pH-Controlled Nanoparticles Formation and Tracking of Lysosomal Zinc Ions in Cancer Cells by Fluorescent Carbazole-Bipyridine Conjugates

K, Koner AL. Review on Lysosomal Metal Ion Detection Using Fluorescent Probes

Metal ions are indispensable and play an important role in living systems. Metal ions coordinated to metalloenzymes pocket activate the bound substrate and labile metal ions maintaining the ionic balance. The amount of metal ions present in various subcellular compartments of the cells is highly regulated for maintaining cellular homeostasis. An imbalance in the metal ion concentration is related to several diseases and results in serious pathological conditions. Mostly the internalized metal ions are processed in the lysosomal compartment of the cell. A delicate regulation of metal ions in the lysosomal compartment can modulate the lysosomal pH and inhibit hydrolytic enzymes, which ultimately causes lysosomal storage disorders. In the past decade, the understanding and regulation of lysosomal metal ions based on fluorometric methods have gained significant attention. In this review, we have comprehensively summarized the development of various fluorescent reporters over the past five years for a selective and sensitive estimation of lysosomal metal ion concentration. We believe this consolidated and timely review will help researchers working in the areas associated with lysosomal metal ions.

Coumarin-based fluorescent probes toward viscosity in mitochondrion/lysosome

Viscosity is an important microenvironmental indicator that plays an important role in the process of information transmission in various regions. Herein, two coumarin-based viscosity-sensitive fluorescent probes (CHB, CHN) were synthesized and the photophysical properties of the two probes were studied. The fluorescence quantum yields of CHB and CHN in glycerol can be as high as 25.2% and 18.3% respectively. The two probes can linearly detect viscosity in the viscosity logarithm range of 0.83-2.07, which is not interfered with pH, metal ions, anions and biomolecules. Fluorescent confocal cell experiments show CHB and CHN have good targeting ability to mitochondrion, lysosome, Endoplasmic reticulum and Golgi apparatus, and can be used to detect viscosity in mitochondrion/lysosome.

pH-Responsive Side Chains as a Tool to Control Aqueous Self-Assembly Mechanisms

pH-Tunable nanoscale morphology and self-assembly mechanism of a series of oligo(p-phenyleneethynylene) (OPE)-based bolaamphiphiles featuring poly(ethylene imine) (PEI) side chains of different length and degree of hydrolysis are described. Protonation and deprotonation of the PEI chains by changing the pH alters the hydrophilic/hydrophobic balance of the systems and, in turn, the strength of intermolecular interactions between the hydrophobic OPE moieties. Low pH values (3) lead to weak interaction between the OPEs and result in spherical nanoparticles, in which aggregation follows an isodesmic mechanism. In contrast, higher pH values (11) induce deprotonation of the polymer chains and lead to a stronger, cooperative aggregation into anisotropic nanostructures. Our results demonstrate that pH-responsive chains can be exploited as a tool to tune self-assembly mechanisms, which opens exciting possibilities to develop new stimuli-responsive materials.

A lysosome-targeting viscosity-sensitive fluorescent probe based on a novel functionalised near-infrared xanthene-indolium dye and its application in living cells

The viscosity of lysosomes plays a significant role in modulating biological processes and reflects the status and function of this kind of organelle, e.g., locations, morphologies, and components.