Fluorescent probes for ferroptosis bioimaging: advances, challenges, and prospects

A novel near-infrared AIE probe for sensitive imaging of lipid droplet and dual-parameter cancer diagnosis

BACKGROUND

Lipid droplets (LDs) are vital intracellular organelles for lipid storage, closely associated with various metabolic disorders and cancers. Fluorescence imaging offers a powerful, non-invasive approach to study LDs in real time, but many existing probes suffer from non-specific staining and aggregation-caused quenching (ACQ), compromising their imaging specificity and contrast.

RESULT

In this study, we synthesized a novel LD fluorescent probe TPC-AN that takes advantage of near-infrared emission, large Stokes shift, high lipophilicity, polarity response and aggregation-induced emission (AIE) characteristics. TPC-AN effectively addresses issues of non-specific staining and ACQ commonly observed with traditional probes, enabling highly specific and high-contrast imaging of LDs. Utilizing TPC-AN, imaging of LDs in several kinds of cells was performed, and discrimination of cancerous and normal cells was achieved using dual-parameter through differences in LD fluorescence area and intensity.

SIGNIFICANCE

This work provides a promising tool for studying LDs in diseases and offers a reliable method for cancer diagnosis, with excellent LD-specificity, low cytotoxicity, and dual-parameter imaging capabilities.

Monitoring Ferroptosis with NIR Fluorescence Probe Capable of Reversible Mitochondria Nucleus Translocation

Ferroptosis, a recently proposed form of regulated cell death, is characterized by a surge in reactive oxygen species and a subsequent depletion of glutathione. The mitochondria and nucleoli play pivotal roles in the process of ferroptosis. Therefore, monitoring the interactions between mitochondria and the nucleoli during ferroptosis is crucial for clarifying its physiological and pathological processes. In this study, we designed and synthesized the near-infrared fluorescence probe MINU, which exhibits excellent stability against biological ions and physiological pH environments. Due to its cationic structure and good DNA affinity, MINU can target both mitochondria and the nucleoli. Cell imaging demonstrates that MINU can reversibly migrate between the mitochondria and the nucleoli in response to changes in mitochondrial membrane potential. By detecting the localization and intensity of fluorescence signals, we can effectively distinguish between normal cell, apoptotic cell, and ferroptotic cell. Monitoring the interactions between mitochondria and the nucleoli allows us to more accurately appreciate the biological processes of ferroptosis.

Regulated cell death mechanisms in mitochondria-targeted phototherapy

Phototherapy, comprising photodynamic therapy (PDT) and photothermal therapy (PTT), was first introduced over a century ago and has since evolved into a versatile cancer treatment modality. While numerous studies have explored regulated cell death (RCD) mechanisms induced by phototherapy, a comprehensive synthesis centered on mitochondria-targeted phototherapeutic strategies and agents as mediators of RCD is still lacking. This review provides a systematic and in-depth analysis of recent advances in mitochondria-centered mechanisms driving phototherapy-induced death pathways, including apoptosis, autophagy, pyroptosis, immunogenic cell death, ferroptosis, and cuproptosis. We highlight the critical role of mitochondria as central regulators of these death pathways in response to phototherapeutic interventions. Moreover, we discuss fundamental design strategies for developing precision-targeted phototherapeutic materials to enhance efficacy and minimize off-target effects. Finally, we identify prevailing challenges and propose future research directions to address these hurdles, paving the way for next-generation mitochondria-targeted phototherapy as a highly effective strategy for cancer management.

Cyclometalated Iridium(III) Schiff Base Complexes for Chemiluminogenic Bioprobes

Chemiluminogenic bioimaging has emerged as a promising paradigm due to its independence from light excitation, thereby circumventing challenges related to light penetration depth and background autofluorescence. However, the availability of effective chemiluminophores remains limited, which substantially impedes their bio-applications. Herein, we discovered for the first time that cyclometalated iridium(III) Schiff base complexes can unexpectedly generate chemiluminescence. Notably, the chemiluminescence reaction was rapid, with a half-life of only 0.86 s, significantly faster than previously reported examples. Unlike conventional chemiluminescent scaffolds, the distinguishing feature of the chemiluminogenic iridium(III) complex is its unique intramolecular imine-to-amide conversion upon reaction with reactive oxygen species (ROS). Intriguingly, the chemiluminogenicity of these complexes is not influenced by the cyclometalating ligands but is closely associated with the Schiff base ligand, allowing for tuning of the emission colors via altering the cyclometalating ligands. Additionally, we formulated one of the Schiff base complexes (1) as water-soluble chemiluminogenic nanoparticles (CLNPs) and successfully employed them as activatable chemiluminescence bioprobes for precise and rapid imaging of hypochlorite-related biological events both in vitro and in vivo. We believe that this significant finding of the development of chemiluminogenic Schiff base complexes will greatly facilitate the designing of innovative chemiluminophores for theranostic applications.

Time Series Imaging the Mitochondrial Microenvironment and Its Interactions with Lysosomes during Ferroptosis

In the realm of cutting-edge scientific inquiry, the development and application of integrated optical molecular probes for the simultaneous detection and tracing of mitochondrial microenvironments during ferroptosis, as well as the visualization of their interactions with lysosomes, stands as a pivotal advancement. In this work, we developed a probe, IMT, that integrates viscosity sensing with mitochondrial targeting, and used it in conjunction with commercial lysosome green tracers (LGT) to investigate mitochondrial-lysosome interactions (MLIs). This approach avoids the uneven labeling caused by subcellular microenvironment differences when using single-molecule dual-targeting probes. Using the developed IMT, we observed an increase in mitochondrial viscosity during erastin-induced ferroptosis and a decrease during ferrostatin-1-inhibited ferroptosis. Moreover, the time series imaging of the mitochondrial profile lighted by the IMT showed that the mitochondrial area, perimeter, aspect ratio, and mitochondrial form factor changed significantly as ferroptosis progressed. In addition, combined with LGT, we visualized the dynamic process of first contact and then separation between lysosomes and mitochondria during ferroptosis, confirming the complexity and variability of MLIs. This work not only enhances our understanding of the complex biochemical processes underlying ferroptosis but also opens new avenues for therapeutic intervention in diseases characterized by this form of cell death.

A bifunctional fluorescent probe for dual-channel detection of H2O2 and HOCl in living cells

Hydrogen peroxide (H2O2) and hypochlorous acid (HOCl) are critical reactive oxygen species (ROS) that play significant roles in regulating oxidative stress, closely tied to various human diseases. However, investigating their interplay within living cells has been challenging due to the lack of effective tools for simultaneous discrimination. Herein, we present a bifunctional fluorescent probe, PTZ-H-H, capable of simultaneously detecting H2O2 and HOCl in living cells via two distinct fluorescence channels. PTZ-H-H exhibits selective and sensitive responses, emitting red fluorescence in the presence of H2O2 and green fluorescence in response to HOCl, with detection limits of 386 nM and 16.8 nM, respectively. The probe was successfully applied in living cells, enabling real-time monitoring of intracellular H2O2 and HOCl. This study demonstrates the potential of PTZ-H-H as a powerful tool for exploring the dynamic roles of H2O2 and HOCl in various physiological and pathological processes.

