Tetrahedral framework nucleic acids linked CRISPR/Cas13a signal amplification system for rare tumor cell detection

The sensitive and accurate detection of rare tumor cells provides precise diagnosis and dynamic assessment information in various tumor spectrums. However, rare tumor cells assay is still a challenge due to the exceedingly rare presence in the blood. In this research, we develop a fluorescent approach for the identification of rare tumor cells based on a combination of immunosorbent capture and a three-step signal amplification strategy. First, rare tumor cells are captured by immunoadsorption on 96-well plates. Second, self-synthesized tetrahedral framework nucleic acids (tFNAs) spontaneously anchor into the lipid bilayer of rare tumor cells, resulting in a "one to more" amplification effect. Then, the double-stranded DNA (dsDNA) binds to the vertices of the tFNAs and generates a large amount of target RNA by T7 polymerase, which is the secondary signal amplification. Finally, the target RNA activates the collateral cleavage ability of CRISPR/Cas13a, and the reporter RNA is cleaved for third signal amplification. The detection limit of the proposed method is down to 1 cell mL^-1. Furthermore, the tFNAs-Cas13a system is also shown to be capable of detecting rare tumor cells in spiked-in samples and clinical blood samples. This platform enables speedy detection of rare tumor cells with high sensitivity and good specificity, and shows great potential for tumor diagnosis.