Well plate-based LF-NMR/colorimetric dual-mode homogeneous immunosensor for Vibrio parahaemolyticus detection

A 96-well plate-based low-field nuclear magnetic resonance (LF-NMR)/colorimetric dual-mode homogeneous immunosensor was developed for the detection of pathogen bacteria, using Vibrio parahaemolyticus (VP) as a detection template. The signal unit MNS@Ab₂ is graphene oxide (GO) simultaneously loaded with VP antibody and Fe₃O₄ nanoparticles. A 96-well plate coated with VP antibody captures the target VP, which then binds the signal unit to form the immunocomplex. After acidolysed, Fe₃O₄ nanoparticles are transformed into Fe³⁺ and Fe²⁺, so the non-homogeneous system is transformed into a homogeneous one. The addition of KMnO₄ can not only convert Fe²⁺ into Fe³⁺ but also provide Mn²⁺, improving the detection sensitivity. And, colorimetric analysis can be achieved by the quantitative reduction of KMnO₄. Under the optimal experimental conditions, the limit of detection was 60 CFU/mL with good selectivity, stability, precision, accuracy, and consistency, providing a simple and reliable detection platform for pathogenic bacteria in food.