Activity-based fluorescence probes for pathophysiological peroxynitrite fluxes

Peroxynitrite activatable NIR-II probe for tumor diagnosis and photothermal therapy in vivo

BACKGROUND

Peroxynitrite (ONOO-) is a bioactive molecule involved in various biochemical processes, and the abnormal concentration fluctuations of ONOO- in living systems are closely associated with various diseases, including cancer. An important characteristic of the tumor microenvironment is the overexpression of ONOO-, highlighting the significance of specific detection of ONOO- in distinguishing between tumor tissue and normal tissue. A single near-infrared second window (NIR-II) molecular probe integrated fluorescence imaging and photothermal therapy can achieve precise localization and effective ablation of deep-seated tumor tissue. However, it still remains challenges. (87) RESULTS: In this study, we present a probe (BDⅡ-ONOO-) that integrates NIR-II fluorescence imaging and photothermal therapy for the specific detection of ONOO-. The probe exhibits excellent selectivity, high sensitivity, low toxicity and high biocompatibility. In the presence of ONOO-, the probe can quickly respond to ONOO- and emit NIR-II fluorescence at 900 nm with 7.6-fold change in fluorescence intensity. In addition, the probe BDⅡ-ONOO- exhibits a high photothermal conversion efficiency of 41.6 % under 808 nm laser irradiation in the presence of ONOO-. In vivo imaging results indicate that the probe BDⅡ-ONOO- not only effectively distinguishes tumor tissue from normal tissue but also performs photothermal treatment on 4T1 tumor without apparent biological toxicity. (112) SIGNIFICANCE: This work provides insights for the future development of tumor-specific diagnostic and therapeutic approaches with good biocompatibility and deep tissue penetration. The probe described in this work may be employed as a powerful tool for the diagnosis and precise treatment of tumors in vivo. (44).

Highly sensitive near-infrared fluorescent probe for monitoring peroxynitrite in nonalcoholic fatty liver disease: Toward early diagnosis and therapeutic evaluation

Nonalcoholic fatty liver disease (NAFLD) poses a significant global health concern, necessitating precise diagnostic tools and effective treatment strategies. Peroxynitrite (ONOO-), a reactive oxygen species, plays a pivotal role in NAFLD pathogenesis, highlighting its potential as a biomarker for disease diagnosis and therapeutic evaluation. This study reports on the development of a near-infrared (NIR) fluorescent probe, designated DRP-O, for the selective detection of ONOO- with high sensitivity and photostability. DRP-O exhibits rapid response kinetics (within 2 min) and an impressive detection limit of 2.3 nM, enabling real-time monitoring of ONOO- dynamics in living cells. Notably, DRP-O demonstrates excellent photostability under continuous laser irradiation, ensuring reliable long-term monitoring in complex biological systems. We apply DRP-O to visualize endogenous ONOO- in living cells, demonstrating its potential for diagnosing and monitoring NAFLD-related oxidative stress. Furthermore, DRP-O effectively evaluates the efficacy of therapeutic drugs in NAFLD cell models, underscoring its potential utility in drug screening studies. Moreover, we confirm DRP-O to enable selective identification of fatty liver tissues in a mouse model of NAFLD, indicating its potential for the early diagnosis of NAFLD. Collectively, DRP-O represents a valuable tool for studying ONOO- dynamics, evaluating drug efficacy, and diagnosing NAFLD, offering insights into novel therapeutic strategies for this prevalent liver disorder.

Simultaneous Imaging of pH and Peroxynitrite in the Endoplasmic Reticulum and Mitochondria: Revealing Organelle Interactions in Alzheimer's Disease Pathogenesis

pH and peroxynitrite (ONOO-) are two critical biomarkers to unveil the corresponding status of endoplasmic reticulum (ER) stress and mitochondrial dysfunction, which are closely related to Alzheimer's disease (AD). Simultaneously monitoring pH and ONOO- fluctuations in the ER and mitochondria during AD progression is pivotal for clarifying the interplay between the disorders of the two organelles and revealing AD pathogenesis. Herein, we designed and synthesized a dual-channel fluorescent probe (DCFP) to visualize pH and ONOO- in the ER and mitochondria. DCFP possessed excellent sensitivity and selectivity to pH and ONOO- without spectral crosstalk and was utilized in monitoring the two analytes within AD model cells and larval zebrafish. Importantly, DCFP could preferentially target mitochondria in normal cells and be enriched in the ER after mitochondrial depolarization. With the aid of DCFP, the slower acidification rate of the ER than that of mitochondria induced by Aβ oligomers (AβOs) was first identified, which could be ascribed to the relief of the AβOs-triggered ER stress through the Ca2+ migration from the ER to mitochondria. Moreover, continuous exposure to AβOs led to mitochondrial Ca2+ overload, accelerating the acidification and ONOO- overproduction within mitochondria. As a result, intracellular oxidative stress levels were elevated, further exacerbating ER stress and aggravating ER acidification in turn. The advanced understanding of the potential interplay between the ER and mitochondria in this work may offer new insights and methodologies for studying AD pathogenesis. The DCFP developed in this work could also be employed to study other diseases related to ER stress and mitochondrial dysfunction.

BODIPY-Based Ratiometric Fluorescent Probe for Sensing Peroxynitrite in Inflammatory Cells and Tissues

Peroxynitrite (ONOO-) plays an important role in many physiological and pathological processes. Excessive ONOO- in cells leads to oxidative stress and inflammation. However, precise monitoring of ONOO- levels in specific organelles (e.g., mitochondria) is still lacking and urgently needed. Herein, we rationally designed a mitochondria-targeted ratiometric fluorescent probe, MOBDP-I, for imaging of ONOO- in the mitochondria of inflammatory cells and model mice. This probe, MOBDP-I, was synthesized by conjugating a BODIPY fluorophore to a mitochondria-targeting moiety-indole-salt group by a carbon-carbon double bond (C=C). In the presence of ONOO-, the C=C bond between the BODIPY backbone and the indole-salt group was oxidized and broken, leading to an 18-fold enhancement of fluorescence at 510 nm, along with a significant fluorescence decrease at 596 nm. The ratiometric response property bestowed the probe with advantages in the precise quantification of ONOO- in cells, thus allowing estimation of the extent of inflammation in living cells and mouse models of rheumatoid arthritis, peritonitis, and brain inflammation. MOBDP-I could act as an effective molecular tool to study the relationship between ONOO- and the occurrence and development of inflammatory diseases.

