Electrochromic gated photoacoustic-electrochemiluminescent bimodal biosensing via domino cascade amplification for...

Achieving intrinsic physical correlation between independent transduction pathways remains a key challenge in multimodal biosensing. Herein, an electrochromism-gated paradigm that synchronously regulates photoacoustic (PA) and electrochemiluminescent (ECL) outputs within a bipolar electrode (BPE) architecture was designed for exosome analysis. This platform was constructed using a bifunctional cathode composed of silver nanoparticles decorated tungsten oxide nanosheets (Ag NPs@WO₃ NSs). In this design, WO₃ NSs act as the core electrochromic component whose voltage-induced reduction significantly enhances optical absorption, thereby generating a strong PA signal under laser excitation. Concurrently, the integrated Ag NPs leverage the same voltage stimulus to catalyze the hydrogen evolution reaction, thereby amplifying the anodic ECL emission of luminol as a complementary signal output. This shared voltage-modulating mechanism ensures the intrinsic synchronization of both the optical and acoustic signals. To validate this unique co-mediation concept and explore its sensing applicability, a target-initiated proximity hybridization coupled with rolling circle amplification was employed to introduce copper nanoclusters-tagged DNA probes. These probes trigger a cascade that converts conductive Ag NPs into poorly conductive AgBr, thus dismantling the electrochromic and catalytic functions of Ag NPs@WO₃ NSs cathode. As anticipated, this domino cascade effect leads to the synchronous attenuation of both ECL and PA outputs, enabling quantitative detection of colorectal cancer-derived exosomes over a concentration range from 10³ to 10⁸ particles/mL with high specificity. By exploiting voltage-gated PA generation via electrochromism, this work pioneers a paradigm-shifting sensing strategy that surpasses conventional indirect coupling methods, providing a promising avenue for developing advanced multimodally integrated diagnostic systems.