초록
<P>This paper presents a comparative study of the toxicity of pristine-ZnO and <SMALL>L</SMALL>-histidine-incorporated ZnO toward <I>Escherichia coli</I> (<I>E. coli</I>) as a Gram-negative model organism. Pristine-ZnO and <SMALL>L</SMALL>-histidine-incorporated ZnO with different <SMALL>L</SMALL>-histidine concentrations were synthesized using an open aqueous solution bath technique. XRD studies revealed the formation of polycrystalline wurtzite ZnO. The average crystallite size of the synthesized <SMALL>L</SMALL>-histidine-incorporated ZnO decreased as the concentration of <SMALL>L</SMALL>-histidine increased. The FTIR spectra showed the presence of Zn-O, CO<SUB>2</SUB><SUP>-</SUP>/CO<SUB>3</SUB><SUP>-</SUP>, and C-N (only in <SMALL>L</SMALL>-histidine-incorporated ZnO samples) and −OH bond vibration signals in all samples. The chemical purity of all the samples was ensured using XPS analysis. The microbial activity of these samples was investigated using <I>E. coli</I>. The solution with 100 μg/mL ZnO in sterile distilled water showed up to 94% growth inhibition of <I>E. coli</I>, establishing antibacterial activity. However, <SMALL>L</SMALL>-histidine incorporated in ZnO showed reduced antibacterial activity with the increase of the concentration of <SMALL>L</SMALL>-histidine in ZnO. Furthermore, flow cytometry studies during the interaction of ZnO and <I>E. coli</I> confirmed the generation of reactive oxygen species (ROS), validating its antibacterial activity. The interaction of <SMALL>L</SMALL>-histidine-incorporated ZnO and <I>E. coli</I> showed declining ROS with the increase in the <SMALL>L</SMALL>-histidine concentration, indicating a ZnO toxicity reduction.</P><BR>[FIG OMISSION]</BR>