A novel AuPt@CeVO4 bifunctional nanozyme with strong cascade SOD/POD-like catalytic activity enhances microfluidic photoelectrochemical signal amplification for ultrasensitive neuron-specific enolase detection.

A newly designed and highly effective cascade difunctional nanozyme, AuPt@CeVO₄, has been developed to function as a microfluidic photoelectrochemical (PEC) signal label, enabling the highly sensitive identification of bioproteins. This study utilized Z-scheme CuI/BiOI photoactive nanocomposites by applying CuI onto the BiOI nanoarray's surface, which serves as a sensor matrix to obtain an improved and stable photocurrent. The nanoarray arrangement in BiOI greatly improves the consistency and durability of the sensing platform. In contrast, the CuI/BiOI Z-scheme heterojunctions markedly enhance the photocurrent by efficiently separating the light-generated electron-hole pairs, which subsequently elevates the rate of·O₂^- generation. To enhance detection sensitivity, a cascade catalysis strategy employing the AuPt@CeVO₄ nanozyme has been reported to achieve PEC signal amplification. At first, the CeVO₄ demonstrates activity similar to superoxide dismutase-like (SOD-like), facilitating the breakdown of superoxide radicals (·O₂^-) into O₂ and H₂O₂. Following this, the produced H₂O₂ undergoes additional catalysis by AuPt enzymes exhibiting peroxidase-like (POD-like) properties, resulting in the formation of O₂ and H₂O. In the end, the generated O₂ partially dissolves in the electrolyte, serving as an efficient electron acceptor for enhancing the separation efficiency of electron-hole pairs, thus completing the enhancement of the PEC signal for the biosensor. Consequently, the proposed biosensor demonstrates exceptional sensitivity and excellent reproducibility, exhibiting extensive linear ranges between 0.01 pg/mL and 100 ng/mL, coupled with a minimum detection threshold of 0.0046 pg/mL for the identification of the small cell lung cancer biomarker, neuron-specific enolase (NSE).