Cerium(iii)-directed assembly of glutathione-capped gold nanoclusters for sensing and imaging of alkaline phosphatase-mediated hydrolysis of adenosine triphosphate

Abstract

Aggregation-induced emission enhancement (AIEE) of thiolated gold nanoclusters (AuNCs) has emerged as an attractive and alternative strategy to improve their brightness. This study demonstrates Ce(III)-triggered AIEE of glutathione-capped AuNCs (GSH-AuNCs) through the coordination between two carboxylic groups of GSH and Ce(III). The cluster size and valence state of GSH-AuNCs are almost identical to those of a Ce(III)-induced assembly of GSH-AuNCs (named Ce(III)-GSH-AuNCs). More importantly, the as-prepared Ce(III)-GSH-AuNCs exhibit a higher quantum yield (up to 13%), longer luminescence lifetime, and shorter maximum luminescence peak than GSH-AuNCs. Additionally, Ce(III)-GSH-AuNCs possess redox-switchable luminescence, high salt stability, and long-term storage stability. These findings provide clear evidence that the Ce(III)-triggered aggregation of GSH-AuNCs is a crucial factor to improve the luminescence property of GSH-AuNCs. Intriguingly, the presence of adenosine triphosphate (ATP) switches off the luminescence of Ce(III)-GSH AuNCs through the significant formation of Ce(III)-ATP complexes. Furthermore, the ATP-induced luminescence quenching of Ce(III)-GSH-AuNCs can be paired with the alkaline phosphatase (ALP)–ATP system to design a turn-on luminescent probe for ALP; the limit of detection for ALP is estimated to be 0.03 U L⁻¹. Also, the biocompatibility of Ce(III)-GSH-AuNCs enables the proposed system to detect ALP in human serum and HeLa cells.