Fluorescent/colorimetric dual-mode for detecting of MC-LR using bidirectional RCA coupled with CdTe QDs.

A fluorescent/colorimetric dual-mode biosensor was designed using CdTe QDs and CRISPR/Cas for the efficient and ultrasensitive detection of microcystin-leucine-arginine (MC-LR). The biosensor mainly activates the trans-cleavage activity of Cas12a through nucleic acid amplification technology, such as bidirectional rolling circle amplification (B-RCA), to perform signal conversion, release Ag+ from the cleaving hairpin, quench QD fluorescence, and perform signal presentation. The biosensor can perform fluorometric and colorimetric detection, enabling rapid field assays. It exhibits enhanced selectivity, increased sensitivity, and greater accuracy. The optimal conditions yield a detection range from 0.05 to 500 nM, with a minimum detectable concentration of 2.137 pM, surpassing the performance of traditional methods. The biosensor can effectively detect MC-LR in actual environmental samples. Overall, this study provided a general detection approach for the application of nucleic acid detection technology to detect trace pollutants in the environment.