Design and Synthesis of a Mitochondrial-Targeted JNK Inhibitor and Its Protective Effect on Parkinson's Disease Phenotypes.

C-Jun N-terminal kinase (JNK) is a key mediator involved in a variety of physiological processes. JNK activation is regulated in a complex manner by upstream kinases and phosphatases, and plays an important role in physiological processes such as the immune response and neuronal function. Therefore, JNK has become a therapeutic target for neurodegenerative diseases, ankylosing spondylitis, psoriasis, arthritis and other diseases. Inhibition of JNK activation in mitochondria holds great potential for Parkinson's disease (PD) therapy. However, no specific mitochondrial-targeted JNK inhibitor has been reported. We have developed a mitochondrial-targeted JNK inhibitor, P2, by linking a mitochondrial-specific cell-penetrating peptide to SP600125 (SP), a commercialized specific inhibitor of JNK. We found that P2 specifically inhibited mitochondrial JNK phosphorylation instead of nuclear JNK signaling. Further studies showed that P2 effectively rescued PD phenotypes both in vitro and in vivo, thus indicating that it is a potential therapeutic for PD.

Rational Design of a Two-Photon Fluorogenic Probe for Visualizing Monoamine Oxidase†A Activity in Human Glioma Tissues.

Monoamine oxidases have two functionally distinct but structurally similar isoforms (MAO-A and MAO-B). The ability to differentiate them by using fluorescence detection/imaging technology is of significant biological relevance, but highly challenging with available chemical tools. Herein, we report the first MAO-A-specific two-photon fluorogenic probe (F1), capable of selective imaging of endogenous MAO-A enzymatic activities from a variety of biological samples, including MAO-A-expressing neuronal SY-SY5Y cells, the brain of tumor-bearing mice and human Glioma tissues by using two-photon fluorescence microscopy (TPFM) with minimal cytotoxicity.

Fast-Response Fluorogenic Probe for Visualizing Hypochlorite in Living Cells and in Zebrafish.

A fast-response fluorogenic probe-compound D1-for monitoring hypochlorite (ClO- ), based on specific ClO- cleavage of a C=N bond and producing results observable to the naked eye, has been developed. The response of the probe to ClO- increases linearly, and the fluorescence intensity was heightened by a factor of about 25. D1 responses to ClO- , with high selectivity and sensitivity, were observable by naked eye within 10 s. D1 can not only detect levels of hypochlorite in vitro, such as in urine, but is also capable of monitoring hypochlorite content under extremely cold conditions, as low as -78 °C. Meanwhile, its good biocompatibility permitted the use of D1 to detect intracellular ClO- by confocal microscopy. Moreover, D1 was successfully applied to monitor exogenous and endogenous ClO- in zebrafish through fluorescence imaging.

A paper-based chemiluminescence immunoassay device for rapid and high-throughput detection of allergen-specific IgE.

The fast and precise detection of potential allergen-specific immunoglobulin E (sIgE) is imperative for the diagnosis and appropriate treatment of allergic diseases. In this study, we have successfully fabricated a novel paper-based immunoassay device for the detection of sIgE in allergic diseases. We used Can f 1, one of the main dog allergens, as a model allergen to detect sIgE in human sera. To achieve excellent performance, the experimental parameters were optimized. Further, we extended this device for potential applications in the clinical diagnosis of allergic diseases: worthwhile clinical performance in the detection of allergens was achieved as compared to that achieved by commercial enzyme-linked immunosorbent assay (ELISA) kit. Therefore, it was proven that this strategy has the advantages of high-throughput, rapid, sensitive, and highly accurate detection of trace amounts of sIgEs. Furthermore, by simply changing the antigen and antibody, this device could be used for the high-throughput detection of other allergens, so as to achieve multiallergen detection and appropriate desensitization therapy, thereby making it promising in the determination of allergic diseases in clinics.

MSN-on-a-Chip: Cell-Based Screenings Made Possible on a Small-Molecule Microarray of Native Natural Products.

