Dynamically Monitoring Cell Viability in a Dual-Color Mode: Construction of an Aggregation/Monomer-Based Probe Capable of Reversible Mitochondria-Nucleus Migration

Electrochemical Single-Cell Protein Therapeutics Using a Double-Barrel Nanopipette

Single-cell protein therapeutics is expected to promote our in-depth understanding of how a specific protein with a therapeutic dosage treats the cell without population averaging. However, it has not yet been tackled by current single-cell nanotools. We address this challenge by the use of a double-barrel nanopipette, in which one lumen was used for electroosmotic cytosolic protein delivery and the other was customized for ionic evaluation of the consequence. Upon injection of protein DJ-1 through the delivery lumen, upregulation of the antioxidant protein could protect neural PC-12 cells against oxidative stress from phorbol myristate acetate exposure, as deduced by targeting of the cytosolic hydrogen peroxide by the detecting lumen. The nanotool developed in this study for single-cell protein therapeutics provides a perspective for future single-cell therapeutics involving different therapeutic modalities, such as peptides, enzymes and nucleic acids.

Modulation of Cellular Fate of Vinyl Triarylamines through Structural Fine Tuning: To Stay or Not To Stay in the Mitochondria?

Mitochondria are involved in many cellular pathways and dysfunctional mitochondria are linked to various diseases. Hence efforts have been made to design mitochondria-targeted fluorophores for monitoring the mitochondrial status. However, the factors that govern the mitochondria-targeted potential of dyes are not well-understood. In this context, we synthesized analogues of the TP-2Bzim probe belonging to the vinyltriphenylamine (TPA) class and already described for its capacity to bind nuclear DNA in fixed cells and mitochondria in live cells. These analogues (TP-1Bzim, TPⁿ -2Bzim, TP¹⁺ -2Bzim, TN-2Bzim) differ in the cationic charge, the number of vinylbenzimidazolium branches and the nature of the triaryl core. Using microscopy, we demonstrated that the cationic derivatives accumulate in mitochondria but do not reach mtDNA. Under depolarisation of the mitochondrial membrane, TP-2Bzim and TP¹⁺ -2Bzim translocate to the nucleus in direct correlation with their strong DNA affinity. This reversible phenomenon emphasizes that these probes can be used to monitor ΔΨ_m variations.

A Single Fluorescent pH Probe for Simultaneous Two-Color Visualization of Nuclei and Mitochondria and Monitoring Cell Apoptosis

Subcellular organelles play indispensable roles in diverse biological processes by their precise mutual cooperation. Thus, the development of a single fluorescent probe (SF-probe) for simultaneous and discriminable visualization of different organelles and their dynamics during certain bioprocess is significant, yet remains greatly challenging. Herein, for the first time, we rationally prepared a pH-sensitive SF-probe (named HMBI) for the simultaneous two-color visualization of nuclei and mitochondria and monitoring cell apoptosis. HMBI shows remarkable ratiometric fluorescence changes toward pH changes. Due to different pH environments in subcellular organelles, HMBI can image nuclei and mitochondria with green and red emission, respectively. HMBI can monitor drug-induced cell apoptosis with dramatically decreased red emission in mitochondria but almost unchanged green emission in nuclei, and the shrinking and pyknotic nuclei are also observed during cell apoptosis. HMBI possesses tremendous potential in two-color biomedical imaging of the dynamic changes of nuclei and mitochondria in many physiological processes.

High-Performance Quinoline-Malononitrile Core as a Building Block for the Diversity-Oriented Synthesis of AIEgens

In vivo fluorescent monitoring of physiological processes with high-fidelity is essential in disease diagnosis and biological research, but faces extreme challenges due to aggregation-caused quenching (ACQ) and short-wavelength fluorescence. The development of high-performance and long-wavelength aggregation-induced emission (AIE) fluorophores is in high demand for precise optical bioimaging. The chromophore quinoline-malononitrile (QM) has recently emerged as a new class of AIE building block that possesses several notable features, such as red to near-infrared (NIR) emission, high brightness, marked photostability, and good biocompatibility. In this minireview, we summarize some recent advances of our established AIE building block of QM, focusing on the AIE mechanism, regulation of emission wavelength and morphology, the facile scale-up and fast preparation for AIE nanoparticles, as well as potential biomedical imaging applications.