Bifunctional MoS₂-BiVO₄ heterojunction boosts photoelectrochemical and colorimetric dual-mode sialic acid sensing

Sialic acid (SA), a vital biomarker, plays a key role in diagnosing and monitoring various diseases. Herein, a dual-mode sensing system integrating photoelectrochemical (PEC) and colorimetric detection approaches was developed for the sensitive and selective detection of sialic acid in serum samples. This system offers cross-validated, independent signal readouts, thereby enhancing detection accuracy and reliability. For the first time, we unveil the dual functionality of the MoS₂-BiVO₄ heterojunction, which significantly boosts both PEC and peroxidase-like nanozyme activities. This synergistic effect simplifies the construction of a dual-mode sensing system by utilizing a single bifunctional indicator rather than combining two separate indicators. A dual-functional MoS₂-BiVO₄ heterojunction with extensive interfacial contact was synthesized via a templating strategy using flower-like MoS₂ to guide the growth of BiVO₄ nanoparticles, resulting in enhanced charge separation and catalytic activity surpassing those of the individual components. To ensure selective recognition, a sialic acid-specific molecularly imprinted polymer (MIP) was further deposited on the MoS₂-BiVO₄ heterojunction, serving as the recognition element of the sensing system. The selective binding of sialic acid led to a decrease in both PEC and colorimetric signals, forming the basis for dual-mode detection. After optimizing preparation and detection conditions, the sensing system demonstrated excellent analytical performance, with a broad linear concentration range from 1 × 10^-11 M to 1 × 10^-6 M and a low detection limit of 3.4 × 10^-12 M. Its successful application to serum samples, with mutually validated dual-mode detection results, further confirmed the high accuracy and practical reliability of this dual-mode sensing system.