Cell membrane-inspired COF/AAO hybrid nanofluidic membrane with ion current rectification properties for ultrasensitive detection of E. coli

Nanofluidic membranes hold great prospects in sensitive and rapid detection of bioanalysts, while remaining lacking robust and general approaches for specificity. In this work, we introduce a cell membrane-inspired nanofluidic membrane with excellent ion current rectification properties as a simple and robust platform for label-free and ultrasensitive biosensing. The asymmetric nanofluidic membrane is prepared by coupling a two-dimensional covalent organic framework (COF) membrane to an anodic aluminum oxide (AAO) nanochannel via hydrogen bonding. The prepared COF/AAO membrane presents selective ion transport due to the asymmetric structure and anion selectivity of COF. With the large surface area and abundant functional modification sites of COF, further grafting of the recognition unit can be easily achieved to mimic the recognition process of receptors and ligands on cell membranes. As a proof of concept, the application in bacterial detection is demonstrated by covalently bonded Concanavalin A as recognition units. The highly amplified ionic current based on ion current rectification properties of the COF/AAO membrane allows sensitive and selective bioanalysis. Specifically, the proposed asymmetric nanofluidic membrane presents a linear detection range from 10 to 10 6 CFU/mL with an ultralow detection limit of 7 CFU/mL for E. coli . This work reveals the great potential of COF/AAO hybrid nanofluidic membrane as a sensor for rapid and precise bioanalysis.