A mitochondria-targeted far-red AIE fluorescent probe for distinguishing between mitophagy and ferroptosis in cancer cells

Endoplasmic reticulum (ER)-targeted ratiometric fluorescent probe for visualization of ER-phagy induced by ONOO- and NIR imaging in mice with drug-induced liver injury

Drug-induced liver injury (DILI) remains a persistent and unavoidable challenge in biomedicine, significantly impacting preclinical drug development and early clinical trials. The liver, as the primary site for endogenous antioxidant production, is particularly sensitive to acute damage mediated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ratiometric and near-infrared (NIR) detection of peroxynitrite (ONOO-), as potential biomarker for DILI, is crucial for enhancing the imaging effectiveness of liver damage. Thus, an ONOO- activated endoplasmic reticulum (ER)-targeted fluorescent probe, named DSA, was easily designed and synthesized using dicyanoisophorone, syringaldehyde and arylboronate, which featured dicyanoisophorone as the fluorophore and an arylboronate group as the ONOO- recognition group. The probe DSA was converted into a long-wavelength DSA-ONOO- fluorophore in the presence of ONOO- with large Stokes shift (172 nm), high selectivity, and low detection limit (98 nM). The ratiometric response to ONOO- provided a more accurate intracellular analysis through a built-in internal reference calibration, successfully enabling sensitive detection of ONOO- in living cells. Additionally, leveraging the optical characteristics of NIR fluorescence imaging, DSA not only detected the ER-phagy process induced by starvation and ONOO- but also accurately monitored minor fluctuations in ONOO- levels during acetaminophen (APAP)-induced hepatotoxicity in mice, aiding in the diagnosis of DILI and the development of therapeutic drugs.

A dual-response fluorescent probe Rh-O-QL for simultaneous monitoring of NAD(P)H and pH during mitochondrial autophagy

Mitochondrial autophagy is closely related to abnormal NAD(P)H and pH. Here, we synthesized a dual-response fluorescent probe with high selectivity for NAD(P)H and sensitivity in the physiological pH range, for simultaneous imaging analysis of mitochondrial NAD(P)H and pH, holding potential as a novel tool for understanding mitochondria-associated diseases.

Light-Enhanced Tandem-Responsive Nano Delivery Platform for Amplified Anti-tumor Efficiency

Designing nanomedicines with low toxicity, high targeting, excellent therapeutic effects, and precise release is always the major challenges in clinical cancer treatment. Here, we report a light-enhanced tandem-responsive nano delivery platform COF-B@X-03 for amplified anti-tumor efficiency. Biotin-loaded COF-B@X-03 could precisely target tumor cells, and the azo and hydrazone bonds in it would be depolymerized by the overexpressed azoreductase and acidic microenvironment in hypoxic tumors. In vitro experimental results indicate mitochondrial and endoplasmic reticulum stress caused by COF-B@X-03 under light is the direct cause of tumor cell death. In vivo experimental data prove COF-B@X-03 achieves low oxygen dependent phototherapy, and the maintenance of intratumoral hypoxia provides the possibility for the continuous degradation of COF-B@X-03 to generate more reactive oxygen species for tumor photodynamic therapy by released X-03. In the end, COF-B@X-03 phototherapy group achieves higher tumor inhibition rate than X-03 phototherapy group, which is 81.37 %. Meanwhile, COF-B@X-03 significantly eliminates the risk of tumor metastasis. In summary, the construction of this tandem-responsive nano delivery platform provides a new direction for achieving efficient removal of solid tumors in clinical practice.

Recent advances of aggregation-induced emission luminogens for point-of-care biosensing systems

The rapid and sensitive detection of chemical compounds in body fluids and tissues is important for diagnosis of diseases and assessment of the effectiveness of treatment programs. Point-of-care (POC) sensors based on fluorescence signals have been widely used in the rapid detection of various infectious diseases. However, the aggregation-caused quenching phenomenon of conventional fluorescent probes limits the sensitivity and accuracy of fluorescent POC sensors. In this review, we first focus on aggregation-induced emission (AIE)-based POC detection for early diagnosis of diseases and then describe how to use mechanisms of AIE to improve the sensitivity of POC testing. This review gives a summary of the design mechanisms of AIE probes in AIE-based biosensors. Subsequently, it summarizes the design strategies of AIE-based POC sensors in the detection of ions, small molecules, nucleic acids, proteins, and whole entity (cells, bacteria, viruses, and exosomes), placing an emphasis on signal amplification. Finally, it gives an overview of AIE-based POC biosensors, including probes, instruments, and applications. We hope that this review will provide valuable guidance for further expanding the application of AIE luminogens in POC biosensors.