Recent progress in small-molecule fluorescent probes for the detection of superoxide anion, nitric oxide, and peroxynitrite anion in biological systems

Superoxide anion (O2˙-), nitric oxide (NO), and peroxynitrite anion (ONOO-) play essential roles in physiological and pathological processes, which are related to various symptoms and diseases. There is a growing need to develop reliable techniques for effectively monitoring the changes in these three reactive species across different molecular events. Currently, small-molecule fluorescent probes have been demonstrated to be reliable imaging tools for the optical detection and biological analysis of reactive species in biological systems due to their high spatiotemporal resolution and in situ capabilities. In consideration of the distinct features of these three reactive species, abundant fluorescent probes have been developed to meet various requirements. In this context, we systematically summarized the latest progress (2020-2023) in organic fluorescent probes for monitoring O2˙-, NO, and ONOO- in living systems. Furthermore, the working principles and biological applications of representative fluorescent probes were illustrated. Moreover, we highlighted the current challenges and future trends of fluorescent probes, offering general insights into future research.

Diaminonaphthalene Boronic Acid (DANBA): New Approach for Peroxynitrite Sensing Site

Selective detection of reactive oxygen species (ROS) is vital for studying their role in brain diseases. Fluorescence probes can distinguish ONOO- species from other ROS; however, their selectivity toward ONOO- species depends on the ONOO- recognition group. Aryl-boronic acids and esters, which are common ONOO- recognition groups, are not selective for ONOO- over H2O2. In this study, we developed a diaminonaphthalene (DAN)-protected boronic acid as a new ONOO- recognition group that selectively reacts with ONOO- over H2O2 and other ROS. Three DAN-protected boronic acid (DANBA)-based fluorophores that emit fluorescence over visible to near-infrared (NIR) regions, Cou-BN, BVP-BN, and HDM-BN, and their aryl-boronic acid-based counterparts (Cou-BO, BVP-BO, and HDM-BO), were developed. The DANBA-based probes exhibited enhanced selectivity toward ONOO- over that of their control group, as well as universality in solution assays and in vitro experiments with PC12 cells. The NIR-emissive HDM-BN was optimized to delineate in vivo ONOO- levels in mouse brains with Parkinson's disease. This DAN-protected boronic acid belongs to a new generation of recognition groups for developing ONOO- probes, and this strategy could be extended to other common hydroxyl-containing dyes to detect ONOO- levels in complex biological systems and processes.

A Bicyclic Dioxetane Chemiluminescence Nanoprobe for Peroxynitrite Imaging in Vivo

Peroxynitrite (ONOO-) is a critical biomarker associated with a wide array of diseases including cancer, inflammatory conditions, and neurodegenerative disorders. This study introduces an innovative chemiluminescence nanoprobe (CLNP) based on a bicyclic dioxetane structure, designed for highly sensitive and specific in vivo imaging of ONOO-. Our CLNP demonstrates exceptional capabilities in generating high-contrast imaging of disease lesions, with applications verified across tumor models, acute inflammation, and acute liver injury scenarios. Key findings highlight the probe's rapid response to oxidative species, superior tissue penetration, and high signal-to-noise ratio, underscoring its potential for real-time diagnostic applications. This work represents an important advance in the field of diagnostic imaging using CL probes, offering promising avenues for the early detection and treatment of ONOO--related pathologies.

Peroxynitrite-Responsive Near-Infrared Fluorescent Imaging Guided Synergistic Chemo-Photodynamic Therapy via Biomimetic Metal-Organic Frameworks

Peroxynitrite (ONOO-) plays a crucial role in maintaining cellular redox homeostasis and regulating diffusive processes, cellular transport, and signal transduction. Extensive studies have revealed that increased ONOO- levels during tumor progression are associated with heightened levels of oxidative stress. However, current methods lack noninvasive visualization, immediate reporting, and highly sensitive fluorescence sensing. In light of this, we have designed a biomimetic fluorescent nanoplatform, named Z-C-T@CM, for peroxynitrite-responsive near-infrared fluorescent imaging guided cancer treatment. The nanoplatform comprises tetrakis(4-carboxyphenyl) porphyrin (TCPP) and curcumin (CCM) encapsulated within a zeolitic imidazolate framework-8 (ZIF-8), which is coated with a mouse breast cancer cell membrane for enhanced biocompatibility and targeting, while evading immune clearance. In vitro experimental results demonstrate that the as-prepared nanoplatform exhibits enhanced near-infrared fluorescence emission upon exposure to ONOO-, indicating a significant potential for noninvasive in vivo imaging of ONOO- during tumor progression. Additionally, Z-C-T@CM readily degrades in the tumor microenvironment, releasing TCPP and CCM, enabling a synergistic chemo-photodynamic therapy with near-infrared illumination. Further investigations indicate that Z-C-T@CM efficiently stimulates a tumor immune response and facilitates therapeutic efficiency. Collectively, this work introduces a novel noninvasive strategy for ONOO- detection, shedding new light on the integration of cancer diagnosis and efficient treatment.

