CRISPR/dCas9-based hotspot self-assembling SERS biosensor integrated with a smartphone for simultaneous, ultrasensitive and robust detection of multiple pathogens

Accurate detection of multiple pathogens in the early stages of infection is critical for guiding treatment and saving patients' lives, but current methods are still challenged by low sensitivity, poor robustness and long turnaround times. Here, we report a CRISPR/dCas9-based hotspot self-assembling surface-enhanced Raman scattering (SERS) biosensor (called dCasSERS) and its integration with a smartphone to address these challenges. In this design, bacterial DNA was pre-amplified by loop-mediated isothermal amplification (LAMP), and the repeat sequences of the amplicons were recognized by CRISPR/dCas9, providing abundant sites for the assembly of gold nanoparticles (AuNPs) and forming numerous hotspots for SERS analysis. Using AuNPs labeled with different Raman molecules as reporters, the presence of Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli O157:H7 (E. coli O157:H7) could be dexterously converted into distinguishable SERS signals. CRISPR/dCas9-based amplicon-specific recognition and SERS hotspot self-assembly improved the specificity and sensitivity, enabling the biosensor to simultaneously detect three target pathogens down to 1 CFU/mL without any cross-reactivity. By introducing a rapid extraction procedure and a smartphone-integrated handheld Raman spectrometer, rapid on-site analysis of multiple pathogens could be achieved in less than 50 min. The accuracy and robustness of the biosensor were demonstrated by 500 real urine specimens. This study displays a new paradigm for CRISPR/Cas-based self-assembly of SERS hotspots and provides insight into the future development of pathogen screening tools.