Hypochlorous acid: a natural adjuvant that facilitates antigen processing, cross-priming, and the induction of adaptive immunity

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.

Microglial suppression by myeloperoxidase inhibitor does not delay neurodegeneration in a mouse model of progressive multiple sclerosis

Drugs able to efficiently counteract the progression of multiple sclerosis (MS) are still an unmet need. Numerous preclinical evidence indicates that reactive oxygen-generating enzyme myeloperoxidase (MPO), expressed by neutrophils and microglia, might play a key role in neurodegenerative disorders. Then, the MPO inhibition has been evaluated in clinical trials in Parkinson's and multiple system atrophy patients, and a clinical trial for the treatment of amyotrophic lateral sclerosis is underway. The effects of MPO inhibition on MS patients have not yet been explored. In the present study, by adopting the NOD mouse model of progressive MS (PMS), we evaluated the pharmacological effects of the MPO inhibitor verdiperstat (also known as AZD3241) on functional, immune, and mitochondrial parameters during disease evolution. We found that daily treatment with verdiperstat did not affect the pattern of progression as well as survival, despite its ability to reduce mitochondrial reactive oxygen species and microglia activation in the spinal cord of immunized mice. Remarkably, verdiperstat did not affect adaptive immunity, neutrophils invasion as well as mitochondrial derangement in the spinal cords of immunized mice. Data suggest that microglia suppression is not sufficient to prevent disease evolution, corroborating the hypothesis that immune-independent components drive neurodegeneration in progressive MS.

Luminescent Lanthanides in Biorelated Applications: From Molecules to Nanoparticles and Diagnostic Probes to Therapeutics

Lanthanides are particularly effective in their clinical applications in magnetic resonance imaging and diagnostic assays. They have open-shell 4f electrons that give rise to characteristic narrow, line-like emission which is unique from other fluorescent probes in biological systems. Lanthanide luminescence signal offers selection of detection pathways based on the choice of the ion from the visible to the near-infrared with long luminescence lifetimes that lend themselves to time-resolved measurements for optical multiplexing detection schemes and novel bioimaging applications. The delivery of lanthanide agents in cells allows localized bioresponsive activity for novel therapies. Detection in the near-infrared region of the spectrum coupled with technological advances in microscopies opens new avenues for deep-tissue imaging and surgical interventions. This review focuses on the different ways in which lanthanide luminescence can be exploited in nucleic acid and enzyme detection, anion recognition, cellular imaging, tissue imaging, and photoinduced therapeutic applications. We have focused on the hierarchy of designs that include luminescent lanthanides as probes in biology considering coordination complexes, multimetallic lanthanide systems to metal-organic frameworks and nanoparticles highlighting the different strategies in downshifting, and upconversion revealing some of the opportunities and challenges that offer potential for further development in the field.

Red Emission Carbon Nanoparticles Which Can Simultaneously Responding to Hypochlorite and pH

Multi-targets detection has obtained much attention because this sensing mode can realize the detection of multi-targets simultaneously, which is helpful for biomedical analysis. Carbon nanoparticles have attracted extensive attention due to their superior optical and chemical properties, but there are few reports about red emission carbon nanoparticles for simultaneous detection of multi-targets. In this paper, a red emission fluorescent carbon nanoparticles were prepared by 1, 2, 4-triaminobenzene dihydrochloride at room temperature. The as-prepared red emission fluorescent carbon nanoparticles exhibited strong emission peak located at 635 nm with an absolute quantum yield up to 24%. They showed excellent solubility, high photostability and good biocompatibility. Furthermore, it could sensitively and selectively response to hypochlorite and pH, thus simultaneous detection of hypochlorite and pH was achieved by combining the red emission fluorescent carbon nanoparticles with computational chemistry. The formation mechanisms of red emission fluorescent carbon nanoparticles and their response to hypochlorite and pH were investigated, respectively.

Sensing mechanism of the benzo-bodipy based fluorescent probe for Hypochlorous acid detection: Invalidity of photoinduced electron transfer

In vivo real-time detection of hypochlorous acid (HClO) in biological systems plays a crucial role in diagnosing immune-related diseases. Experimentally, a benzo-bodipy probe based on the photo-induced electron transfer (PeT) sensing mechanism has been developed for live fluorescence imaging. However, there have been no theoretical studies conducted to substantiate the precision of the sensing mechanism. This paper employs density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods to investigate the fluorescence detection mechanism of benzo-bodipy derivatives (BBy-T and BBy-TO), proposing a detection approach based on dark nπ* state quenching. The study reveals that the fluorescence quenching mechanism of BBy-T is primarily regulated by a thiomorpholine moiety, involving a dark nπ* state transition non-radiatively. Furthermore, this paper explains the fluorescence enhancement observed in BBy-TO. Theoretical investigations demonstrate, based on frontier molecular orbitals (FMOs) and hole-electron analysis, that the fluorescence enhancement for BBy-TO is not governed by the previously proposed intramolecular charge transfer (ICT) mechanism in experiments but rather follows a locally excited (LE) ππ* pattern. This work offers new insights for the design of novel fluorescence probes based on bodipy and benzo derivatives, expanding the understanding of their fluorescence properties.

Anti-Tumor Immunity to Patient-Derived Breast Cancer Cells by Vaccination with Interferon-Alpha-Conditioned Dendritic Cells (IFN-DC)

BACKGROUND

Breast cancer represents one of the leading causes of death among women. Surgery can be effective, but once breast cancer has metastasized, it becomes extremely difficult to treat. Conventional therapies are associated with substantial toxicity and poor efficacy due to tumor heterogeneity, treatment resistance and disease relapse. Moreover, immune checkpoint blockade appears to offer limited benefit in breast cancer. The poor tumor immunogenicity and the immunosuppressive tumor microenvironment result in scarce T-cell infiltration, leading to a low response rate. Thus, there is considerable interest in the development of improved active immunotherapies capable of sensitizing a patient's immune system against tumor cells.