Splitting and Aggregation of Carbon Dots: Wavelength-Shifted and Ratiometric Fluorescence Sensing of Peroxynitrite

Peroxynitrite (ONOO-) is a short-term reactive biological oxidant and plays an important role in cellular signal transduction and homeostatic regulation. However, excess ONOO- is associated with neurodegenerative and cardiovascular diseases. Therefore, rapid, sensitive, and accurate assays for ONOO- detection are essential for exploring its physiological and pathological function. In this work, a wavelength-shifted and ratiometric fluorescent sensing platform for ONOO- is constructed by splitting green fluorescent carbon dots (G-CDs) and aggregating orange fluorescent carbon dots (O-CDs). The mixed G-CDs and O-CDs (M-CDs) show a fast and precise response to ONOO- in the range of 0-250 μM, with a detection limit of 10 nM. In the linearity range within 3 μM ONOO-, an obvious wavelength shift of G-CDs from 495 to 475 nm is observed owing to the oxidation and nitration of ONOO- to the surface-state fluorescence of G-CDs, accompanied by the splitting of G-CDs. In the linearity range of 3-250 μM ONOO-, the fluorescence of G-CDs remains constant, while the molecular-state fluorescence of O-CDs gradually quenches by the oxidation and nitration of ONOO- through the fluorescence static process and induces their aggregation. Additionally, M-CDs show favorable intracellular imaging of endogenous and exogenous ONOO-. This study not only presents a new fluorescence wavelength shift mechanism for ONOO- sensing but also provides insights into CDs' fluorescence mechanism by exploring their morphology and structure via reacting with reactive oxygen species (ROS).

Development of a hybrid rhodamine-hydrazine NIR fluorescent probe for sensitive detection and imaging of peroxynitrite in necrotizing enterocolitis model

This study describes the synthesis and characterization of a novel near-infrared (NIR) fluorescent probe RBNE based on a hybrid rhodamine dye, which shows excellent optical capability for detecting and imaging ONOO- in necrotizing enterocolitis (NEC) mouse model. The probe RBNE undergoes hydrazine redox-process, and subsequently the spirocyclic structure's opening, resulting in a turn-on fluorescence emission with the presence of ONOO-, which exhibits several excellent features, including a significant Stokes shift of 108 nm, near-infrared emission at 668 nm, a lower detection limit of 56 nM, low cytotoxicity, and excellent imaging ability for ONOO- both in vitro and in vivo. The presented study introduces a novel optical tool that has the potential to significantly advance our understanding of peroxynitrite (ONOO-) behaviors in necrotizing enterocolitis (NEC).

A mitochondria-targeted fluorescent sensor for imaging endogenous peroxynitrite changes in acute lung injury

Acute lung injury (ALI) is a serious pulmonary inflammatory disease resulting from excessive reactive oxygen species (ROS) which could cause the damage of the alveolar epithelial cells and capillary endothelial cells. Peroxynitrite, as one of short-lived reactive oxygen species, is closely related to the process of ALI. Thus, it is important to monitor the fluctuation of peroxynitrite in living system for understanding the process of ALI. Herein, the novel mitochondria-targeted fluorescent probe BHMT was designed to respond to peroxynitrite and pH with distinct fluorescence properties respectively. The absorption spectrum of the probe BHMT exhibited a notable red shift as the pH value declined from 8.8 to 2.6. Upon reaction with peroxynitrite, BHMT had a significant increase of fluorescence intensity (63-fold) with maintaining a detection limit of only 43.7 nM. Furthermore, BHMT could detect the levels of endogenous peroxynitrite and image the intracellular pH in ratiometric channels utilizing cell imaging. In addition, BHMT was successfully applied to revealing the relationship between the peroxynitrite and the extent of ALI. Thus, these results indicated the probe BHMT could be a potential tool for diagnosing the early stage of ALI and revealed the peroxynitrite was likely to be a crucial therapeutic target in ALI treatment.

Hybridized and engineered microbe for catalytic generation of peroxynitrite and cancer immunotherapy under sonopiezo initiation

Living therapeutics is an emerging antitumor modality by living microorganisms capable of selective tropism and effective therapeutics. Nevertheless, primitive microbes could only present limited therapeutic functionalities against tumors. Hybridization of the microbes with multifunctional nanocatalysts is of great significance to achieve enhanced tumor catalytic therapy. In the present work, nitric oxide synthase (NOS)-engineered Escherichia coli strain MG1655 (NOBac) was used to hybridize with the sonopiezocatalytic BaTiO3 nanoparticles (BTO NPs) for efficient tumor-targeted accumulation and antitumor therapy. Under ultrasound irradiation, superoxide anions created by the piezocatalytic reaction of BTO NPs could immediately react with nitric oxide (NO) generated from NOBac to produce highly oxidative peroxynitrite ONOO- species in cascade, resulting in robust tumor piezocatalytic therapeutic efficacy, prompting prominent and sustained antitumoral immunoactivation simultaneously. The present work presents a promising cancer immunotherapy based on the engineered and hybridized microbes for highly selective and sonopiezo-controllable tumor catalytic therapy.

Albumin host for supramolecular fluorescence recognition

Synthetic molecular sensors are crucial for real-time monitoring in biological systems and biotechnological applications, where detecting targets amidst potential interferents is essential. This task is particularly challenging in competitive environments that lacking chemically reactive functional groups, common in agricultural, biological, and environmental contexts. Consequently, scientific efforts have focused on developing sensitive and rapid analytical techniques, with fluorescent sensors emerging as prominent tools. Among these, the albumin-based supramolecular fluorescent indicator displacement assay (AS-FIDA) represents a significant advancement. Our research group has extensively contributed to this field, demonstrating the practical utility of various AS-FIDAs. We pioneered the use of albumin (ALB) as a host molecule in these synthetic chemical sensors, marking a notable advancement. AS-FIDA employs ALB as a versatile host molecule with multiple flexible and asymmetrical binding pockets capable of forming complexes with guest dyes, resulting in ALB@dye ensembles tailored for specific analyte recognition. Recent advancements in AS-FIDA have significantly expanded its applications. This review explores recent advances in ALB-based supramolecular sensors and sensor arrays for detecting biologically and environmentally significant molecules, such as pesticides, hormones, biomarkers, reactive species, mycotoxins, drugs, and carcinogens. The versatility of AS-FIDA positions it as a valuable tool in diverse settings, from laboratory research to practical applications in portable devices, smartphone-assisted on-site monitoring, imaging of living cells, and real sample analysis.

