Apoptosis and inhibition of human epithelial cancer cells by ZnO nanoparticles synthesized using plant extract

The present research work reports in-<i>vitro</i> anti-cancer activity of biologically synthesized ZnO nanoparticles (ZnO NPs) against human carcinoma cells viz SCC-40, SK-MEL-2 and SCC-29B using Sulforhodamine-B (SRB) Assay. ZnO NPs were synthesized by a unique and novel biological route using Temperature-gradient phenomenon where the extract of combination of <i>Catharanthus roseus</i> (L.) G. Don (C. <i>roseus</i>), <i>Azadirachta indica</i> (A. <i>indica</i>), <i>Ficus religiosa</i> (F. <i>religiosa</i>) and NaOH solution were used as synthesis medium. The morphology of the ZnO NPs was characterized by Transmission Electron Microscopy (TEM). TEM images reveal that particle size of the samples reduces from 76 nm to 53 nm with the increase in reaction temperature and 68 nm to 38 nm with the increase in molar concentration of NaOH respectively. XRD study confirms the presence of elements and reduction in crystallite size with increase in reaction temperature and NaOH concentration. The diffraction peaks show broadening and a slight shift towards lower Bragg angle (2<i>