A CATER Logic-Gated Nanodevice for Single Nucleotide Polymorphism Discrimination in Whole Blood

Single nucleotide polymorphisms (SNPs) are critical genetic markers for disease diagnosis and personalized medicine, yet their precise detection remains challenging. Conventional DNA strand displacement-based SNP assays employ either toehold-mediated or toehold-free strategies. Toehold-mediated strategies exhibit rapid kinetics but are limited to mutations located in or near the toehold, whereas toehold-free strategies provide broad flexibility in mutation placement but are hampered by slow reaction kinetics. To address this, we develop a comb-type cationic copolymer-accelerated toehold-free strand displacement reaction (CATER) platform that enables rapid, robust, and mismatch-sensitive electrochemical SNP detection without relying on toehold regions or enzymes. The cationic copolymer acts as a molecular chaperone to accelerate hybridization kinetics, while a dual-reporter system (methylene blue and ferrocene) enables ratiometric signal readout. Importantly, SNP discrimination is quantitatively achieved through kinetic signal separation and nonoverlapping ratiometric threshold intervals, with the latter further processed by a cascade logic-gate framework to generate discrete digital outputs for unambiguous mutation discrimination. The platform enables accurate determination of both mismatch positions and substitution types and retains discrimination capability in whole blood. This work establishes a generalizable strategy for high-resolution SNP analysis by integrating polymer-assisted kinetics with logic-gated electrochemical signal processing, highlighting its translational potential for SNP genotyping.