Standard small-molecule microarrays (SMMs) are not well-suited for cell-based screening assays. Of the few attempts made thus far to render SMMs cell-compatible, all encountered major limitations. Here we report the first mesoporous silica nanoparticle (MSN)-on-a-chip platform capable of allowing high-throughput cell-based screening to be conducted on SMMs. By making use of a glass surface on which hundreds of MSNs, each encapsulated with a different native natural product, were immobilized in spatially defined manner, followed by on-chip mammalian cell growth and on-demand compound release, high-content screening was successfully carried out with readily available phenotypic detection methods. By combining this new MSN-on-a-chip system with small interfering RNA technology for the first time, we discovered that (+)-usniacin possesses synergistic inhibitory properties similar to those of olaparib (an FDA-approved drug) in BRCA1-knockdown cancer cells.

Nanoquencher-Based Selective Imaging of Protein Glutathionylation in Live Mammalian Cells.

Changes in the cellular levels of glutathione (GSH) and protein S-glutathionylation (PSSG) are closely associated with a number of human diseases. Despite recent advances, few thiol-reactive, small-molecule GSH sensors could selectively detect GSH over other endogenous thiols, and none was capable of detecting PSSG in live mammalian cells. By using a dye-loaded mesoporous silica nanoquencher (qMSN) capped with anti-GSH antibody capable of highly selective binding toward GSH and glutathionylated proteins over other molecules, we have successfully developed a fluorescence GSH/PSSG nanosensor, which showed unprecedented selectivity toward PSSG even in the presence of GSH, had amplifiable and programmable fluorescence Turn-ON properties, and could be used to image endogenous PSSG in live mammalian cells under stimulated conditions for the first time.

Simultaneous Imaging of Endogenous Survivin mRNA and On-Demand Drug Release in Live Cells by Using a Mesoporous Silica Nanoquencher.

The design of multifunctional drug delivery systems capable of simultaneous target detection, imaging, and therapeutics in live mammalian cells is critical for biomedical research. In this study, by using mesoporous silica nanoparticles (MSNs) chemically modified with a small-molecule dark quencher, followed by sequential drug encapsulation, MSN capping with a dye-labeled antisense oligonucleotide, and bioorthogonal surface modification with cell-penetrating poly(disulfide)s, the authors have successfully developed the first mesoporous silica nanoquencher (qMSN), characterized by high drug-loading and endocytosis-independent cell uptake, which is able to quantitatively image endogenous survivin mRNA and release the loaded drug in a manner that depends on the survivin expression level in tumor cells. The authors further show that this novel drug delivery system may be used to minimize potential cytotoxicity encountered by many existing small-molecule drugs in cancer therapy.

Intracellular Delivery of Functional Native Antibodies under Hypoxic Conditions by Using a Biodegradable Silica Nanoquencher.

Antibodies are important biopharmaceuticals, but almost all existing antibody-based drugs are limited to targeting antigens located at the cell exterior because of the inability of antibodies to enter the cell interior. Available methods for intracellular delivery of antibodies have major shortcomings. Herein, we report an approach to encapsulate native antibodies in a biodegradable silica nanoquencher (BS-qNP), which could undergo efficient cellular uptake and intracellular degradation to release antibodies only under hypoxic conditions. By coating the surface of BS-qNP with cell-penetrating poly(disulfide)s (CPD), the delivered antibodies (or other proteins) avoided endolysosomal trapping. Doping of the silica coating with a fluorescent dye and a dark hole quencher further endowed BS-qNP with hypoxia-responsive fluorescence turn-on property. Our antibody delivery system thus provides the first platform capable of stable encapsulation, efficient uptake, on-demand antibody release, and imaging of release/cell state.

Cell-Penetrating Poly(disulfide) Assisted Intracellular Delivery of Mesoporous Silica Nanoparticles for Inhibition of miR-21 Function and Detection of Subsequent Therapeutic Effects.

The design of drug delivery systems capable of minimal endolysosomal trapping, controlled drug release, and real-time monitoring of drug effect is highly desirable for personalized medicine. Herein, by using mesoporous silica nanoparticles (MSNs) coated with cell-penetrating poly(disulfide)s and a fluorogenic apoptosis-detecting peptide (DEVD-AAN), we have developed a platform that could be uptaken rapidly by mammalian cells via endocytosis-independent pathways. Subsequent loading of these MSNs with small molecule inhibitors and antisense oligonucleotides resulted in intracellular release of these drugs, leading to combination inhibition of endogenous miR-21 activities which was immediately detectable by the MSN surface-coated peptide using two-photon fluorescence microscopy.

