Targeted platelet with hydrogen peroxide responsive behavior for non-alcoholic steatohepatitis detection

The most common chronic liver illness, non-alcoholic fatty liver disease (NAFLD), refers to a range of abnormalities of the liver with varying degrees of steatosis. When the clinical symptoms including liver damage, inflammation, and fibrosis, are added to the initial steatosis, NAFLD becomes non-alcoholic steatohepatitis (NASH), the problematic and severe stage. The diagnosis of NASH at the right time could therefore effectively prevent deterioration of the disease. Considering that platelets (PLTs) could migrate to the sites of inflamed liver sinusoids with oxidative stress during the development of NASH, we purified the PLTs from fresh blood and engineered their surface with hydrogen peroxide (H2O2) responsive fluorescent probe (5-DP) through lipid fusion. The engineered PLT-DPs were recruited and trapped in the inflammation foci of the liver with NASH through interaction with the extracellular matrix, including hyaluronan and Kupffer cells. Additionally, the fluorescence of 5-DP on the surface of PLT-DP was significantly enhanced upon reacting with the elevated level of H2O2 in the NASH liver. Thus, PLT-DP has great promise for NASH fluorescence imaging with high selectivity and sensitivity.

Precise molecular engineering for the preparation of pyridinium photosensitizers with efficient ROS generation and photothermal conversion

Organic photosensitizers (PSs) with aggregation-induced emission properties have great development potential in the integrated application of multi-mode diagnosis and treatment of photodynamic therapy (PDT) and photothermal therapy (PTT). However, preparing high-quality PSs with both optical and biological properties, high reactive oxygen species (ROS) and photothermal conversion ability are undoubtedly a great challenge. In this work, a series of pyridinium AIE PSs modified with benzophenone have been synthesized. A wide wavelength range of fluorescent materials was obtained by changing the conjugation and donor-acceptor strength. TPAPs5 has a significant advantage over similar compounds, and we have also identified the causes of high ROS generation and high photothermal conversion in terms of natural transition orbitals, excited state energy levels, ground-excited state configuration differences and recombination energy. Interestingly, migration of target sites was also found in biological imaging experiments, which also provided ideas for the design of double-targeted fluorescent probes. Therefore, the present work proposed an effective molecular design strategy for synergistic PDT and PTT therapy.

Liquid core fluorescent organic nanoprobes: Long-term stability and highly selective lipid droplets bio-imaging

Lipid droplets (LDs) are important subcellular organelles that play a huge role in cell metabolism and growth. In this study, we synthesized two LDs fluorescent probes with benzothiadiazole (BTH) as electron acceptor and triphenylamine (TPA) as electron donor, which named as TPA-BTH1 and TPA-BTH2, respectively. Meanwhile, we introduced long alkyl chain to the probe as a shielding group and LDs targeting enhancement group. The results showed that the two probes were too sensitive to solvents' polarity because of the D-A structures possessed twisted intramolecular charge-transfer (TICT) effect. Furthermore, we prepared the two probes into nanoprobes by nanoprecipitation, which named as TPA-BTH1-20 and TPA-BTH2-20, respectively. The nanoprobes also had excellent fluorescence emission abilities and biocompatibility, as well as high photostability and accurately target LDs ability, which could be successfully applied in cell fluorescence imaging experiments.

Reactive Species-Activatable AIEgens for Biomedical Applications

Precision medicine requires highly sensitive and specific diagnostic strategies with high spatiotemporal resolution. Accurate detection and monitoring of endogenously generated biomarkers at the very early disease stage is of extensive importance for precise diagnosis and treatment. Aggregation-induced emission luminogens (AIEgens) have emerged as a new type of excellent optical agents, which show great promise for numerous biomedical applications. In this review, we highlight the recent advances of AIE-based probes for detecting reactive species (including reactive oxygen species (ROS), reactive nitrogen species (RNS), reactive sulfur species (RSS), and reactive carbonyl species (RCS)) and related biomedical applications. The molecular design strategies for increasing the sensitivity, tuning the response wavelength, and realizing afterglow imaging are summarized, and theranostic applications in reactive species-related major diseases such as cancer, inflammation, and vascular diseases are reviewed. The challenges and outlooks for the reactive species-activatable AIE systems for disease diagnostics and therapeutics are also discussed. This review aims to offer guidance for designing AIE-based specifically activatable optical agents for biomedical applications, as well as providing a comprehensive understanding about the structure-property application relationships. We hope it will inspire more interesting researches about reactive species-activatable probes and advance clinical translations.

A novel hydrogen peroxide fluorescent probe for bioimaging detection and enables multiple redox cycles

In this subject, a novel hydrogen peroxide (H₂O₂) fluorescent probe (MNG) was designed and developed using naphthalimide derivatives and selenomorpholine. In PBS buffer (10 mM, pH = 7.4, 1 %DMSO), the selenomorpholine on the probe is capable of qualitatively and quantitatively detecting (H₂O₂) at a small amount under a detection limit of 61 nM. The probe follows a mechanism that Se (Ⅱ) in selenomorpholine is transformed to Se (Ⅳ), thus changing the spectra of the probe MNG. It is noteworthy that MNG can continuously make a cyclic response to H₂O₂ and glutathione (GSH), so it can potentially achieve redox process imaging in vivo. Moreover, this subject verified the redox process of the probe's continuous redox response in the Gaussian 09 programme through simulation calculation and mass spectrometry. The probe exhibits high biocompatibility. Moreover, it can detect H₂O₂ in MCF-7 cells and Argentine Bloodfin.

