Enzymatic Catalysis in Size and Volume Dual‐Confined Space of Integrated Nanochannel‐Electrodes Chip for Enhanced Impedance Detection of Salmonella

Abstract

Nanochannel‐based confinement effect is a fascinating signal transduction strategy for high‐performance sensing, but only size confinement is focused on while other confinement effects are unexplored. Here, a highly integrated nanochannel‐electrodes chip (INEC) is created and a size/volume‐dual‐confinement enzyme catalysis model for rapid and sensitive bacteria detection is developed. The INEC, by directly sandwiching a nanochannel chip (60 µm in thickness) in nanoporous gold layers, creates a micro‐droplet‐based confinement electrochemical cell (CEC). The size confinement of nanochannel promotes the urease catalysis efficiency to generate more ions, while the volume confinement of CEC significantly enriches ions by restricting diffusion. As a result, the INEC‐based dual‐confinement effects benefit a synergetic enhancement of the catalytic signal. A 11‐times ion‐strength‐based impedance response is obtained within just 1 min when compared to the relevant open system. Combining this novel nanoconfinement effects with nanofiltration of INEC, a separation/signal amplification‐integrated sensing strategy is further developed for Salmonella typhimurium detection. The biosensor realizes facile, rapid (<20 min), and specific signal readout with a detection limit of 9 CFU mL−1 in culturing solution, superior to most reports. This work may create a new paradigm for studying nanoconfined processes and contribute a new signal transduction technique for trace analysis application.

Monitoring Enzymatic Reaction Kinetics and Activity Assays in Confined Nanospace

“… This indicated that the enzymatic reaction kinetics of TYR was higher in our present confined environment, suggesting that a suitable confinement could enhance enzyme activity. Reasonably, this finding could be ascribed to the strengthened molecular collision between the substrate and enzyme. , In addition, the observed K m value was lower than that previously identified in the process of catechol catalytic oxidization as catechol was usually regarded as the most suitable substrate for TYR. Therefore, in a restricted nanospace, TYR exhibited a much higher affinity for Tyr, implying that Tyr may be the most suitable substrate for TYR in this given scenario.…”