Intracellular Delivery of Functional Proteins and Native Drugs by Cell-Penetrating Poly(disulfide)s.

The efficient delivery of bioactive compounds into cells is a major challenge in drug discovery. We report herein the development of novel methods for intracellular delivery of functional proteins (including antibodies) and native small-molecule drugs by making use of cell-penetrating poly(disulfide)s (CPDs). CPDs were recently shown to be rapidly taken up by mammalian cells in endocytosis-independent pathways, but their applications for delivery of proteins and native small-molecule drugs have not been demonstrated. With our newly developed, CPD-assisted approaches, rapid and "bioorthogonal" loading of cargos was carried out with pre-synthesized CPDs, in two steps and in a matter of minutes under aqueous conditions. The resulting CPD-cargo conjugates were used immediately for subsequent cell delivery studies. With the versatility and flexibility of these methods, we further showed that they could be used for immediate delivery of a variety of functional cargos with minimum chemical and genetic manipulations. The minimal cell cytotoxicity of these CPDs and their cargo-loaded conjugates further highlights the unique advantage of this new cell-transduction method over other existing strategies and ensures that our entire delivery protocol is compatible with subsequent live-cell experiments and biological studies.

Single-Vehicular Delivery of Antagomir and Small Molecules to Inhibit miR-122 Function in Hepatocellular Carcinoma Cells by using "Smart" Mesoporous Silica Nanoparticles.

MicroRNAs (miRNAs) regulate a variety of biological processes. The liver-specific, highly abundant miR-122 is implicated in many human diseases including cancer. Its inhibition has been found to result in a dramatic loss in the ability of Hepatitis C virus (HCV) to infect host cells. Both antisense technology and small molecules have been used to independently inhibit endogenous miR-122 function, but not in combination. Intracellular stability, efficient delivery, hydrophobicity, and controlled release are some of the current challenges associated with these novel therapeutic methods. Reported herein is the first single-vehicular system, based on mesoporous silica nanoparticles (MSNs), for simultaneous cellular delivery of miR-122 antagomir and small molecule inhibitors. The controlled release of both types of inhibitors depends on the expression levels of endogenous miR-122, thus enabling these drug-loaded MSNs to achieve combination inhibition of its targeted mRNAs in Huh7 cells.

Preparation of a mitochondria-targeted and NO-releasing nanoplatform and its enhanced pro-apoptotic effect on cancer cells.

The therapeutic applications of exogenous nitric oxide are usually limited by its short half-life and its vulnerability to many biological substances, thus straightforward and precise spatiotemporal control of NO delivery may be critical to its therapeutic effects. Herein, the mitochondria-targeted and photoresponsive NO-releasing nanosystem is demonstrated as a new approach for cancer treatment. The nanosystem is fabricated by covalently incorporating a NO photo-donor and a mitochondria targeting ligand onto carbon-dots; accordingly, multi-functionalities (mitochondria-targeting, light-enhanced efficient NO-releasing, and cell imaging) are achieved. The in vitro NO release profiles for the nanosystem show that the duration of NO release from the present C-dot-based nanosystem containing immobilized SNO can be extended up to 8 hours or more. Upon cellular internalization, the nanosystem can target mitochondria and release NO. The action of the nanosystem on three cancer cell lines is evaluated; it is found that the targeted NO-releasing system can cause high cytotoxicity towards the cancer cells by specifically damaging their mitochondria. Additionally, light irradiation can amplify the cell apoptosis by enhancing NO release. These observations demonstrate that incorporating mitochondria-targeting ligand onto a NO-releasing system can enhance its pro-apoptosis action, thereby providing new insights for exploiting NO in cancer therapy.

Biodegradable Mesoporous Organosilica-Based Nanostabilizer Targeting Mast Cells for Long-Term Treatment of Allergic Diseases.