High-Throughput Screening of Antioxidant Drug Candidates from Natural Antioxidants with a "Zero" Intrinsic Fluorescence Peroxynitrite Sensing Precursor

The fluorescence high-throughput screening method is of importance for new antioxidant drug candidate discovery for the treatment of serious hepatorenal syndrome, which displayed an obvious upregulated peroxynitrite level. However, most of the current ONOO- probes possessed incomplete fluorescence quenching efficiency, which can result in non-negligible probe inherent fluorescence. Hence, we utilized the probe conjugated structure disruption strategy to construct hydrogenation phosphorus-substituted rhodamine (H-PRh) with "zero" probe inherent fluorescence character. Based on the precursor, a series of natural products were screened for identifying antioxidant drug candidates. Luteolin was screened out by activating the Sirt1-Nrf2-HO-1 signaling pathway to regulate the accumulation of ONOO- in the hepatorenal syndrome. Overall, the "zero" probe inherent fluorescence ONOO- sensor constructed here applies for a promising and versatile toolbox for illuminating the ONOO--related pathological process in the hepatorenal syndrome. Besides, this strategy of constructing highly sensitive sensors could serve as a valuable reference for further fluorescent probes.

Molecular Logic Gate for Sensing pH/Peroxynitrite with Potential Applications in Cisplatin Treatment

Cisplatin is a common chemotherapy drug for multiple solid tumors; however, due to the nitrification of peroxynitrite (ONOO-), a series of side effects seriously affect its dose and efficacy. Considering that the reactivity of ONOO- is significantly affected by pH in vitro, revealing their roles in living cells contributes to understanding the side-effect process induced by cisplatin. Herein, we present a near-infrared fluorescent logic gate for sensing pH/ONOO-, which can accurately discriminate four scenarios (no analyte, analyte H+ alone, analyte ONOO- alone, and H+ + ONOO-) and which one comes first. With this probe, the significant roles of pH and ONOO- in cisplatin treatment are disclosed, in which the cell account shows a dramatic reduction accompanied by decreased pH and upregulated ONOO- levels. By artificially recovering the pH, the ONOO- content and cell account can maintain a stable state, possibly due to the protection from acidification and nitration. This work provides an ideal pH/ONOO- logical sensor for revealing their potential roles under cisplatin, which is expected to proffer new insights into more related diseases and drug research.

A Carbazole-based Fluorescent Probe with AIE Performance and a Large Stokes Shift for Peroxynitrite Detection and Imaging in Live Cells

A carbazole-based fluorescent probe YCN with AIE performance and a large Stokes shift (242 nm) shift was synthesized by attaching 4-acetonitrile pyridine to the 3-phenylaldehyde butylcarbazole. Its structure was characterized by 1H NMR, 13C NMR and MS. Probe YCN has high selectivity and sensitivity toward ONOO-. The addition of ONOO- to the probe YCN solution results in a noticeable color change from pale yellow to colorless under natural light, and a fluorescent color change from bright orange-yellow to bright yellow-green under a 365 nm UV lamp, which can be distinguished by the naked eye. The research results on the reaction mechanism showed that when YCN reacted with ONOO-, -C = C- was oxidized and broken into -CHO, and the ICT effect was significantly inhibited, resulting in changes in UV absorption and fluorescence emission phenomenon. The recognition mechanism was verified by 1H NMR, mass spectrometry (MS) and density function theory (DFT) calculations. The experiments of live cells imaging suggested that compound YCN can be used as a fluorescent probe for the detection of ONOO- in HeLa cells. This result indicates that YCN has potential application prospects in the biological aspects.

Theoretical insights into a turn-on fluorescence probe based on naphthalimide for peroxynitrite detection

Compared with other reactive oxygen species, peroxynitrite (ONOO-) has diversified reactions and transformations in organisms, and its specific action mechanism is not very clear. The study of reactive oxygen species is of great significance in the field of physiology and pathology. Recently an effective on/off fluorescent probe HCA-OH was designed by Liu et al. through tethering p-aminophenol to 1,8-naphthalimide directly. The probe HCA-OH could release the fluorophore HCA-NH2 with good photostability and high fluorescence quantum yield under oxidation of ONOO- via dearylation process. In this work, the sensing mechanism and spectrum character of probe HCA-OH were studied in detail under quantum chemistry calculation. The electronic structures, reaction sites and fluorescent properties of the probe were theoretically analyzed to benefit us for in-depth understanding the principle of detection on reactive oxygen species (ONOO-) with the fluorescent probe HCA-OH. These theoretical results could inspire the medical research community to design and synthesize highly efficient fluorescent probe for reactive oxygen species detection.

Development of a ratiometric fluorescent probe for the detection of peroxynitrite

Peroxynitrite is one of the important reactive oxygen species in the human body and is closely related to the physiological and pathological processes of many diseases. Therefore, the development of probes to detect peroxynitrite is important for diagnostic and pathologic studies of many diseases. In this work, a ratiometric probe was designed using benzopyran as the recognition site, and the sensitivity and selectivity of the probe were tuned by modification of substituents on benzopyran. Upon reaction with peroxynitrite, the color of the solution changes to the naked eye (from blue to yellow), and the fluorescence changes from red to blue. The probe SJ has the advantages of large Stokes shift (237 nm), fast response (≤10 s), wide linear range, good selectivity, low detection line (21.3 nm), and low cytotoxicity. Probe SJ has been successfully used for bioimaging of endogenous and exogenous peroxynitrite.

