A fluorene–thiophene oligomer turn-on fluorescence probe with high-fold fluorescence enhancement for acetaldehyde dehydrogenase detection in cells

Abstract

Cancer stem cell (CSC)-targeted therapy is a promising approach for overcoming tumor resistance and improving the efficiency of current cancer treatments. Aldehyde dehydrogenase (ALDH) was considered a reliable endogenous marker of CSCs in various cancers. Herein, we designed and synthesized F-TAO, a fluorene–thiophene oligomer-based “turn-on” fluorescent probe to detect the ALDH activity in living cells. The response of F-TAO to ALDH involved the intramolecular charge transfer (ICT) mechanism, which endowed F-TAO and its ALDH-oxidized product with a distinguishable fluorescence spectrum. The fluorescence intensity and fluorescence quantum yield of F-TAO were enhanced by 365 and 9.5-fold after ALDH oxidation, which was the highest-fold fluorescence enhancement in the current studies. Moreover, the response of F-TAO to ALDH oxidation was quick (about 5 min) and sensitive (LOD of 0.0013 U mL⁻¹). We confirmed the response of F-TAO to ALDH in a constructed ALDH 1A1-high expression cell line ALDH1A1-MCF-7 and MCF-7 cells and conducted ALDH activity imaging in SK-BR-3 and HCT-116 cells. F-TAO was realized as a “turn-on” strategy to detect and image ALDH in living cells with a high signal/noise ratio.