Allergic diseases are immune system dysfunctions mediated by mast cell (MC) activation stimulated by specific allergens. However, current small molecular MC stabilizers for allergic disease prevention often require multiple doses over a long period of time and are associated with serious side effects. Herein, we develop a diselenide-bridged mesoporous silica nanostabilizer, proving that it could specifically target sensitized MCs via the recognition of IgE aptamer and IgE. Meantime, the IgE aptamer can also mitigate allergic reactions by preventing re-exposure of allergens from the surface of sensitized MCs. Furthermore, the diselenide-bridged scaffold can be reduced by the intracellular excessive ROS, subsequently achieving redox homeostasis via ROS depletion. Finally, the precise release of small molecular MC stabilizers along with the biodegradation of nanocarrier can stabilize the membranes of MCs. In vivo assays in passive cutaneous anaphylactic (PCA) and allergic rhinitis (AR) mice indicated that our current strategy further endowed it with a high efficacy, long-term therapeutic time window, as well as negligible inflammatory side effects for allergic diseases, offering a promising therapeutic strategy for the clinical generalization of allergic diseases.

Stimuli-responsive biodegradable silica nanoparticles: From native structure designs to biological applications.

Due to their inherent advantages, silica nanoparticles (SiNPs) have greatly potential applications as bioactive materials in biosensors/biomedicine. However, the long-term and nonspecific accumulation in healthy tissues may give rise to toxicity, thereby impeding their widespread clinical application. Hence, it is imperative and noteworthy to develop biodegradable and clearable SiNPs for biomedical purposes. Recently, the design of multi-stimuli responsive SiNPs to improve degradation efficiency under specific pathological conditions has increased their clinical trial potential as theranostic nanoplatform. This review comprehensively summaries the rational design and recent progress of biodegradable SiNPs under various internal and external stimuli for rapid in vivo degradation and clearance. In addition, the factors that affect the biodegradation of SiNPs are also discussed. We believe that this systematic review will offer profound stimulus and timely guide for further research in the field of SiNP-based nanosensors/nanomedicine.

A near-infrared fluorescent probe with two-photon excitation for in situ imaging of NQO1 in human colorectum cancer tissue.

Colorectum cancer has become one of the most fatal cancer diseases, in which NAD(P)H: quinone oxidoreductase 1 (NQO1) plays a role in intracellular free radical reduction and detoxification and has been linked to colorectum cancer and chemotherapy resistance. Therefore, rational design of optical probe for NQO1 detection is urgent for the early diagnosis of colorectum cancer. Herein, we have developed a novel two-photon fluorescent probe, WHFD, which is capable of selectively detecting of intracellular NQO1 with two-photon (TP) absorption (800 nm) and near-infrared emission (620 nm). Combination with a substantial Stokes shift (175 nm) and biocompatibility, we have assessed its suitability for in vivo imaging of endogenous NQO1 activities from HepG2 tumor-bearing live animals with high tissue penetration up to 300 µm. Particularly, we for the first time used the probe to image NQO1 activities from human colorectum cancer samples by using TP microscopy, and proving our probe possesses reliable diagnostic performance to directly in situ imaging of cancer biomarker and can clearly distinguish the boundary between human colorectum cancer tissue and their surrounding normal tissue, which shows great potential for the intraoperative navigation.

A PEGylated fluorescent turn-on sensor for detecting fluoride ions in totally aqueous media and its imaging in live cells.

Owing to the considerable significance of fluoride anions for health and environmental issues, it is of great importance to develop methods that can rapidly, sensitively and selectively detect the fluoride anion in aqueous media and biological samples. Herein, we demonstrate a robust fluorescent turn-on sensor for detecting the fluoride ion in a totally aqueous solution. In this study, a biocompatible hydrophilic polymer poly(ethylene glycol) (PEG) is incorporated into the sensing system to ensure water solubility and to enhance biocompatibility. tert-Butyldiphenylsilyl (TBDPS) groups were then covalently introduced onto the fluorescein moiety, which effectively quenched the fluorescence of the sensor. Upon addition of fluoride ion, the selective fluoride-mediated cleavage of the Si-O bond leads to the recovery of the fluorescein moiety, resulting in a dramatic increase in fluorescence intensity under visible light excitation. The sensor is responsive and highly selective for the fluoride anion over other common anions; it also exhibits a very low detection limit of 19 ppb. In addition, this sensor is operative in some real samples such as running water, urine, and serum and can accurately detect fluoride ions in these samples. The cytotoxicity of the sensor was determined to be Grade I toxicity according to United States Pharmacopoeia and ISO 10993-5, suggesting the very low cytotoxicity of the sensor. Moreover, it was found that the senor could be readily internalized by both HeLa and L929 cells and the sensor could be utilized to track fluoride level changes inside the cells.