METHODS

We evaluated the in vitro anti-tumor activity of a personalized vaccine based on dendritic cells generated in the presence of interferon (IFN)-α and granulocyte-macrophage colony-stimulating factor (IFN-DC) and loaded with an oxidized lysate from autologous tumor cells expanded as 3D organoid culture maintaining faithful tumor antigenic profiles.

RESULTS

Our findings demonstrate that stimulation of breast cancer patients' lymphocytes with autologous IFN-DC led to efficient Th1-biased response and the generation in vitro of potent cytotoxic activity toward the patients' own tumor cells.

CONCLUSIONS

This approach can be potentially applied in association with checkpoint blockade and chemotherapy in the design of new combinatorial therapies for breast cancer.

Oxidized Melanoma Antigens Promote Activation and Proliferation of Cytotoxic T-Cell Subpopulations

Increasing evidence suggests the role of reactive oxygen and nitrogen species (RONS) in regulating antitumor immune effects and immunosuppression. RONS modify biomolecules and induce oxidative post-translational modifications (oxPTM) on proteins that can alarm phagocytes. However, it is unclear if and how protein oxidation by technical means could be a strategy to foster antitumor immunity and therapy. To this end, cold gas plasma technology producing various RONS simultaneously to oxidize the two melanoma-associated antigens MART and PMEL is utilized. Cold plasma-oxidized MART (oxMART) and PMEL (oxPMEL) are heavily decorated with oxPTMs as determined by mass spectrometry. Immunization with oxidized MART or PMEL vaccines prior to challenge with viable melanoma cells correlated with significant changes in cytokine secretion and altered T-cell differentiation of tumor-infiltrated leukocytes (TILs). oxMART promoted the activity of cytotoxic central memory T-cells, while oxPMEL led to increased proliferation of cytotoxic effector T-cells. Similar T-cell results are observed after incubating splenocytes of tumor-bearing mice with B16F10 melanoma cells. This study, for the first time, provides evidence of the importance of oxidative modifications of two melanoma-associated antigens in eliciting anticancer immunity.

In-situ evaluation the fluctuation of hypochlorous acid in acute liver injury mice models with a mitochondria-targeted NIR ratiometric fluorescent probe

Acute liver injury (ALI) is a frequent and devastating liver disease that has been made more prevalent by the excessive use of chemicals, drugs, and alcohol in modern life. Hypochlorous acid (HClO), an important biomarker of oxidative stress originating mainly from the mitochondria, has been shown to be intimately connected to the development and course of ALI. Herein, a novel BODIPY-based NIR ratiometric fluorescent probe Mito-BS was constructed for the specific recognition of mitochondrial HClO. The probe Mito-BS can rapidly respond to HClO within 20 s with a ratiometric fluorescence response (from 680 nm to 645 nm), 24-fold fluorescence intensity ratio enhancement (I645/I680), a wide pH adaptation range (5-9) and the low detection limit (31 nM). The probe Mito-BS has been effectively applied to visualize endogenous and exogenous HClO fluctuations in living zebrafish and cells based on its low cytotoxicity and prominent mitochondria-targeting ability. Furthermore, the fluorescent probe Mito-BS makes it possible to achieve the non-invasive in-situ diagnosis of ALI through in mice, and provides a feasible strategy for early diagnosis and drug therapy of ALI and its complications.

The effect of hypochlorous acid inhalation on the activity of antioxidant system enzymes in rats of different ages

Hypochlorous acid HOCl is an effective disinfectant with a broad spectrum and high rate of microbicidal action. Its use for air treatment can be an effective tool for the prevention and therapy of infectious diseases. In this work, the in vivo study was conducted on 110 Wistar Han rats (12 and 72 weeks old) on the effect of a single inhalation of air containing gaseous HOCl on the activity of antioxidant system enzymes. For this, a special installation was designed to uniformly maintain the concentration of HOCl in the air and regulate it over a wide range. Inhalation exposure was carried out for 4 h at total chlorine concentrations in the air of approximately 2.0 mg/m3 and 5.0 mg/m3, after which the animals were observed for 14 days. The effect of inhalation on the antioxidant system activity varied significantly in animals of different ages. Catalase activity in young rats increased approximately 2-fold on days 1-2 after inhalation, regardless of the HOCl concentration, while in old animals a sharp dose-dependent decrease was initially observed. The glutathione peroxidase activity in animals of both ages increased upon inhalation of air with 5.0 mg/m3 HOCl, and in old animals this was more pronounced; when the HOCl concentration decreased to 2.0 mg/m3, this indicator increased slightly in old rats and remained virtually unchanged in young ones. The glutathione reductase activity when exposed to 2.0 mg/m3 HOCl did not change for both age groups, and with increasing HOCl concentration it increased by 1.5-2.0 times in all animals.

Development of a turn-on fluorescent probe for the imaging of intracellular hypochlorous acid (HClO) during ferroptosis

Ferroptosis is a burgeoning iron-dependent cell death form, and has close relation with hypochlorous acid (HClO). Exploring the fluctuation of the HClO level in living cells during ferroptosis could contribute to the profound study of the biological functions of HClO during ferroptosis. Here, we present a turn-on probe (RH-C) for the imaging of intracellular HClO during ferroptosis. The probe RH-C utilized the N,N-dimethylthiocarbamate group as a selective recognition site for HClO, and displayed desirable sensitivity and selectivity to HClO. The probe RH-C could detect the exogenous and endogenous HClO in living cells. Furthermore, RH-C was competent in monitoring the changes of endogenous HClO level during the process of ferroptosis. Biological imaging results suggested that erastin-induced ferroptosis can result in the excessive production of the endogenous HClO, and ferrostatin-1 (Fer-1) and vitamin E (VE) could block the massive accumulation of HClO in living cells.

