An amperometric glutathione biosensor based on chitosan-iron coated gold nanoparticles modified Pt electrode

A method is described for development of an amperometric biosensor for determination of glutathione (GSH), by immobilizing covalently a glutathione oxidase (GSHOx) onto the surface of gold coated magnetic nanoparticles (Fe@AuNPs) modified Pt electrode. Chitosan was used to introduce amino groups onto the surface of Fe@AuNPs. The morphology and covalent linkage of GSHOx led to high enzyme loading and better shelf life. The enzyme electrode was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), Fourier transform infrared (FTIR) and electrochemical impedance spectroscopy (EIS). The electrode showed maximum response within 4 s, when polarized at +0.4 V, pH 7.0 and 25 °C. There was a linear relationship between electrode response and glutathione concentrations in the range 5.0-4000 μmol L−1 with a detection limit of 0.1 μmol L−1. An amperometric method of GSH determination was developed using this biosensor. The evaluation studies showed that the method was reliable as mean analytic recoveries of 50 μM and 100 μM of GSH were 97.5 ± 1.7 and 96.1 ± 1.3 respectively and within and between CVs for glutathione determination in blood RBCs were <2.14% and <2.39% respectively. The biosensor showed 50% loss in its initial activity after its 150 uses over a period 4 months, when stored at 4 °C. GSH concentration in hemolysated erythrocytes as measured by the present biosensor was 2.8 mmol L−1 in apparently healthy persons.