Precipitated Fluorophore-Based Probe for Accurate Detection of Mitochondrial Analytes

A mitochondria-targeted fluorescent probe based on an anti-diffusion strategy for in situ imaging of fatty liver, inflammation and cancer

Abnormal mitochondrial viscosity is closely associated with a wide range of diseases and cellular dysfunction. It is crucial to develop fluorescent probes for precisely monitoring changes of mitochondrial viscosity in the detection and treatment of associated diseases. However, mitochondria-targeted fluorescent probes currently faced off-target problems because their high water-solubility could hinder the accurate detection of mitochondrial viscosity. Herein, a viscosity-sensitive fluorescent probe, HPQ-MV was designed and synthesized in this work. The indole cation and HPQ (2-(2'-hydroxyphenyl)-4(3H)-quinazolinone) moiety were introduced could make the probe HPQ-MV have excellent mitochondrial targeting properties and reduce the aqueous solubility of HPQ-MV made the probe less susceptible to diffusion, respectively. When the mitochondrial membrane potential was decreased, HPQ-MV could remain stable in the mitochondria and not cause false-negative signals. HPQ-MV had a signal-to-noise ratio of up to 2900-fold with respect to viscosity which was unaffected by pH and polarity. Additionally, HPQ-MV possessed a tissue permeability of up to 62.6 μM and had effectively facilitated in vivo imaging of fatty liver, inflammation, and in situ tumors.

Developing dual-responsive quinolinium prodrugs of 8-hydroxyquinoline by harnessing the dual chelating sites

The bidentate metal ion chelator 8-hydroxyquinoline (8-HQ) demonstrates significant potential in anticancer therapy but is hindered by adverse effects due to nonspecific chelation in normal tissues. The phenolic hydroxyl oxygen of 8-HQ has been extensively exploited to develop O-masked 8-HQ prodrugs aimed at achieving on-demand chelation. However, the equally crucial quinoline nitrogen for chelation remains underutilized. By alkylating the quinoline nitrogen of 8-HQ, we synthesized a series of N-masked quinolinium (QUM) prodrugs that release 8-HQ upon activation by various stimuli. Comprehensive in vitro and in vivo studies were conducted with QUM-1 and QUM-4, which are activated by H2O2 and β-glucosidase, respectively. Both QUM-1 and QUM-4 exhibit improved cancer cell selectivity compared to 8-HQ or the O-masked isomeric prodrug, attributed to unique properties such as enhanced mitochondrial targeting and increased glucose transporter-mediated cellular uptake. Additionally, by leveraging both chelating sites, we constructed dual-masked 8-HQ prodrugs that are activated non-sequentially by two stimuli to release 8-HQ. QUM-5 demonstrates anticancer activity upon activation by UV/H2O2 and shows improved safety in mice compared to 8-HQ. Our research presents novel applications for the construction of quaternary ammonium prodrugs utilizing aromatic tertiary amines and underscores the potential of dual-responsive prochelators for targeted cancer therapy.

Visualizing Hydrogen Peroxide Diffusion in Soils with Precipitation-Based Fluorescent Probe

Hydrogen peroxide (H2O2)-based advanced oxidation technology has emerged as a cost-effective and green solution for tackling soil pollution. Given the highly heterogeneous nature of soil, the effectiveness of H2O2 remediation is significantly influenced by its diffusion distance in soils. However, the dynamics of H2O2 diffusion and its effective range remain largely unexplored, primarily due to the lack of analytical methods for mapping H2O2 in soils. This study introduces a precipitation-based fluorescent probe (PFP) method for in situ, high-resolution (micrometer scale) mapping of H2O2 diffusion in soils. Using the PFP method, we visualized real-time H2O2 diffusion in various types of soils, revealing distinct diffusion patterns with rates ranging from 0.011 to >0.56 mm min-1. The observed differences in diffusion rates are associated with soil permeability. Additionally, soils exhibited a wide range of diffusion distances, from 0.22 to >11 mm in 20 min. Soil's reactivity for H2O2 decomposition, a previously overlooked factor, is critical in determining the diffusion distance of H2O2. We further demonstrate that the efficacy of H2O2 diffusion in soils is a pivotal factor in controlling pollutant degradation and soil remediation efficiency. These findings enhance our understanding of reagent diffusion processes in soil remediation, informing the optimization of more efficient soil remediation strategies.

