Visual colorimetric detection platform of Salmonella typhimurium based on PtRu@ZrFe-MOFs nanozymes integrated with...

Quantitative detection of Salmonella typhimurium is of vital importance for promoting food safety monitoring and control. This study successfully developed a 3D-printed microchannel device that integrates cleaning and detection functions, enabling sensitive and semi-automatization colorimetric detection of Salmonella typhimurium. Firstly, the magnetic beads modified monoclonal antibody (MBs-Anti), Salmonella typhimurium and PtRu@ZrFe-MOFs@Apt nanozymes were successively added to the centrifuge tube to facilitate the formation of the MBs-Anti-Salmonella typhimurium-PtRu@ZrFe-MOFs@Apt sandwich complex. Then, the above incubated mixture was injected into the reaction tank of the microchannel device and washed with PBS containing hydrogen peroxide to separate the sandwich complex from the impurities in the sample solution. Subsequently, the TMB substrate solution was added to facilitate the catalytic oxidation of the sandwich complex, thereby forming the blue oxidized TMB product. The RGB image of the blue product was captured using a portable smartphone device, and the colorimetric signal of the image was analyzed to determine the concentration of Salmonella typhimurium. The microchannel device can detect Salmonella typhimurium within a concentration range 10¹ to 10⁶ CFU/mL within 75 min, with a detection limit of 3.3 CFU/mL. It is worth noting that the 3D-printed microchannel device constructed has good universality. By replacing the corresponding antibodies, aptamers and other biological recognition elements, it can be extended to the detection of other pathogenic bacteria.