On the role of cysteamine modification of gold electrodes in redox reactions with dopamine

Abstract

While cysteamine (CystAm) is widely used for forming thiol-based self-assembled monolayers on gold electrodes in biosensor applications, its broader influence on dopamine (DA) sensing mechanisms remains underexplored. This study re-evaluates the impact of CystAm on both electrochemical and biochemical reactions involving DA. Using model electro chemical experiments supported by X-ray photoelectron spectroscopy, oxygen mini-sensor, and quartz crystal microbalance studies, it was shown that CystAm primarily suppresses the gold electrode’s oxygen reduction reaction, thereby altering non-enzymatic DA redox behavior. In contrast, it does not significantly affect enzyme immobilization, retained mass, elution rates, or enzymatic activity on the electrode surface. Based on this knowledge, a CystAm-modified gold electrode function alized with a tyrosinase–chitosan biosensing layer was produced. The resulting electrode was evaluated in artificial saliva spiked with low concentrations of DA. It exhibited high reliability, achieving average DA recovery rates of 99–100% with precision values < 10%, demonstrating its potential for accurate analysis in biological samples.