Construction of a novel NIR-emissive rhodamine derivative for monitoring mitochondrial viscosity in ferroptosis

Ferroptosis, an iron-dependent programmed cell death mechanism, is mediated by distinct molecular pathways of lipid peroxidation caused by intracellular iron supplementation and glutathione synthesis inhibition that cause oxidative damage to the cell membrane. Monitoring viscosity changes of mitochondria is essential for a deeper understanding of ferroptosis, as mitochondria will be shrunk with increased membrane density and leading to drastic mitochondrial viscous changes during ferroptosis process. Thus, it is essential to explore novel and efficient fluorescent probes for monitoring viscosity in organisms. In this work, we designed and synthesized a mitochondria-targeting probe TJ-FRP for cellular viscosity measurement via fluorescence imaging method. To obtain this probe, we firstly developed a novel modifiable fluorescent π-extended xanthene dye TJ-FR by replacing the benzoic acid group with a strong electron-withdrawing perfluorobenzoic acid group at the 9-position of xanthene framework. The dye not only presents emission wavelength at 758 nm and a large stokes shift of 142 nm in water, but also the dye is low biotoxic, membrane permeable. By reaction with 4-aminobutyltriphenylphosphonium bromide, TJ-FR was converted to the mitochondria-targeting probe TJ-FRP. TJ-FRP was successfully applied for the imaging of viscosity in living cells. Especially, the probe can be applied for visualizing mitochondrial viscosity changes during various inducers-stimulated ferroptosis process in model cells. These findings suggest that this novel NIR fluorescent probe can serve as a powerful tool to monitor the viscosity in biological samples and may provide new insights for various diseases during ferroptosis.

Chemical Design of Magnetic Nanomaterials for Imaging and Ferroptosis-Based Cancer Therapy

Ferroptosis, an iron-dependent form of regulatory cell death, has garnered significant interest as a therapeutic target in cancer treatment due to its distinct characteristics, including lipid peroxide generation and redox imbalance. However, its clinical application in oncology is currently limited by issues such as suboptimal efficacy and potential off-target effects. The advent of nanotechnology has provided a new way for overcoming these challenges through the development of activatable magnetic nanoparticles (MNPs). These innovative MNPs are designed to improve the specificity and efficacy of ferroptosis induction. This Review delves into the chemical and biological principles guiding the design of MNPs for ferroptosis-based cancer therapies and imaging-guided therapies. It discusses the regulatory mechanisms and biological attributes of ferroptosis, the chemical composition of MNPs, their mechanism of action as ferroptosis inducers, and their integration with advanced imaging techniques for therapeutic monitoring. Additionally, we examine the convergence of ferroptosis with other therapeutic strategies, including chemodynamic therapy, photothermal therapy, photodynamic therapy, sonodynamic therapy, and immunotherapy, within the context of nanomedicine strategies utilizing MNPs. This Review highlights the potential of these multifunctional MNPs to surpass the limitations of conventional treatments, envisioning a future of drug-resistance-free, precision diagnostics and ferroptosis-based therapies for treating recalcitrant cancers.

Iron homeostasis and ferroptosis in muscle diseases and disorders: mechanisms and therapeutic prospects

The muscular system plays a critical role in the human body by governing skeletal movement, cardiovascular function, and the activities of digestive organs. Additionally, muscle tissues serve an endocrine function by secreting myogenic cytokines, thereby regulating metabolism throughout the entire body. Maintaining muscle function requires iron homeostasis. Recent studies suggest that disruptions in iron metabolism and ferroptosis, a form of iron-dependent cell death, are essential contributors to the progression of a wide range of muscle diseases and disorders, including sarcopenia, cardiomyopathy, and amyotrophic lateral sclerosis. Thus, a comprehensive overview of the mechanisms regulating iron metabolism and ferroptosis in these conditions is crucial for identifying potential therapeutic targets and developing new strategies for disease treatment and/or prevention. This review aims to summarize recent advances in understanding the molecular mechanisms underlying ferroptosis in the context of muscle injury, as well as associated muscle diseases and disorders. Moreover, we discuss potential targets within the ferroptosis pathway and possible strategies for managing muscle disorders. Finally, we shed new light on current limitations and future prospects for therapeutic interventions targeting ferroptosis.

Radical-triggered ring-opening of aminocyclopropane for detection of hydroxyl radicals in living cells

Hydroxyl radicals (˙OH), highly reactive oxygen species involved in oxidative stress and cancer therapy, are challenging to detect intracellularly due to their short lifetime, low concentration, and high reactivity. To address this, a novel ˙OH-specific fluorescent probe, CC-7, was developed by integrating an aminocyclopropane group into a coumarin derivative. This design was inspired by the radical-mediated ring-opening of aminocyclopropanes in synthetic chemistry. The ring-opening reaction triggered by ˙OH in CC-7 produces a significant "Fluorescence-ON" response with a 10-fold increase in intensity, demonstrating high selectivity for ˙OH over other reactive oxygen species. CC-7 effectively visualized intracellular ˙OH, distinguished between normal (HEK-293T) and cancer cells (4T1), and monitored ˙OH generated by chemotherapeutic agents like doxorubicin and cisplatin. This study highlights CC-7 as a powerful tool for selectively detecting ˙OH in living cells, with potential applications in investigating oxidative stress-related diseases and monitoring cancer therapy.

A steric hindrance-regulated probe with single excitation dual emissions for self-adaptive detection of biothiols and H2S in human urine samples and living cells

Sulfur-containing small molecules, mainly including cysteine (Cys), homocysteine (Hcy), glutathione (GSH), and hydrogen sulfide (H2S), are crucial biomarkers, and their levels in different body locations (living cells, tissues, blood, urine, saliva, etc.) are inconsistent and constantly changing. Therefore, it is highly meaningful and challenging to synchronously and accurately detect them in complex multi-component samples without mutual interference. In this work, we propose a steric hindrance-regulated probe, NBD-2FDCI, with single excitation dual emissions to achieve self-adaptive detection of four analytes. This probe was meticulously designed and constructed from a pKa-tuned 2FDCI fluorophore and a thiol-specific recognition moiety NBD. Except for 661 nm fluorescence for indicating the total biothiols and H2S, Cys and Hcy could trigger an additional 550 nm fluorescence. Utilizing the distinctive responses, the probe NBD-2FDCI exhibited exclusive linear ranges for GSH, Cys/Hcy, and H2S to avoid high-level component interference. Thus, the probe was then applied for sulfur compound measurements in urine samples, indicating metabolic disorder of Cys and H2S in bladder cancer patients. Moreover, adaptive imaging of probe NBD-2FDCI in cells was performed with the results being consistent with in vitro testing. In a word, spatial hindrance strategy-guided probes may exhibit broader prospects in the detection of similar components in complex samples.

