Microfluidic-Integrated CRISPR-Cas Biosensor for Marine Pollutant and Pathogen Monitoring: A Review

Marine ecosystems face escalating threats from heavy metals, harmful algal bloom toxins, pathogens, and antibiotic resistance genes, yet conventional detection methods remain laboratory-dependent and incapable of real-time, multiplexed field monitoring. CRISPR-Cas diagnostics, leveraging programmable Cas12a/Cas13a trans-cleavage for attomolar-level sensitivity, offers a transformative solution when integrated with microfluidic platforms that provide the automation and miniaturisation required for field deployment. This review systematically examines this emerging convergence across four marine target classes: heavy metals, biotoxins, pathogens, and resistance genes alongside integration architectures, signal readout strategies, and comparative performance benchmarking. We identify that only a small fraction of reported platforms have been validated in authentic seawater, with cross-class multiplexing, biofouling resistance during autonomous deployment, and regulatory standardisation remaining largely unaddressed. By synthesising this rapidly developing literature and articulating these unresolved challenges, this review provides a foundational reference and research agenda for translating microfluidic-CRISPR biosensors from laboratory proof-of-concept to operational marine environmental surveillance.