Signal transduction and engineering strategies of CRISPR-Cas biosensors: A review

Class 2 CRISPR-Cas systems are characterized by their single-component architecture and RNA-guided effector proteins such as Cas9, Cas12, and Cas13. They have established a versatile molecular framework for developing a new generation of biosensing platforms. The programmability of these systems, combined with their unique enzymatic properties, particularly the target-activated trans-cleavage of reporters, allows molecular detection with exceptional specificity and sensitivity. However, translation of these advantages into practical applications and resource-limited settings remains challenging due to complex signal readout, engineering constraints, and integration hurdles.

This review systematically examines the current CRISPR-Cas biosensing landscape, focusing on the operational mechanisms of major effector proteins and the broad spectrum of signal transduction methodologies that convert molecular recognition into measurable signals. These approaches encompass optical techniques (fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence) and electrochemical-based methods (conventional electrochemistry, photoelectrochemistry, electrochemiluminescence). We further highlight engineering advances that enhance performance through protein engineering, amplification-free strategies, and expansion to non-nucleic acid targets and multiplexed assays. Integration with miniaturized platforms, digital readouts, and artificial intelligence is accelerating the transition toward practical use. We conclude that CRISPR-Cas biosensors hold considerable potential to advance decentralized diagnostics, biomedical research, and global health surveillance.