L-cysteine gold nanoparticles for colorimetric and electrochemical detection of spermine and histamine

Biogenic amines (BAs) are metabolic products of living cells and have a pronounced impact on human physiological processes. They are also renowned food spoilage indicators as they are produced in higher quantities during food spoilage by bacteria. The higher concentration of these compounds in food can cause serious health concerns. Therefore, the detection of these compounds is of great significance. Herein, we developed a simple and rapid dual-mode colorimetric and an electrochemical method for detecting two representative BAs, i.e., spermine and histamine, using gold nanoparticles (AuNPs). The AuNPs were synthesized using the Turkevich method and functionalized with a simple molecule, L-Cysteine. The interaction of BAs with L-Cysteine-AuNPs demonstrates the naked eye color change at lower concentrations of BAs. The same L-Cysteine-AuNPs show enhanced electrochemical oxidation signals for histamine when immobilized on the surface of a glassy carbon electrode. The proposed detection method demonstrates the colorimetric changes from red to blue for the spermine concentration of 0.1-1 mu M with a detection limit of 0.37 mu M. Similarly, the colorimetric change was observed for histamine in the range of 1-10 mu M concentration with a detection limit of 3.7 mu M. In comparison, spermine is more sensitive at lower concentrations due to more binding sites forming stronger electrostatic interactions with the functionalized nanoparticles. The electrochemical oxidation signals were observed for histamine in the range of 5-60 mu M with a detection limit of 11.1 mu M. We demonstrate that the same functionalized nanoparticles remain sensitive to detecting histamine at higher concentrations despite the lack of pronounced colorimetric change.