Copper-Enhanced Gold Nanoparticle Sensor for Colorimetric Histamine Detection

A rapid, colorimetric sensor for histamine detection is presented using citrate-stabilized gold nanoparticles enhanced with Cu2+ coordination. The sensing mechanism involves dual recognition: protonated histamine first adsorbs electrostatically onto AuNP surfaces at pH 5.5, followed by Cu2+-mediated coordination between imidazole rings that induces interparticle coupling, resulting in a characteristic shift of the localized surface plasmon resonance from 520 to 620 nm. The optical response, measured as the absorbance ratio A620/A520, exhibits excellent linearity over the range of 1.25–10 μM with a detection limit of 0.95 μM and total assay time under 30 min. The dual-recognition mechanism provides high selectivity for histamine over structural analogs, including L-histidine, imidazole, and L-lysine. The metal ion-mediated colorimetric approach described here achieves sub-micromolar sensitivity in simple buffer solutions, which is comparable to the histamine level used in in vitro cell assays and food-related studies. Thus, the present system is best viewed as a mechanistic model that can inform the design of future biosensing and analytical methods, rather than as a fully optimized sensor for direct clinical measurements in complex biofluids.