Fe-doped carbon dots: a novel fluorescent nanoprobe for cellular hypochlorous acid imaging

Real-time monitoring of hypochlorous acid (HClO) in biological systems is of great significance for exploring and regulating its pathological functions because abnormal production of HClO is closely related with many diseases, such as atherosclerosis, rheumatoid arthritis, and cancer. Herein, we developed a reliable fluorescent Fe-doped carbon dots (Fe-CDs) for the sensitive and selective detection of biological HClO using ferrocenecarboxylic acid and m-phenylenediamine as precursors through a one-step solvothermal procedure. The Fe-CDs exhibited excellent a wide HClO detection range from 20 nmol/L to 1000 nmol/L with corresponding limits of detection at 7.8 nmol/L. The sensing mechanism is based on the chemical oxidation of the hydroxyl groups on the surface of Fe-CDs by HClO. In addition, Fe-CDs also displayed high photoluminescence yield, excitation-independence emission, as well as good biocompatibility, enabling the successful imaging of endogenous and exogenous HClO in HeLa cells. These results revealed that Fe-CDs holds great promise as a robust fluorescent probe for investigating HClO-mediated biological events.

A ratiometric fluorescent probe for rapid and specific detection of hypochlorite

Hypochlorite (ClO- ), as a kind of essential reactive oxygen species, plays a crucial role in vitro and in vivo. Here, a ratiometric fluorescent probe (TPAM) was designed and constructed for sensing ClO- based on substituted triphenylamine and malononitrile, which exhibited obvious colour transfer from orange to colourless under daylight accompanied by noticeable fluorescence change from red to green in response to ClO- . TPAM could effectively monitor ClO- with the merits of fast response, excellent selectivity, high sensitivity and a low detection limit of 0.1014 μM. 1 H NMR, mass spectra and theoretical calculations proved that ClO- caused the oxidation of the carbon-carbon double bond in TPAM, resulting in compound 1 and marked changes in colour and fluorescence. In addition, TPAM was utilized for imaging ClO- in living cells successfully with good photostability and biocompatibility.

Bioimaging of a chromenoquinoline-based ratiometric fluorescent probe for detecting ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023;303:123256. [PMID: 37579661 DOI: 10.1016/j.saa.2023.123256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Hypochlorous acid (HClO) is a reactive oxygen species and a relatively strong antibacterial substance in the immune defense system. The normal concentration of HClO in the human body is approximately 200 μM, and its high concentration can cause tissue damage and some diseases. Herein, a chromenoquinoline-based ratiometric fluorescent probe was developed to detect and quantify HClO. The developed Probe 1 exhibited the advantages of large Stokes shift (137 nm), high synthetic yield (84.7 %), simple synthesis method, short response time (<4 min), low detection limit (5.1 nM), and low toxicity. The probe was successfully validated in live cells and zebrafish.

A turn-on fluorescence strategy for hypochlorous acid detection based on DNAzyme-assisted cyclic signal amplification

Hypochlorous acid (HClO) is a crucial active oxygen component and one of the innate immunity's barrier substances in the body. Abnormal fluctuations in HClO concentration can lead to increased oxidative stress, cellular dysfunction, and the onset of various diseases. Thus, developing convenient, affordable, efficient, and sensitive methods to monitor HClO concentration in healthcare and pathophysiology research is highly significant. In this study, we developed a novel fluorescence strategy for HClO detection based on nucleic acid oxidative cleavage and Pb2+-dependent DNAzyme. By introducing a phosphorothioate site in the hairpin-structured nucleic acid sequence, the nucleic acid probe specifically recognized HClO and underwent oxidative cleavage. Upon cleavage, the enzyme strand is liberated, forming DNAzyme. This DNAzyme then cleaves the substrate strand, liberating the initially quenched fluorescent dyes and generating a turn-on fluorescent signal. The enzyme strand produced by the oxidative cleavage of HClO can be repeatedly utilized, thus realizing the cyclic signal amplification to reduce background noise. We verified the detection mechanism of this strategy through stepwise fluorescence spectroscopy analysis and electrophoresis. Under optimal experimental conditions, the method achieved a detection limit of 5.38 nM and a linear range of 1 nM-800 nM. This method demonstrated exceptional performance in actual biological sample testing and presented an exciting opportunity for expanded utilization in clinical diagnosis and medical research.

Pan msr gene deleted strain of Salmonella Typhimurium suffers oxidative stress, depicts macromolecular damage and attenuated virulence

Salmonella encounters but survives host inflammatory response. To defend host-generated oxidants, Salmonella encodes primary antioxidants and protein repair enzymes. Methionine (Met) residues are highly prone to oxidation and convert into methionine sulfoxide (Met-SO) which compromises protein functions and subsequently cellular survival. However, by reducing Met-SO to Met, methionine sulfoxide reductases (Msrs) enhance cellular survival under stress conditions. Salmonella encodes five Msrs which are specific for particular Met-SO (free/protein bound), and 'R'/'S' types. Earlier studies assessed the effect of deletions of one or two msrs on the stress physiology of S. Typhimurium. We generated a pan msr gene deletion (Δ5msr) strain in S. Typhimurium. The Δ5msr mutant strain shows an initial lag in in vitro growth. However, the Δ5msr mutant strain depicts very high sensitivity (p < 0.0001) to hypochlorous acid (HOCl), chloramine T (ChT) and superoxide-generating oxidant paraquat. Further, the Δ5msr mutant strain shows high levels of malondialdehyde (MDA), protein carbonyls, and protein aggregation. On the other side, the Δ5msr mutant strain exhibits lower levels of free amines. Further, the Δ5msr mutant strain is highly susceptible to neutrophils and shows defective fitness in the spleen and liver of mice. The results of the current study suggest that the deletions of all msrs render S. Typhimurium highly prone to oxidative stress and attenuate its virulence.

