Establishment of an immunoassay for detection of melatonin and 2-mydroxymelatonin based on computer-aided design

Melatonin (MT) is a popular ingredient in food and supplements due to its health benefits. However, unregulated use and labeling inaccuracies in commercial products pose safety risks. Establishing reliable monitoring methods is therefore essential for consumer protection. In this study, haptens were screened through computer simulations based on structural, charge, and electrostatic potential properties. Using the selected optimal hapten, a monoclonal antibody capable of simultaneously recognizing MT and 2-hydroxymelatonin (2-MT) was successfully developed. The half-maximal inhibitory concentrations for MT and 2-MT were 47.89 ng/mL and 185.09 ng/mL, respectively. Furthermore, a colloidal gold immunochromatographic assay was established to detect MT and 2-MT in milk, wine, and tablets. The visual limit of detection was 20–100 ng/mL for MT and 50–200 ng/mL (or μg/kg) for 2-MT, respectively. The method demonstrated reliable results when validated by LC-MS/MS. Meanwhile, the developed strips exhibited good stability.