Monitoring Endoplasmic Reticulum Stress Using Self-Targeting Water-Activated Pure Afterglow Luminescence Materials

The endoplasmic reticulum (ER) plays a critical role in regulating diverse cellular processes. Monitoring ER behavior under cellular stress is of great significance, however, time-gated afterglow imaging of ER physiology remains challenging due to the water-quenching effect on triplet excitons. Herein, we have developed a water-activated crystallization engineering strategy to achieve pure afterglow luminescence (PAL) in carbon dots-doped B₂O₃ matrices (CDs@B₂O₃) for ER stress afterglow imaging. In their dry state, CDs@B₂O₃ exhibit strong prompt fluorescence (PF) and room-temperature phosphorescence (RTP). Notably, the introduction of water induces the transformation of amorphous B₂O₃ matrices into highly crystalline boric acid (BA) matrices, resulting in the formation of CDs@BA with a rigid structure. This crystalline transition completely suppresses PF, enabling high-performance PAL through intense thermally activated delayed fluorescence (TADF) with a record-breaking lifetime of 632.0 ms. Furthermore, owing to the strong ER affinity of BA groups and their efficient aqueous afterglow performance, CDs@BA are particularly suitable for high-contrast, self-targeting imaging of the ER in living cells, while effectively eliminating autofluorescence interference. The imaging results clearly demonstrate that the ER can be effectively degraded by lysosomes under nutrient deprivation stress. This work not only develops an effective crystallization engineering strategy to achieve efficient aqueous PAL, but also provides a valuable tool for studying cellular physiology under ER stress.