AMPEROMETRIC BIOSENSORS FOR THE DETERMINATION OF TETRACYCLINE

Abstract

Amperometric biosensors based on planar graphite electrodes modified by multi-walled carbon nanotubes (CNTs) in chitosan, reduced graphene oxide (RGO), gold nanoparticles (Au NPs) in chitosan, nanocomposites based on them, and immobilized tyrosine enzyme for the determination of tetracycline have been developed. It is shown that tetracycline is a tyrosinase inhibitor, which provides the determination of tetracycline using a tyrosinase biosensor in the concentration range from 1 nM to 1 pM with LOD 0.5 nM. According to the results of kinetic studies of the reaction of the enzymatic conversion of phenol, it is found that in the presence of tetracycline, uncompetitive inhibition is observed on the tyrosinase biosensor. Electrodes modified with nanomaterials can be used as primary transducers of biosensors for fast and accurate determination of the tetracycline concentration. Combination of carbon nanomaterials with metal nanoparticles can form a nanocomposite with a synergistic effect. The use of carbon nanomaterials and metal nanoparticles as modifiers of the electrode surface made it possible to improve the analytical characteristics of the developed sensors: the range of determined concentrations in case of a biosensor modified with CNT/Au NPs and RGO/Au NPs was 1 nM - 1 pM and 0.1 nM - 1 pM, respectively. The correlation coefficient was 0.9925, and the lower limit of the determined concentrations was 50 pM (biosensor with CNT/Au NPs) and 0.7 nM (biosensor with RGO/Au NPs), respectively. The relative standard deviation of the results obtained using biosensors did not exceed 0.078. Methods for the determination of tetracycline using the proposed biosensors in milk and cosmetics have been tested. The compounds present in these samples, structurally unrelated to tetracycline, do not interfere with the determination.