Live cell imaging of lipid droplets: fluorescent chalcones as probes for lipophagy and lipid-mitochondria interactions.

Lipid droplets are crucial organelles involved in cellular energy storage and metabolism, which is key in maintaining energy homeostasis through lipophagy. In this work, we successfully synthesized donor-acceptor chalcone derivatives (M1-M3) with improved photophysical characteristics, such as significant Stokes shifts and strong emission features. DFT and TDDFT calculations have been employed to evaluate the structure-property relationship of the chalcone derivatives.

Fluorescent -oxides: applications in bioimaging and sensing.

-Oxides, due to their zwitterionic nature and ability to form hydrogen bonds through the oxide ion, are highly water-soluble and widely used in biological and pharmacological studies. The -oxide structural scaffold is introduced into molecules, enabling "" fluorescence an intramolecular charge transfer (ICT) process. This process occurs when the N-O bond is cleaved, either through an enzymatic reaction under hypoxic conditions or by using Fe(II), which allows rapid and selective detection of Fe(II) at nanomolar concentrations both and .

Diphenylbutadiene Fluorescent Analogues in Sub-Cellular Imaging and Monitoring Mitophagy.

A series of donor-acceptor (D-π-A) substituted diphenylbutadienes exhibiting solvatochromic emission and a large Stokes shift (100-200 nm) were designed and synthesized for distinctive organelle labelling, enabling real-time monitoring of organelle behaviour such as lysosomal dynamics, mitophagy monitoring, and stress responses. The morpholine-substituted D-A-D diphenylbutadiene (M2) was employed to investigate selective imaging of lysosomes, the uptake of damaged mitochondria through mitophagy, and monitoring lysosomal viscosity or pH changes. Other diphenylbutadiene derivatives (M1, M3, M4) selectively accumulated in lipid droplets.

Substitution Effects on Subcellular Organelle Localization in Live-cell Imaging.

A series of D-π-A indole-containing fluorescent probes were developed, followed by an investigation of their photophysical properties and compounds' suitability for subcellular imaging in living cells. We demonstrate that the preference for mitochondrial localization was lost when morpholine was substituted, resulting in the accumulation of the molecule in the lysosomes. However, interestingly, the presence of a nitro group led to their localization within the lipid droplets despite the presence of the morpholine pendant.

Detecting labile heme and ferroptosis through 'turn-on' fluorescence and lipid droplet localization post Fe sensing.

Iron, a crucial biologically active ion essential for metabolic processes in living organisms, plays a vital role in biological functions, and imbalances in iron levels can lead to various diseases. In this study, we have developed two simple "turn-on" fluorescent probes, NOPy and NOCN, for the quick and selective detection of Fe at nanomolar levels (LOD of 35 nM), accompanied by significant absorption and emission shifts, along with colorimetric demarcation. Both fluorophores exhibit an excellent "turn-on" emission response upon encountering Fe in the cells.

A multipurpose mitochondrial NIR probe for imaging ferroptosis and mitophagy.

This paper explores the use of a di-cationic fluorophore for visualizing mitochondria in live cells independent of membrane potential. Through the synthesized di-cationic fluorophore, we investigate the monitoring of viscosity, ferroptosis, stress-induced mitophagy, and lysosomal uptake of damaged mitochondria. The designed fluorophore is based on DQAsomes, cationic vesicles responsible for transporting drugs and DNA to mitochondria.

Fluorescent styrenes for mitochondrial imaging and viscosity sensing.

Fluorophores bearing cationic pendants, such as the pyridinium group, tend to preferentially accumulate in mitochondria, whereas those with pentafluorophenyl groups display a distinct affinity for the endoplasmic reticulum. In this study, we designed fluorophores incorporating pyridinium and pentafluorophenyl pendants and examined their impact on sub-cellular localization. Remarkably, the fluorophores exhibited a notable propensity for the mitochondrial membrane.

A two-in-one probe: imaging lipid droplets and endoplasmic reticulum in tandem.

The endoplasmic reticulum (ER) and lipid droplets (LDs) intricately interact in cellular processes, with the ER serving as a hub for lipid synthesis and LDs acting as storage organelles for lipids. Developing fluorescent probes that can simultaneously visualise the ER and LDs provides a means for real-time and specific visualisation of these subcellular organelles and elucidating their interaction. Herein, we present synthetically simple and novel donor-π-acceptor styryl fluorophores (PFC, PFN and PFB) incorporating pentafluorophenyl (PFP) to demonstrate exquisite discriminative imaging of ER and LD with a single excitation wavelength.

