A new split DNA-based activation of CRISPR/Cas12a for amplification-free and dual-stimulus responsive detection and precise imaging of miRNA-221.

The CRISPR/Cas12a system is a genome editing technology that has been widely applied in biosensing and molecular diagnostics. However, the detection and regulation of its core components remain challenging. Therefore, we constructed a new split DNA-based activation method for the regulation of CRISPR/Cas12a, and based on that, an APE1-assisted activation CRISPR/Cas12a system for miRNA detection and a precise imaging method was also developed without amplification and complex design. Two split DNA were used as activators and embedded in two hairpins. When APE1 and miRNA-221 were simultaneously input, the DNA logic gate was started, thus releasing the determinant activation chain to activate the trans-shearing activity of the CRISPR/Cas12a system, so that the fluorescent probe signal can be significantly recovered. Different cleavage-activated chain hairpins were designed, and the influence on the trans-shear activity of CRISPR/Cas12a and the activation effect were discussed. And the method was successfully applied to detect the expression levels of miRNA-221 in cell lysates. The detection limit for miRNA-221 is 9.71 pmol/L (S/N = 3). At the same time, the method was applied for precise imaging of miRNA-221 within different cells and can effectively distinguish tumor cells. This study combines the regulation of the CRISPR/Cas system by split activators with the advantages of dual-responsive DNA logic circuits. The dual-response activation design effectively reduces false positive signals, thereby enhancing the detection and imaging accuracy. This method provides a novel design concept for utilizing split-DNA activation of the CRISPR/Cas system for nucleic acid detection and cell imaging.