Synthesis, Characterisation, Antibacterial and Cytotoxic Assay of Zinc Oxide (ZnO) Nanoparticles

Aims: The objective of the present experiment was to synthesise ZnO nanoparticles by the environmental friendly process of bioreduction of ZnO salt with Camellia sinensis crop shoot extract and post synthesis to characterise and check their antibacterial potentiality and cytotoxicity.

Place and Duration of Study: Fermentation technology lab, School of biosciences and technology, VIT University, Vellore between July 2013 to December 2013.

Methodology: Green tea leaf extract (5%, 10% and 15%) and ZnO salt solution (0.1 M and 0.01 M) were prepared in different concentrations and mixed in three volumetric ratios (1:1, 1:2 and 1:3) to make a total of 18 combinations. The mixtures were incubated in a rotary shaker for 24-48 h. The synthesised nanoparticles were characterised subsequently by UV-Vis absorption spectroscopy, atomic force microscopy (AFM), particle size analysis, Fourier transfer infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. Upon characterization antibacterial activity of the nanoparticles were tested on three gram positive (Staphylococcus aureus, Salmonella sp., Bacillus sp.) and two gram negative (Escherichia coli, Pseudomonas sp.) bacteria. Finally haemolytic activity of the ZnO nanoparticles were compared with bulk ZnO salt and plant extract on RBC.

Results: The 370 nm peak obtained in UV-Vis spectrophotometer confirmed about the synthesis in case of only 15% extract. The AFM and particle size analysis revealed size of the nanoparticles at about 70 nm. FTIR analysis confirmed identical functional groups like tea leaf extract. Finally the crystalline nature of the nanoparticles were evident from XRD experiment. Antibacterial assay revealed inhibitory effect of the nanoparticles on all the five bacterial strains by producing prominent zone of inhibition. From the haemolytic assay the synthesised ZnO nanoparticles were found out to be biocompatible and non-toxic up to a conc. of 60 µg/ml.

Conclusion: The present experiment provided a simple, rapid and environmentally benign technique of synthesising spherical to elliptical ZnO nanoparticles having efficient antibacterial activity and non-toxicity which can be used for developing a successful drug delivery system.