In-field screening of pathogenic bacteria is important for preventing food poisoning. Here, a portable pipette-adapted biosensor using magnetic grid separation and nanocatalyst signal amplification was elaboratively developed for rapid detection of Salmonella typhimurium. A common pipette was innovatively adapted with multiple functions to complete the whole bacterial detection procedure, including mixing, separation, catalysis, washing, detection, analysis and display. The target bacteria were effectively captured by the immune magnetic nanobeads and labeled with immune gold@platinum nanocatalysts through pipette-blowing mixing to form the nanobeads-bacteria-nanocatalyst complexes, which were separated against the magnetic grid separation tip under the magnetic field. The pressure change resulting from oxygen production due to mimicking catalysis of hydrogen peroxide by these nanocatalysts on the complexes was quantified through measuring the moving duration of the conductive liquid in the pipette for bacteria determination. Under optimal conditions, this biosensor could detect target bacteria in 90 min with low detection limit of 180 CFU/mL. This pipette-adapted biosensor is affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users (ASSURED), and has the potential for in-field testing of foodborne pathogens to ensure food safety, especially in resource-constrained areas.
Keywords: Biosensor; Gold@platinum nanocatalyst; Magnetic nanobead; Pipette; Salmonella.
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