Hepatocellular carcinoma (HCC) typically develops in a clinically silent manner, and the suboptimal sensitivity and specificity of currently available diagnostic biomarkers remain significant obstacles to its accurate and early detection. To improve molecular diagnostic performance, we developed a dual-function CRISPR/Cas12a assisted strand displacement reaction (dCas12a-SDR) with hexaammine ruthenium(III) chloride (RuHex)-loaded DNA condensate for ultrasensitive and highly specific detection of HCC-associated mRNAs. Upon target recognition, the previously sequestered Cas12a activation site within the electrode-immobilized capture probe is exposed, thereby inducing hybridization between the accessible single-stranded domains retained in RuHex-loaded DNA condensates (RuDC) and the displacement strand (Ds), which ultimately leads to the release of electroactive Ds-RuDC condensates and the effective activation of Cas12a. Activated Cas12a then removes the activation site via cis-cleavage, releasing the target to enter subsequent reaction cycles; concurrently, the activated system initiates trans-cleavage of adjacent capture probes and Ds-RuDC assemblies on the electrode that harbor trans-cleavage motifs, thereby promoting the release of RuDC from the electrode interface. This cascade ultimately leads to a pronounced reduction in the electrochemical signal. Owing to this target-triggered dual cis- and trans-cleavage mechanism mediated by Cas12a, the biosensor achieves highly efficient signal amplification. The platform affords a limit of detection as low as 39.2 aM for PD-L1 mRNA and exhibits excellent specificity, stability, and reproducibility. Moreover, by jointly detecting a panel of HCC-associated mRNAs (PD-L1, GPC3, EpCAM, and FGA), the platform successfully discriminated healthy individuals from patients with early-stage hepatocellular carcinoma in clinical serum samples. Collectively, this platform provides a powerful tool for molecular diagnosis of hepatocellular carcinoma.
