Design and synthesis of RNA-responsive o-phenanthroline Eu(iii) complexes as probes for STED super-resolution dual-targeted bioimaging

Abstract

Interactions between lipid droplets (LDs) and mitochondria play a critical role in beta-oxidation and the storage of fatty acids (FAs). These interactions can be influenced by adverse external conditions such as nutritional deficiencies. However, studying these interactions using two different fluorescent dyes often yields low signal-to-noise ratios due to overlapping spectra, photobleaching, and weak penetration. These limitations hinder in-depth research into the interactions between LDs and mitochondria. To address this issue, we developed a series of rare earth complexes named Eu(TTA)₃-L1–3. By leveraging its property of changing fluorescence from a ‘turn-off’ to a ‘turn-on’ state upon interacting with RNA in a hydrophilic environment, Eu(TTA)₃-L3 has been successfully applied to monitor changes in LDs and mitochondria during oleic acid treatment and starvation-induced autophagy under two-photon conditions. This research provides an effective tool for the comprehensive study of the interaction between LDs and mitochondria. Furthermore, it broadens the perspective for the design of dual-targeting single fluorescent probes.