New AIE-active terpyridyl-based pyridinium salt with good water-soluble: Membrane-permeable probe for cellular endoplasmic reticulum imaging

As a cardinal membrane-bound organelle, endoplasmic reticulum (ER) plays a critical role in maintaining cellular and organismic metabolic homeostasis. Accurately detecting the dynamic changes of ER is essential for understanding their biological functions and pathological roles. Here, a novel water-soluble terpyridyl-based derivative L with aggregation-induced emission (AIE) property was synthesized, which can be used as a fluorescent probe to track ER in cells for its good photostability, membrane permeability and biocompatibility. The selective experiments, molecular modeling calculations and 1H NMR titration showed that positively charged characteristic and amphiphilic properties of L were the main reason of enhanced emission for probe L in ER. Probe L bound with cells through electrostatic interactions, and then the hydrophobic group embedded into phospholipid contents in ER membranes, which allowed its fluorescence emission based on the progress of restriction of intramolecular motion.