Switching off-on colorimetric sensor for rapid and selective detection of histamine in aquatic products based on Cu2+-mediated laccase-mimic activity of Mn3O4 nanoparticles

Food poisoning caused by excessive intake of histamine is a significant public health concern. Traditional analytical methods struggle to meet the demands for on-site monitoring of histamine in food. Colorimetry based on nanozyme catalysis can be applied to rapidly detect histamine, but some challenges remain in the specific response of nanozymes to histamine. Herein, a novel “off-on” colorimetric sensor was first established for histamine detection based on Cu²⁺-mediated laccase-mimic activity of flower-like Mn₃O₄ nanoparticles (Mnf). This work proved that Cu²⁺ can inhibit the laccase-mimic activity by hindering the electron transfer between Mnf and 2,4-DP molecules. Once histamine was present in the system, Cu²⁺ was first consumed due to the coordination with histamine, resulting in the recovery of laccase-mimic activity of Mnf. The color of sensing solution can be converted to the corresponding RGB value by a smartphone for on-site detection of histamine in food. The colorimetric sensor has a limit of detection as low as 0.148 μg mL⁻¹, which is comparable to that of most colorimetric methods. Moreover, the colorimetric sensor exhibits high selectivity, and has considerable applicability for histamine detection in aquatic products.