Red-emission molecular rotors for ultrafast and wash-free imaging mitochondria viscosity in cells and tissues

Mitochondrial viscosity is an important parameter in biological system, of which the abnormality is related to a variety of diseases. Therefore, it is necessary to develop fluorescent probes for imaging mito-chondrial viscosity. Herein, two red-emission fluorophores (L1 and L2) with donor-p-bridge-acceptor (D -p-A) structure were facilely synthesized and systematically studied. These fluorophores were demon-strated to be viscosity-sensitive, and particularly, L2 could precisely target mitochondria through a wash-free procedure. Moreover, probe L2 was membrane potential-independent, and it was capable of perme-ating the cell membrane within a short time (<= 30 s). Importantly, L2 was workable in fresh tissues with a favorable penetration depth of 33.89 lm. All these excellent performances endow probe L2 promising capability to investigate the correlation between mitochondrial viscosity and related diseases.(c) 2023 Elsevier Ltd. All rights reserved.