Plasma-generated RONS in liquid transferred into cryo-microneedles patch for skin treatment of melanoma

Malignant melanoma is the most lethal form of skin cancer. As a promising anti-cancer agent, plasma-activated water (PAW) rich in reactive oxygen and nitrogen species (RONS) has shown significant potential for melanoma treatment. However, rapid decay of RONS and inefficient delivery of PAW in conventional injection methods limit its practical applications. To address this issue, here we report a new approach for the production of plasma-activated cryo-microneedles (PA-CMNs) patches using custom-designed plasma devices and processes. Our innovation is to incorporate PAW into the PA-CMNs that are fabricated using a fast cryogenic micro-molding method. It is demonstrated that PA-CMNs can be easily inserted into skin to release RONS and slow the decay of RONS thereby prolonging their bioactivity and effectiveness. The new insights into the effective melanoma treatment suggest that the rich mixture of RONS within PA-CMNs prepared by custom-developed hybrid plasma-assisted configuration induces both ferroptosis and apoptosis to selectively kill tumor cells. A significant inhibition of subcutaneous A375 melanoma growth was observed in PA-CMNs-treated tumor-bearing nude mice without any signs of systemic toxicity. The new approach based on PA-CMNs may potentially open new avenues for a broader range of disease treatments.

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

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

Multifunctional fluorescent probe for simultaneous revealing Cys and ONOO- dynamic correlation in the ferroptosis

Ferroptosis is a type of lipid peroxidation-induced apoptosis brought on by imbalances in iron metabolism and redox. It involves both the thiol-associated anti-ferroptosis pathway and the excessive buildup of reactive oxygen species (ROS), which stimulates the ferroptosis pathway. Determining the precise control mechanism of ferroptosis requires examining the dynamic connection between reactive sulfur species (RSS) and ROS. Cysteine (Cys) and peroxynitrite (ONOO-) are highly active redox species in organisms and play dynamic roles in the ferroptosis process. In this study, a coumarin dye was conjugated with specific response sites for Cys and ONOO-, enabling the simultaneous detection of Cys and ONOO- through the green and red fluorescence channels, respectively (λem = 498 nm for Cys and λem = 565 nm for ONOO-). Using the probe LXB, we monitored the changes in Cys and ONOO- levels in the ferroptosis pathway induced by erastin. The results demonstrate a significant generation of ONOO- and a noticeable decrease in intracellular Cys levels at the beginning upon erastin treatment and finally maintains a relatively low level. This study presents the first probe to investigate the intracellular redox modulation and control between Cys and ONOO- during ferroptosis, providing valuable insights into the potential mutual correlation between Cys and ONOO- in this process.

Mitochondria-Targetable Near-Infrared Fluorescent Probe for Visualization of Hydrogen Peroxide in Lung Injury, Liver Injury, and Tumor Models

Hydrogen peroxide (H2O2) overexpressed in mitochondria has been regarded as a key biomarker in the pathological processes of various diseases. However, there is currently a lack of suitable mitochondria-targetable near-infrared (NIR) probes for the visualization of H2O2 in multiple diseases, such as PM2.5 exposure-induced lung injury, hepatic ischemia-reperfusion injury (HIRI), nonalcoholic fatty liver (NAFL), hepatic fibrosis (HF), and malignant tumor tissues containing clinical cancer patient samples. Herein, we conceived a novel NIR fluorescent probe (HCy-H2O2) by introducing pentafluorobenzenesulfonyl as a H2O2 sensing unit into the NIR hemicyanine platform. HCy-H2O2 exhibits good sensitivity and selectivity toward H2O2, accompanied by a remarkable "turn-on" fluorescence signal at 720 nm. Meanwhile, HCy-H2O2 has stable mitochondria-targetable ability and permits monitoring of the up-generated H2O2 level during mitophagy. Furthermore, using HCy-H2O2, we have successfully observed an overproduced mitochondrial H2O2 in ambient PM2.5 exposure-induced lung injury, HIRI, NAFL, and HF models through NIR fluorescence imaging. Significantly, the visualization of H2O2 has been achieved in both tumor-bear mice as well as surgical specimens of cancer patients, making HCy-H2O2 a promising tool for cancer diagnosis and imaging-guided surgery.

Visualizing the crucial roles of plasma membrane and peroxynitrite during abdominal aortic aneurysm using two-photon fluorescence imaging

Peroxynitrite (ONOO-) and cell plasma membrane (CPM) are two key factors in cell pyroptosis during the progression of abdominal aortic aneurysm (AAA). However, their combined temporal and spatial roles in initiating AAA pathogenesis remain unclear. Herein, we developed a two-photon fluorescence probe, BH-Vis, enabling real-time dynamic detection of CPM and ONOO- changes, and revealing their interplay in AAA. BH-Vis precisely targets CPM with reduced red fluorescence intensity correlating with diminished CPM tension. Concurrently, a blue shift of the fluorescence signal of BH-Vis occurs in response to ONOO- offering a reliable ratiometric detection mode with enhanced accuracy by minimizing external testing variables. More importantly, two photon confocal imaging with palmitic acid (PA) and ganglioside (GM1) manipulation, which modulating cell pyroptosis, showcases reliable fluorescence fluctuations. This groundbreaking application of BH-Vis in a mouse AAA model demonstrates its significant potential for accurately identifying cell pyroptosis levels during AAA development.

An AIE-based fluorescent probe to detect peroxynitrite levels in human serum and its cellular imaging

An AIE-based fluorescent probe was designed to evaluate peroxynitrite levels in complex biological samples. The newly synthesized hydrazone-conjugated probe fluoresces strongly in the presence of peroxynitrite. Clinically, the peroxynitrite levels can be measured in human serum and cellular mitochondria with an LOD of 6.5 nM by fluorescence imaging in vitro.