General (hetero)polyaryl amine synthesis via multicomponent cycloaromatization of amines

(Hetero)polyaryl amines are extensively prevalent in pharmaceuticals, fine chemicals, and materials but the intricate and varied nature of their structures severely restricts their synthesis. Here, we present a selective multicomponent cycloaromatization of structurally and functionally diverse amine substrates for the general and modular synthesis of (hetero)polyaryl amines through copper(I)-catalysis. This strategy directly constructs a remarkable range of amino group-functionalized (hetero)polyaryl frameworks (194 examples), including naphthalene, binaphthalene, phenanthren, benzothiophene, dibenzothiophene, benzofuran, dibenzofuran, quinoline, isoquinoline, quinazoline, and others, which are challenging or impossible to obtain using alternative methods. Copper(III)-acetylide species are involved in driving the exclusive 7-endo-dig cyclization, suppressing many side-reactions that are susceptible to occur. Due to the easy introduction of various functional units into heteropolyarylamines, multiple functionalized fluorescent dyes can be arbitrarily synthesized, which can serve as effective fluorescent probes for monitoring the pathological processes (e.g. chemotherapy-induced cell apoptosis) and studying the related disease mechanisms.

Reactive oxygen species-mediated organic long-persistent luminophores light up biomedicine: from two-component separated nano-systems to integrated uni-luminophores

Organic luminophores have been widely utilized in cells and in vivo fluorescence imaging but face extreme challenges, including a low signal-to-noise ratio (SNR) and even false signals, due to non-negligible background signals derived from real-time excitation lasers. To overcome these challenges, in the last decade, functionalized organic long-persistent luminophores have gained much attention. Such luminophores could not only overcome the biological toxicity of inorganic long-persistent luminescent materials (metabolic toxicity and leakage risk of inorganic heavy metals), but also continue to emit long-persistent luminescence after removing the excitation source, thus effectively improving imaging quality. More importantly, organic long-persistent luminophores have good structure tailorability for the construction of activable probes, which is favorable for biosensing. Recently, the development of reactive oxygen species (ROS)-mediated long-persistent (ROSLP) luminophores (especially organic small-molecule ROSLP luminophores) is still in the rising stage. Notably, ROSLP luminophores for in vivo imaging have experienced from two-component separated nano-systems to integrated uni-luminophores, which obtained gradually better designability and biocompatibility. In this review, we summarize the progress and challenges of organic long-persistent luminophores, focusing on their development history, long-persistent luminescence working mechanisms, and biomedical applications. We hope that these insights will help scientists further develop functionalized organic long-persistent luminophores for the biomedical field.

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

Activatable organic probes for in situ imaging of biomolecules

Biomolecules are fundamental for various chemical and biological processes of living organisms. High-resolution in situ imaging of the dynamics and local distribution of biomolecules may facilitate better interpretation of diverse complex cell events in the biomedicine field. In different advanced imaging tools, fluorescence imaging-based activatable organic probes can be noninvasively and effortlessly internalized into cells and can be easily modified, which is essential for the in situ imaging of targets in living organisms. We here briefly summarize the existing general design strategies of activatable organic probes for retaining the fluorescence signal inside cells. We particularly describe the bioapplication of these probes for the in situ bioimaging. This review is expected to promote the development of new molecular tools for extending the application of these in situ imaging strategies to other biomolecules.

Recent Advances in Organic Molecular-to-Supramolecular Self-Assembled Room-Temperature Phosphorescent Materials for Biomedical Applications

This minireview focuses on recent advancements in organic molecular-to-supramolecular self-assembled room-temperature phosphorescent (RTP) materials and their prospective biomedical applications. RTP materials, having their unique capacity to emit long-lasting phosphorescence at ambient temperature, have piqued researchers' interest in various biological applications, including biosensing, bioimaging, drug delivery, and photodynamic therapy (PDT). These materials have several benefits, including high sensitivity, remarkable photostability, and low cytotoxicity. RTP materials' self-assembly into supramolecular structures improves their performance and broadens their uses. Researchers have built organic RTP systems with long-lasting phosphorescence by leveraging weak noncovalent interactions in aquatic conditions. These materials have demonstrated incredible promise as biosensors that enable sensitive analyte detection and as photosensitizers in PDT that target and sensitize specific cell types. The review also outlines future directions and challenges in developing and utilizing pure organic RTP materials for biological imaging purposes, providing valuable guidelines for their future design and application.

