A dual-mode sensor for rapid detection of procymidone: "Dark box" qualitative analysis and electrochemical quantification mediated by PdHPCN-222/PEI-rGO and CRISPR/Cas12a.

This study presents an integrated dual-mode sensing strategy, in which qualitative fluorescence screening is followed by quantitative electrochemical detection, improving detection efficiency and enabling rapid PCM analysis. It develops a novel fluorescence electrochemical aptasensor that combines in vitro "Dark-box" applications with CRISPR/Cas12a system electrode surface sensing technology. PCM activates the DNA walker, and the DNAzyme induces cyclic cleavage of DNA strands bearing the Carboxyfluorescein (FMA) group. After magnetic separation, the fluorescence reaction combined with the "Dark box" enables the preliminary qualitative analysis of procymidone (PCM). Following the preliminary qualitative detection, the solution is introduced to the electrochemical aptasensor platform integrated with the CRISPR/Cas12 system. The Cas12a system triggers cyclic cleavage, producing a signal change that enables the electrochemical quantitative detection of PCM. An fluorescence (FL) response occurs when the PCM concentration in spiked samples is at or above 1 pg·mL, allowing for qualitative fluorescence detection. The EC platform's detection limit is 8.51 × 10 ng·mL, with a range of 1 × 10 ng·mL to 1 × 10 ng·mL. The designed dual-mode sensor provides reliable monitoring of PCM in real samples.