Accelerated Activity-Based Sensing by Fluorogenic Reporter Engineering Enables to Rapidly Determine Unstable Analyte

Accurate detection of labile analytes through activity based fluorogenic sensing is meaningful but remains a challenge because of nonrapid reaction kinetic. Herein, we present a signaling reporter engineering strategy to accelerate azoreduction reaction by positively charged fluorophore promoted unstable anion recognition for rapidly sensing sodium dithionite (Na2S2O4), a kind of widespread used but harmful inorganic reducing agent. Its quick decomposition often impedes application reliability of traditional fluorogenic probes in real samples because of their slow responses. In this work, four azo-based probes with different charged fluorophores (positive, zwitterionic, neutral, and negative) were synthesized and compared. Among of them, with sequestration effect of positively charged anthocyanin fluorophore for dithionite anion via electrostatic attraction, the cationic probe Azo-Pos displayed ultrafast fluorogenic response (∼2 s) with the fastest response kinetic (kpos' = 0.373 s-1) that is better than other charged ones (kzwi' = 0.031 s-1, kneu' = 0.013 s-1, kneg' = 0.003 s-1). Azo-Pos was demonstrated to be capable to directly detect labile Na2S2O4 in food samples and visualize the presence of Na2S2O4 in living systems in a timely fashion. This new probe has potential as a robust tool to fluorescently monitor excessive food additives and biological invasion of harmful Na2S2O4. Moreover, our proposed accelerating strategy would be versatile to develop more activity-based sensing probes for quickly detecting other unstable analytes of interest.

A highly sensitive and selective chemiluminescent probe for peroxynitrite detection in vitro, in vivo and in human liver cancer tissue

Peroxynitrite (ONOO-) is one of the important active nitrogen/reactive oxygen species that plays various roles in biological processes, such as inducing apoptosis and necrosis. Recent studies have shown that a significant increases in ONOO- content during tumor development, which is closely related to the level of oxidative stress within the tumor. It has been found that herbicide paraquat (PQ) can significantly increase the level of ONOO- in cells. Therefore, accurate monitoring abnormal changes in ONOO- caused by environmental hazardous materials and tumors is helpful in promoting the diagnosis and treatment of oxidative stress diseases (tumors), evenly environmental detection. Currently, traditional fluorescent probes for ONOO- detection have background interference. To address this, we developed a chemiluminescent probe (CL-1) and a fluorescent probe (Flu-1), using diphenyl phosphonate as a recognition group. CL-1 shows extremely sensitivity (9.8 nM), a high signal-to-noise(S/N) ratio (502), and excellent bioimaging capabilities compared to fluorescent probe (Flu-1). We have successfully used CL-1 to detect ONOO- produced by PQ stimulated cells, as well as endogenous ONOO- in tumor cells, mice, and human liver cancer tissues. Therefore, CL-1 can not only be a valuable tool for visualizing tumor and studying the role of ONOO- in tumor pathology, but the probe has the potential to be a powerful molecular imaging tool for exploring the complex biological role of ONOO- in a variety of biological Settings.

Shedding light on ONOO- detection: the emergence of a fast-response fluorescent probe for biological systems

ONOO-, a bioactive molecule, plays a critical role in inflammation-related signaling pathways and pathological mechanisms. Numerous studies have established a direct correlation between elevated ONOO- levels and tumor progression. Therefore, investigating ONOO- levels in inflammation and tumors is of utmost importance. Fluorescence imaging presents a highly sensitive, non-invasive, easily operable, selective, and efficient method for ONOO- detection in situ. In this study, we designed and synthesized a rhodamine-based probe, NRho, which effectively identifies tumors, inflammatory cells, tissues, and organs by detecting ONOO- content. The synthesis process of NRho is simple, yielding a probe with favorable spectral characteristics and rapid response. Our cell imaging analysis has provided novel insights, revealing distinct ONOO- levels among different types of cancer cells, with hepatocellular carcinoma cells exhibiting higher ONOO- content than the others. This observation marks the proposal of such variations in ONOO- levels across cancer cell types. Furthermore, our study has showcased the practicality of our probe in live organ imaging, enabling the identification of tumors from living organs within a brief 5-minute incubation period. Additionally, our findings highlight the rapid detection capability of the probe NRho in various tissue samples, effectively identifying inflammation. This research holds important promise in advancing biomedical research and clinical diagnosis.

A Fluorescent Probe with Zwitterionic ESIPT Feature for Ratiometric Monitoring of Peroxynitrite In Vitro and In Vivo

Peroxynitrite (ONOO-), as a short-term reactive biological oxidant, could lead to a series of effects in various physiological and pathological processes due to its subtle concentration changes. In vivo monitoring of ONOO- and relevant physiological processes is urgently required. Herein, we describe a novel fluorescent probe termed HBT-Fl-BnB for the ratiometric detection of ONOO- in vitro and in vivo. The probe consists of an HBT core with Fl groups at the ortho and para positions responding to the zwitterionic excited-state intramolecular proton-transfer (zwitterionic ESIPT) process and a boronic acid pinacol ester with dual roles that block the zwitterionic ESIPT and recognize ONOO-. Thanks to the specificity as well as low cytotoxicity, success in imaging of endogenous and exogenous ONOO- in living cells by HBT-Fl-BnB was obtained. Additionally, the applicability of HBT-Fl-BnB to tracking the abnormal expression of ONOO- in vivo induced by inactivated Escherichia coli was also explored. This is the first report of a fluorescent probe for ONOO- sensing via a zwitterionic ESIPT mechanism.

