A dual organelle-targeting mechanosensitive probe.

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.

Substituent engineering of the diboron molecular architecture for a nondoped and ultrathin emitting layer.

Owing to the high technology maturity of thermally activated delayed fluorescence (TADF) emitter design with a specific molecular shape, extremely high-performance organic light-emitting diodes (OLEDs) have recently been achieved via various doping techniques. Recently, undoped OLEDs have drawn immense attention because of their manufacturing cost reduction and procedure simplification. However, capable materials as host emitters are rare and precious because general fluorophores in high-concentration states suffer from serious aggregation-caused quenching (ACQ) and undergo exciton quenching. In this work, a series of diboron materials, CzDBA, iCzDBA, and tBuCzDBA, is introduced to realize the effect of steric hindrance and the molecular aspect ratio via experimental and theoretical studies. We computed transition electric dipole moment (TEDM) and molecular dynamics (MD) simulations as a proof-of-concept model to investigate the molecular stacking in neat films. It is worth noting that the pure tBuCzDBA film with a high horizontal ratio of 92% is employed to achieve a nondoped OLED with an excellent external quantum efficiency of 26.9%. In addition, we demonstrated the first ultrathin emitting layer (1 nm) TADF device, which exhibited outstanding power efficiency. This molecular design and high-performance devices show the potential of power-saving and economical fabrication for advanced OLEDs.

Oxygen Quenching-Resistant Nanoaggregates with Aggregation-Induced Delayed Fluorescence for Time-Resolved Mapping of Intracellular Microviscosity.

Microviscosity is a fundamental parameter in the biophysics of life science and governs numerous cellular processes. Thus, the development of real-time quantitative monitoring of microviscosity inside cells is important. The traditional probes for detecting microviscosity via time-resolved luminescence imaging (TRLI) are generally disturbed by autofluorescence or surrounding oxygen in cells. Herein, we developed loose packing nanoaggregates with aggregation-induced delayed fluorescence (FKP-POA and FKP-PTA) and free from the effect of oxygen and autofluorescence for viscosity mapping via TRLI. The feasibility of FKP-PTA nanoparticles (NPs) for microviscosity mapping through TRLI was demonstrated by monitoring the variation of microviscosity inside HepG2 cancer cells, which demonstrated a value change from 14.9 cP to 216.9 cP during the apoptosis. This indicates that FKP-PTA NP can be used as a probe for cellular microviscosity mapping to help people to understand the physiologically dynamic microenvironment. The present results are expected to promote the advancement of diagnostic and therapeutic methods to cope with related diseases.

Simple synthesis of multifunctional photosensitizers for mitochondrial and bacterial imaging and photodynamic anticancer and antibacterial therapy.

Photosensitizers (PSs), a critical drug administered for successful photodynamic therapy (PDT), have been well researched regarding their anticancer or bactericidal capability with high precision and low invasiveness. Although traditional PSs have been explored either in photodynamic anticancer or in antibiosis, they usually require synthesis with multiple steps, harsh synthetic conditions, and a complicated purification process for a single targeted product. Therefore, developing new multifunctional PSs with a simple synthesis and reactant flexibility which combine mitochondrial and bacterial imaging, efficient photodynamic anticancer and antibacterial effects is of the utmost urgency and of great importance for clinical applications. Herein, a large structural investigation of isoquinolinium-based PSs synthesized by a simple Rh-catalysed annulation reaction with high yields is presented. These lipophilic cationic PSs have a tunable photophysical property. LIQ-6 was found to perform not only as an ideal mitochondria targeting probe but also an effective cancer cell killing PS, and moreover, a tracker for bacterial imaging and ablation. LIQ-6 can be used to image a wide range of cancer cells and to monitor the photo-induced cell apoptosis, and simultaneously, it can also image and be a photodynamic germicide for both Gram-positive and Gram-negative bacteria. Furthermore, LIQ-6 shows great effectiveness in the wound healing process, showing its ability to be an ideal PS in vivo as well. This contribution is believed to offer a new platform for the construction of a theragnostic system for future practical applications in biology and biomedicine.

A simple yet effective AIE-based fluorescent nano-thermometer for temperature mapping in living cells using fluorescence lifetime imaging microscopy.

We designed and synthesized a novel nano-thermometer using aggregation-induced-emission (AIE) dye as the reporter and household butter as the matrix. This temperature nanosensor showed decreased fluorescence intensities (∼2%/°C) and shorter fluorescence lifetimes (∼0.11 ns/°C) upon increasing the environmental temperature in the physiological temperature range. Such fluorescence responses were reversible and independent of the environmental pH and ionic strength. The application of these nano-thermometers in temperature sensing in living cells using fluorescence lifetime imaging microscopy (FLIM) was also demonstrated. To the best of our knowledge, this is the first example of AIE-based nano-thermometer for temperature sensing in living cells. This work also provides us with a simple and low-cost method for rapid fabrication of an effective nanosensor based on AIE mechanism.

Pyridine-Carbonitrile-Carbazole-Based Delayed Fluorescence Materials with Highly Congested Structures and Excellent OLED Performance.

Three pyridine-carbonitrile-carbazole-based thermally activated delayed fluorescence (TADF) materials with highly sterically congested structures have been synthesized. The donor-acceptor-type TADF emitters (26-, 246-, and 35tCzPPC) consist of a 2,6-diphenylpyridine-3,5-dicarbonitrile core (PPC) as the acceptor and a di( t-butyl)carbazole-substituted phenyl group attached to C4 of the PC core as the donor. The molecules show a unique structure containing two consecutive large twisted angles along the donor and acceptor groups. The structure leads to a nearly complete space separation of the highest occupied molecular orbital and lowest unoccupied molecular orbital, a small Δ EST value, and excellent TADF property. Moreover, the 26- and 246tCzPPC dopants favor a horizontal alignment enhancing the light outcoupling of the device. In contrast, 35tCzPPC favors a perpendicular alignment reducing the light outcoupling efficiency of the device. The 246tCzPPC-based devices show external quantum efficiency as high as 29.6% because of excellent TADF property, very high photoluminescence quantum yield, and high Θ value in the thin films. The device performance is the best among the pyridine-carbonitrile-based TADF emitters.