Amplified Voltammetric Detection of Tyrosinase and Its Activity with Dopamine-Gold Nanoparticles as Redox Probes

Dopamine (DA) is an electrochemically active compound. In this work, we reported an electrochemical affinity biosensor for the detection of tyrosinase activity with DA-modified gold nanoparticles (DA-AuNPs) as redox probes. Hydrophilic boronic acids are well known to form tight diol-boronate ester covalent bonds with members of the diol family. In the sensing platform, monophenols of tyrosine residues immobilized onto gold electrode were catalytically oxidized by tyrosinase to o-diphenols. The resultant o-diphenols captured 4-mercaptophenylboronic acid (MBA)-capped AuNPs (MBA-AuNPs) through the formation of tight covalent bonds between o-diphenols and boronic acids of MBA-AuNPs. Electrochemically active DA-AuNPs were then attached by the anchored MBA-AuNPs via the interaction of MBA with DA, which facilities the amplified voltammetric detection. The current increased with the increase of tyrosinase concentration. The well-defined redox waves and high sensitivity resulting from dual-amplification of MBA-AuNPs and DA-AuNPs demonstrated that this method would be valuable for probing the activity of enzymes by generating a diol-containing substrate, and designing new types of electrochemical biosensor for sensitive detection of diol derivatives.