CRISPR/Cas12a-Enhanced Cascade Amplification for Ultra-sensitive DNA Ligase Detection

DNA ligases are essential enzymes for maintaining genomic integrity, serving as critical biomarkers for the early diagnosis of various malignancies. However, current detection paradigms are often hindered by laborious workflows, high costs associated with chemical modifications, and insufficient sensitivity for low-abundance targets. In this study, we developed an integrated, label-free detection system where DNA ligase serves as a molecular gatekeeper to initiate CRISPR/Cas12a activity. This strategy exploits the discovery that nicked activators exhibit significantly attenuated affinity for the Cas12a-crRNA ribonucleoprotein complex, whereas ligase-mediated repair restores backbone continuity to create a high-affinity intact activator. Upon this ligation-gated activation, the system triggers a subsequent circular DNA-mediated autocatalytic cascade, exponentially amplifying the initial enzymatic signal. Through this dual-stage amplification, we achieved an ultimate limit of detection (LOD) of 2.59 × 10^-6 U/mL. Notably, the platform can reach the analytical sensitivity of established methods in as little as 30 min (LOD of 6.12 × 10^-5 U/mL), significantly compressing the diagnostic time frame. The system demonstrates high selectivity against diverse physiological interferents and has been successfully validated for quantifying endogenous DNA ligase in MC38 tumor cell extracts. This innovative ligase-gated CRISPR cascade provides a modular and robust framework for rapid clinical diagnostics and advanced enzymology research.