Advances and challenges of signal readout systems in CRISPR-based biosensors for point-of-care testing of nucleic acid

In recent years, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) systems have emerged as promising tools in point-of-care testing (POCT) for nucleic acids. However, they still suffer from various challenges, including dependency on professional instruments and skilled operators. To address these issues, the integration of portable signal readout methods with CRISPR systems shows great potential in expediting their development and practical deployment in POCT. Consequently, this review provides a concise overview of the structures and characteristics of prevalent Cas nucleases, such as Cas9, Cas12, and Cas13, and summarizes the representative CRISPR-based biosensors employing the mentioned signal readout systems, including fluorescence, electrochemistry, glucose, color, and distance. Finally, we propose current challenges and insights into potential future developments in signal readout methods for CRISPR nucleic acid detection platforms and their prospects for integration into useful detection toolboxes. We hope this review can provide readers with a fresh perspective on the distinctive features and application potential of CRISPR-based biosensors in the context of POCT.