Application of Glutathione Coated ZnO Nanoparticles to Study the Oxidative Stress in Bacterial Cells

摘要

In this study, oxidative stress in the bacterial culture of gram negative i.e., Escherichia coli (E. coli), and gram positive i.e., Staphyllococcous aureus (S. aureus) are studied using bare and glutathione (GSM, reduced) coated ZnO nanoparticles (NPs). ZnO-NPs were synthesized at pH 7.2 through non-aqueous sol-gel method using zinc acetate dihydrate precursors. Reduced glutathione (GSH) was coated on ZnO by physical mixing in a 1:1 ratio. Morphological observations revealed crystalline spherical particles of ～15 nm in size with almost uniform shape and size distribution. The FTIR studies, confirmed GSH coating on ZnO surface evidenced by mixed vibrational bands. Both the bacteria were cultured in Luria-Bertani (LB) media at 37 ℃ and 160 RPM, with different concentrations of bare ZnO-NPs and GSH-coated ZnO-NPs separately. Minimum Inhibitory Concentration (MIC) of the ZnO-NPs for E-coli is found as 6 mM and for GSH-coated ZnO-NPs it is 11 mM. However, MIC of ZnO-NP for S-aureus is found as 14 mM whereas that for GHS coated ZnO-NPs it is 26 mM. This means irrespective of the type of bacteria, MIC has increased by ～1.8 times after GHS coating on the ZnO-NPs. This study reveals that ZnO nanoparticles were found more toxic due to comparatively high density of reactive oxygen species (ROS) on surface than GSH coated ZnO-NPs i.e., GSH functionalized ZnO-NPs which exhibits effectively lesser oxidative stress to the system. Hence, GSH coated ZnO-NPs exhibits better biocompatibility and reduce the degree of inhibition to the bacterial growth probably because of the presence of thiol group in GSH.