc oxide nanoparticles incorporating plant extracts in advancing wound care therapies through their multifaceted biological applications.