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. The PFP moiety aids the ER selectivity, while the overall hydrophobicity of the molecule aids in the LD targeting. Furthermore, the fluorophores are utilised in studying the changes in size, distribution, and biogenesis of LDs within ER regions after treatment with oleic acid. Strong emission, lower concentrations ∼100 nM requirement, minimal cytotoxicity, and photostability make these fluorophores excellent tools for probing sub-cellular dynamics.

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. Notably, the probes exhibit a substantial Stokes shift, with 143 nm for DCS and 201 nm for DCN with selective targeting of the lipid droplets. Our experimental investigations successfully differentiated morphological variations between diseased and normal tissues in three distinct tissue types: liver, adipose, and small intestine. They could help provide pointers for improved detection and understanding of LD-related pathologies.

Large Room-Temperature Magnetoresistance in a High-Spin Donor-Acceptor Conjugated Polymer.

Open-shell conjugated polymers (CPs) offer new opportunities for the development of emerging technologies that utilize the spin degree of freedom. Their light-element composition, weak spin-orbit coupling, synthetic modularity, high chemical stability, and solution-processability offer attributes that are unavailable from other semiconducting materials. However, developing an understanding of how electronic structure correlates with emerging transport phenomena remains central to their application. Here, the first connections between molecular, electronic, and solid-state transport in a high-spin donor-acceptor CP, poly(4-(4-(3,5-didodecylbenzylidene)-4H-cyclopenta[2,1-b:3,4-b']dithiophen-2-yl)-6,7-dimethyl-[1,2,5]-thiadiazolo[3,4-g]quinoxaline), are provided. At low temperatures (T < 180 K), a giant negative magnetoresistance (MR) is achieved in a thin-film device with a value of -98% at 10 K, which surpasses the performance of all other organic materials. The thermal depopulation of the high-spin manifold and negative MR decrease as temperature increases and at T > 180 K, the MR becomes positive with a relatively large MR of 13.5% at room temperature. Variable temperature electron paramagnetic resonance spectroscopy and magnetic susceptibility measurements demonstrate that modulation of both the sign and magnitude of the MR correlates with the electronic and spin structure of the CP. These results indicate that donor-acceptor CPs with open-shell and high-spin ground states offer new opportunities for emerging spin-based applications.

Ultrasensitive Room Temperature Infrared Photodetection Using a Narrow Bandgap Conjugated Polymer.

Photodetectors operating across the short-, mid-, and long-wave infrared (SWIR-LWIR, λ = 1-14 µm) underpin modern science, technology, and society in profound ways. Narrow bandgap semiconductors that form the basis for these devices require complex manufacturing, high costs, cooling, and lack compatibility with silicon electronics, attributes that remain prohibitive for their widespread usage and the development of emerging technologies. Here, a photoconductive detector, fabricated using a solution-processed narrow bandgap conjugated polymer is demonstrated that enables charge carrier generation in the infrared and ultrasensitive SWIR-LWIR photodetection at room temperature. Devices demonstrate an ultralow electronic noise that enables outstanding performance from a simple, monolithic device enabling a high detectivity (D*, the figure of merit for detector sensitivity) >2.44 × 109 Jones (cm Hz1/2 W-1 ) using the ultralow flux of a blackbody that mirrors the background emission of objects. These attributes, ease of fabrication, low dark current characteristics, and highly sensitive operation overcome major limitations inherent within modern narrow-bandgap semiconductors, demonstrate practical utility, and suggest that uncooled detectivities superior to many inorganic devices can be achieved at high operating temperatures.

Fluorescent styryl pyridine-N-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. To target LDs, we designed and synthesized fluorophores with a styryl scaffold bearing electron-donating amino groups and pyridine-N-oxide, a zwitterionic acceptor moiety. We explored their photophysical properties in various solvents and conducted systematic DFT calculations on the synthesized fluorescent molecules, comparing them with neutral pyridine and cationic pyridinium styryl dyes. The results demonstrate that diphenylaminostyryl pyridine-N-oxide (TNO) shows excellent imaging of LDs, in contrast to the behavior of cationic styrylpyridinium (TNC), which primarily localizes within the mitochondria. Notably, pyridine N-oxide offers several benefits: an increased dipole moment facilitating charge separation between donors and acceptors, substantial HOMO and LUMO stabilization, improved water solubility, favorable redox properties, and bathochromic-shifted absorption/emission spectra, showing promise as a fluorescent tool for probing the cellular-biological realm.

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. Excellent localization is noted with the lipid droplets. Subsequently, DNS was used to monitor the variations in the LD viscosity during erastin-induced ferroptosis followed by ferroptosis inhibition. Additionally, we explored variations in the LD quantity, size, and accumulation when subjected to oleic acid stimulation. Extensive DFT and TDDFT investigations have been employed to understand the effect of NO2 substitution on the linear and branched molecular derivatives. Our results with the improved lipophilic fluorophore, exhibiting excellent colocalization with LDs, offer valuable insights into sensing erastin-induced ferroptosis and have the potential for real-time diagnostic applications.

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. Additionally, it shows a rapid response to HOCl with high selectivity among different reactive oxygen/nitrogen compounds with a detection limit of 2.31 µM. Moreover, it is also utilized for the exogenous and endogenous detection of HOCl in live cells, which may help study the role of hypochlorite in organelles at the cellular level. DFT and TDDFT calculations have been carried out to understand the relationship between the structure and properties of the cationic probes with respect to the α-cyano substitution and extension of π-conjugation. The selective detection of HOCl by C4 over other cationic probes has also been well-demonstrated, showing how the binding of HOCl affects the electronic properties of C4 through the analysis of non-bonding orbitals (NBO) population, electrostatic potential surface (ESP), and density of states (DOS) projected DOS investigations.

Magnetic Ordering in a High-Spin Donor-Acceptor Conjugated Polymer.

The development of open-shell organic molecules that magnetically order at room temperature,which can be practically applied, remains a grand challenge in chemistry, physics, and materials science. Despite the exploration of vast chemical space, design paradigms for organic paramagnetic centers generally result in unpaired electron spins that are unstable or isotropic. Here, a high-spin conjugated polymer is demonstrated, which is composed of alternating cyclopentadithiophene and benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole heterocycles, in which macromolecular structure and topology coalesce to promote the spin center generation and intermolecular exchange coupling. Electron paramagnetic resonance (EPR) spectroscopy is consistent with spatially localized spins, while magnetic susceptibility measurements show clear anisotropic spin ordering and exchange interactions that persist at room temperature. The application of long-range π-correlations for spin center generation promotes remarkable stability. This work offers a fundamentally new approach to the implementation of this long-sought-after physical phenomenon within organic materials and the integration of manifold properties within emerging technologies.

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. Considering this, herein, we highlight the structure-property relationship of α-cyanostilbene-based AIE frameworks for tuning the aggregation through molecular displacement with reference to transition dipoles based on the following parameters: (i) positional substitution and orientation of the α-cyano unit, (ii) π-conjugation length (da or db), (iii) molecular size (DAr) of the peripheral substitutions with respect to the α-cyano unit, and (iv) branching effect. In addition, we explain the utility of their unique AIE characteristics for various optoelectronic applications, including self-assembled nanostructures, chemical sensing, organogelation, white light emission, molecular switches, multiphoton absorption, liquid crystals, anion receptors, and biological probes. It is anticipated that organic materials with a cyanostilbene framework will continue to garner attention in the interdisciplinary fields of biology, chemistry, and materials science for diverse applications.