Green inspired synthesis of ZnO nanoparticles and its characterizations with biofilm, antioxidant, anti-inflammatory, and anti-diabetic activities

In recent times, the simple, eco-friendly, cost-effective synthesis of nanoparticles via green technology is developing interest on scientific community. In this report, the ZnO nanoparticles were synthesized via green and chemical routes. The green synthesis of nanoparticles were performed using Erythrina variegata leaf extract as capping and stabilizing agent whereas for comparative analysis chemical synthesis was carried out using sodium hydroxide as reducing agent. The gas chromatography-mass spectrometry (GC-MS) analysis listed the twenty phytochemicals in leaf extract. The green synthesized ZnO nanoparticles were analyzed by various techniques such as UV-visible, X-ray diffraction (XRD), Fourier transform infrared (FTIR), dynamic light scattering (DLS), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray (EDX) and mapping analyses. XRD showed the high crystalline characteristic of ZnO nanoparticles. The UV-visible analysis revealed the SPR (Surface Plasmon Resonance) band at 389 nm. The FTIR spectrum exposed the metal oxygen bonding vibrations at 864, 688 and 520 cm−1. The DLS analysis showed the formed particles were mostly at 25–35 nm and its poly dispersity index was 0.297. HR-TEM analysis illustrated the hexagonal and rectangular shaped nanoparticles in 15–30 nm. EDX and mapping analyses confirmed the presence of Zn and O elements in nanoparticles. The antibacterial activity exposed the strong inhibition of green-ZnO nanoparticles on both Gram-negative (Salmonella typhi) and Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacteria. The biofilm activity confirmed the antibacterial properties of green-ZnO nanoparticles on both Gram-negative (S. typhi) and Gram-positive (B. subtilis and S. aureus) bacteria by disintegrated films. The antioxidant activity, anti-inflammatory and anti-diabetic activities showed the effectual characteristic of green-ZnO nanoparticles. These results confirmed the Erythrina variegata leaf extract mediated green synthesized ZnO nanoparticles have interesting applications as antibacterial and antioxidant agents.