Rapid and accurate SERS assay of disease-related nucleic acids based on isothermal cascade signal amplifications of CRISPR/Cas13a system and catalytic hairpin assembly.

Developing rapid, accurate and convenient nucleic acid diagnostic techniques is essential for the prevention and control of contagious diseases that are prone to gene mutations and may have homologous sequences, especially emerging infectious diseases such as the SARS-CoV-2 pandemic. Herein, a one-pot SERS assay integrating isothermal cascade signal amplification strategy (i.e., CRISPR/Cas13a system (Cas13a) and catalytic hairpin assembly (CHA), Cas13a-CHA) and SERS-active silver nanorods (AgNRs) sensing chips was proposed for rapid and accurate detection of disease-related nucleic acids. Taking SARS-CoV-2 RNA assay as a model, the Cas13a-CHA based SERS sensing strategy can achieve ultra-high sensitivity low to 5.18 × 10 copies·mL within 60 min, and excellent specificity, i.e., not only the ability to identify SARS-CoV-2 RNA from gene mutations, but also incompatibility with coronaviruses such as severe acute respiratory syndrome (SARS-CoV), Middle East respiratory syndrome (MERS-CoV), and other respiratory viruses. The proposed Cas13a-CHA based SERS assay for SARS-CoV-2 RNA has satisfactory sensitivity, specificity, uniformity, and repeatability, and can be easily expanded and universalized for screening different viruses, which is expected to promise as a crucial role for diagnosis of disease-related nucleic acids in various medical application scenarios.