Enzyme electrode for aromatic compounds exploiting the catalytic activities of microperoxidase-11

Microperoxidase-11 (MP-11) which has been immobilised in a matrix of chitosan-embedded gold nanoparticles on the surface of a glassy carbon electrode catalyzes the conversion of aromatic substances. This peroxide-dependent catalysis of microperoxidase has been applied in an enzyme electrode for the first time to indicate aromatic compounds such as aniline, 4-fluoroaniline, catechol and p-aminophenol. The electrode signal is generated by the cathodic reduction of the quinone or quinoneimine which is formed in the presence of both MP-11 and peroxide from the substrate. The same sensor principle will be extended to aromatic drugs.

► We demonstrate for the first time the analytical application of the peroxidatic, peroxygenatic and dehalogenase activity of microperoxydase-11 in a sensor configuration.
► In contrast to HRP, MP-11 catalyzes the peroxide-dependent hydroxylation of aromatic substances.
► The sequential conversion of 4-fluoroaniline via aniline and pAP into the electrodeactive quinoneimine illustrates the catalytic capability of MP-11.
► LOD of phenolic substances is in the lower nanomolar, more than one order of magnitude lower than for the direct anodic oxidation or than for enzyme electrodes based on peroxygenases or cytochrome P450.