A new Biosensor for rapid and sensitive detection of Salmonella using magnetic separation and enzymatic catalysis was developed

Hou et al. from China Agricultural University published in Food Control (A microfluidic signal-off biosensor for rapid and sensitive detection of Salmonella using magnetic separation and enzymatic catalysis @ https://www.sciencedirect.com/science/article/pii/S0956713519301550?dgcid=rss_sd_all Food Control 2019, 103: 186-193.) about a rapid and sensitive method for the detection of Salmonella typhimurium using a microfluidic biosensor containing magnetic nanoparticles (MNPs) with catalases. Catalases, are common enzymes found in all living organisms and were used in the biosensor to amplify the biological signal greatly. The MNPs was modified with anti-Salmonella monoclonal antibodies and used to separate and enrich Salmonella from sample background flora. The Salmonella was further reacted with polystyrene microspheres (PSs) modified with anti-Salmonella polyclonal antibodies and catalases. Then, the conjugated bacteria were injected into the capillary in a microfluidic chip and captured by high gradient magnetic field. After washing to remove unbound PSs, hydrogen peroxide was finally injected and catalyzed by the catalases on enzymatic bacteria to produce oxygen gaps in the capillary, leading to an electrical signal. A linear relationship was found between the change of electrical voltage and the concentration of target bacteria from 3.7 × 101 to 3.7 × 106 CFU/mL. The biosensor was able to detect Salmonella as low as 33 CFU/mL within 2 h, and could be further combined with microfluidic to develop a lab-on-a-chip system. In testing using salmonella-spiked milk, the mean recovery was 104.7%.