Asymmetrically modified hydrogel nanochannel biosensor for label-free and selective kanamycin monitoring

Nanochannel sensors have attracted much attention in the field of biosensing due to their unique domain-limiting effect and signal transduction mechanism. However, the traditional surface modification strategy often suffers from the low probe immobilisation efficiency, channel clogging and limited modification sites. To address these challenges, this study proposes a synergistic construction strategy combining hydrogel filling and asymmetric modification. Using polyethylene terephthalate (PET) membranes as the substrate, we constructed acrylic acid (AAc)-co-acrylamide (AAm)-co-methyl methacrylate (MMA) ternary copolymerised hydrogel within cylindrical nanochannel through free radical polymerisation reaction. Further functionalization was achieved through PEI/Zr⁴⁺ asymmetric modification, enabling precise charge gradient regulation and yielding a composite nanochannel with significant ionic current rectification (ICR) effect. As a proof of concept, kanamycin was detected with high sensitivity through aptamer recognition, triggered DNA conformational transitions, and specific coordination of Zr⁴⁺ to double-stranded DNA (dsDNA). The hydrogel's three-dimensional porous architecture significantly improves the probe loading capacity while the charge gradient optimization and the signal amplification mechanism collectively enables the sensing platform to exhibit excellent analytical performance and stability. It provides a new idea for the development of high-performance biosensors with important applications in the fields of food safety and clinical diagnosis.