Novel Synthesis of Thiolated Gold Nanoclusters Induced by Lanthanides for Ultrasensitive and Luminescent Detection of the Potential Anthrax Spores' Biomarker

In this study, we reported a facile, one-pot, and "green" synthesis of glutathione-protected gold nanoclusters (GSH@AuNCs) initiated by samarium (Sm³⁺) lanthanides for the first time. Sm³⁺ lanthanides more efficiently induced the formation of GSH@AuNCs with significantly enhanced luminescence than other lanthanides or heavy metal ions (Cd²⁺, Pb²⁺) did. Using this strategy, a detection for Sm³⁺ was made with a linearity range of (10.0-100.0 μM) and a limit of detection (LOD) of 0.5 μM. The Sm³⁺-based GSH@AuNCs were characterized by eco-friendliness, photostability, and low-cost synthesis with low biological toxicity and had great potential in the application for biosensing and bioimaging. They were successfully employed in the detection of dipicolinic acid (DPA), a well-reported biomarker for sensing potential infection by strongly hazardous anthrax spores. A good linear response was obtained for DPA detection ranging from 1.0 to 120.0 μM with a low LOD of 0.1 μM, which was much lower (600 times) than the infectious dosage of anthrax spores (6 × 10^-5 M). The detection was due to the strong binding affinity and strong chelation capability of DPA to Sm³⁺ lanthanides, which caused the dissociation of the aggregates with an obvious decrease or even a turning-off effect of their luminescence.

Keywords: AuNCs; aggregation-induced emission (AIE); anthrax spores; dipicolinic acid (DPA); glutathione; lanthanides; samarium (Sm3+).