This paper reports a novel electrochemical method for detection of Glutathione (GSH) using Glutathione-S-Transferase (GST) – ZnO composite nanoparticles to investigate the prospects of the method for detection of cancer at an early stage. The purified GST enzyme was bound with ZnO nanoparticles by electrostatic interactions and the nanocomposite was dropcast on a silicon dioxide wafer. The GST functionalized deposited layer was then used as a chemiresistive channel to detect conjugation reaction between GSH and 1-Chloro-2,4-Dinitrobenzene (CDNB). The zeta potential values of the ZnO nanoparticles and the GST were found to be 13.4 mV and -6.21 mV, respectively. Around 73.8% binding was observed between the enzyme and ZnO nanoparticles. I-V analysis of the chemiresistive channel showed an increase in conductivity of the channel due to conjugation reaction between GSH and CDNB as compared to that of GSH or CDNB alone. I-V characterization of the GST functionalized layer was performed at various concentrations of GSH and a sensitivity and LOD (Limit of Detection) of 5.68 nA/μM and 41.9 nM were obtained, respectively. Thus from I-V analysis of the chemiresistive channel, the detection and quantification of GSH could be obtained. The kinetic parameters of both GST and nanoconjugate of ZnO nanoparticles and GST were determined with respect to its substrates, GSH and CDNB, using Michaelis–Menten model. This novel approach of detection of GSH by means of ZnO nanoparticle and GST enzyme composite can be further analyzed for in-vitro experiments, which will lead us to a new and efficient way of detecting certain types of cancers at an early stage.
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