High Contrast Bioimaging of Tumor and Inflammation with a Bicyclic Dioxetane Chemiluminescent Probe

The link between inflammation and the evolution of cancer is well established. Visualizing and tracking both tumor proliferation and the associated inflammatory response within a living organism are vital for dissecting the nexus between these two processes and for crafting precise treatment modalities. We report the creation and synthesis of an advanced NIR chemiluminescence probe that stands out for its exceptional selectivity, extraordinary sensitivity at nanomolar concentrations, swift detection capabilities, and broad application prospects. Crucially, this probe has been successfully utilized to image endogenous ONOO- across different inflammation models, including abdominal inflammation triggered by LPS, subcutaneous inflammatory conditions, and tumors grafted onto mice. These findings highlight the significant promise of chemiluminescence imaging in enhancing our grasp of the intricate interplay between cancer and inflammation and in steering the development of potent, targeted therapeutic strategies.

Mitochondria-targetable small molecule fluorescent probes for the detection of cancer-associated biomarkers: A review

Cancer represents a global threat to human health, and effective strategies for improved cancer early diagnosis and treatment are urgently needed. The detection of tumor biomarkers has been one of the important auxiliary means for tumor screening and diagnosis. Mitochondria are crucial subcellular organelles that produce most chemical energy used by cells, control metabolic processes, and maintain cell function. Evidence suggests the close involvement of mitochondria with cancer development. As a consequence, the identification of cancer-associated biomarker expression levels in mitochondria holds significant importance in the diagnosis of early-stage diseases and the monitoring of therapy efficacy. Small-molecule fluorescent probes are effective for the identification and visualization of bioactive entities within biological systems, owing to their heightened sensitivity, expeditious non-invasive analysis and real-time detection capacities. The design principles and sensing mechanisms of mitochondrial targeted fluorescent probes are summarized in this review. Additionally, the biomedical applications of these probes for detecting cancer-associated biomarkers are highlighted. The limitations and challenges of fluorescent probes in vivo are also considered and some future perspectives are provided. This review is expected to provide valuable insights for the future development of novel fluorescent probes for clinical imaging, thereby contributing to the advancement of cancer diagnosis and treatment.

Design a dual-response two-photon fluorescent probe for simultaneous imaging of mitochondrial viscosity and peroxynitrite in a thrombosis model

BACKGROUND

Venous thromboembolism is a sudden cardiovascular disease that can lead to death, and its pathologic development is closely related to vascular viscosity and inflammation. However, direct evidence from in vivo is really scarce. The key limitation is that the combined probes cannot detect multiple markers simultaneously, which may lead to unreliable results. Therefore, to develop a single probe that can simultaneously monitor the variations of viscosity in the vascular microenvironment as well as inflammation level during venous thrombosis.

RESULTS

A dual-responsive two-photon fluorescent probe, Cou-ONOO, was designed and synthesized. Cou-ONOO provides a visualization tool for monitoring the viscosity of the vascular as well as the inflammatory marker ONOO‾ during thromboembolism via dual-channel simultaneous imaging. As a single probe that can recognize dual targets, Cou-ONOO effectively avoids the problems from unreliable results caused by complex synthesis and differences in intracellular localization, diffusion, and metabolism of different dyes as using combinatorial probes. Using Cou-ONOO, simultaneous imaging the variations of viscosity and ONOO‾at the cellular and tissue levels was successfully performed. In addition, Cou-ONOO also successfully visualized and tracked the viscosity of the vascular microenvironment and ONOO‾ during venous embolism in mice.

SIGNIFICANCE

Experimental results show that both viscosity and inflammation are abnormally overexpressed in the microenvironment at the thrombus site during venous thrombosis. An intuitive visualization tool to elucidate the variations of viscosity as well as inflammation level in the vascular microenvironment during thrombosis was provided, which will facilitate a better clinical understanding of the pathological process of thrombosis.

Engineering an activatable fluorescent probe for studying ONOO- in pyroptotic process

Pyroptosis, a recently discovered form of programmed cell death, plays a pivotal role in oncological treatment. Howbeit, the mechanisms underlying pyroptosis in tumor treatment remain unclear. Previous research has demonstrated that the occurrence of pyroptosis generally accompanies a surge of reactive oxygen species (ROS) generation, with ONOO- being one of these ROS and closely linked to numerous diseases. Therefore, it is imperative to investigate the potential association between ONOO- and pyroptosis. Herein, a highly sensitive and rapidly responsive near-infrared (NIR) probe, Rd700-PN, is fabricated for exploring unrevealed relationships between ONOO- and pyroptosis. We successfully harness Rd700-PN to detect ONOO- fluctuation during cellular pyroptosis for the first time. Furthermore, the results demonstrate that Rd700-PN can scout the chemotherapeutic drug's induction ability of tumor pyroptosis in vivo. Notably, this study provides an excellent means to shed light on the correlation between ONOO- and pyroptosis and to screen antitumor drugs activating pyroptosis.

De Novo Design of Near-Infrared Fluorescent Agents Activated by Peroxynitrite and Glutathione-Responsive Imaging for Diabetic Liver Disease

Diabetes and its complications, such as diabetes liver disease, is a major problem puzzling people's health. The detection of redox states in its pathological process can effectively help us gain a deeper understanding of the disease. The pair of oxidation-reduction substances peroxynitrite (ONOO- ) and glutathione (GSH) is considered to be closely related to their occurrence and development. Thus, direct visualization of ONOO- and GSH in diabetes liver disease is critical to evaluate the disease at the molecular level. Herein, two activatable agents NTCF-ONOO- and NTCF-GSH are prepared for selectively detecting ONOO- and GSH through protection and deprotection strategies based on hydroxyl and amino groups of near-infrared fluorophore. Fluorescence imaging of exogenous and endogenous ONOO- and GSH changes in living cells and in vivo is observed. The ONOO- and GSH level in the diabetes liver disease cellular model are visualized and the possible redox imbalance mechanism related to the oxidized (NAD+ ) and reduced (NADH) nicotinamide adenine dinucleotides is explored in this process. Moreover, these probes can sensitively recognize ONOO- and GSH in the process of oxidative stress resulting from streptozotocin and streptozotocin/acetaminophen-induced complex diabetic liver disease in vivo. In addition, they can be applied for monitoring the clinical serum sample related with diabetic patients.

