Hybridization chain reaction and CRISPR/Cas12a-integrated biosensor for precise Ago2 detection.

This study introduces an innovative electrochemiluminescence (ECL) biosensor for the highly sensitive and specific detection of Argonaute 2 (Ago2) activity. Ago2, a key enzyme in the RNA interference (RNAi) pathway, plays a crucial role in gene regulation, and its dysregulation is associated with diseases such as cancer and viral infections. The biosensor integrates hybridization chain reaction (HCR) amplification and the CRISPR/Cas12a system, leveraging a multi-stage signal amplification strategy. The detection mechanism begins with Ago2-mediated cleavage of a designed hairpin RNA (HP-RNA), releasing single-stranded RNA (ssRNA) that triggers HCR. This amplification step generates long DNA polymers, which serve as activators for the CRISPR/Cas12a system. Cas12a's collateral cleavage activity amplifies the signal further by cleaving a DNA reporter labeled with a ruthenium-based luminophore, enhancing the ECL output. This dual amplification strategy achieves exceptional sensitivity, with a detection limit of 0.126 aM. The biosensor demonstrates excellent specificity, distinguishing Ago2 from other Argonaute proteins, and maintains high reproducibility and stability, retaining 94 % of its signal after two weeks of storage. Real-world applicability was confirmed by accurately detecting Ago2 in spiked cell lysates, with recovery rates exceeding 100 %. The combination of HCR, CRISPR/Cas12a, and ECL establishes a robust platform for biomarker detection, offering superior sensitivity and adaptability for clinical diagnostics, disease monitoring, and therapeutic evaluation. This biosensor represents a significant advancement in the development of next-generation diagnostic tools.