Fabrication of a Redox-Reversible Near-Infrared Fluorogenic Probe for Ferroptosis Process Monitoring and the Early Diagnosis of Diabetes

Ferroptosis is a type of cell death triggered by the iron-dependent accumulation of lipid peroxides in cells. Diabetes, a chronic metabolic disorder characterized by hyperglycemia, can lead to various health complications. The process of ferroptosis and the progression of diabetes are closely linked to redox homeostasis, which is regulated by the levels of reactive oxygen and sulfur species. Currently, there are no fluorescent probes available to monitor changes in redox homeostasis during ferroptosis and diabetes. Here, we report the first endeavor to create a reversible near-infrared fluorogenic (NIRF) probe for monitoring the process of ferroptosis reversal and precise diabetes diagnosis. In vitro data demonstrated that NIR-CSTe could cyclically and reversibly detect ONOO- and GSH up to four times with minimal loss in fluorescence intensity. With the help of NIR-CSTe, we observed that HT-1080 cells, induced to undergo ferroptosis by erastin after being washed with PBS for 24 h and then treated with ferrostatin-1, showed a recovery in intracellular GSH levels. In contrast, treatment with deferoxamine did not yield similar results. Lastly, NIR-CSTe was also utilized for the early diagnosis and efficacy assessment of diabetes in relation to ONOO-/GSH redox balance, with results illustrating that the combined administration of metformin and empagliflozin was more effective than using either drug alone. Thus, this smart probe holds significant potential as an essential tool for clinical diagnosis and treatment of diseases associated with redox homeostasis.

Alginate-derived carbon dots for "turn off-on" anti-neoplastic 5-fluorouracil sensing in biological samples

As a chemotherapy drug, 5-fluorouracil (5-FU) has been used for colon cancer for decades. Excessive levels of 5-FU in the human body can lead to notable adverse effects, including severe diarrhea, infection, mouth sores, skin peeling, skin inflammation, and ulcers, which are important and relatively common digestive side effects. In addition, 5-FU is an analog of uracil and also has similarities to pyrimidines. Therefore, it is not easy to separate them. This research presented a sensor capable of detecting drugs in minimal amounts. An alginate-derived carbon dot (CD) was synthesized by unique optical properties that obey an on-off fluorescence mechanism for 5-FU sensing. Introducing copper (Cu(I)) to CDs results in fluorescence quenching through electron transfer. However, when 5-FU is added to the system as an oxidizing agent, a redox reaction occurs on the surface of the CDs, which leads to the restoration of fluorescence as Cu(I) is altered to Cu(II). Experimental results showed a strong linear correlation (R2 = 0.99) in the concentration range of 1.00-45.00 nM, with the following linear regression, and revealed the relative standard deviation (RSD%) and detection limit of 2.57%, and 1.00 nM, respectively. These results validated the excellent detection capability of the proposed method even at low concentrations of 5-FU and in the presence of other drugs and interfering substances. Also, the recovery of 5-FU (varies from 100.46% to 113.7%, with RSD equal to 1.89-3.63) in serum samples indicates the absence of matrix interference in the determination of 5-FU. In summary, this novel approach to developing a cost-effective and sensitive sensor holds great potential for future applications in healthcare and related fields.

Novel ruthenium(II) complex-based two-photon luminescent probe for visualizing biothiols in ferroptosis-mediated hepatic ischemia-reperfusion injury

Ferroptosis exhibits a critical role in the occurrence and progression of hepatic ischemia-reperfusion injury (HIRI), which is closely linked to the down regulation of biothiols. Visualization of biothiols in ferroptosis is of great significance for elucidating the pathological mechanism of HIRI as well as developing new clinical treatment strategies. However, reliable tools for monitoring biothiols and demonstrating their dynamic changes in ferroptosis-mediated HIRI are still lacking. Herein, this work developed an innovative Ru(II) complex-based two-photon luminescent probe, named Ru-PDBS, for accurate tracking the biothiols fluxes in ferroptosis-mediated HIRI. The newly developed probe possessed high sensitivity, good selectivity and favorable biocompatibility, which makes it to be used for imaging and dynamic monitoring of biothiols in living cells during ferroptosis-mediated HIRI. Furthermore, visualization of biothiols in mouse livers during ferroptosis-mediated HIRI and drug treatment was achieved for the first time. All these results suggested that Ru-PDBS can serve as a reliable tool for elucidating the pathogenesis of ferroptosis-mediated HIRI, as well as for developing of new therapies.

Mitochondria-targeted fluorescent probes based on coumarin-hemicyanine for viscosity changes and their applications in cells and mice

As an important parameter of the cellular microenvironment, the changes in mitochondrial viscosity are closely related to various life activities. Therefore, the development of fluorescent probes for test the changes of mitochondrial viscosity has great significance. In this study, we developed two fluorescent probes for the detection of the mitochondrial viscosity changes. The probes exhibited different fluorescence intensities at different viscosity based on the twisted intramolecular charge transfer process. The characteristics of high anti-interference performance, wide pH applicability, low cytotoxicity and excellent mitochondrial targeting performance made the probes successfully used to distinguish normal cells from cancer cells, achieving visualization of viscosity changes. Furthermore, probes P1 and P2 can also be used as early diagnosis of tumors in mice and reveal the pathology of tumor development. The probes could be serve as a promising viscosity detection tool for discriminating normal cells and cancer cells in biology-related research.

Development of a fast fluorescent probe for sensitive detection of glutathione in 100 % aqueous solution and its applications in real samples, oxidative stress model and ferroptosis model

Glutathione (GSH) plays a crucial role in several physiological processes, including anti-oxidation and heavy metal detoxification. GSH is produced endogenously in the human body and can also be obtained through diet. The development of fast, highly sensitive, and multi-application fluorescent probes remains a challenging task. In this study, we have designed and synthesized a coumarin-based fluorescent probe (NFRF) for the sensitive and rapid detection of GSH in 100 % aqueous solution. By loading probe NFRF on the filter paper, the real-time visual detection of GSH is achieved in both daylight and fluorescence modes, providing a convenient, economical and rapid on-site detection tool. Probe NFRF could be used for the detection of GSH in real samples, with recoveries rates of 81.74 %-115.12 %. Notably, the probe imaged changes in GSH concentrations in oxidative stress environments and during ferroptosis. This work provides a prospective method for GSH detection in food and complex biological systems.

A near-infrared fluorescent molecular rotor for viscosity detection in biosystem and fluid beverages

Viscosity is closely associated with physiological and pathological processes, as well as food quality. Herein, a novel fluorescent molecular rotor, BMCY-V, was presented and applied for detection of viscosity. BMCY-V contained a benzoindole unit as electron donor and a malononitrile group as acceptor. In low-viscous solvents, the rotor can freely rotate, leading to dissipation of excited-state energy. In high-viscous media, however, the free rotation of the rotor is severely restricted, thus reducing non-radiative transition and resulting in significantly enhanced fluorescence intensity. BMCY-V is extremely sensitive to viscosity, showing about 3968 times increase of fluorescence intensity at 728 nm from water to 95 % glycerol. Due to the excellent photophysical property such as near-infrared emission, BMCY-V was successfully used to visualize viscosity in live cells and in liver tissues. In addition, BMCY-V can also evaluate the thickening effect of various thickeners and visualize the changes of viscosity during deterioration of fluid drinks.

