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MicroRNAs extracted from exosomes (exosomal miRNAs) have recently emerged as promising biomarkers for early prognosis and diagnosis. Thus, the development of an effective approach for exosomal miRNA monitoring has triggered extensive attention. Herein, a sensitive photoelectrochemical (PEC) biosensing platform is demonstrated for exosomal miRNA assay via the target miRNA-powered λ-exonuclease for the amplification strategy. The metal−organic framework (MOF)-decorated WO 3 nanoflakes heterostructure is constructed and implemented as the photoelectrode. Also, a target exosomal miRNA-activatable programmed release nanocarrier was fabricated, which is responsible for signal control. Hemin that acted as the electron acceptor was prior entrapped into the programmed control release nanocarriers. Once the target exosomal miRNAs-21 was introduced, the as-prepared programmed release nanocarriers were initiated to trigger the release of hemin, which enabled the quenching of the photocurrent. Under the optimized conditions, the level of exosomal miRNAs-21 could be accurately tracked ranging from 1 fM to 0.1 μM with a low detection limit of 0.5 fM. The discoveries illustrate the possibility for the rapid and efficient diagnosis and prognosis prediction of diseases based on the detection of exosomal miRNAs-21 and would provide feasible approaches for the fabrication of an efficient platform for clinical applications.

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