Lipid Droplets Specific Fluorophore for Demarcation of Normal and Diseased Tissues.

Using high-fidelity, permeable, lipophilic, and bright fluorophores for imaging lipid droplets (LDs) in tissues holds immense potential in diagnosing conditions such as diabetic or alcoholic fatty liver disease. In this work, we utilized linear and Λ-shaped polarity-sensitive fluorescent probes for imaging LDs in both cellular and tissue environments, specifically in rats with diabetic and alcoholic fatty liver disease. The fluorescent probes possess several key characteristics, including high permeability, lipophilicity, and brightness, which make them well-suited for efficient LD imaging.

Improved lipophilic probe for visualizing lipid droplets in erastin-induced ferroptosis.

Studying the viscosity of lipid droplets (LDs) provides insights into various diseases associated with LD viscosity. Ferroptosis is one such process in which LD viscosity increases due to the abnormal accumulation of lipid ROS (reactive oxygen species) caused by peroxidation. For investigating the LD imaging and ferroptosis, we developed two molecules (NNS and DNS) that show significant Stokes shifts (182-232 nm) and utilized them for sub-cellular imaging.

Fluorescent styryl pyridine--oxide probes for imaging lipid droplets.

Lipid droplets (LDs) have emerged as major regulators of cellular metabolism, encompassing lipid storage, membrane synthesis, viral replication, and protein degradation. Exclusive studies have suggested a direct link between LDs and cancer, as a notable abundance of LDs is found in cancerous cells. Therefore, monitoring the location, distribution, and movements of LDs is of paramount importance for understanding their involvement in biological processes.

-Functionalized fluorophores: detecting urinary albumin and imaging lipid droplets.

A series of novel -sulfonyl pyridinium fluorophores were designed, synthesized, and explored in terms of their ability to bind with serum albumins. Upon binding the fluorophores with BSA, noticeable emission wavelength or intensity changes accompanied by color changes were observed. Competitive binding studies revealed that the fluorophore selectively binds to the warfarin site, but the binding affinity also depends on the nature of the scaffold.

Styryl-NIR Mitochondrial Probes with Rapid HOCl Detection in Live-Cells.

Hypochlorous acid (HOCl) is critical for maintaining immune system balance, but it can harm mitochondria by hindering enzyme activity, leading to decreased ATP and increased cell death. In this study, we have designed a fluorophore with a pyridinium scaffold for selective staining of the mitochondria and to detect hypochlorite. The fluorophore exhibits strong solvatochromic emission due to intramolecular charge transfer and excellent sub-cellular localization in the mitochondria.

Imaging of mitochondria/lysosomes in live cells and .

Two rhodamine-phenothiazine conjugates, RP1 and RP2, were synthesized, and their photophysical properties, subcellular localization, and photocytotoxicity were investigated. We observed robust localization of RP1 in mitochondria and dual localization in mitochondria and lysosomes with RP2 in live cells. Live cell imaging with these probes allowed us to track the dynamics of mitochondria and lysosomes during ROS-induced mitochondrial damage and the subsequent lysosomal digestion of the damaged mitochondria.

Imaging of lipid droplets using coumarin fluorophores in live cells and C. elegans.

Fluorescent probes offer incredibly effective tools for visualizing the dynamic morphology of lipid droplets (LDs) and investigating their physiological interactions. In this work, we have utilized solvatochromic coumarin probes bearing nitrile and ester substituents for live-cell imaging. The fluorescence probes are characterized by a donor (diethylamino) and acceptor (nitrile and/or ester) substituents and a rotatable double bond.

Fluorescent sterol probes for intracellular transport, imaging, and therapeutics.

Sterols play a significant role in many physiological processes affecting membrane organization, transport, permeability, and signal transduction. The development of fluorescent sterol analogs that have immediate functional relevance to the natural biomolecules is one approach to understanding the sterol-driven physiological processes. Visualizing cellular compartments with tailor-made fluorescent molecules through specific labeling methods enables organelle targeting and reveals dynamic information.