Development of a polarity-sensitive ratiometric fluorescent probe based on the intramolecular reaction of spiro-oxazolidine and its applications for in situ visualizing the fluctuations of polarity during ER stress

Polarity is a vital element in endoplasmic reticulum (ER) microenvironment, and its variation is closely related to many physiological and pathological activities of ER, so it is necessary to trace fluctuations of polarity in ER. However, most of fluorescent probes for detecting polarity dependent on the changes of single emission, which could be affected by many factors and cause false signals. Ratiometric fluorescent probe with "built-in calibration" can effectively avoid detection errors. Here, we have designed a ratiometric fluorescent probe HM for monitoring the ER polarity based on the intramolecular reaction of spiro-oxazolidine. It forms ring open/closed isomers driven by polarity to afford ratiometric sensing. Probe HM have manifested its ratiometric responses to polarity in spectroscopic results, which could offer much more precise information for the changes of polarity in living cells with the internal built-in correction. It also showed large emission shift ( 133 nm), high selectivity and photo-stability. In biological imaging, HM could selectively accumulate in ER with high photo-stability. Importantly, HM has ability for in situ tracing the changes of ER polarity with ratiometric behavior during the ER stress process with the stimulation of tunicamycin, dithiothreitol and hypoxia, suggesting that HM is an effective molecule tool for monitoring the variations of ER polarity.

Ternary recognition fluorescent probe for lysosome acidification counter-ion studies via Cl-, K+, and pH

Lysosomal acidity relies on H+ inflow, which requires counter-ion flows (Cl- and K+) to balance charge. A lysosome targeting ternary recognition fluorescent probe for Cl-, K+, and pH was developed for lysosome acidification counter-ion research. The probe was used to study counter-ion changes when the Cl- channel was blocked and under oxidative pressure.

Ratiometric Near-Infrared Fluorescent Probe Monitors Ferroptosis in HCC Cells by Imaging HClO in Mitochondria

Hypochlorous acid (HClO) is a typical endogenous ROS produced mainly in mitochondria, and it has strong oxidative properties. Abnormal HClO levels lead to mitochondrial dysfunction, strongly associated with various diseases. It has been shown that HClO shows traces of overexpression in cells of both ferroptosis and hepatocellular carcinoma (HCC). Therefore, visualization of HClO levels during ferroptosis of HCC is important to explore its physiological and pathological roles. So far, there has been no report on the visualization of HClO in ferroptosis of HCC. Thus, we present a ratiometric near-infrared (NIR) fluorescent probe Mito-Rh-S which visualized for the first time the fluctuation of HClO in mitochondria during ferroptosis of HCC. Mito-Rh-S has an ultrafast response rate (2 s) and large emission shift (115 nm). Mito-Rh-S was constructed based on the PET sensing mechanism and thus has a high signal-to-noise ratio. The cell experiments of Mito-Rh-S demonstrated that Fe2+- and erastin-induced ferroptosis in HepG2 cells resulted in elevated levels of mitochondrial HClO and that high concentration levels of Fe2+ and erastin cause severe mitochondrial damage and oxidative stress and had the potential to kill HepG2 cells. By regulating the erastin concentration, erastin induction time, and treatment of the ferroptosis model, Mito-Rh-S can accurately detect the fluctuation of mitochondrial HClO levels during ferroptosis in HCC.

Fluorogenic Rhodamine Probes with Pyrrole Substitution Enables STED and Lifetime Imaging of Lysosomes in Live Cells

Fluorogenic dyes with high brightness, large turn-on ratios, excellent photostability, favorable specificity, low cytotoxicity, and high membrane permeability are essential for high-resolution fluorescence imaging in live cells. In this study, we endowed these desirable properties to a rhodamine derivative by simply replacing the N, N-diethyl group with a pyrrole substituent. The resulting dye, Rh-NH, exhibited doubled Stokes shifts (54 nm) and a red-shift of more than 50 nm in fluorescence spectra compared to Rhodamine B. Rh-NH preferentially exists in a non-emissive but highly permeable spirolactone form. Upon binding to lysosomes, the collective effects of low pH, low polarity, and high viscosity endow Rh-NH with significant fluorescence turn-on, making it a suitable candidate for wash-free, high-contrast lysosome tracking. Consequently, Rh-NH enabled us to successfully explore stimulated emission depletion (STED) super-resolution imaging of lysosome dynamics, as well as fluorescence lifetime imaging of lysosomes in live cells.