Dual-Mode Detection of Cysteamine Using Ag Nanoparticle-Riboflavin Composites

Riboflavin (RF) and cysteamine (Cys) are vital in clinical and other fields, but their detection is often intricate and reliant on costly equipment and materials. Plasmon-enhanced fluorescence (PEF) using plasmonic nanoparticles offers a solution to enhance the optical properties of fluorophores. Additionally, fluorescence quenching becomes apparent when the distance between the fluorophores and nanostructures shrinks to a few nanometers. Harnessing these effects holds tremendous promise for improved detection performance. In this study, the PEF of RF by Ag@SiO2 nanoparticles was presented and used to improve RF detection. The fluorescence enhancement of RF was "turned off" in the presence of Cys because of the aggregation of Ag@SiO2 nanoparticles caused by Cys, which can be used for the detection of Cys. On the other hand, the quenched fluorescence of RF caused by small Ag nanoparticles was "turned on" in the presence of Cys, which can further realize the detection of Cys with lower concentrations. Additionally, the color of the Ag NPs-RF composites changed in the presence of Cys, which can also be used for the colorimetric detection of Cys. A minimum detected concentration as low as 16.6 nM was realized by fluorescence and colorimetric dual-mode detection. Depending on the interactions between the plasmonic nanoparticles and Cys, the plasmonic nanoparticles show great potential for the dual-mode detection strategy in the sensitive evaluation of analytes. The dual-mode detection based on the Ag nanoparticles provides the feasibility of the nanoprobe in potential applications, which opens a promising avenue for simple, sensitive, and selective detection.