Assessing Early Atherosclerosis by Detecting and Imaging of Hypochlorous Acid and Phosphorylation Using Fluorescence Nanoprobe

The assessment of early atherosclerosis (AS) is of great significance for the early diagnosis and mechanism research. Herein, a novel nanoprobe PCN@FL is developed to realize the simultaneous detection and imaging of phosphorylation and hypochlorous acid (HClO). The selective recognition of HClO is achieved through the specific interaction between DMTC and HClO, while the levels of phosphorylation are detected via the specific interaction between Zr (IV) and phosphates. The nanoprobe can be utilized to monitor the fluctuations in HClO and phosphate in early atherosclerosis. It is observed that the levels of HClO and phosphate in the serum of early AS mice are higher than those of the normal mice. Ultimately, the levels of hypochlorous acid and phosphorylation in the inner wall of aortic vessels are imaged by two-photon microscope. The results show that the levels of HClO and phosphorylation in the early atherosclerotic mice are significantly higher than those of in normal mice. The nanoprobe provides a suitable fluorescent tool for simultaneous detection and imaging of HClO and phosphorylation, which holds promise for early atherosclerotic disease assessment.

New dual-responsive fluorescent sensor for hypochlorite and cyanide sensing and its imaging application in live cells and zebrafish

Excessive levels of cyanide (CN-) and hypochlorite (ClO-) anions are the significant threats to the human health and the environment. Thus, great efforts have been to design and synthesize molecular sensors for the simple, instantaneous and efficient detecting environmentally and biologically important anions. Currently, developing a single molecular sensor for multi-analyte sensing is still a challenging task. In our present work, we developed a new molecular sensor (3TM) based on oligothiophene and Meldrum's acid units for detecting cyanide and hypochlorite anions in biological, environmental and food samples. The detecting ability of 3TM has been examined to various testing substances containing amino acids, reactive oxygen species, cations and anions, showing its high selectivity, excellent sensitivity, short response time (ClO-: 30 s, CN-: 100 s), and broad pH working range (4-10). The detection limits were calculated as 4.2 nM for ClO- in DMSO/H2O (1/8, v/v) solution and 6.5 nM for CN- in DMSO/H2O (1/99, v/v) solution. Sensor 3TM displayed sharp turn-on fluorescence increasement (555 nm, 435 nm) and sensitive fluorescence color changes caused by CN-/ClO-, which is ascribed to the nucleophilic addition and oxidation of ethylenic linkage by cyanide and hypochlorite, respectively. Moreover, sensor 3TM was applied for hypochlorite and cyanide detecting in real-world water, food samples and bio-imaging in live cells and zebrafish. To our knowledge, the developed 3TM sensor is the seventh single-molecular sensor for simultaneous and discriminative detecting hypochlorite and cyanide in food, biological and aqueous environments using two distinct sensing modes.

A new hydrazone linkage-based covalent organic framework for ratiometric fluorescent probe detection of hypochlorite

A new hydrazone-linked covalent organic framework (TFTH-COF) was synthesized and characterized. TFTH-COF has porous crystalline framework structure with high thermal stability. TFTH-COF exhibited highly selective fluorescence blue-shift response towards hypochlorite (ClO-) in ethanol and accompanied by the obvious color change under both day light and UV light. TFTH-COF has the ratiometric fluorescence sensing ability for hypochlorite with high sensitivity. The ratiometric fluorescence intensity of TFTH-COF presented a linear change against hypochlorite concentration with a low detection limit of 0.417 μM. The results of XPS, FT-IR and fluorescence lifetime indicated the formation of hydrogen bond between the O and N atoms of hydroxyl and amine of TFTH-COF with hypochlorite. The DFT calculation further confirmed the formation of hydrogen bond and resulted in the change of fluorescence spectra. Its practical application ability was confirmed by good recovery rate of TFTH-COF in the quantitative detection of hypochlorite in 84 disinfectants and water samples. Moreover, TFTH-COF can also identify hypochlorite through fluorescent test strips by the naked eye. This work sheds light on the fabrication of COFs as ratiometric fluorescence probes for easily-operable, instantaneous and accurate detection and identification of different analytes.

Bifunctional near-infrared fluorescent probe for the selective detection of bisulfite and hypochlorous acid in food, water samples and in vivo

We report the development of a bifunctional near-infrared fluorescent probe (QZB) for selective sensing of bisulfite (HSO3-) and hypochlorous acid (HOCl). The synergistic detection of HSO3- and HOCl was achieved via a C=C bond recognition site. In comparison with the red-fluorescence QZB, two different products with non-fluorescence and paleturquoise fluorescence were produced by the recognition of QZB towards HSO3- and HOCl respectively, which can realize effectively the dual-functional detection of HSO3- and HOCl. QZB features prominent preponderances of dual-function response, near-infrared emission, reliability at physiological pH, low cytotoxicity and high sensitivity to HSO3- and HOCl. The detection of HSO3- in actual food samples has been successfully achieved using QZB. Utilization of QZB-based test strip to semi-quantitatively detect HSO3- and HOCl in real-world water samples by the "naked-eye" colorimetry are then demonstrated. Simultaneously, the determination of HSO3- and HOCl in real-world water sample has been achieved by smartphone-based standard curves. Additionally, the applications of QZB for imaging HSO3- and HOCl in vivo are successfully demonstrated. Consequently, the successful development of QZB could be promising as an efficient tool for researching the role of HSO3-/HOCl in the regulation of redox homeostasis regulation in vivo and complex signal transduction and for future food safety evaluation.

