Synthesis of ZnO nanoparticles using the cell extract of the cyanobacterium, Anabaena strain L31 and its conjugation with UV-B absorbing compound shinorine.

In the present work, we describe a cheap, unexplored and simple procedure for the synthesis of zinc oxide nanoparticles (ZnONPs) using the cell extract of the cyanobacterium, Anabaena strain L31. An attempt was also made to conjugate synthesized ZnONPs with a UV-absorbing water soluble compound shinorine. UV-vis spectroscopy, X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, transmission electron microscopy (TEM) and TEM-selected area electron diffraction (SAED) analyses were made to elucidate the formation and characterization of ZnONPs and ZnONPs-shinorine conjugate. The synthesized ZnONPs were characterized by a sharp peak at 370 nm in UV-vis spectrum. TEM images showed the formation of spherical shaped nanoparticles with an average size of 80 nm. Results of selective area electron diffraction (SAED) pattern showed a set of rings which suggested uniform shape with hexagonal structure of ZnONPs. XRD spectra confirmed the crystalline structure of particles. Conjugation of ZnONPs with shinorine was successfully achieved at pH 7.0 and 10mM concentration of shinorine. The conjugate showed a zeta potential value of -3.75 mV as compared to +30.25 mV of ZnONPs. The change in zeta potential value of ZnONPs-shinorine conjugate was attributed to the changes in the surface functionalities after conjugation. The generation of in vivo reactive oxygen species (ROS) by Anabaena strain L31 with treatment of ZnONPs-shinorine conjugate showed approximately 75% less ROS generation as compared to ZnONPs. Properties exhibited by the ZnONPs-shinorine conjugate suggest that it may be used as a potential agent in developing environmental-friendly sunscreen filters of biological origin.