Illuminating cisplatin-induced ferroptosis in non-small-cell lung cancer with biothiol-activatable fluorescent/photoacoustic bimodal probes

Ferroptosis modulation represents a pioneering therapeutic approach for non-small-cell lung cancer (NSCLC), where precise monitoring and regulation of ferroptosis levels are pivotal for achieving optimal therapeutic outcomes. Cisplatin (Cis), a widely used chemotherapy drug for NSCLC, demonstrates remarkable therapeutic efficacy, potentially through its ability to induce ferroptosis and synergize with other treatments. However, in vivo studies of ferroptosis face challenges due to the scarcity of validated biomarkers and the absence of reliable tools for real-time visualization. Biothiols emerge as suitable biomarkers for ferroptosis, as their concentrations decrease significantly during this process. To address these challenges, fluorescence/photoacoustic (PA) bimodal imaging offers a promising solution by providing more accurate in vivo information on ferroptosis. Therefore, the development of methods to detect biothiols using fluorescence/PA bimodal imaging is highly desirable for visualizing ferroptosis in NSCLC. In this study, we designed and constructed two activatable near-infrared (NIR) fluorescent/PA bimodal imaging probes specifically for visualizing ferroptosis by monitoring the fluctuations in biothiol levels. These probes exhibited excellent bimodal response performance in solution, cells, and tumors. Furthermore, they were successfully applied for real-time monitoring of biothiol changes during the ferroptosis process in NSCLC cells and tumors. Importantly, our findings revealed that the combined use of erastin and cisplatin exacerbates the consumption of biothiols, suggesting an enhancement of ferroptosis in NSCLC. This work not only provides powerful tools for monitoring in vivo ferroptosis but also facilitates the study of ferroptosis mechanisms and holds the potential to further advance the treatment of NSCLC.

Rational design of an AIEgen for imaging lipid droplets polarity change during ferroptosis

Ferroptosis can regulate cell death by accumulating lipid peroxides, affecting the structure and polarity of lipid droplets (LDs), but clear evidence is still lacking. Fluorescence imaging is the most powerful technique for studying LDs' function. However, developing AIE fluorescent probes with high selectivity and sensitivity for targeting LDs remains challenging. In this study, we rationally designed an AIEgen, as a novel fluorescent probe TPE-BD, by constructing a push-pull electron structure. The probe has benzo[b]thiophene-3(2H)-one 1,1-dioxide as the electron acceptor, tetraphenylethylene (AIE skeleton) as the electron donor, and thiophene as the bridging group. The optical performance of probe TPE-BD indicated that the UV-visible absorption spectrum of the probe was minimally affected by solvent polarity (except for glycerol and PBS solvents), but the fluorescence of probe is very sensitive to changes in polarity, achieving the goal of polarity detection in LDs. CCK-8 assay and cell imaging experiments demonstrated that probe TPE-BD exhibited good cell compatibility and effectively targeted LDs, enabling the monitoring of LDs' polarity and quantity during ferroptosis.

Mitochondria-Targetable Cyclometalated Iridium(III) Complex-Based Luminescence Probe for Monitoring and Assessing Treatment Response of Ferroptosis-Mediated Hepatic Ischemia-Reperfusion Injury

Ferroptosis plays an essential role in the pathological progression of hepatic ischemia-reperfusion injury (HIRI), which is closely related to iron-dependent lipid peroxidation. Since mitochondria are thought to be the major site of reactive oxygen species (ROS) production and iron storage, monitoring the variations of mitochondrial hypochlorous acid (HClO) (an important member of ROS) has important implications for the assessment of ferroptosis status, as well as the formulation of treatment strategies for HIRI. However, reliable imaging tools for the visualization of mitochondrial HClO and monitoring its dynamic changes in ferroptosis-mediated HIRI are still lacking. Herein, in this work, an HClO-activated near-infrared (NIR) cyclometalated iridium(III) complex-based probe, named NIR-Ir-HClO, was developed for the visual monitoring of the mitochondrial HClO fluxes in ferroptosis-mediated HIRI. The newly prepared probe showed fast response (<30 s), good sensitivity, excellent selectivity, good cell biocompatibility, and satisfactory mitochondrial-targeting performance, making it suitable for accurate monitoring of mitochondrial HClO in living cells. Moreover, visualization of the variations of mitochondrial HClO in ferroptosis-mediated HIRI and monitoring of the treatment response of ferroptosis-mediated HIRI to the ferroptosis inhibitors were achieved for the first time. All these show that probe NIR-Ir-HClO can be utilized as a reliable imaging tool for revealing the pathological mechanism of mitochondrial HClO in ferroptosis-mediated HIRI, as well as for the formulation of new treatment strategies for HIRI.

Red-Light Triggered H-Abstraction Photoinitiators for the Efficient Oxygen-Independent Therapy of Hypoxic Tumors

The clinical application of photodynamic therapy (PDT) is limited by oxygen-dependence and side effects caused by photosensitizer residues. Photoinitiators based on the H-abstraction reaction can address these challenges because they can generate alkyl radical-killing cells independently of oxygen and undergo rapid bleaching following H-abstraction. Nonetheless, the development of photoinitiators for PDT has been impeded by the absence of effective design strategies. Herein, we have developed aryl-ketone substituted cyanine (ACy-R), the first red-light triggered H-abstraction photoinitiators for hypoxic cancer therapy. These ACy-R molecules inherited the near-infrared absorption of cyanine dye, and aryl-ketone modification imparted H-abstraction capability. Experimental and quantum calculations revealed that modifying the electron-withdrawing groups of the aryl (e.g., ACy-5F) improved the contribution of the O atom to the photon excitation process promoting intersystem crossing and H-abstraction ability. Particularly, ACy-5F rapidly penetrated cells and enriched in the endoplasmic reticulum. Even under severe hypoxia, ACy-5F initiated red-light induced H-abstraction with intracellular biomolecules, inducing necroptosis and ferroptosis. Moreover, ACy-5F was degraded after H-abstraction, thus avoiding the side effects of long-term phototoxicity after therapy. This study not only provides a crucial molecular tool for hypoxic tumors therapy, but also presents a promising strategy for the development of multifunctional photosensitizers and photoinitiators.

γ-Glutamyltranspeptidase fluorescence lifetime response probe for precision tumor detection unveiling A549 cancer cell specificity

γ-Glutamyltranspeptidase (γ-GGT), as a key enzyme, exhibits markedly higher expression levels in tumor cells compared to normal cells. Under normal conditions, γ-GGT activity on the cell membrane is relatively low, but it undergoes a significant upregulation in cancer cells, making it a potential cancer biomarker. Particularly in A549 cells, a prominent cancer cell line, the pronounced upregulation of γ-GGT expression emphasizes its potential as a unique recognition target and a robust marker for A549 cells. This study successfully synthesized a highly selective γ-GGT fluorescent probe, the exhibits commendable sensitivity (LOD = 0.0021U/mL) and selectivity, achieving efficient detection at the cellular level and providing accurate insights into differential expression between normal and cancer cells. The alterations in fluorescence lifetime observed before and after the probe's reaction with γ-GGT serve as a crucial foundation for fluorescence lifetime imaging on living cells. The probe has become a powerful tool for precise localization of tumor cells, particularly demonstrating its capability for specific recognition in A549 cells. Overall, this research highlights the potential of γ-GGT as a target for fluorescent probes, emphasizing its prospects in specific recognition, particularly in A549 cells, with profound implications for advancing early cancer diagnosis and treatment methods.