Chemical Probes for Profiling of MALT1 Protease Activity

The paracaspase MALT1 is a key regulator of the human immune response. It is implicated in a variety of human diseases. For example, deregulated protease activity drives the survival of malignant lymphomas and is involved in the pathophysiology of autoimmune/inflammatory diseases. Thus, MALT1 has attracted attention as promising drug target. Although many MALT1 inhibitors have been identified, molecular tools to study MALT1 activity, target engagement and inhibition in complex biological samples, such as living cells and patient material, are still scarce. Such tools are valuable to validate MALT1 as a drug target in vivo and to assess yet unknown biological roles of MALT1. In this review, we discuss the recent literature on the development and biological application of molecular tools to study MALT1 activity and inhibition.

Recent progress of self-immobilizing and self-precipitating molecular fluorescent probes for higher-spatial-resolution imaging

Flourished in the past two decades, fluorescent probe technology provides researchers with accurate and efficient tools for in situ imaging of biomarkers in living cells and tissues and may play a significant role in clinical diagnosis and treatment such as biomarker detection, fluorescence imaging-guided surgery, and photothermal/photodynamic therapy. In situ imaging of biomarkers depends on the spatial resolution of molecular probes. Nevertheless, the majority of currently available molecular fluorescent probes suffer from the drawback of diffusing from the target region. This leads to a rapid attenuation of the fluorescent signal over time and a reduction in spatial resolution. Consequently, the diffused fluorescent signal cannot accurately reflect the in situ information of the target. Self-immobilizing and self-precipitating molecular fluorescent probes can be used to overcome this problem. These probes ensure that the fluorescent signal remains at the location where the signal is generated for a long time. In this review, we introduce the development history of the two types of probes and classify them in detail according to different design strategies. In addition, we compare their advantages and disadvantages, summarize some representative studies conducted in recent years, and propose prospects for this field.

Orderly Self-Assembly of Organic Fluorophores for Sensing and Imaging

Fluorescence imaging utilizing traditional organic fluorophores is extensively applied in both cellular and in vivo studies. However, it faces significant obstacles, such as low signal-to-background ratio (SBR) and spurious positive/negative signals, primarily due to the facile diffusion of these fluorophores. To cope with this challenge, orderly self-assembled functionalized organic fluorophores have gained significant attention in the past decades. These fluorophores can create nanoaggregates via a well-ordered self-assembly process, thus prolonging their residency time within cells and in vivo settings. The development of self-assembled-based fluorophores is an emerging field, and as such, in this review, we present a summary of the progress and challenges of self-assembly fluorophores, focusing on their development history, self-assembly mechanisms, and biomedical applications. We hope that the insights provided herein will assist scientists in further developing functionalized organic fluorophores for in situ imaging, sensing, and therapy.

Functional Materials for Subcellular Targeting Strategies in Cancer Therapy: Progress and Prospects

Neoadjuvant and adjuvant therapies have made significant progress in cancer treatment. However, tumor adjuvant therapy still faces challenges due to the intrinsic heterogeneity of cancer, genomic instability, and the formation of an immunosuppressive tumor microenvironment. Functional materials possess unique biological properties such as long circulation times, tumor-specific targeting, and immunomodulation. The combination of functional materials with natural substances and nanotechnology has led to the development of smart biomaterials with multiple functions, high biocompatibilities, and negligible immunogenicities, which can be used for precise cancer treatment. Recently, subcellular structure-targeting functional materials have received particular attention in various biomedical applications including the diagnosis, sensing, and imaging of tumors and drug delivery. Subcellular organelle-targeting materials can precisely accumulate therapeutic agents in organelles, considerably reduce the threshold dosages of therapeutic agents, and minimize drug-related side effects. This review provides a systematic and comprehensive overview of the research progress in subcellular organelle-targeted cancer therapy based on functional nanomaterials. Moreover, it explains the challenges and prospects of subcellular organelle-targeting functional materials in precision oncology. The review will serve as an excellent cutting-edge guide for researchers in the field of subcellular organelle-targeted cancer therapy.

