Sensitive colorimetric aptasensor based on peroxidase-like activity of ZrPr-MOF to detect Salmonella Typhimurium in water and milk

A colorimetric biosensor based on a novel metal-organic framework (MOF) composed of Zirconium (Zr) and Praseodymium (Pr) is presented as a nanozyme to detect Salmonella Typhimurium (S. typhimurium). The ZrPr-MOF poses extreme peroxidase-mimic activity, and it interacts with an aptamer. In the presence of hydrogen peroxide (H2O2), the intense blue color is observed via the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by ZrPr-MOF. However, the interaction of aptamer on the surface of ZrPr-MOF leads to a sharp decline in the catalytic activity of the nanozyme. The addition of S. typhimurium enhanced the produced blue color. Under optimal pH and temperature conditions, our biosensor can detect S. typhimurium in the linear range of 102–108 CFU/mL, with a limit of detection (LOD) of 37 CFU/mL. Moreover, the paper-based model of this biosensor was used successfully for point-of-care and portable analysis. Detection and measuring of S. typhimurium in a spiked milk sample revealed the potential of this platform for sensitive, selective, and rapid monitoring of S. typhimurium in real samples.