Biotoxic trace metal ion detection by enzymatic inhibition of a glucose biosensor based on a poly(brilliant...

A highly sensitive glucose oxidase (GOx) electrochemical biosensor for the determination of the biotoxic trace metal ions Hg²⁺, Cd²⁺, Pb²⁺ and Cr^VI by enzyme inhibition has been developed. GOx was immobilized on a novel sensing platform consisting of poly(brilliant green) films formed by potential cycling electropolymerization in sulfuric acid doped ethaline deep eutectic solvent on multiwalled carbon nanotube modified glassy carbon electrodes. Polymer films produced in this medium presented more uniform morphology and better electrochemical sensing properties than those prepared in aqueous solution. The inhibitor concentration necessary to give 50% inhibition, I₅₀, was used for the determination of the type of reversible inhibition, and the relationship between I₅₀ and the inhibition constant K_i is discussed. The new biosensor was successfully used for the determination of biotoxic trace metal ions with a nanomolar limit of detection, lower than in the literature, very good repeatability, stability and selectivity, and was applied successfully to detection of the toxic trace metal species in milk samples.