A tumor-targeting two-photon fluorescent probe with a far-red to NIR emission for imaging basal hypochlorite in cancer cells and tumor

Cancer cells have a high abundance of hypochlorite compared to normal cells, which can be used as the biomarker for imaging cancer cells and tumor. Developing the tumor-targeting fluorescent probe suitable for imaging hypochlorite in vivo is urgently demanded. In this article, based on xanthene dye with a two-photon excited far-red to NIR emission, a tumor-targeting two-photon fluorescent probe (Biotin-HClO) for imaging basal hypochlorite in cancer cells and tumor was developed. For ClO-, Biotin-HClO (20.0 μM) has a linear response range from 15.0 × 10-8 to 1.1 × 10-5 M with a high selectivity and a high sensitivity, a good detection limit of 50 nM and a 550-fold fluorescence enhancement with high signal-to-noise ratio (20 mM PBS buffer solution with 50 % DMF; pH = 7.4; λex = 605 nm; λem = 635 nm). Morover, Biotin-HClO exhibited excellent performance in monitoring exogenous and endogenous ClO- in cells, and has an outstanding tumor-targeting ability. Subsequently, Biotin-HClO has been applied for imaging ClO- in 4T1 tumor tissue to distinguish from normal tissue. Furthermore, Biotin-HClO was successfully employed for high-contrast imaging 4T1 tumor in mouse based on its tumor-targeting ability. All these results proved that Biotin-HClO is a useful analytical tool to detect ClO- and image tumor in vivo.

Recent development in dual function fluorescence probes for HOCl and interaction with different bioactive molecules

Reactive oxygen species (ROS), reactive sulfur species (RSS), metal ions, and nitrogen species (RNS) play important roles in a variety of biological processes, such as a signal transduction, inflammation, and neurodegenerative damage. These species, while essential for certain functions, can also induce stress-related diseases. The interrelation between ROS, RSS, Metal ions and RNS underscores the importance of quantifying their concentrations in live cells, tissues, and organisms. The review emphasizes the use of small-molecule-based fluorescent/chemodosimeter probes to effectively measure and map the species' distribution with high temporal and spatial precision, paying particular attention to in vitro and in vivo environments. These probes are recognized as valuable tools contributing to breakthroughs in modern redox biology. The review specifically addresses the relationship of HOCl/ClO‾ (hypochlorous acid/Hypochlorite) with other reactive species. (Dual sensing probes).

Visulization of peroxynitrite variation for accurate diagnosis and assessing treatment response of hepatic fibrosis using a Golgi-targetable ratiometric fluorescent probe

Hepatic fibrosis (HF) is caused by persistent inflammation, which is closely associated with hepatic oxidative stress. Peroxynitrite (ONOO-) is significantly elevated in HF, which would be regarded as a potential biomarker for the diagnosis of HF. Research has shown that ONOO- in the Golgi apparatus can be overproduced in HF, and it can induce hepatocyte injury by triggering Golgi oxidative stress. Meanwhile, the ONOO- inhibitors could effectively relieve HF by inhibiting Golgi ONOO-, but as yet, no Golgi-targetable fluorescent probe available for diagnosis and assessing treatment response of HF through sensing Golgi ONOO-. To this end, we reported a ratiometric fluorescent probe, Golgi-PER, for diagnosis and assessing treatment response of HF through monitoring the Golgi ONOO-. Golgi-PER displayed satisfactory sensitivity, low detection limit, and exceptional selectivity to ONOO-. Combined with excellent biocompatibility and good Golgi-targeting ability, Golgi-PER was further used for ratiometric monitoring the Golgi ONOO- fluctuations and screening of ONOO- inhibitors from polyphenols in living cells. Meanwhile, using Golgi-PER as a probe, the overexpression of Golgi ONOO- in HF and the treatment response of HF to the screened rosmarinic acid were precisely visualized for the first time. Furthermore, the screened RosA has a remarkable therapeutic effect on HF, which may be a new strategy for HF treatment. These results demonstrated the practicability of Golgi-PER for monitoring the occurrence, development, and personalized treatment response of HF.

A dual-labeling fluorescent probe to track lysosomal polarity and endoplasmic reticulum dynamics during ferroptosis

A polarity-sensitive probe was developed to simultaneously label lysosomes and endoplasmic reticulum (ER) via its dansylamide and rhodamine fluorescence, respectively, enabling ratiometric polarity detection and stable dual-labeling. The fragmented ER network and increased lysosomal polarity during ferroptosis were revealed, which facilitates the understanding of ferroptotic mechanisms.

Ratiometric Fluorescent Probe for Super-Resolution Imaging of Lysosome HClO in Ferroptosis Cells

Ferroptosis is an iron-dependent programmed cell death that is characterized by the dysregulation of lipid reactive oxygen species (ROS) production, causing abnormal changes in hypochlorous acid (HClO) levels in lysosomes. Super-resolution imaging can observe the fine structure of the lysosome at the nanometer level; therefore, it can be used to detect lysosome HClO levels during ferroptosis at the suborganelle level. Herein, we utilize a ratiometric fluorescent probe, SRF-HClO, for super-resolution imaging of lysosome HClO. Structured-illumination microscopy (SIM) improves the accuracy of lysosome targeting and enables the probe SRF-HClO to be successfully applied to rapidly monitor the up-regulated lysosome HClO at the nanoscale during inflammation and ferroptosis. Importantly, the probe SRF-HClO can also detect HClO changes in inflammatory and ferroptosis mice and evaluate the inhibitory effect of ferroptosis on mice tumors.

A TICT-AIE activated dual-channel fluorescence-on probe to reveal the dynamics mechanosensing of lipid droplets during ferroptosis

Mechanical forces play a crucial role in cellular processes, including ferroptosis, a form of regulated cell death associated with various diseases. However, the mechanical aspects of organelle lipid droplets (LDs) during ferroptosis are poorly understood. In this study, we designed and synthesized a fluorescent probe, TPE-V1, to enable real-time monitoring of LDs' viscosity using a dual-channel fluorescence-on model (red channel at 617 nm and NIR channel at 710 nm). The fluorescent imaging of using TPE-V1 was achieved due to the integrated mechanisms of the twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE). Through dual-emission channel fluorescence imaging, we observed the enhanced mechanical energy of LDs triggering cellular mechanosensing, including ferroptosis and cell deformation. Theoretical calculations confirmed the probe's behavior, showing that high-viscosity media prevented the rotation processes and restored fluorescence quenching in low viscosity. These findings suggest that our TICT-TPE design strategy provides a practical approach to study LDs' mechanical properties during ferroptosis. This development enhances our understanding of the interplay between mechanical forces and LDs, contributing to the knowledge of ferroptotic cell death and potential therapeutic interventions targeting dysregulated cell death processes.

A Near-Infrared Colorimetric Fluorescent Probe for Ferrous Ion Detection and Imaging

Based on the N-redox mechanism, a turn-on near-infrared fluorescence probe (SWJT-15) with cyano isophorone as skeleton was designed and synthesized for the detection of ferrous ions (Fe2+). The probe has a lower detection limit (83 nM) and fast response (200 s) to Fe2+ ions. And the probe has unique selectivity and good anti-interference performance against Fe2+ ions compared to other metal ions. Moreover, the probe has been successfully applied to imaging Fe2+ ions in HeLa cells.

