Exploiting the Potential of Spherical PAM Antenna for Enhanced CRISPR-Cas12a: A Paradigm Shift toward a Universal Amplification-Free Nucleic Acid Test Platform

The CRISPR-Cas12a system has shown tremendous potential for developing efficient biosensors. Albeit important, current CRISPR-Cas system-based diagnostic technologies (CRISPR-DX) highly rely on an additional preamplification procedure to obtain high sensitivity, inevitably leading to issues such as complicated assay workflow, cross-contamination, etc. Herein, a spherical protospacer-adjacent motif (PAM)-antenna-enhanced CRISPR-Cas12a system is fabricated for universal amplification-free nucleic acid detection with a detection limit of subfemtomolar. Meanwhile, the clinical detection capability of this sensor was further verified using gold-standard real-time quantitative polymerase chain reaction through <i>Mycobacterium tuberculosis</i> measurement, which demonstrated its good reliability for practical applications. Importantly, its excellent sensitivity is mainly ascribed to high efficiency of target search induced by a localized PAM-enriched microenvironment and improved catalytic activity of Cas12a (up to 4 folds). Our strategy provides some new insights for rapid and sensitive detection of nucleic acids in an amplification-free fashion.