Nanobody-based immunochromatographic biosensor for colorimetric and photothermal dual-mode detection of foodborne pathogens

Abstract

Conventional immunochromatographic test strip (ITS) biosensing technologies face the formidable challenge of insufficient sensitivity for the short time frames of point-of-care testing. Here, we developed a K0.27MnO2·0.54 H2O (KMO) @Au and nanobody (Nb) assisted colorimetric and photothermal dual-mode immunochromatographic test strip (KNb-DITS) for rapid and sensitive detection of Salmonella Typhimurium (S. Typhimurium) in food. Au nanoparticles (AuNPs) decorated on the surface of 3-dimensional (3D) KMO enhanced the photothermal conversion efficiency of the KMO@Au photothermal sensing probes and could be attributed to sufficient adsorption sites for coupling of antibodies. Meanwhile, small dimension of Nb9 was chosen to effectively couple the flower-like 3D KMO@Au photothermal agents to improve detection sensitivity and specificity synergistically. The simple biosensor KNb-DITS has realized colorimetric detection of 104 CFU mL−1S. Typhimurium, and 103 CFU mL−1S. Typhimurium can be detected in photothermal mode with an infrared camera. In addition, the proposed method was successfully applied in real sample analysis with high accuracy. This study connected Nb with photothermal nanomaterials to form photothermal immune probes applying to ITS, which provides guidelines for monitoring other foodborne pathogens.