Development of an electrochemical biosensor for Nevirapine, based on a zinc oxide-nanoclay human serum albumin composite

Abstract

The optical and electrochemical features of ZnO synthesized samples with various precursor salts (zinc nitrate, acetate, and chloride) yielded acceptable surface nature and diagnostic functional groups. Significant trends related to precursors showed aggregation of nanoparticles, size distribution, stability, and conductivity. The crystallinity of ZnO crystals showed preferred growth planes while electrochemical parameters indicated reversibility of the electrochemical behaviour of ZnO. Under the specific electrolyte conditions, the rate of electron transfer translated to current density, and electrical resistance and revealed that the nitrate precursor produced the preferred ZnO product. Preparing different ratios of nanoclay (PGV and 1.44P) to ZnO composites, provided information about the best performing composite based on optical and electrochemical qualities. HR TEM images and SAED patterns showed laminated clay layers and crystallinity in pristine 1.44P, including partial agglomeration and spherical particles in ZnO as well as exfoliation and amorphous nature of the 1.44P ZnO composite. FTIR and XRD confirmed the chemical identity of PGV and 1.44P ZnO composites while cyclic voltammetry suggested that 0.5g 1.44P ZnO has the best electron transfer. The use of this composite with HSA-modified glassy carbon electrode as a platform for electrooxidation of NVP resulted in a single peak at 0.63V as previously reported. The supporting electrolyte, 1x (0.1M) PBS and optimization of the differential pulse voltammetry methodology led to selectivity over a wide concentration range which was 2 to 38μM. A low LOD of 0.39μM and LOQ at 1.30μM indicates sensitivity and hence superiority of the modified electrode. Reproducibility of the modified glassy carbon electrode fabrication protocol resulted in RSD figures of 1.17% while the precision was 1.35% for single concentration measurements. The repeatability of the modified electrode for consecutive measurements was RSD of 0.99% whereas the percentage of accuracy to evaluate stability was 98.65%. The 0,5g 1.44P ZnO HSA biosensor was furthermore used in samples of spiked urine and pharmaceutical tablet producing RSD values of 4.47% and 2.64% respectively for determinations of the analyte.