Visualization of Acrolein Upregulation during Ferroptosis by a Ratiometric Fluorescent Probe

Ferroptosis is a pattern of cell death caused by iron-dependent accumulation of lipid peroxides and is closely associated with the occurrence and development of multiple diseases. Acrolein (ACR), one of the final metabolites of lipid peroxidation, is a reactive carbonyl species with strong biotoxicity. Effective detection of ACR is important for understanding its role in the progression of ferroptosis and studying the specific mechanisms of ferroptosis-mediated diseases. However, visualization detection of ACR during ferroptosis has not yet been reported. In this work, the first ratiometric fluorescent probe (HBT-SH) based on 2-(2'-hydroxyphenyl) benzothiazole (HBT) was designed for tracing endogenous ACR with an unprecedented regiospecific ACR-induced intramolecular cyclization strategy, which employs 2-aminoethanethiol as an ACR-selective recognition receptor. The experimental results showed that HBT-SH has excellent selectivity, high sensitivity (LOD = 0.26 μM) and good biocompatibility. More importantly, the upregulation of ACR levels was observed during ferroptosis in HeLa cells and zebrafish, indicating that ACR may be a specific active molecule that plays an essential biological role during ferroptosis or may serve as a potential marker of ferroptosis, which has great significance for studying the pathological process and treatment options of ferroptosis-related diseases.

Dissecting lysosomal viscosity fluctuations in live cells and liver tissues with an ingenious NIR fluorescent probe

Viscosity is a pivotal component in the cell microenvironment, while lysosomal viscosity fluctuation is associated with various human diseases, such as tumors and liver diseases. Herein, a near-infrared fluorescent probe (BIMM) based on merocyanine dyes was designed and synthesized for detecting lysosomal viscosity in live cells and liver tissue. The increase in viscosity restricts the free rotation of single bonds, leading to enhanced fluorescence intensity. BIMM exhibits high sensitivity and good selectivity, and is applicable to a wide pH range. BIMM has near-infrared emission, and the fluorescent intensity shows an excellent linear relationship with viscosity. Furthermore, BIMM possessing excellent lysosomes-targeting ability, and can monitor viscosity changes in live cells stimulated by dexamethasone, lipopolysaccharide (LPS), and nigericin, and differentiate between cancer cells and normal cells. Noticeably, BIMM can accurately analyze viscosity changes in various liver disease models with HepG2 cells, and is successfully utilized to visualize variations in viscosity on APAP-induced liver injury. All the results demonstrated that BIMM is a powerful wash-free tool to monitor the viscosity fluctuations in living systems.

NIR Fluorescent/Photoacoustic Bimodal Imaging of Ferroptosis in Pancreatic Cancer Using Biothiols-Activable Probes

Ferroptosis modulation is a powerful therapeutic option for pancreatic ductal adenocarcinoma (PDAC) with a low 5-year survival rate and lack of effective treatment methods. However, due to the dual role of ferroptosis in promoting and inhibiting pancreatic tumorigenesis, regulating the degree of ferroptosis is very important to obtain the best therapeutic effect of PDAC. Biothiols are suitable as biomarkers of imaging ferroptosis due to the dramatic decreases of biothiol levels in ferroptosis caused by the inhibited synthesis pathway of glutathione (GSH) and the depletion of biothiol by reactive oxygen species. Moreover, a very recent study reported that cysteine (Cys) depletion can lead to pancreatic tumor ferroptosis in mice and may be employed as an effective therapeutic strategy for PDAC. Therefore, visualization of biothiols in ferroptosis of PDAC will be helpful for regulating the degree of ferroptosis, understanding the mechanism of Cys depletion-induced pancreatic tumor ferroptosis, and further promoting the study and treatment of PDAC. Herein, two biothiol-activable near-infrared (NIR) fluorescent/photoacoustic bimodal imaging probes (HYD-BX and HYD-DX) for imaging of pancreatic tumor ferroptosis were reported. These two probes show excellent bimodal response performances for biothiols in solution, cells, and tumors. Subsequently, they have been employed successfully for real-time visualization of changes in concentration levels of biothiols during the ferroptosis process in PDAC cells and HepG2 cells. Most importantly, they have been further applied for bimodal imaging of ferroptosis in pancreatic cancer in mice, with satisfactory results. The development of these two probes provides new tools for monitoring changes in concentration levels of biothiols in ferroptosis and will have a positive impact on understanding the mechanism of Cys depletion-induced pancreatic tumor ferroptosis and further promoting the study and treatment of PDAC.

A Red-Emission Fluorescent Probe with Large Stokes Shift for Detection of Viscosity in Living Cells and Tumor-Bearing Mice

Abnormal viscosity is closely related to the occurrence of many diseases, such as cancer. Therefore, real-time detection of changes in viscosity in living cells is of great importance. Fluorescent molecular rotors play a critical role in detecting changes in cellular viscosity. Developing red emission viscosity probes with large Stokes shifts and high sensitivity and specificity remains an urgent and important topic. Herein, a novel viscosity-sensitive fluorescent probe (TCF-VIS1) with a large stokes shift and red emission was prepared based on the 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) skeleton. Due to intramolecular rotation, the probe itself does not fluorescence at low viscosity. With the increase in viscosity, the rotation of TCF-VIS1 is limited, and its fluorescence is obviously enhanced. The probe has the advantages of simple preparation, large Stokes shift, good sensitivity and selectivity, and low cytotoxicity, which make it successfully used for viscosity detection in living cells. Moreover, TCF-VIS1 showed its potential for cancer diagnosis at the cell level and in tumor-bearing mice by detecting viscosity. Therefore, the probe is expected to enrich strategies for the detection of viscosity in biological systems and offer a potential tool for cancer diagnosis.

Unraveling Ferroptosis Mechanisms: Tracking Cellular Viscosity with Small Molecular Fluorescent Probes

Ferroptosis is a recently identified form of regulated cell death characterized by iron accumulation and lipid peroxidation. Numerous functions for ferroptosis have been identified in physiological as well as pathological processes, most notably in the treatment of cancer. The intricate balance of redox homeostasis is profoundly altered during ferroptosis, leading to alteration in cellular microenvironment. One such microenvironment is viscosity among others such as pH, polarity, and temperature. Therefore, understanding the dynamics of ferroptosis associated viscosity levels within organelles is crucial. To date, there are a very few reviews that detects ferroptosis assessing reactive species. In this review, we have summarized organelle's specific fluorescent probes that detects dynamics of microviscosity during ferroptosis. Also, we offer the readers an insight of their design strategy, photophysics and associated bioimaging concluding with the future perspective and challenges in the related field.

Golgi apparatus-targeting fluorescent probe for the imaging of superoxide anion (O2•-) in living cells during ferroptosis

Ferroptosis is an emerging iron-dependent oxidative cell death type, and recently has been demonstrated to show close relation with Golgi apparatus (GA). Exploring the fluctuation of superoxide anion (O2•-) level in GA during ferroptosis is of great significance to profoundly study the biological functions of GA in ferroptosis. Here, we present a GA-targeting probe (N-GA) to monitor cellular O2•- during ferroptosis. N-GA employed a triflate group and a tetradecanoic amide unit as the recognition site for O2•- and GA-targeting unit, respectively. After the response of N-GA to O2•-, the triflate unit of N-GA converted into hydroxyl group with strong electron-donating ability, generating bright green fluorescence under UV light. N-GA exhibited excellent sensitivity and selectivity towards O2•-. Fluorescence imaging results showed that N-GA could be applied as a GA-targeting probe to monitor cellular O2•-. The stimulation of cells with PMA and rotenone could result in the massive generation of endogenous O2•- in GA. Erastin-induced ferroptosis can markedly induce the increase of O2•- level in GA. Similar to Fer-1 and DFO, dihydrolipoic acid (DHLA) and rutin were demonstrated to inhibit the enormous production of O2•- in GA of the living cells during ferroptosis.

