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Functional fluorophores represent an emerging research field, distinguished by their diverse applications, especially in sensing and cellular imaging. After the discovery of quinine sulfate and subsequent elucidation of the fluorescence mechanism by Sir George Stokes, research in the field of fluorescence gained momentum. Over the past few decades, advancements in sophisticated instruments, including super-resolution microscopy, have further promoted cellular imaging using traditional fluorophores. These advancements include deciphering sensing mechanisms via photochemical reactions and scrutinizing the applications of fluorescent probes that specifically target organelles. This approach elucidates molecular interactions with biomolecules. Despite the abundance of literature illustrating different classes of probe development, a concise summary of newly developed fluorophores remains inadequate. In this review, we systematically summarize the chronological discovery of traditional fluorophores along with new fluorophores. We briefly discuss traditional fluorophores ranging from visible to near-infrared (NIR) in the context of cellular imaging and in vivo imaging. Furthermore, we explore ten new core fluorophores developed between 2007 and 2022, which exhibit advanced optical properties, providing new insights into bioimaging. We illustrate the utilization of new fluorophores in cellular imaging of biomolecules, such as reactive oxygen species (ROS), reactive nitrogen species (RNS), and proteins and microenvironments, especially pH and viscosity. Few of the fluorescent probes provided new insights into disease progression. Furthermore, we speculate on the potential prospects and significant challenges of existing fluorophores and their potential biomedical research applications. By addressing these aspects, we intend to illuminate the compelling advancements in fluorescent probe development and their potential influence across various fields. [ABSTRACT FROM AUTHOR]

Mitochondria are valuable subcellular organelles and play crucial roles in redox signaling in living cells. Substantial evidence proved that mitochondria are one of the critical sources of reactive oxygen species (ROS), and overproduction of ROS accompanies redox imbalance and cell immunity. Among ROS, hydrogen peroxide (H2O2) is the foremost redox regulator, which reacts with chloride ions in the presence of myeloperoxidase (MPO) to generate another biogenic redox molecule, hypochlorous acid (HOCl). These highly reactive ROS are the primary cause of damage to DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and proteins, leading to various neuronal diseases and cell death. Cellular damage, related cell death, and oxidative stress are also associated with lysosomes which act as recycling units in the cytoplasm. Hence, simultaneous monitoring of multiple organelles using simple molecular probes is an exciting area of research that is yet to be explored. Significant evidence also suggests that oxidative stress induces the accumulation of lipid droplets in cells. Hence, monitoring redox biomolecules in mitochondria and lipid droplets in cells may give a new insight into cell damage, leading to cell death and related disease progressions. Herein, we developed simple hemicyanine-based small molecular probes with a boronic acid trigger. A fluorescent probe AB that could efficiently detect mitochondrial ROS, especially HOCl, and viscosity simultaneously. When the AB probe released phenylboronic acid after reacting with ROS, the product AB–OH exhibited ratiometric emissions depending on excitation. This AB–OH nicely translocates to lysosomes and efficiently monitors the lysosomal lipid droplets. Photoluminescence and confocal fluorescence imaging analysis suggest that AB and corresponding AB–OH molecules are potential chemical probes for studying oxidative stress. [ABSTRACT FROM AUTHOR]

Abstract: Organelle‐targeted photosensitizers (PSs) having luminescence properties are potential theranostic agents for simultaneous luminescence imaging and photodynamic therapy. Herein, we report a water‐soluble luminescent cyclometalated IrIII complex, Ir‐Bp‐Ly, as a lysosome‐targeted theranostic probe. Ir‐Bp‐Ly exhibits exceptional photophysical properties, with good triplet‐state quantum yield (0.90), singlet oxygen generation quantum yield (0.71 at pH 4), and long lifetime (1.47 μs). Interestingly, Ir‐Bp‐Ly localizes mostly in lysosomes due to the presence of morpholine units, suggesting its potential use as a lyso‐tracker. Ir‐Bp‐Ly displays a notable PDT effect in C6 glioma cells, efficiently generating reactive oxygen species owing to close proximity between the energy levels of its triplet state and those of molecular oxygen (3O2). The mechanism of cell death has been studied through caspase‐3/7 and flow cytometry analyses, which clearly established the apoptotic pathway. [ABSTRACT FROM AUTHOR]

A diradical approach to obtain stable organic dyes with intense absorption around λ=1100 nm is reported. The para- and meta-quinodimethane-bridged BODIPY dimers BD-1 and BD-2 were synthesized and were found to have a small amount of diradical character. These molecules exhibited very intense absorption at λ=1088 nm ( ɛ=6.65×105 M−1 cm−1) and 1136 nm ( ɛ=6.44×105 M−1 cm−1), respectively, together with large two-photon-absorption cross-sections. Structural isomerization induced little variation in their diradical character but distinctive differences in their physical properties. Moreover, the compounds showed a selective fluorescence turn-on response in the presence of the hydroxyl radical but not with other reactive oxygen species. [ABSTRACT FROM AUTHOR]