Integration of redox cycling in a photoelectrochemical sensing platform for tyrosinase activity evaluation

Photoelectrochemical (PEC) sensors have shown great promise in bioanalysis and diagnostic applications while redox cycling has offered a convenient approach for electrochemical signal amplification. Herein, we reported an innovative PEC sensing strategy for sensitive and selective detection of tyrosinase (Tyr) activity by utilizing the redox cycling of enzymatic generated electron donor on a visible light-responsive photoelectrode. In this protocol, phenol was enzymatically oxidized to catechol by dissolved O2 in the presence of Tyr. The subsequent oxidation of catechol by photogenerated-holes of graphene-Bi2S3 nanocomposites under visible light illumination could be cycled via the regeneration of catechol by tris(2-carboxyethyl)phosphine (TCEP) from the oxidized product (o-benzoquinone). Thus, the PEC platform could generate an amplified photocurrent signal correlated to the activity of Tyr. Our work demonstrated a new perspective for the design and development of highly sensitive and selective PEC sensors by utilizing the high efficiency and diversity of redox cycling strategies.