Exploration of Novel Meso-C═N-BODIPY-Based AIE Fluorescent Rotors with Large Stokes Shifts for Organelle-Viscosity Imaging

The research on fluorescent rotors for viscosity has attracted extensive interest to better comprehend the close relationships of microviscosity variations with related diseases. Although scientists have made great efforts, fluorescent probes for cellular viscosity with both aggregation-induced emissions (AIEs) and large Stokes shifts to improve sensing properties have rarely been reported. Herein, we first report four new meso-C═N-substituted BODIPY-based rotors with large Stokes shifts, investigate their viscosity/AIE characteristics, and perform cellular imaging of the viscosity in subcellular organelles. Interestingly, the meso-C═N-phenyl group-substituted probe 6 showed an obvious 594 nm fluorescence enhancement in glycerol and a moderate 650 nm red AIE emission in water. Further, on attaching CF3 to the phenyl group, a similar phenomenon was observed for 7 with red-shifted emissions, attributed to the introduction of a phenyl group, which plays a key role in the red AIE emissions and large Stokes shifts. Comparatively, for phenyl-group-free probes, both the meso-C═N-trifluoroethyl group and thiazole-substituted probes (8 and 9) exhibited good viscosity-responsive properties, while no AIE was observed due to the absence of phenyl groups. For cellular experiments, 6 and 9 showed good lysosomal and mitochondrial targeting properties, respectively, and were further successfully used for imaging viscosity through the preincubation of monensin and lipopolysaccharide (LPS), indicating that C═N polar groups potentially work as rotatable moieties and organelle-targeting groups, and the targeting difference might be ascribed to increased charges of thiazole. Therefore, in this study, we investigated the structural relationships of four meso-C═N BODIPY-based rotors with respect to their viscosity/AIE characteristics, subcellular-targeting ability, and cellular imaging for viscosity, potentially serving as AIE fluorescent probes with large Stokes shifts for subcellular viscosity imaging.

Microenvironment-differential Imaging of Demethylated Metabolites of Methionine for Identifying Ferroptosis Regional Preferences with Path-independent Equifinal Fluorescence Probes

We realized the microenvironment-differential Imaging of demethylated metabolites of methionine and the regional regulation of ferroptosis.

Reversible Dual Fluorescence-Lifetime Imaging of Mitochondrial GSH and Microviscosity: Real-Time Evaluation of Ferroptosis Status

Ferroptosis, as a new form of regulated cell death, is implicated in various physiological and pathological processes. Developing a single probe for an independent analysis of multiple analytes related to ferroptosis can provide more accurate information and simplify the detection procedures, but it faces great challenges. In this work, we develop a fluorescent probe for the simultaneous detection of GSH through ratiometric fluorescence response and microviscosity via a fluorescence lifetime model. Based on the reversible Michael addition reaction between GSH and unsaturated C═C bond, the probe responds reversibly to GSH with a ratiometric fluorescence variation and a fast response time (t1/2 = 4.7 s). At the same time, the probe is sensitive to environmental viscosity by changing its fluorescence lifetimes. The probe was applied to monitor the drug-induced ferroptosis process through both the classical Xc-/GSH/GPX4- and DHODH-mediated defense mechanisms. We hope that the probe will provide a useful molecular tool for the real-time live-cell imaging of GSH dynamics, which is benefit to unveiling related physiological and pathological processes.

Hydrogen peroxide fluorescent probe-monitored butyric acid inhibition of the ferroptosis process

Short-chain fatty acids, such as butyrate, play pivotal roles in various physiological processes within the human body. Recent advances in understanding cell death pathways, specifically ferroptosis, have unveiled unique opportunities for therapeutic development. Ferroptosis is linked to iron accumulation and oxidative stress, whereas butyrate has emerged as a cellular protector against oxidative stress, potentially inhibiting ferroptosis. Hydrogen peroxide (H2 O2 ) is a key player in oxidative stress, and its monitoring has gained significance in disease mechanisms. We present an innovative fluorescent probe, HOP, capable of dynamically tracking intracellular H2 O2 levels, enabling spatial and temporal visualization. The probe exhibits high accuracy (limit of detection = 0.14 μM) and sensitivity, paving the way for disease diagnosis and treatment innovations. Importantly, HOP displayed minimal toxicity, making it suitable for cellular applications. Cellular imaging experiments demonstrated its ability to penetrate cells and monitor intracellular H2 O2 levels accurately. The HOP probe confirmed H2 O2 as a critical marker in ferroptosis. Our innovative HOP provides a powerful tool for tracking intracellular H2 O2 levels and offers insights into the modulation of ferroptosis, potentially opening new avenues for disease research and therapeutic interventions.

Development of bishydrazide-based fluorescent probes for the imaging of cellular peroxynitrite (ONOO-) during ferroptosis

Peroxynitrite (ONOO-) is a critical ROS in living systems, and could induce lipid peroxidation which is the driver of ferroptotic cell death. Therefore, precise and rapid detection of cellular ONOO- is critical for the deep study of the biological functions of ONOO- during ferroptosis. Herein, we developed fluorescent probes (Rh-1, Rh-2 and Rh-3) for the rapid detection of intracellular ONOO- during ferroptosis. These probes used bishydrazide groups as the reactive sites for ONOO-. The response of these probes to ONOO- resulted in the production of the emissive xanthene fluorophore, providing a marked enhancement in the fluorescence intensity at 561 nm. The probe Rh-3 exhibited prominent selectivity and sensitivity towards ONOO-. Bioimaging experiments suggested that Rh-3 could be applied to image exogenous and endogenous ONOO- in living cells. By fluorescence imaging, it was demonstrated that erastin-induced ferroptosis caused increased levels of the endogenous ONOO-, and ferrostatin-1 (Fer-1) and vitamin E (VE) could markedly inhibit the excessive production of ONOO- during ferroptosis in living cells.

A COX2-targeting cancer-specific fluorescent probe for hydrogen sulfide detection in living cells, Caenorhabditis elegans, and zebrafish

A novel cyclooxygenase-2 (COX-2) targeted H2S-activated cancer-specific fluorescent probe, namely, COX2-H2S, was designed and synthesized, with naphthalimide as the fluorophore and indomethacin as the targeting group. This H2S-sensing probe was developed to differentiate tumor cells from normal cells and was tested in living cells, Caenorhabditis elegans (C. elegans), and zebrafish. The probe could successfully be used for imaging endogenous and exogenous H2S in living cells, demonstrating high sensitivity and specificity and strong anti-interference. COX2-H2S had the ability to not only discern cancer cells from normal cells but also specifically recognize 9L/lacZ cells from other glioblastoma cells (U87-MG and LN229). It could also be successfully applied for the fluorescent live imaging of H2S in both C. elegans and zebrafish.

