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As a diagnostic biomarker, the detection of circular RNA (circRNA) is vital for the early screening of bladder cancer. Usually, the low abundance of circRNA in clinic samples results in the necessarily complicated extraction before detection. In this work, a tetrahedron supported CRISPR/Cas13a cleavage has been explored for direct electrochemical detection of circRNA in urine from bladder cancer. CRISPR/Cas13a system has been reasonably designed to recognize the characteristic back-splice junction site of circRNA. The activated CRISPR/Cas13a by circRNA can cleave uracil bases composed of DNA tetrahedron immobilized on the surface of gold electrode, resulting in the breakage of DNA tetrahedron and the release of electrochemical active molecule methylene blue. By virtue of highly catalytic efficiency of CRISPR/Cas13a and rigid structure of tetrahedron, the developed electrochemical biosensor can directly detect circRNA in 25 μL urine sample with the lowest detection limit of 0.089 fM and linear detection range from 10 fM to 50 nM in less than 10 min, so as to avoid complicated extraction process and benefit for on-site detection. [ABSTRACT FROM AUTHOR]

The accurate detection of immune checkpoint molecules on the surface of tumor cells is of great significance for immunotherapy. Herein, we propose a method based on cellular interface supported cascade signal amplification mediated by CRISPR/Cas13a system for in situ analysis of immune checkpoint molecules on bladder cancer cells. CD47 and EpCAM on bladder cancer cells can be sensitively monitored through T7 transcription amplification, CRISPR/Cas13a system and HCR triple signal amplification. Moreover, the established method can specifically differentiate EpCAM and CD47 positive bladder cancer cells and well serve for the evaluation of two kinds of membrane protein inhibitors. In a word, the method we proposed can successfully realize in situ analysis of immune checkpoint molecules on bladder cancer cells for guiding immunotherapy. • Immune checkpoint molecules can be analyzed in situ by our established new method. • The method is based on cellular interface supported cascade signal amplification. • Triple signal amplification is firstly explored based on CRISPR/Cas13a system. [ABSTRACT FROM AUTHOR]