Cells are responsive to the mechanical environment, but the methods to detect simultaneously how different organelles react in mechanobiological processes remain largely unexplored. We herein report a dual organelle-targeting fluorescent probe, ( E )-1-[3-(diethoxyphosphoryl)propyl]-4-[4-(diethylamino)styryl]pyridin-1-ium bromide (ASP-PE), for mechanical mapping in live cells. ASP-PE is aggregation-induced emission active and is sensitive to the local mechanical environment. It targets the plasma membrane (PM) and intracellular mitochondria in cells by its phosphonate moiety and pyridinium. In this work, through ASP-PE staining, changes of membrane tension in the PM and mitochondria in response to varied osmotic pressure and substrate stiffness are visualized using fluorescence lifetime imaging microscopy. The mechanobiological importance of actin filaments and microtubules in the PM and mitochondria is also investigated using this probe. Computational simulations are applied to study the sensing mechanism of the probe. This study introduces a unique tool for mapping the membrane tension in the PM and mitochondria together, providing us great opportunities to study organelle’s interactions in mechanobiology.

Currently, metal–organic frameworks (MOFs) with thiol functionalities are used as advanced robust materials to solve the problems of pollution and damage caused by metal ions in water. Herein, we report a framework assembled by reacting cadmium nitrate with a new ligand, 4-methylthiopyridine-2,6-dicarboxylic acid, which possesses methylthio and carboxyl functional groups. The resultant MOFs exhibit 5-c net, fnb-type, uninodal net topology with {33·4·64·72} point symbols. The thiol-functionalized MOF features good thermal, water, and pH stabilities and luminescence emission at different temperatures. The methylthio-containing cadmium MOF (Cd-MOF) selectively detects the heavy-metal ions Cu2+, Hg2+, and Pb2+ in water by luminescence quenching, with low limits of detection (LODs) of 22.60 × 10–7, 11.07 × 10–6, and 9.58 × 10–6 M, respectively. The highly selective response and performance of the Cd-MOF probe toward Cu2+, Hg2+, and Pb2+ ions were determined by investigating the effects of other interfering ions and different pH values, and the reusability performance was evaluated.

Figure 4. Top: Normalized prompt and delayed (1 ms) PL spectra; middle: CPL spectra; bottom: g lum of a) as-prepared and b) treated PVA films with doped (R)-1 (w (R)-1 :w PVA = 1 : 600) at room temperature with 290 nm excitation. Phosphorescent decay curves of c) as-prepared and d) treated PVA films with doped (R)-1 (w (R)-1 :w PVA = 1 : 600) at room temperature with 290 nm excitation. (inset: photographs of films under 254 nm excitation on and off).

Poly(vinyl alcohol) (PVA) has been found as a wonderful matrix for chromophores to boost their room-temperature phosphorescence (RTP) character by forming abundant hydrogen bonding. Despite the well-utilized protective effect, the constructive role in accelerating the intersystem crossing is less investigated. Here, we focus on its role in manipulating the excitedstate energy level to facilitate multiple intersystem crossing channels. Six benzoyl carbazole derivatives do not emit RTP in their solutions, powders, or crystals but exhibit significantly persistent RTP signals when embedded into the PVA matrix. Charge-transfer excited states were trapped by cofacial stacking in crystal, which blocks the intersystem crossing channels. In the PVA matrix, the allowed broad distribution of charge-transfer states covers the locally excited states, offering multiple intersystem crossing pathways via spin−vibronic orbit coupling. Consequently, efficient and persistent heavy-atom-free phosphors have been developed with the highest quantum yields of 7.7% and the longest lifetime of 2.3 s.