Biomimetic Neurostimulation Framework for Probing Bacterial Metabolism with Anisotropic Au@PDA Nanoassemblies

Microbial contamination poses significant risks, urgently requiring ultrasensitive and highly selective detection methods that are practical for real-world use. Inspired by the nervous system, we report anisotropic gold-polydopamine (Au@PDA) nanoassemblies that enable real-time probing of Escherichia coli metabolic dynamics within complex urban water systems. The anisotropic Au@PDA nanoassemblies combine high conductivity and excellent electron-accepting/donating properties, forming an extensive redox-active, conductive, biomimetic neurostimulation framework that facilitates efficient dual-mediator (Ru3+/PAP) redox cycling. Detection of E. coli metabolism dynamics is based on the bacterium's inherent secretion of β-galactosidase (β-gal), which hydrolyzes a substrate to generate the redox-active reporter p-aminophenol, thereby participating in dual-mediator redox cycling for significant electrochemical signal amplification. Exceptional selectivity and anti-interference in turbid samples arise from three proposed integrated mechanisms: mediator potential modulation, specificity of β-gal-based enzymatic reactions, and nanopore size exclusion limiting access to larger interferents. This label-free platform achieves a low detection limit of 10 CFU/mL within 30 min directly in complex matrices (milk, beer, and lake water) without preprocessing. Continuous monitoring over 4 days tracks bacterial proliferation via exponential current growth, demonstrating long-term sensing stability. We believe that this bioelectronics device establishes a new paradigm for on-site, real-time food safety and water quality diagnostics for E. coli, bridging laboratory precision with point-of-need applications.