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

A ratiometric electrochemical sensor based on poly(neutral red)-silver nanorods-carbon nanotubes (PNR-AgNRs/CNTs) composite was constructed for rapid, sensitive, and an-ti-interference detection of histamine in crayfish (Procambarus clarkii). Silver nanorods (AgNRs) were synthesized via a liquid-phase reduction method using 2-mercaptobenzoic acid (2-MBA) as both reducing and stabilizing agent, and subse-quently composited with carbon nanotubes (CNTs) through ultrasonic dispersion to form a three-dimensional conductive network. Poly(neutral red) (PNR) was electro-chemically polymerized onto the AgNRs-CNTs modified glassy carbon electrode (GCE) surface via cyclic voltammetry, serving as an electrochemical signal probe. The resulting PNR-AgNRs-CNTs/GCE exhibited significantly enhanced electrochemical performance with approximately 5-fold increase in electrochemically active surface area compared to bare GCE. Histamine competitively inhibited the electrochemical signal of PNR without affecting the AgNRs signal, enabling ratiometric detection based on the current signal ratio (IPNR/IAgNRs). Under optimized conditions (pH 6.0, adsorption time 6 min, material loading 0.08 mg/cm²), the IPNR/IAgNRs ratio exhibited a good linear relationship with the logarithm of histamine concentration in the range of 1–150 μmol/L, with a linear equa-tion of I/I = −0.3152 ln(C) + 5.0613, correlation coefficient R² = 0.995, and detection limit of 0.16 μmol/L (S/N = 3). The sensor demonstrated excellent anti-interference ability against common interfering substances such as Na⁺, Ca²⁺, K⁺, PO₄³⁻, and NO₃⁻. The relative standard deviations (RSD) for continuous 8-day detection and 8 parallel electrodes were 2.56% and 1.28%, respectively, indicating superior stability and reproducibility. The spiked recoveries in crayfish samples ranged from 95.9% to 102.3% with RSD < 3%, showing no significant difference from the national standard method (GB 5009.208-2016). The developed sensor effectively eliminated interference from complex biological ma-trices through the dual-signal ratio strategy and solved the detection problem of hista-mine lacking direct electrochemical response, providing a new approach for rapid on-site detection of histamine in aquatic products.