Near-Infrared Fluorescence Probe for Indication of the Pathological Stages of Wound Healing Process and Its Clinical Application

Chronic wound healing is one of the most complicated biological processes in human life, which is also a serious challenge for human health. During the healing process, multiple biological pathways are activated, and various kinds of reactive oxygen species participate in this process. Hydrogen peroxide (H2O2) involves in chronic wounds and its concentration is fluctuated in different pathological stages during the wound healing process. Therefore, H2O2 may be recognized as a powerful biomarker to indicate the wound healing process. However, the pathological roles of H2O2 cannot be fully understood yet. Herein, we proposed a near-infrared fluorescent probe DCM-H2O2 for highly sensitive and rapid detection of H2O2 in living cells and scald and incision wound mice models. DCM-H2O2 exhibited a low detection limit and high specificity with low cytotoxicity for H2O2, which had great potential for its application in vivo. The probe was successfully utilized to monitor the fluctuation of endogenous H2O2 in the proliferation process of human immortalized epidermal (HACAT) cells, which confirmed that H2O2 participated in the cells' proliferation activity through a growth factor signaling pathway. In the scald and incision wound mice models, H2O2 concentration fluctuations at different pathological stages during the wound healing process could be obtained by in vivo fluorescence imaging. Finally, H2O2 concentrations in different stages of human diabetic foot tissues were also confirmed by the proposed probe. We expect that H2O2 could be a sensitive biomarker to indicate the wound healing process.

Ferroptosis-Based Therapeutic Strategies toward Precision Medicine for Cancer

Ferroptosis is a type of iron-dependent programmed cell death characterized by the dysregulation of iron metabolism and the accumulation of lipid peroxides. This nonapoptotic mode of cell death is implicated in various physiological and pathological processes. Recent findings have underscored its potential as an innovative strategy for cancer treatment, particularly against recalcitrant malignancies that are resistant to conventional therapies. This article focuses on ferroptosis-based therapeutic strategies for precision cancer treatment, covering the molecular mechanisms of ferroptosis, four major types of ferroptosis inducers and their inhibitory effects on diverse carcinomas, the detection of ferroptosis by fluorescent probes, and their implementation in image-guided therapy. These state-of-the-art tactics have manifested enhanced selectivity and efficacy against malignant carcinomas. Given that the administration of ferroptosis in cancer therapy is still at a burgeoning stage, some major challenges and future perspectives are discussed for the clinical translation of ferroptosis into precision cancer treatment.

Rational design of an iminocoumarin-based fluorescence probe for peroxynitrite with high signal-to-noise ratio

As a high reactive oxygen species (ROS) and a reactive nitrogen species (RNS), peroxynitrite anion (ONOO- ) is widely present in organisms and plays influential roles in physiological and pathological processes. It is of great significance to develop effective fluorescent probes for imaging peroxynitrite variation in living systems. Herein we present a novel fluorescent probe TQC0 for monitoring ONOO- based on the iminocoumarin platform, and this probe was synthesized by the knoevenagel condensation between a dihydropyridine-salicylaldehyde derivative and 2-benzothiazole-acetonitrile, and subsequently masked with the boronate moiety. The obtained probe TQC0 exhibited a high signal-to-noise ratio (206-fold) and a quick 'turn-on' response (about 10 min) with great selectivity and sensitivity. Furthermore, the probe TQC0 was successfully applied for imaging ONOO- in living cells with low cytotoxicity.

pH-Sensitive Glucose-Powered Nanomotors for Enhanced Intracellular Drug Delivery and Ferroptosis Efficiency

We propose a glucose-powered Janus nanomotor where two faces are functionalized with glucose oxidase (GOx) and polydopamine-Fe3+ chelates (PDF), respectively. In the glucose fuel solution, the GOx on the one side of these Janus nanomotors catalytically decomposes glucose fuels into gluconic acid and hydrogen peroxide (H2 O2 ) to drive them at a speed of 2.67 μm/s. The underlying propulsion mechanism is the glucose-based self-diffusiophoresis owing to the generated local glucose concentration gradient by the enzymatic reaction. Based on the enhanced diffusion motion, such nanomotors with catalytic activity increase the uptake towards cells and subsequently exhibit excellent capabilities for Fe3+ ions delivery and H2 O2 generation for enhancing ferroptosis efficiency for inducing cancer cell death. In particular, the Fe3+ ions are released from nanomotors in a slightly acidic environment, and subsequently generate toxic hydroxyl radicals via Fenton reactions, which accumulation reactive oxygen species (ROS) level (~300 %) and further lipid peroxidation (LPO) strengthened ferroptosis therapy for cancer treatment. The as-developed glucose-powered Janus nanomotor with efficient diffusion and Fe ions delivery capabilities show great promise as a potential in biomedical applications.

Ferroptosis resistance in cancer: recent advances and future perspectives

Ferroptosis is an iron-dependent, non-apoptotic form of regulated cell death and has been implicated in the occurrence and development of various diseases, including heart disease, nervous system diseases and cancer. Ferroptosis induction recently emerged as an attractive strategy for cancer therapy. Ferroptosis has become a potential target for intervention in these diseases or injuries in relevant preclinical models. This review summarizes recent progress on the mechanisms of ferroptosis resistance in cancer, highlights redox status and metabolism's role in it. Combination therapy for ferroptosis has great potential in cancer treatment, especially malignant tumors that are resistant to conventional therapies. This review will lead us to have a comprehensive understanding of the future exploration of ferroptosis and cancer therapy. A deeper understanding of the relationship between ferroptosis resistance and metabolism reprogramming may provide new strategies for tumor treatment and drug development based on ferroptosis.

Recent advances in melittin-based nanoparticles for antitumor treatment: from mechanisms to targeted delivery strategies

As a naturally occurring cytolytic peptide, melittin (MLT) not only exhibits a potent direct tumor cell-killing effect but also possesses various immunomodulatory functions. MLT shows minimal chances for developing resistance and has been recognized as a promising broad-spectrum antitumor drug because of this unique dual mechanism of action. However, MLT still displays obvious toxic side effects during treatment, such as nonspecific cytolytic activity, hemolytic toxicity, coagulation disorders, and allergic reactions, seriously hampering its broad clinical applications. With thorough research on antitumor mechanisms and the rapid development of nanotechnology, significant effort has been devoted to shielding against toxicity and achieving tumor-directed drug delivery to improve the therapeutic efficacy of MLT. Herein, we mainly summarize the potential antitumor mechanisms of MLT and recent progress in the targeted delivery strategies for tumor therapy, such as passive targeting, active targeting and stimulus-responsive targeting. Additionally, we also highlight the prospects and challenges of realizing the full potential of MLT in the field of tumor therapy. By exploring the antitumor molecular mechanisms and delivery strategies of MLT, this comprehensive review may inspire new ideas for tumor multimechanism synergistic therapy.

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.

A dual-responsive crimson fluorescent probe for real-time diagnosis of alcoholic acute liver injury

The polarity and viscosity of the microenvironment are associated with the control of the onset and progression of pathological diseases, including inflammation, immuno-suppression and cancer. If appropriate treatment is neglected, alcoholic acute liver injury (AALI), the initial sign of alcoholic liver diseases, may transform into hepatic lesions. Therefore, it's crucial to create a particular probe to detect AALI swiftly and track its progression. Herein a polarity and viscosity dual-responsive crimson fluorescent probe (PPBI) was designed and developed, which can target mitochondria and lipid droplets. PPBI possesses aggregation-induced emission properties, good photostability and strong anti-interference ability against pH, metal ions, anions and biomolecules. This probe can distinguish cancer cells from normal ones using changes of green and red fluorescence, as well as identify changes in the cellular microenvironment associated with inflammatory and ferroptosis processes. In addition, changes in polarity and viscosity can be amplified by in vivo imaging in a mouse model to monitor alcohol-induced acute liver injury and to effectively detect the course of pharmacological intervention therapy. All the results suggest that PPBI could be a promising real-time fluorescence imaging tool for diagnosis and treatment of acute alcoholic liver injury.