Nanoclay silver protein HSA electrochemical sensor for Zidovudine

Abstract

The synthesis process of AgNPs has attracted a lot in the field of biosensors, diagnostics and therapeutically application. An attempt to understand the effect of different concentrations of reducing agents in the synthetic design process has been investigated. In this study, we gather information on the voltammetry studies and relate it with UV- Vis and SEM analysis. Given the kinetics, LSPR band, and narrow size distribution of these methods, it was possible to compare the obtained measurements and clearly distinguish sizes and aggregation. AgNPs measured by SEM showed a statistically significant reduction of the nanoparticle sizes from 65 to 17.5 nm as the reducing agent was increased. The UV-Vis studies showed SPR bands shifting towards the blue region as the reducing agent concentration was increased, indicating a decrease in the particle sizes. It is worth emphasizing that CV and DPV coincide well with SEM on the aggregation of AgNPs at higher concentrations. 10 mM reducing agent concentration resulted in uniform outcomes for producing AgNPs with the smallest size in terms of FWHM in all the methods used in this study, while UV –Vis band gaps increased with increasing reducing agent concentration. In agreement with all the methods investigated, the results suggested that the best concentration of the reducing agent is 10 mM trisodium citrate for a target application. Furthermore, three different fractions of nanoclay (0.5, 1 and 1.5 g 1.44P) were functionalised with Ag forming silver nanoclay composites (Ag/1.44P) and the optical and electrochemical properties of nanoclay were studied. Optical, morphology and electrochemical techniques were used for the characterisation of the synthesised Ag/1.44P composites. The presence and the absence of functional groups observed in FTIR spectrum of Ag/1.44P, compared with those found in the spectra of silver and pure 1.44P proves that a reaction took place, thus a successful functionalisation of 1.44P with silver. All X-ray data of the composites showed four diffraction peaks within the silver spectrum range, with intensity of silver decreasing with increasing concentration of 1.44P. SEM represented well dispersed particles of different shapes with average particle sizes of 2.5, 27.5, 5 nm with enhanced concentration of 1.44P. The decrease in diffusion coefficient (D) values from 4.26x10-10, 2.50x10-13, 1.40x10-13 cm2.s-1 and electron transfer rate constant (Ks) 1.50x10-5, 3.94x10-7, 2.86x10-7 cm.s-1 with proportional 1.44P concentration depicted greater nanocomposites size. These findings suggest the usefulness of voltammetry as a complementary method that can be used as a qualitative guide to identify the size and aggregation of nanoparticles. Subsequently, AgNPs with 10 mM trisodium citrate and 0.5 g Ag/1.44P were used in the fabrication of sensor for zidovudine detection. The redox properties of the sensor (GCE/Ag/1.44P/HSA) were studied with cyclic voltammetry with varied scan rates using Randles-Sevcik equation, where diffusion coefficient was calculated as 1.55x10-11 cm2.s-1and Ks which was 3.40x10-6 cm.s-1, with one electron transfer process. The developed sensor produced acceptable %RSD for reproducibility and repeatability, with limit of detection of 0.3 M and 1.0 M limit of quantification. It was also found to be stable for 10 days and unaffected by the presence of interferences. The sensor can be applied in pharmaceuticals as it was able to successfully detect the target analyte in commercial tablets.