Sensitive Fluorescent Determination of Silver Ion and Glutathione in Human Serum Using Polydopamine Nanodots as the Probe

Glutathione (GSH)-switched fluorescent assays have received attention due to their rapid signal changes of fluorescent nanoprobes. Small polydopamine nanodots (PDs) exhibit remarkable photoluminescent properties. In this work, fluorescent PDs were synthesized through oxidation using dopamine as precursor. The prepared PDs had rich surface functionalities and exhibited good optical properties with maximum emission using 330 nm excitation. The fluorescence was quenched by Ag+ through the interaction with catechols in the PDs. After the addition of GSH, Ag was bound with sulfhydryl groups in GSH and the fluorescence of the PDs was restored. Therefore, a fluorescence turn on-off-on strategy was constructed for Ag+ and GSH using the synthesized PDs as the probe. The PDs showed good performance for Ag+ from 0.01 to 1 μM, with a limit of detection (LOD) equal to 2.82 nM. The system also exhibited a linear relationship for GSH from 0.01 to 0.5 μM with a LOD equal to 1.93 nM. GSH was determined in human serum to demonstrate a practical application of the assay. This work expands the application of PDs in biological analysis.