Novel probe based on rhodamine B and quinoline as a naked-eye colorimetric probe for dual detection of nickel and hypochlorite ions

This work demonstrates the design and straightforward syntheses of several novel probe-based on rhodamine B and 2-mercaptoquinoline-3-carbaldehydes as a naked-eye colorimetric probe, indicating a sensitive and selective recognition towards nickel (II) with a limit of detection 0.30 μmol L-1 (0.02 mg L-1). Further, by employing the oxidation property of hypochlorite (OCl-), this novel probe parallelly has been deployed to detect hypochlorite in laboratory conditions with a limit of detection of 0.19 μmol mL-1 and in living cells. Regarded to negligible cell toxicity toward mammalian cells, this probe has the potential to determine these analytes in in-vivo investigation and foodstuff samples.

Organelle-targeting ratiometric fluorescent probes: design principles, detection mechanisms, bio-applications, and challenges

Biological species, including reactive oxygen species (ROS), reactive sulfur species (RSS), reactive nitrogen species (RNS), F-, Pd2+, Cu2+, Hg2+, and others, are crucial for the healthy functioning of cells in living organisms. However, their aberrant concentration can result in various serious diseases. Therefore, it is essential to monitor biological species in cellular organelles such as the cell membrane, mitochondria, lysosome, endoplasmic reticulum, Golgi apparatus, and nucleus. Among various fluorescent probes for species detection within the organelles, ratiometric fluorescent probes have drawn special attention as a potential way to get beyond the drawbacks of intensity-based probes. This method depends on measuring the intensity change of two emission bands (caused by an analyte), which produces an efficient internal referencing that increases the detection's sensitivity. This review article discusses the literature publications (from 2015 to 2022) on organelle-targeting ratiometric fluorescent probes, the general strategies, the detecting mechanisms, the broad scope, and the challenges currently faced by fluorescent probes.

Investigation of the Immunogenic Properties of Ovalbumin Modified by Urban Airborne Particulate Matter

Exposure to air particulate matter (PM) is linked to the blood oxidative stress and systemic inflammation. The aim of this study was to elucidate whether oxidative PM modification of ovalbumin (OVA), the major antioxidant serum protein, may alter its antigenicity and/or immunogenicity. Ovalbumin was exposed via dialysis to the standard urban PM (SRM 1648a) or to PM with removed organic content (encoded as LAP). Both structural changes and biological properties of PM-modified OVA were measured. T lymphocytes and dendritic cells (the major antigen-presenting cells) isolated from C57BL/6 and OT-II (323-339 epitope) OVA-specific T cell receptor (TCR)-transgenic mice were used to test the effect of PM on OVA immunogenicity. The immunogenicity of both SRM 1648a and LAP-modified OVA was significantly higher than that of control OVA, as measured by the epitope-specific T cell proliferation and interferon γ production by the stimulated cells. This effect was associated with mild oxidative changes in the carrier molecule outside the structure of the OVA epitope and with increased resistance to proteolysis of PM-modified OVA. Interestingly, dendritic cells showed enhanced capacity for the uptake of proteins when the cells were cultured with PM-modified OVA. Our results suggest that the enhanced immunogenicity of PM-modified OVA is not associated with altered antigenicity or antigen presentation. However, it may result from slower degradation and longer persistence of modified antigens in dendritic cells. Whether this phenomenon is associated with enhanced risk prevalence of autoimmune diseases observed in the areas with high urban PM pollution needs to be explained.

Current State of Cold Atmospheric Plasma and Cancer-Immunity Cycle: Therapeutic Relevance and Overcoming Clinical Limitations Using Hydrogels

Cold atmospheric plasma (CAP) is a partially ionized gas that gains attention as a well-tolerated cancer treatment that can enhance anti-tumor immune responses, which are important for durable therapeutic effects. This review offers a comprehensive and critical summary on the current understanding of mechanisms in which CAP can assist anti-tumor immunity: induction of immunogenic cell death, oxidative post-translational modifications of the tumor and its microenvironment, epigenetic regulation of aberrant gene expression, and enhancement of immune cell functions. This should provide a rationale for the effective and meaningful clinical implementation of CAP. As discussed here, despite its potential, CAP faces different clinical limitations associated with the current CAP treatment modalities: direct exposure of cancerous cells to plasma, and indirect treatment through injection of plasma-treated liquids in the tumor. To this end, a novel modality is proposed: plasma-treated hydrogels (PTHs) that can not only help overcome some of the clinical limitations but also offer a convenient platform for combining CAP with existing drugs to improve therapeutic responses and contribute to the clinical translation of CAP. Finally, by integrating expertise in biomaterials and plasma medicine, practical considerations and prospective for the development of PTHs are offered.

Design and Synthesis of Novel Fluorescent Probe Based on Cyanobiphenyl and its Application in Detection of Hypochlorite

Hypochlorite is an important biological reactive oxygen species, which plays a pivotal role in various life activities. Excessive presence in the human body or excessive intake in life causes a series of diseases. To monitor the hypochlorite level in living cells, organisms and environment water samples, we herein designed and synthesized three organic small molecule fluorescent probes with different recognition sites based on nitrile biphenyl. Through performance comparison, it was found that probe A-HM exhibited the best detection performance for hypochlorite with a low detection limit of 2.47 × 10^-6 M. The introduction of hypochlorite will induce probe fluorescence A-HM to turn on, and the fluorescence colour will change from colourless to green. The application of A-HM in biological systems has been demonstrated by the imaging monitoring of hypochlorite in MCF-7, L929 cells and zebrafish. Furthermore, A-HM was also used for the accurate determination of the hypochlorite level in real water samples with high sensitivity and good recoveries.

