Reversible AIE self-assembled nanohybrids coordinated by La3+ for ratiometric visual acid phosphatase monitoring and intracellular imaging

Abstract

Herein, a ratiometric fluorescence method was established for sensing acid phosphatase (ACP) activity based on La3+ ions coordinated self-assembled carbon nanodots-templated copper nanoclusters. La3+-induced aggregation-induced emission (AIE), reversible competition between adenosine triphosphate (ATP) and La3+, and ACP-induced dephosphorylation are cleverly combined. At 350 nm excitation wavelength, carbon nanodots-templated copper nanoclusters, denoted as nanohybrids, exhibited blue and red fluorescence. However, blue fluorescence intensity (FL) decreased due to static quenching, while red FL enhanced in the nanohybrids due to AIE when adding La3+. Interestingly, La3+-induced nanohybrids self-assembly process could be inhibited by ATP through a stronger interaction between ATP and La3+ relative to carboxyl group and La3+. ACP catalyzed the directed hydrolysis of ATP, thereby dissociating the La3+-ATP complexes. The ratio (F610/F452) had a good correlation with ACP concentration in the range of 0.1–10 U/L, and the detection limit is 0.024 U/L. The introduction of smartphones has successfully implemented the visual analysis of ACP. This study demonstrates that La3+-induced AIE has emerged as a competitive candidate strategy to boost the brightness and stability of CuNCs and their nanohybrids. Furthermore, thanks to the good biocompatibility of La3+-nanohybrids, ACP detection in serums and imaging of HeLa cells have been successfully achieved.