Fluorescence-enhanced MOF-encapsulated AuNCs for highly sensitive detection of melanin

Melanin is an important marker of human disease and aging. It is necessary to quickly and sensitively detect melanin . In this study, a novel fluorescence strategy for the rapid and sensitive detection of melanin was established based on a nanocomposite (AuNCs@ZIF-8) consisting of gold nanoclusters (AuNCs) and a zeolite-imidazole framework (ZIF-8). The confined space of ZIF-8 restricted the rotation and vibration of the AuNCs , reducing their free movement. Thus, the non-radiative transition energy of the AuNCs decreased, leading to stronger fluorescence intensity of AuNCs@ZIF-8. Melanin acted as an electron acceptor while AuNCs@ZIF-8 acted as an electron donor. Through electron transfer, the fluorescence of the AuNCs@ZIF-8 was effectively quenched. Compared to the AuNCs, AuNCs@ZIF-8 showed a more significant quenching effect. Therefore, using the fluorescence value of AuNCs@ZIF-8 as the reporting part, the melanin level could be detected by the fluorescence quenching in 24 min. The range of linearity of the approach was 0.1–500.0 μg⋅mL −1 , and the detection limit of melanin is 0.03 μg⋅mL −1 .