DNA Hydrogel-Templated Synthesis of Electrochemiluminescence Active Gold Nanoclusters with T7 Exonuclease Amplification for Ultrasensitive Microcystin-LR Detection

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Eutrophication-induced microcystin-LR (MC-LR), a potent hepatotoxin, poses significant threats to aquatic ecosystems and human health, necessitating the development of sensitive detection methods. In this study, we report, for the first time, a programmable gold nanoclusters (AuNCs) gel sphere used as an emitter for constructing an electrochemiluminescence (ECL) biosensor. The presence of MC-LR initiates a T7 exonuclease-mediated cyclic cleavage of the hybridization chain, releasing a single strand that captures the nanoprobe. A rolling circle amplification-synthesized, polyadenine-rich three-dimensional DNA nanohydrogel ball (DGB) serves as a dual-functional scaffold, enabling the in situ growth of AuNCs while simultaneously acting as a signal-amplifying carrier. During AuNCs synthesis, the DGB undergoes a blooming structural transition, exposing additional binding sites that hybridize with the electrode surface, thereby generating quantifiable ECL signals. The biosensor exhibits outstanding performance, with a linear detection range from 0.1 pM to 1 nM and a detection limit of 62.3 fM (S/N = 3). Its successful applications in real water and serum samples underscore its potential for environmental monitoring and clinical diagnostics, offering a novel paradigm for trace contaminant detection.