Photophysical characterization and fluorescence cell imaging applications of 4-N-substituted benzothiadiazoles

In this work, a series of fluorescent 2,1,3-benzothiadiazole derivatives with various N-substituents in the 4-position was synthesized and photophysically characterized in various solvents. Three compounds emerged as excellent fluorescent probes for imaging lipid droplets in cancer cells. A correlation between their high lipophilicity and lipid droplet specificity could be found, with log P ≥ 4 being characteristic for lipid droplet accumulation.

Construction of heteroaryl-bridged NIR AIEgens for specific imaging of lipid droplets and its application in photodynamic therapy

As a kind of subcellular organelle, lipid droplets (LDs) play a critical role in the body's normal metabolism. LDs have gained increasing attention as a fluorescent photodynamic target site. Near-infrared (NIR) organic light-emitting luminescent materials, with aggregation-induced emission (AIE)-active feature, preeminent LD-imaging ability, and effective reactive oxygen species (ROS) production property, have been widely used for photodynamic therapy (PDT) in diagnostic therapeutics, but its application remains challenging. In the present work, three novel NIR organic compounds with AIE-active feature, namely, TPET-Is, TPET-Fu, and TPEF-Is, were developed and synthesized. These heteroaryl-bridged molecules possess a donor-donor-π-acceptor structure and strong intramolecular charge transfer character. These AIEgens are capable of high-fidelity LD imaging in living cells (Pearson's coefficient values: 0.94, 0.96, 0.97) due to their biocompatibility, good photostability, and strong lipophilicity (LogP values: 9.39, 7.89, 8.03), respectively. Moreover, they can be also applied in bright imaging the LDs of oil-rich plant tissues, such as those of sunflower seeds. The respective AIEgens TPET-Fu of these compounds can also produce ROS in the condition of white light to effectively kill live Hela cells. The present study thus provides a potential strategy through heteroaryl-bridged molecular engineering for LD-targeted imaging and PDT application.

Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

We report herein the design and mechanochemical synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), an orange aggregation-induced emission (AIE), for the selective detection of H2O2 in a turn-on manner.

Fluorescent Benzothiadiazole Derivatives as Fluorescence Imaging Dyes: A Decade of New Generation Probes

The current review describes advances in the use of fluorescent 2,1,3-benzothiadiazole (BTD) derivatives after nearly one decade since the first description of bioimaging experiments using this class of fluorogenic dyes. The review describes the use of BTD-containing fluorophores applied as, inter alia, bioprobes for imaging cell nuclei, mitochondria, lipid droplets, sensors, markers for proteins and related events, biological processes and activities, lysosomes, plasma membranes, multicellular models, and animals. A number of physicochemical and photophysical properties commonly observed for BTD fluorogenic structures are also described.

An activatable near-infrared fluorescent probe facilitated high-contrast lipophagic imaging in live cells

A new fluorescent probe (Q-lipo) was developed by conjugating a xanthene scaffold with a quinoline moiety for activatable imaging of lipophagy. Q-lipo with acidic pH activated near infrared fluorescence and the lipid droplet targeting ability allowed activatable fluorescence imaging and flow cytometry detection of lipophagy in live cells with high contrast. It was further utilized to study the effect of tumor-microenvironment related conditions on lipophagy. Q-lipo would provide a useful tool for studying lipophagy in live cells.

A Polarity-Sensitive Ratiometric Fluorescence Probe for Monitoring Changes in Lipid Droplets and Nucleus during Ferroptosis

Ferroptosis regulates cell death through reactive oxygen species (ROS)-associated lipid peroxide accumulation, which is expected to affect the structure and polarity of lipid droplets (LDs), but with no clear evidence. Herein, we report the first example of an LD/nucleus dual-targeted ratiometric fluorescent probe, CQPP, for monitoring polarity changes in the cellular microenvironment. Due to the donor-acceptor structure of CQPP, it offers ratiometric fluorescence emission and fluorescence lifetime signals that reflect polarity variations. Using nucleus imaging as a reference, CQPP was applied to report the increase in LD polarity and the homogenization of polarity between LDs and cytoplasm in the ferroptosis model. This LD/nucleus dual-targeted fluorescent probe shows the great potential of using fluorescence imaging to study ferroptosis and ferroptosis-related diseases.

Light-Up Lipid Droplets Dynamic Behaviors Using a Red-Emitting Fluorogenic Probe

Intracellular lipid metabolism occurs in lipid droplets (LDs), which is critical to the survival of cells. Imaging LDs is an intuitive way to understand their physiology in live cells. However, this is limited by the availability of specific probes that can properly visualize LDs in vivo. Here, an LDs-specific red-emitting probe is proposed to address this need, which is not merely with an ultrahigh signal-to-noise (S/N) ratio and a large Stokes shift (up to 214 nm) but also with superior resistance to photobleaching. The probe has been successfully applied to real-time tracking of intracellular LDs behaviors, including fusion, migration, and lipophagy processes. We deem that the proposed probe here offers a new possibility for deeper understanding of LDs-associated behaviors, elucidation of their roles and mechanisms in cellular metabolism, and determination of the transition between adaptive lipid storage and lipotoxicity as well.

Tetranitrile-anthracene as a probe for fluorescence detection of viscosity in fluid drinks via aggregation-induced emission

An AIE-based fluorescent probe was developed for monitoring the viscosity change during the spoilage process of fluid drinks.