Fluorescence microscopic platforms imaging mitochondrial abnormalities in neurodegenerative diseases

Neurodegenerative diseases (NDs) are progressive disorders that cause the degeneration of neurons. Mitochondrial dysfunction is a common symptom in NDs and plays a crucial role in neuronal loss. Mitochondrial abnormalities can be observed in the early stages of NDs and evolve throughout disease progression. Visualizing mitochondrial abnormalities can help understand ND progression and develop new therapeutic strategies. Fluorescence microscopy is a powerful tool for dynamically imaging mitochondria due to its high sensitivity and spatiotemporal resolution. This review discusses the relationship between mitochondrial dysfunction and ND progression, potential biomarkers for imaging dysfunctional mitochondria, advances in fluorescence microscopy for detecting organelles, the performance of fluorescence probes in visualizing ND-associated mitochondria, and the challenges and opportunities for developing new generations of fluorescence imaging platforms for monitoring mitochondria in NDs.

In situ orderly self-assembly strategy affording NIR-II-J-aggregates for in vivo imaging and surgical navigation

J-aggregation, an effective strategy to extend wavelength, has been considered as a promising method for constructing NIR-II fluorophores. However, due to weak intermolecular interactions, conventional J-aggregates are easily decomposed into monomers in the biological environment. Although adding external carriers could help conventional J-aggregates stabilize, such methods still suffer from high-concentration dependence and are unsuitable for activatable probes design. Besides, these carriers-assisted nanoparticles are risky of disassembly in lipophilic environment. Herein, by fusing the precipitated dye (HPQ) which has orderly self-assembly structure, onto simple hemi-cyanine conjugated system, we construct a series of activatable, high-stability NIR-II-J-aggregates which overcome conventional J-aggregates carrier's dependence and could in situ self-assembly in vivo. Further, we employ the NIR-II-J-aggregates probe HPQ-Zzh-B to achieve the long-term in situ imaging of tumor and precise tumor resection by NIR-II imaging navigation for reducing lung metastasis. We believe this strategy will advance the development of controllable NIR-II-J-aggregates and precise bioimaging in vivo.

Recent Development of Advanced Fluorescent Molecular Probes for Organelle-Targeted Cell Imaging

Fluorescent molecular probes are very powerful tools that have been generally applied in cell imaging in the research fields of biology, pathology, pharmacology, biochemistry, and medical science. In the last couple of decades, numerous molecular probes endowed with high specificity to particular organelles have been designed to illustrate intracellular images in more detail at the subcellular level. Nowadays, the development of cell biology has enabled the investigation process to go deeply into cells, even at the molecular level. Therefore, probes that can sketch a particular organelle's location while responding to certain parameters to evaluate intracellular bioprocesses are under urgent demand. It is significant to understand the basic ideas of organelle properties, as well as the vital substances related to each unique organelle, for the design of probes with high specificity and efficiency. In this review, we summarize representative multifunctional fluorescent molecular probes developed in the last decade. We focus on probes that can specially target nuclei, mitochondria, endoplasmic reticulums, and lysosomes. In each section, we first briefly introduce the significance and properties of different organelles. We then discuss how probes are designed to make them highly organelle-specific. Finally, we also consider how probes are constructed to endow them with additional functions to recognize particular physical/chemical signals of targeted organelles. Moreover, a perspective on the challenges in future applications of highly specific molecular probes in cell imaging is also proposed. We hope that this review can provide researchers with additional conceptual information about developing probes for cell imaging, assisting scientists interested in molecular biology, cell biology, and biochemistry to accelerate their scientific studies.

