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.
Keywords: Biosensor; CRISPR-Cas systems; Fluorescence; Rare tumor cells; Tetrahedral framework nucleic acids.
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