Bioactive properties of ZnO nanoparticles synthesized using Cocos nucifera leaves

Biosynthesis of zinc oxide nanoparticles has been reported using Cocos nucifera leaf (CNL) extract along with estimation of their antimicrobial potential before and after calcination using different micro-organisms. UV-visible spectra of ZnO nanoparticles showed absorption maxima at 383 nm and 363 nm, respectively, with 3.237 eV and 3.416 eV, respectively, as the corresponding band gap energies. FESEM and TEM images showed spherical morphologies of ZnO nanoparticles within the size range 109-215 nm. XRD analysis confirmed the formation of hexagonal wurtzite structures. ATR-IR spectra revealed the presence of stretching vibrations of N-H, O-H, C=C, C=O and NH2 groups along with C-H and N-H deformation involving biomolecules from CNL extract responsible for reduction and stabilization of ZnO nanoparticles. Uncalcinated ZnO nanoparticles displayed antibacterial activities only against S. aureus and P. aeruginosa whereas calcinated ZnO nanoparticles did not show antibacterial activities against E. coli, S. aureus, P. aeruginosa and B. subtilis. ZnO nanoparticles were not active against Penicillium spp., Fusarium oxysporum, Aspergillus flavus, Rhizoctonia solani as well as HCT-116 cancer cells before as well as after calcination. Antimicrobial nature and biocompatibility of ZnO nanoparticles were influenced by different parameters of the nanoparticles along with micro-organisms and the human cells. Non-antimicrobial properties of ZnO nanoparticles can be treated as a pre-requisite for its biocompatibility due to its inert nature. These ZnO nanoparticles can serve a dual purpose by facilitating use as antibacterial agent against susceptible micro-organisms as well as a biocompatible carrier molecule in drug delivery applications.