A dual-responsive fluorescent turn-on sensor for sensitively detecting and bioimaging of hydrazine and hypochlorite in biofluids, live-cells, and plants

Hydrazine (N₂H₄) and hypochlorite (ClO^-) are extremely harmful to the public health, so it is vitally necessary to detect them in living system. Herein, we developed a new phenthiazine-thiobarbituric acid based dual-analyte responsive fluorescent sensor PT for visually distinguishing and detecting N₂H₄ and ClO^-. PT underwent N₂H₄/ClO^--induced CC breakage, achieving olive-drab/brilliant green fluorescence lighting-up response towards N₂H₄/ClO^- with superb specifity, ultra-sensitivity (detection limit: 15.4 nM for N₂H₄, 13.7 nM for ClO^-), and ultra-fast response (N₂H₄: <15 s, ClO^-: <20 s). The mechanisms for sensing N₂H₄ and ClO^- were investigated with support of spectral measurements and DFT investigation. Sensor based paper-strip/silica-gel device was developed for in-field supervision and on-site monitoring of gaseous and aqueous N₂H₄ and ClO^- solution. In addition, the PT was also applied for quantitatively detecting N₂H₄ and ClO^- in soil, food, plants and bio-fluids. Moreover, PT was utilized to visualize exogenous N₂H₄ and ClO^- in living plants and live-cells, demonstrating this sensor utilized as a powerful tool to detect N₂H₄ and ClO^- in biological fields.

Oxidized Proteins Differentially Affect Maturation and Activation of Human Monocyte-Derived Cells

In cancer, antigen-presenting cells (APC), including dendritic cells (DCs), take up and process proteins to mount adaptive antitumor immune responses. This often happens in the context of inflamed cancer, where reactive oxygen species (ROS) are ubiquitous to modify proteins. However, the inflammatory consequences of oxidized protein uptake in DCs are understudied. To this end, we investigated human monocyte-derived cell surface marker expression and cytokine release profiles when exposed to oxidized and native proteins. Seventeen proteins were analyzed, including viral proteins (e.g., CMV and HBV), inflammation-related proteins (e.g., HO1 and HMGB1), matrix proteins (e.g., Vim and Coll), and vastly in the laboratory used proteins (e.g., BSA and Ova). The multifaceted nature of inflammation-associated ROS was mimicked using gas plasma technology, generating reactive species cocktails for protein oxidation. Fourteen oxidized proteins led to elevated surface marker expression levels of CD25, CD40, CD80, CD86, and MHC-II as well as strongly modified release of IL6, IL8, IL10, IL12, IL23, MCP-1, and TNFα compared to their native counterparts. Especially IL8, heme oxygenase 2, and vimentin oxidation gave pronounced effects. Furthermore, protein kinase phospho-array studies in monocyte-derived cells pulsed with native vs. oxidized IL8 and insulin showed enhanced AKT and RSK2 phosphorylation. In summary, our data provide for the first time an overview of the functional consequences of oxidized protein uptake by human monocyte-derived cells and could therefore be a starting point for exploiting such principle in anticancer therapy in the future.

Lysosome-targetable brightly green fluorescence carbon dots for real-time monitoring in cell and highly efficient removal in environment of hypochlorite

Due to the lacks of lysosome localization group and reaction/interaction site for hypochlorite (ClO^-) on the surface of the carbon dots (C-dots), no C-dots-based lysosome-targeted fluorescence probes have, so far, been reported for real-time monitoring intracellular ClO^-. In this work, 1,3,6-trinitropyrene (TNP) was used as a precursor to prepare C-dots with maximum excitation and emission wavelengths at 485 and 532 nm, respectively, and quantum yield ∼ 27% by a hydrothermal approach at 196 °C for 6 h under a reductive atmosphere. The brightly green C-dots can sensitively and quickly respond to ClO^- in aqueous solution through surface chemical reaction, showing a linear relationship in the range of 0.5-120 μΜ ClO^- with 0.27 μΜ of limit of detection (LOD). Most significantly, the C-dots can localize at intracellular lysosome to image ClO^- in lysosomes. Also, the magnetic nanocomposites (C-dots@Fe₃O₄ MNCs) were fabricated via a simple electrostatic self-assembly between Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) and C-dots for highly efficient removal of ClO^- in real samples. Therefore, lysosome-targetable C-dots-based probes for real-time monitoring ClO^- were successfully constructed, opening up a promising door to investigate the biological functions and pathological roles of ClO^- at organelle levels.

Gas Plasma Protein Oxidation Increases Immunogenicity and Human Antigen-Presenting Cell Maturation and Activation

Protein vaccines rely on eliciting immune responses. Inflammation is a prerequisite for immune responses to control infection and cancer but is also associated with disease onset. Reactive oxygen species (ROSs) are central during inflammation and are capable of inducing non-enzymatic oxidative protein modifications (oxMods) associated with chronic disease, which alter the functionality or immunogenicity of proteins that are relevant in cancer immunotherapy. Specifically, antigen-presenting cells (APCs) take up and degrade extracellular native and oxidized proteins to induce adaptive immune responses. However, it is less clear how oxMods alter the protein's immunogenicity, especially in inflammation-related short-lived reactive species. Gas plasma technology simultaneously generates a multitude of ROSs to modify protein antigens in a targeted and controlled manner to study the immunogenicity of oxMods. As model proteins relevant to chronic inflammation and cancer, we used gas plasma-treated insulin and CXCL8. We added those native or oxidized proteins to human THP-1 monocytes or primary monocyte-derived cells (moDCs). Both oxidized proteins caused concentration-independent maturation phenotype alterations in moDCs and THP-1 cells concerning surface marker expression and chemokine and cytokine secretion profiles. Interestingly, concentration-matched H2O2-treated proteins did not recapitulate the effects of gas plasma, suggesting sufficiently short diffusion distances for the short-lived reactive species to modify proteins. Our data provide evidence of dendric cell maturation and activation upon exposure to gas plasma- but not H2O2-modified model proteins. The biological consequences of these findings need to be elucidated in future inflammation and cancer disease models.

