Dual-functional manganese dioxide nanoclusters for power-free microfluidic biosensing of foodborne bacteria

Point-of-care testing (POCT) of pathogens is important for avoiding food poisoning. Here, dual-functional manganese dioxide nanoclusters (MnO2 NCs) were elaboratively used as the fluidic driver and signal amplifier for exploring a new power-free biosensor for POCT of Salmonella. First, H2O2 in three chambers of a microfluidic chip was finger driven simultaneously to dissolve MnO2 NCs, resulting in the production of O-2 to respectively push preloaded immune magnetic nanobeads (IMNBs), bacterial sample and immune MnO2 NCs (IMONCs) into a sinusoidal convergence-divergence micromixer. After they were efficiently mixed and incubated in a serpentine channel, IMNB-bacteria-IMONC conjugates were obtained and magnetically separated in a multifunctional chamber. Then, two washing solution were successively driven to rinse these conjugates. Finally, colorless H2O2-TMB substrate was driven to the multifunctional chamber and catalyzed by the IMONCs on the conjugates into blue catalysate, which was analyzed by developed smartphone APP to determinate bacteria amount. The biosensor enabled quantitative detection of 63 CFU/mL Salmonella within 30 min. The complete bacteria detection procedure was achieved on a single microfluidic chip without any peripheral equipment, and it has great potential for POCT of bacteria.