A pd/pt nanocluster enhanced colorimetric biosensor for large-volume Salmonella detection

A novel colorimetric biosensor was constructed by integrating a piston-structure immune reactor with dandelion-shape Pd/Pt nanoclusters for the enhanced specific isolation and quantitative detection of Salmonella in large-volume samples. The immune reactor was consisted of an outside 50 mL centrifuge tube and a coaxially inside glass tube to form a ring chamber, and an aluminum rod connected at one end with a pair of repelling ring magnets as the piston, facilitating the capture and movement of magnetic nanoparticles and their conjugates. The immune magnetic nanoparticles, bacterial sample and immune Pd/Pt nanoclusters were first mixed in the ring chamber when the glass tube was repeatedly moved up and down to generate chaotic flows, leading to forming of nanoparticle-bacteria-nanocluster complexes. The complexes were then isolated by the ring magnets, washed with the buffer and finally used to trigger the catalytic conversion of colorless H 2 O 2 -TMB into blue TMBox for quantification of Salmonella . Under optimal conditions, this biosensor could specifically isolate ∼82% of Salmonella from 10 mL bacterial sample and quantitatively detect Salmonella from 1.8 × 10 1 to 1.8 × 10 5 CFU/mL in 30 min with the lower detection limit of 18 CFU/mL. The mean recovery for Salmonella in spiked pork sample was 95.2%. • A colorimetric biosensor was developed in disposable tube for Salmonella detection. • A piston-structured immune reactor was used to generate chaotic flow for mixing. • The dandelion-shape Pd/Pt nanoclusters were used to amplify the biological signal. • This biosensor could efficiently separate the target bacteria in 10 mL sample. • This biosensor was able to detect Salmonella as low as 18 CFU/mL within 35 min.