A Precipitation-Enhanced Emission (PEE) Strategy for Increasing the Brightness and Reducing the Liver Retention of NIR-II Fluorophores

The lack of organic fluorophores with high quantum yields (QYs) and low liver retention in the second near-infrared (NIR-II) window has become a bottleneck in the bioimaging field. An approach to address these problems is proposed by encapsulating phosphorylated fluorescent dyes into biodegradable calcium phosphate nanoparticles. First, an NIR-II molecule, LJ-2P, is designed with increased water solubility by introducing two phosphate groups. Meanwhile, LJ-2P co-precipitates with calcium ions to form LJ-2P nanoparticles (NPs). The QYs of LJ-2P NPs in aqueous solution is increased by 36.57-fold to 5.12% compared with that of LJ-2P. This unique phenomenon is named as precipitation-enhanced emission (PEE), whose detailed mechanism is explored by femtosecond transient absorption. It is demonstrated that co-precipitation of LJ-2P with calcium ions changes the micro-environment, which restricts the molecular rotation and reduces the interaction of water molecules, especially the excited-state proton transfer. In addition, due to the pH-sensitive nature, more than 80% of the LJ-2P NPs are metabolized in the liver within 24 h. Based on the excellent optical properties and good biocompatibility, high-contrast vascular visualization and breast tumor detecting are achieved. This strategy can apply to other NIR-II fluorophores to achieve high QYs and low liver retention.

Rational Design of Novel Lipophilic Aggregation-Induced Emission Probes for Revealing the Dynamics of Lipid Droplets during Lipophagy and Ferroptosis

Lipid droplets (LDs), as crucial organelles, play a significant role in some physiological processes. Monitoring the concentration of LDs and dynamic behaviors between LDs and other organelles during some physiological processes is important for studying their biological function and medical diagnosis. Herein, we report a series of aggregation-induced emission (AIE) probes AIE-Cbz-LD-C_n (n = 1, 3, 5, 7, OMe) based on the conjugation of quinoline-malononitrile (QM) and carbazole for tracking the dynamic changes of LDs and studying the association between LDs and lysosome/endoplasmic reticulum (ER). To our great delight, AIE-Cbz-LD-C₃, AIE-Cbz-LD-C₅, and AIE-Cbz-LD-C₇ could aggregate in LDs accurately and light up the LDs with good photostability. Among them, AIE-Cbz-LD-C₇ was used to visualize the interplay between LDs and lysosomes during lipophagy due to the excellent LD-specificity. We also succeeded in tracking the number of newborn LDs generated near the endoplasmic reticulum regions revealing that the number increased considerably during ferroptosis by using AIE-Cbz-LD-C₇, which supplies useful evidence for the hypothesis that LDs generate from the ER. We expect the probe AIE-Cbz-LD-C₇ would be a practical tool for tracking the physiological and pathological processes contacted with LDs.

Chemical Probes and Activity-Based Protein Profiling for Cancer Research

Chemical probes can be used to understand the complex biological nature of diseases. Due to the diversity of cancer types and dynamic regulatory pathways involved in the disease, there is a need to identify signaling pathways and associated proteins or enzymes that are traceable or detectable in tests for cancer diagnosis and treatment. Currently, fluorogenic chemical probes are widely used to detect cancer-associated proteins and their binding partners. These probes are also applicable in photodynamic therapy to determine drug efficacy and monitor regulating factors. In this review, we discuss the synthesis of chemical probes for different cancer types from 2016 to the present time and their application in monitoring the activity of transferases, hydrolases, deacetylases, oxidoreductases, and immune cells. Moreover, we elaborate on their potential roles in photodynamic therapy.

Concise Biothiol-Activatable HPQ-NBD Conjugate as a Targeted Theranostic Probe for Tumor Cells

Cancer, as a malignant tumor, seriously endangers human health. The study of cancer diagnosis and therapy has great practical significance. The development of theranostic agents has become a very important research topic. Nevertheless, some existing agents still have imperfections, such as complex structures and difficult syntheses. Therefore, it is urgent for researchers to develop simple novel theranostic agents. In this study, the precipitated fluorophore HAPQ was used as a simple drug molecule for the first time and combined with NBD-Cl to construct a simple and efficient theranostic probe (HAPQ-NBD). The theranostic probe can distinguish between tumor cells and normal cells based on the higher levels of biothiol in tumor cells. In addition, the probe can use biothiol as a control switch to release higher levels of precipitated fluorophore HAPQ in tumor cells, leading to selective high toxicity to tumor cells, thus achieving the goal of selectively killing tumor cells. The construction of probe HAPQ-NBD provides a practical tool for the diagnosis and therapy of cancer. It is expected that the development and utilization of precipitated fluorophore will provide a new method and strategy for cancer diagnosis and therapy.