α-Cyanostilbene: a multifunctional spectral engineering motif.

Aggregation-induced emission (AIE) is a unique photophysical phenomenon of organic chromophores, exhibiting a significant emission enhancement in the condensed phase (aggregate/solid/film) than in the solution phase. This remarkable feature offers excellent strategies to obtain molecular materials possessing unique spectral signatures such as high fluorescence intensity, excellent quantum yield, large Stokes shift, and exquisite optoelectronic properties. Unlike a great library of articles with propeller-shaped tetraphenylethene molecular frameworks, reviews based on the mechanistic understandings of α-cyanostilbenes are relatively rare.

Lutidine derivatives for live-cell imaging of the mitochondria and endoplasmic reticulum.

The mitochondria and endoplasmic reticulum (ER) are highly dynamic subcellular structures essential for several biological functions. The development of non-toxic, wash-free fluorophores to visualize these structures inside cells aid in understanding their localization and dynamics in diverse cellular processes. In this paper, we report the synthesis and characterization of lutidine-based cationic fluorophores bearing push-pull substituents exhibiting emission in green and red wavelength regions and their subcellular localization in living cells.

Fluorescent probes for targeting endoplasmic reticulum: design strategies and their applications.

Advances in developing organic fluorescent probes and fluorescence imaging techniques have enhanced our understanding of cell biology. The endoplasmic reticulum (ER) is a dynamic structure that plays a crucial role in protein synthesis, post-translational modifications, and lipid metabolism. The malfunction of ER contributes to several physiological and pathological conditions.

Stress-responsive rhodamine bioconjugates for membrane-potential-independent mitochondrial live-cell imaging and tracking.

The 'powerhouses' of cell, mitochondria have seen an upsurge of interest in investigations pertaining to the imaging and mapping of physiological processes. By utilizing sterol-modified rhodamine, we have performed the live-cell imaging of mitochondria without dependence on a membrane potential. The sterol probes are highly biocompatible, and they can track the mitochondrial live-cell dynamics in a background-free manner with improved brightness and impressive contrast.

Probing Variations of Reduction Activity at the Plasma Membrane Using a Targeted Ratiometric FRET Probe.

Plasma membrane (PM) is the turntable of various reactions that regulate essential functionalities of cells. Among these reactions, the thiol disulfide exchange (TDE) reaction plays an important role in cellular processes. We herein designed a selective probe, called membrane reduction probe (MRP), that is able to report TDE activity at the PM.

Live-cell imaging of the nucleolus and mapping mitochondrial viscosity with a dual function fluorescent probe.

Visualization of sub-cellular organelles allows the determination of various cellular processes and the underlying mechanisms. Herein, we report a fluorescent probe, bearing push-pull substituents emitting at 600 nm and its application in cellular imaging. The probe shows dual imaging of mitochondria and nucleoli and maps mitochondrial viscosity in live cells under various physiological variations and show minimum cytotoxicity.

Live-cell imaging of lipid droplets using solvatochromic coumarin derivatives.

Lipid droplets (LDs), the lipid-rich intracellular organelles, serve to regulate many physiological processes and therefore attention has been attracted towards their selective detection. We report positively solvatochromic lipophilic dyes, based on the push-pull framework containing coumarin-pyridine heterocycles for selective live-cell imaging of lipid droplets (LDs) in Cos-7 and McA-RH7777 cells at ultralow concentrations (200 nM). The fluorescent probes show a remarkable increase in fluorescence intensity with time with the hydrophobic core of the lipid droplets contributing to the observed intensity enhancement.

Superior Resonant Nanocavities Engineering on the Photonic Crystal-Coupled Emission Platform for the Detection of Femtomolar Iodide and Zeptomolar Cortisol.

Although luminescence spectroscopy has been a promising sensing technology with widespread applications in point-of-care diagnostics and chem-bio detection, it fundamentally suffers from low signal collection efficiency, considerable background noise, poor photostability, and intrinsic omnidirectional emission properties. In this regard, surface plasmon-coupled emission, a versatile plasmon-enhanced detection platform with >50% signal collection efficiency, high directionality, and polarization has previously been explored to amplify the limit of detection of desired analytes. However, high Ohmic loss in metal-dependent plasmonic platforms has remained an inevitable challenge.