CRISPR/Cas14a-based logic system for intelligent microplastic monitoring based on multiple DNA walking mechanisms

In this research article, an intelligent clustered regularly interspaced short palindromic repeats (CRISPR)/Cas14a-based logic system was developed for microplastic monitoring on the basis of catalytic hairpin assembly (CHA) and DNA walkers on magnetic beads. Polyvinyl chloride (PVC) and polystyrene (PS) can activate the CHA-DNA walker sensing system to generate numerous single-stranded DNA fragments that can be recognized by Cas14a. After the cleavage reaction targeting the fluorophore-quencher reporter, a high Cy5 signal can be observed. The fluorescent biosensor is ultrasensitive, with a limit of detection of 3.4 ng/ml for PVC and 4.1 ng/ml for PS. Using PVC and PS as the two inputs, an OR logic gate was further developed. The input combinations of (10), (01), and (11) can give an output of 1. The sensing system is robust and can work in real water samples with good accuracy. Our proposed biosensor can provide an ultrasensitive and intelligent tool for microplastic monitoring.