Poly(Neutral Red)–Silver Nanorods–Carbon Nanotubes Composite-Based Ratiometric Electrochemical Sensor for Rapid Detection of Histamine in Crayfish

Histamine accumulation in spoiled aquatic products poses significant food safety risks, yet rapid and accurate on-site detection remains challenging due to the lack of direct electrochemical activity of histamine and severe matrix interference in complex biological samples. Herein, we report a ratiometric electrochemical sensor based on a poly(neutral red)–silver nanorods–carbon nanotubes (PNR-AgNRs/CNTs) composite for rapid histamine detection in crayfish. The sensor leverages a dual-signal strategy wherein histamine competitively suppresses the PNR electrochemical signal while leaving the AgNRs signal unaffected, enabling self-referencing quantification via the IPNR/IAgNRs ratio. This design effectively eliminates interference from instrument drift and sample matrix. The sensor exhibited a linear response range of 1–150 μmol/L with a detection limit of 0.16 μmol/L, along with excellent stability and reproducibility. When applied to crayfish samples, the method achieved satisfactory recoveries (95.9–102.3%) and showed no significant difference compared to the national standard method. By circumventing the need for histamine’s direct electrochemical response, this ratiometric approach provides a robust platform for rapid on-site assessment of aquatic product freshness.