A microfluidic SlipChip integrated with magnetic rotating fluidized bed and distance readout for Salmonella detection

Target bacteria enrichment and signal amplification are crucial for sensitive detection of foodborne pathogens. Here, a simple-to-operate, easy-to-fabricate and rapid-to-detect microfluidic SlipChip was developed for enrichment and visual sensing of pathogenic bacteria, utilizing magnetic rotating fluidized bed (MRFB) and distance indicator. The MRFB was engineered for effective separation and enrichment of target bacteria from complex samples, achieving about 30% increase in bacterial enrichment efficiency compared to traditional magnetic fluidized bed. Gold platinum palladium nanocatalyst (AuPtPd NC) was synthesized for signal amplification, which could catalyze H₂O₂ generating O₂ to propel the dye for naked-eye distance readout to achieve quantitative detection of Salmonella. The integrated SlipChip, comprising two polydimethylsiloxane (PDMS) layers and a chip holder, was capable of executing the whole sequential detection process, including bacterial enrichment, washing, and quantification. It demonstrated the ability to detect Salmonella with a linear range of 2.0 × 10¹ to 2.0 × 10⁶ CFU/mL within 30 min, with a detection limit as low as 20 CFU/mL. This method integrated MRFB into the microfluidic SlipChip, achieving enhanced sensitivity for Salmonella detection and holding promise for the detection of large volume samples with low concentrations.