Unique assemble of carbonylpyridinium and chromene reveal mitochondrial thiol starvation under ferroptosis and novel ferroptosis inducer

To reveal the delicate function of mitochondrial, precise detection tools in spatiotemporal manner remains highly desirable. However, current probes with positive charge warheads for targeting mitochondria diffuse out of the...

Progress and Perspective of Solid-State Organic Fluorophores for Biomedical Applications

Fluorescent organic dyes have been extensively used as raw materials for the development of versatile imaging tools in the field of biomedicine. Particularly, the development of solid-state organic fluorophores (SSOFs) in the past 20 years has exhibited an upward trend. In recent years, studies on SSOFs have focused on the development of advanced tools, such as optical contrast agents and phototherapy agents, for biomedical applications. However, the practical application of these tools has been hindered owing to several limitations. Thus, in this Perspective, we have provided insights that could aid researchers to further develop these tools and overcome the limitations such as limited aqueous dispersibility, low biocompatibility, and uncontrolled emission. First, we described the inherent photophysical properties and fluorescence mechanisms of conventional, aggregation-induced emissive, and precipitating SSOFs with respect to their biomedical applications. Subsequently, we highlighted the recent development of functionalized SSOFs for bioimaging, biosensing, and theranostics. Finally, we elucidated the potential prospects and limitations of current SSOF-based tools associated with biomedical applications.

Molecular engineering of organic-based agents for in situ bioimaging and phototherapeutics

In situ monitoring of the location and transportation of bioactive molecules is essential for deciphering diverse biological events in the field of biomedicine. In addition, obtaining the in situ information of lesions will provide a clear perspective for surgeons to perform precise resection in clinical surgery. Notably, delivering drugs or operating photodynamic therapy/photothermal therapy in situ by labeling the lesion regions of interest can improve treatment and reduce side effects in vivo. In various advanced imaging and therapy modalities, optical theranostic agents based on organic small molecules can be conveniently modified as needed and can be easily internalized into cells/lesions in a non-invasive manner, which are prerequisites for in situ bioimaging and precision treatment. In this tutorial review, we first summarize the in situ molecular immobilization strategies to retain small-molecule agents inside cells/lesions to prevent their diffusion in living organisms. Emphasis will be focused on introducing the application of these strategies for in situ imaging of biomolecules and precision treatment, particularly pertaining to why targeting therapy in situ is required.

Novel Mitochondria-Targeting and Naphthalimide-based Fluorescent Probe for Detecting HClO in Living Cells

As a key reactive oxygen species (ROS), hypochlorous acid (HClO) plays an important role in many physiological and pathological processes. The mitochondria-targeting probes for the highly sensitive detection of HClO are desirable. In present work, we designed and synthesized an original mitochondria-localizing and turn-on fluorescent probe for detecting HClO. 4-Aminonaphthalimide was employed as the fluorescent section, the (2-aminoethyl)-thiourea unit was utilized as a typical sensing unit, and the quaternized pyridinium moiety was used as a mitochondria-targeted localization group. When HClO was absent, the probe showed weak fluorescence. In the existence of HClO, the probe revealed a blue fluorescence. Moreover, the turn-on fluorescent probe was able to function in a broad pH scope. There was an excellent linearity between the fluorescence emission intensity at 488 nm and the concentrations of HClO in the range of 5.0 × 10^-7 to 2.5 × 10^-6 mol·L^-1. Additionally, the probe had almost no cell toxicity and possessed an excellent mitochondria-localizing capability. Furthermore, the probe was able to image HClO in mitochondria of living PC-12 cells. The above remarkable properties illustrated that the probe was able to determine HClO in mitochondria of living cells.