Hyperbranched polyester-based fluorescent probe for histone deacetylase via aggregation-induced emission.

Aberrant expression of histone deacetylases (HDACs) is related to various types of cancer and is associated with increased proliferation of tumor cells. Hence, the detection of HDAC activities is of great significance for medical sciences as well as biological diagnostics. Herein, we report a hyperbranched polyester-based one-step fluorescent assay for HDAC. This assay system consists of two water-soluble components: the hyperbranched polyester coupled with the acetylated lysine groups (H40-Lys(Ac)) and the negatively charged TPE derivative bearing two sulfonic acid groups (TPE-2SO3(-)). HDAC triggers the deacetylation of H40-Lys(Ac), thereby turning the electroneutral polymer into the positively charged one. Consequently, complexation occurs between the positively charged polymer and the negatively charged TPE-2SO3(-), thereby leading to the formation of nanoaggregates due to electrostatic interaction. Eventually, the fluorescence enhancement as a result of AIE effect is achieved. This assay system is operable in aqueous media with very low detection limit of 25 ng/mL. The system is capable of detecting HDAC in such biological fluid as serum, and this strategy may provide a new and effective approach for enzyme assay.

A low cytotoxic and ratiometric fluorescent nanosensor based on carbon-dots for intracellular pH sensing and mapping.

Intracellular pH plays a critical role in the function of cells, and its regulation is essential for most cellular processes. In this study, we demonstrate a fluorescence resonance energy transfer (FRET)-based ratiometric pH nanosensor with carbon-dot (CD) as the carrier. The sensor was prepared by covalently linking a pH-sensitive fluorescent dye (fluorescein isothiocyanate, FITC) onto carbon-dot. As the FRET donor, the carbon-dot exhibits bright fluorescence emission as well as λex-dependent photoluminescence emission, and a suitable excitation wavelength for the donor (CD) can be chosen to match the energy acceptor (fluorescein moiety). The fluorescein moieties on a CD undergo structural and spectral conversion as the pH changes, affording the nanoplatform a FRET-based pH sensor. The CD-based system exhibits a significant change in fluorescence intensity ratio between pH 4 and 8 with a pKa value of 5.69. It also displays excellent water dispersibility, good spectral reversibility, satisfactory cell permeability and low cytotoxicity. Following the living cell uptake, this nanoplatform with dual-chromatic emissions can facilitate real-time visualization of the pH evolution involved in the endocytic pathway of the nanosensor. This reversible and low cytotoxic fluorescent nanoplatform may be highly valuable in a variety of biological studies, such as endocytic trafficking, endosome/lysosome maturation, and pH regulation in subcellular organelles.

Current and Future of "Turn-On" Based Small-Molecule Copper Probes for Cuproptosis.

Increasing evidence shows that abnormal copper (Cu) metabolism is highly related to many diseases, such as Alzheimer's disease, Wilson's disease, hematological malignancies and Menkes disease. Very recently, cuproptosis, a Cu-dependent, programmed cell death was firstly described by Tsvetkov et al. in 2022. Their findings may provide a new perspective for the treatment of related diseases. However, the concrete mechanisms of these diseases, especially cuproptosis, remain completely unclear, the reason of which may be a lack of reliable tools to conduct highly selective, sensitive and high-resolution imaging of Cu in complex life systems. So far, numerous small-molecular fluorescent probes have been designed and utilized to explore the Cu signal pathway. Among them, fluorescence turn-on probes greatly enhance the resolution and accuracy of imaging and may be a promising tool for research of investigation into cuproptosis. This review summarizes the probes developed in the past decade which have the potential to study cuproptosis, focusing on the design strategies, luminescence mechanism and biological-imaging applications. Besides, we put forward some ideas concerning the design of next-generation probes for cuproptosis, aiming to tackle the main problems in this new field. Furthermore, the prospect of cuproptosis in the treatment of corresponding diseases is also highlighted.