Fig. 1: EZ-READ platform for reliable profiling of circulating RNAs.

a EZ-READ technology. EZ-READ leverages an RNA-responsive transducer to regeneratively convert and catalytically enhance rare RNA targets. Each transducer carries catalytic nanoparticles – horseradish peroxidase (HRP) encapsulated in metal organic frameworks (ZIF-8) – via specific DNA probes. The scaffolded HRP@ZIF-8 nanoparticles thus bear strong catalytic activity and confer robust protection against environmental effects. During regenerative transduction, upon specific hybridization by RNA targets (e.g., miRNA and mRNA), the transducer activates directly, through selective cleavage of RNA-bound DNA linkers by duplex-specific nuclease (DSN), to release HRP@ZIF-8 nanoparticles in a target-recyclable manner. When partitioned within a fractal branching microfluidic chip, the released nanoparticles can singly catalyze strong chemifluorescence reaction to achieve digital quantification. b RNA-responsive transducer. Scanning electron micrograph of the assembled transducer confirmed high-density coverage by HRP@ZIF-8 nanoparticles. This experiment was repeated thrice independently with similar results. c Catalytic digital quantification. To exploit the potent activity of HRP@ZIF-8 nanoparticles for digital counting, we developed a fractal branching microfluidic chip with resistance-matched microwells to enable even nanoparticle partitioning and independent catalysis. Left: exploded view of the microfluidic chip. Middle: schematics of catalytic digital quantitation. HRP@ZIF-8 nanoparticles, reaction substate and air are sequentially introduced into the chip through vacuum loading to achieve independent catalysis. Right, fluorescence image of the reacted chip for digital counting. This experiment was repeated thrice independently with similar results. d Direct and reliable RNA detection by EZ-READ. As compared to conventional approaches (e.g., PCR) which require target amplification and are susceptible to variable amplification efficiencies, EZ-READ bypasses all steps of conventional PCR detection and achieves direct transduction and catalytic signal enhancement. e Clinical application. Leveraging its programmable detection, we applied EZ-READ to measure various RNA subtypes in clinical blood samples and developed multi-step classification models to accurately diagnose GBM patients and molecularly subtype the tumors.