BODIPY-Based Fluorescent Probes for Selective Visualization of Endogenous Hypochlorous Acid in Living Cells via Triazolopyridine Formation

In this work, the two pyridylhydrazone-tethered BODIPY compounds (2 and 3) were synthesized. These compounds aimed to detect hypochlorous acid (HOCl) species via cyclic triazolopyridine formation. The open forms and the resulting cyclic forms of BODIPYs (2, 3, 4, and 5) were fully characterized by nuclear magnetic resonance, mass spectrometry, infrared spectroscopy, and single-crystal X-ray diffraction. These two probes can selectively detect HOCl through a fluorescence turn-on mechanism with the limit of detections of 0.21 µM and 0.77 µM for compounds 2 and 3, respectively. This fluorescence enhancement phenomenon could be the effect from C = N isomerization inhibition due to HOCl-triggered triazolopyridine formation. In cell imaging experiments, these compounds showed excellent biocompatibility toward RAW 264.7 murine live macrophage cells and greatly visualized endogenous HOCl in living cells stimulated with lipopolysaccharide.

A novel near-infrared fluorescent probe for rapid sensing of HClO in living cells and zebrafish

Reactive oxygen species (ROS) are significant active species in living organisms, and their coordination maintains the function of organelles to resist the invasion of foreign substances. Hypochlorous acid (HClO) is not only an eventful signaling species but also a kind of ROS, which plays an irreplaceable role in the immune system. However, its abnormal levels can cause cell damage or even apoptosis, which in turn leads to the onset of a series of diseases such as inflammation, neurological diseases, and even cancer. Based on this, we designed a near-infrared fluorescent probe with a large Stokes shift for ultrafast response to HClO. Furthermore, the probe exhibits excellent sensitivity and selectivity toward HClO over other species. The probe was successfully applied to visualize endogenous and exogenous HClO in living cells and in zebrafish. This unique study is the key to providing a trustworthy tool for imaging based on the in vitro and in vivo imaging of endogenous HClO, which possesses great potential for the use in future studies of HClO-related biology and pathology.

Tumor cell-based vaccine: an effective strategy for eradication of cancer cells

Whole tumor cell-based vaccines include all potential antigen-rich cell lysates to target a specific type of tumor without the need to find the best antigen candidate in protein- or peptide-based vaccines. Preparation of whole tumor cell lysates inducing cell death and inactivating immunosuppressive cytokine secretion from the tumor cells is highly enviable. Generally, modified whole tumor cells, tumor cell-derived exosomes, autologous tumor cell-derived ribonucleic acid, and personalized mutanome-derived tumor antigen are promising immunotherapeutic approaches. Autologous dendritic cells loaded with tumor-associated antigens also induce the generation of immunological memory and antitumor response as an effective method for the treatment of cancer. The present review briefly describes tumor cell-based vaccines as a promising strategy for eradication of cancer cells.

Hypochlorous Acid: From Innate Immune Factor and Environmental Toxicant to Chemopreventive Agent Targeting Solar UV-Induced Skin Cancer

A multitude of extrinsic environmental factors (referred to in their entirety as the 'skin exposome') impact structure and function of skin and its corresponding cellular components. The complex (i.e. additive, antagonistic, or synergistic) interactions between multiple extrinsic (exposome) and intrinsic (biological) factors are important determinants of skin health outcomes. Here, we review the role of hypochlorous acid (HOCl) as an emerging component of the skin exposome serving molecular functions as an innate immune factor, environmental toxicant, and topical chemopreventive agent targeting solar UV-induced skin cancer. HOCl [and its corresponding anion (OCl-; hypochlorite)], a weak halogen-based acid and powerful oxidant, serves two seemingly unrelated molecular roles: (i) as an innate immune factor [acting as a myeloperoxidase (MPO)-derived microbicidal factor] and (ii) as a chemical disinfectant used in freshwater processing on a global scale, both in the context of drinking water safety and recreational freshwater use. Physicochemical properties (including redox potential and photon absorptivity) determine chemical reactivity of HOCl towards select biochemical targets [i.e. proteins (e.g. IKK, GRP78, HSA, Keap1/NRF2), lipids, and nucleic acids], essential to its role in innate immunity, antimicrobial disinfection, and therapeutic anti-inflammatory use. Recent studies have explored the interaction between solar UV and HOCl-related environmental co-exposures identifying a heretofore unrecognized photo-chemopreventive activity of topical HOCl and chlorination stress that blocks tumorigenic inflammatory progression in UV-induced high-risk SKH-1 mouse skin, a finding with potential implications for the prevention of human nonmelanoma skin photocarcinogenesis.

Biophysics involved in the process of tumor immune escape

Much of the current research into immune escape from cancer is focused on molecular and cellular biology, an area of biophysics that is easily overlooked. A large number of immune drugs entering the clinic are not effective for all patients. Apart from the molecular heterogeneity of tumors, the biggest reason for this may be that knowledge of biophysics has not been considered, and therefore an exploration of biophysics may help to address this challenge. To help researchers better investigate the relationship between tumor immune escape and biophysics, this paper provides a brief overview on recent advances and challenges of the biophysical factors and strategies by which tumors acquire immune escape and a comprehensive analysis of the relevant forces acting on tumor cells during immune escape. These include tumor and stromal stiffness, fluid interstitial pressure, shear stress, and viscoelasticity. In addition, advances in biophysics cannot be made without the development of detection tools, and this paper also provides a comprehensive summary of the important detection tools available at this stage in the field of biophysics.

Nitrogen-doped carbon quantum dots as fluorescent nanosensor for selective determination and cellular imaging of ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022;271:120941. [PMID: 35114635 DOI: 10.1016/j.saa.2022.120941]

The carbon nanomaterial based fluorescent probes have been widely applied in biological imaging. In the current research, we propose an interesting strategy for selective sensing of hypochlorite (ClO^-) by a water-soluble and highly fluorescent nanosensor based on the N-doped carbon quantum dots (CDs) which was fabricated by a facile and environmental friendly hydrothermal approach from polyvinyl pyrrolidone, L-arginine and tryptophan. The structural characteristics of the probe were measured by multitudinous methods which proved the nanometer spherical structure of the probe and the successfully N-doping. Fluorescent investigation demonstrated that the probe is not only highly stable under interferences of pH, ionic strength, and irradiation, but also significantly selective toward ClO^- amongst a variety of attractive bioactive species through the fluorescent quenching process which was correlative with the concentration of ClO^- and linearly in the range of 0.1-50 μmol·L^-1 with the sensitivity of 0.03 μmol·L^-1. The probe can also be further illustrated in a prospective application for determination of ClO^- in environmental water through both solution response and filer paper sensing. Moreover, the positive biocompatibility and ignorable cytotoxicity made the probe a promising effective agent for detection and visualizing ClO^- in living cells which can facilitate the understanding the oxidative stress from the overexpressing ClO^-.

Evoking Highly Immunogenic Ferroptosis Aided by Intramolecular Motion-Induced Photo-Hyperthermia for Cancer Therapy

Immunogenic cell death (ICD) through apoptosis or necroptosis is widely adopted to improve the therapeutic effect in cancer treatment by triggering a specific antitumor immunity. However, the tumor resistance to apoptosis/necroptosis seriously impedes the therapeutic effect. Recently, ferroptosis featured with excessive lipid peroxidation is demonstrated capable of bypassing the apoptosis/necroptosis resistance to kill cancer cells. To date, numerous efficient ferroptosis inducers are developed and successfully utilized for sensitizing cancer cells to ferroptosis. Unfortunately, these inducers can hardly generate adequate immunogenicity during induction of ferroptotic cancer cell death, which distinctly attenuates the efficacy of triggering antitumor immune response, therefore leads to unsatisfactory therapeutic effect. Herein, a novel high-performance photothermal nanoparticle (TPA-NDTA NP) is designed by exploiting energy via excited-state intramolecular motion and employed for immensely assisting ferroptosis inducer to evoke highly efficient ICD through ferroptosis pathway. Tumor models with poor immunogenicity are used to demonstrate the tremendously enhanced therapeutic effect endowed by highly enhanced immunogenic ferroptosis in vitro and in vivo by virtue of the NPs. This study sheds new light on a previously unrecognized facet of boosting the immunogenicity of ferroptosis for achieving satisfactory therapeutic effect in cancer therapy.

A novel fluorescent probe with large Stokes shift for accurate detection of HOCl in mitochondria and its imaging application

Hypochlorous acid (HOCl), mainly generated in mitochondria, plays a critical role in various physiological processes. To better understand the role and function of HOCl in mitochondria, herein, we present the design and synthesis of a Mito-QL reporter for probing the HOCl within mitochondria without other interference generated in living cells. Through the combination of TICT/ICT mechanisms, probe Mito-QL, with large stokes shift (203 nm) and low background fluorescence, exhibited excellent sensitivity (900-fold fluorescence enhancement) and selectivity towards HOCl (LOD = 2.4 nM). The co-location experiments confirmed that probe Mito-QL can firstly localize in the mitochondria and then react with HOCl in mitochondria. Also, the probe is capable of imaging endogenous and exogenous HOCl even the generation of HOCl during the ferroptosis of cells, which is beneficial for more efficient application in biological imaging.

Exploring the relationship between the "ON-OFF" mechanism of fluorescent probes and intramolecular charge transfer properties

In this study, the excited state charge distribution characteristics and fluorescence mechanism of HClO detection probes HN-ClO (weak fluorescence) and HN-ClO-F (strong fluorescence) probes were investigated based on density functional theory (DFT) and time-dependent density functional theory (TDDFT). The results of electrostatic potential (ESP) map and hole-electron analysis show that the HN-ClO and HN-ClO-F probes have obvious charge separation characteristics in the excited state. The excited state energy decomposition and Merz-Kollman charge analysis demonstrate the existence of distinct planar intramolecular charge transfer (PICT) features in HN-ClO and HN-ClO-F. Due to the strong charge coupling caused by the planar structure, the fluorescence of HN-ClO-F could occur. Furthermore, the weak fluorescence of HN-ClO is caused by inter-system crossing (ISC) between S₁ and T₁ state. Our result proves that the ICT process could exist in HN-ClO-F, but the PICT process does not cause fluorescence quenching, which have provided an excellent supplement to the mechanism of fluorescent probes. The conclusion is consistent with the fluorescence phenomenon observed in the experiment.

An ICT-FRET-based fluorescent probe for ratiometric sensing hypochlorous acid based on a coumarin-naphthalimide derivative

Hypochlorous acid (HOCl) is one of the most important reactive oxygen species (ROS), and plays an important role in pathological processes and relevant diseases. However, the highly sensitive/selective detection of...

Lysosome-targeting luminescent lanthanide complexes: From molecular design to bioimaging

Lysosomes are essential acidic cytoplasmic membrane-bound organelles in human cells that play a critical role in many cellular events. A comprehensive understanding of lysosome-specific imaging can ultimately help us to...

Chlorination-induced pKa decrease: an improved strategy to design ratiometric hypochlorite fluorescent probes with ideally high selectivity

Based on the ClO−-triggered chlorination reaction and the subsequent pKa decrease, a two-photon ratiometric ClO− fluorescent probe was designed.