Photo-Triggered Cascade Therapy: A NIR-II AIE Luminogen Collaborating with Nitric Oxide Facilitates Efficient Collagen Depletion for Boosting Pancreatic Cancer Phototheranostics

The dense extracellular matrix (ECM) in the pancreatic cancer severely hampers the penetration of nanodrugs, which causes inferior therapeutic efficacy. To address this issue, a multifunctional liposome, namely, Lip-DTI/NO, integrating a type-I photosensitizer DTITBT with glutathione (GSH) or heat-responsive nitric oxide (NO) donor S-nitroso-N-acetyl-D-penicillamine (SNAP) is constructed to deplete the tumor ECM, leading to enhanced drug delivery and consequently improved phototherapy. The loaded DTITBT possesses multiple functions including NIR-II fluorescence imaging, efficient superoxide radical (O2 •- ) generation and excellent photothermal conversion efficiency, making it feasible for precisely pinpointing the tumor in the phototherapy process. Responding to the intracellular overexpressed glutathione or heat produced by photothermal effect of DTITBT, NO can be released from SNAP. Upon 808 nm laser irradiation, Lip-DTI/NO could selectively induce in situ generation of peroxynitrite anion (ONOO- ) in tumor after cascade processes including O2 •- production, GSH or heat-triggered NO release, and rapid reaction between O2 •- and NO. The generated ONOO- could activate the expression of endogenous matrix metalloproteinases which could efficiently digest collagen of tumor ECM, thus facilitating enhanced penetration and accumulation of Lip-DTI/NO in tumor. In vivo evaluation demonstrates the notable therapeutic efficacy via ONOO- -potentiated synergistic photodynamic-photothermal therapies on both subcutaneous and orthotopic pancreatic cancer model.

FRET Luminescent Probe for the Ratiometric Imaging of Peroxynitrite in Rat Brain Models of Epilepsy-Based on Organic Dye-Conjugated Iridium(III) Complex

Epilepsy is a chronic neurological disorder characterized by recurrent seizures globally, imposing a substantial burden on patients and their families. The pathological role of peroxynitrite (ONOO-), which can trigger oxidative stress, inflammation, and neuronal hyperexcitability, is critical in epilepsy. However, the development of reliable, in situ, and real-time optical imaging tools to detect ONOO- in the brain encounters some challenges related to the depth of tissue penetration, background interference, optical bleaching, and spectral overlapping. To address these limitations, we present Ir-CBM, a new one-photon and two-photon excitable and long-lived ratiometric luminescent probe designed specifically for precise detection of ONOO- in epilepsy-based on the Förster resonance energy transfer mechanism by combining an iridium(III) complex with an organic fluorophore. Ir-CBM possesses the advantages of rapid response, one-/two-photon excitation, and ratiometric luminescent imaging for monitoring the cellular levels of ONOO- and evaluating the effects of different therapeutic drugs on ONOO- in the brain of an epilepsy model rat. The development and utilization of Ir-CBM offer valuable insights into the design of ratiometric luminescent probes. Furthermore, Ir-CBM serves as a rapid imaging and screening tool for antiepileptic drugs, thereby accelerating the exploration of novel antiepileptic drug screening and improving preventive and therapeutic strategies in epilepsy research.

Direct assessment of nitrative stress in lipid environments: Applications of a designer lipid-based biosensor for peroxynitrite

Lipid membranes and lipid-rich organelles are targets of peroxynitrite (ONOO-), a highly reactive species generated under nitrative stress. We report a membrane-localized phospholipid (DPPC-TC-ONOO-) that allows the detection of ONOO- in diverse lipid environments: biomimetic vesicles, mammalian cell compartments, and within the lung lining. DPPC-TC-ONOO- and POPC self-assemble to membrane vesicles that fluorogenically and selectively respond to ONOO-. DPPC-TC-ONOO-, delivered through lipid nanoparticles, allowed for ONOO- detection in the endoplasmic reticulum upon cytokine-induced nitrative stress in live mammalian cells. It also responded to ONOO- within lung tissue murine models upon acute lung injury. We observed nitrative stress around bronchioles in precision cut lung slices exposed to nitrogen mustard and in pulmonary macrophages following intratracheal bleomycin challenge. Results showed that DPPC-TC-ONOO- functions specifically toward iNOS, a key enzyme modulating nitrative stress, and offers significant advantages over its hydrophilic analog in terms of localization and signal generation.

A Small-Molecule Fluorescent Probe for the Detection of Mitochondrial Peroxynitrite

Reactive oxygen species (ROS) are pivotal signaling molecules that control a variety of physiological functions. As a member of the ROS family, peroxynitrite (ONOO-) possesses strong oxidation and nitrification abilities. Abnormally elevated levels of ONOO- can lead to cellular oxidative stress, which may cause several diseases. In this work, based on the rhodamine fluorophore, we designed and synthesized a novel small-molecule fluorescent probe (DH-1) for ONOO-. Upon reaction with ONOO-, DH-1 exhibited a significant fluorescence signal enhancement (approximately 34-fold). Moreover, DH-1 showed an excellent mitochondria-targeting capability. Confocal fluorescence imaging validated its ability to detect ONOO- changes in HeLa and RAW264.7 cells. Notably, we observed the ONOO- generation during the ferroptosis process by taking advantage of the probe. DH-1 displayed good biocompatibility, facile synthesis, and high selectivity, and may have potential applications in the study of ONOO--associated diseases in biosystems.

A near-infrared fluorescent probe with remarkably large stokes shift for specifical imaging of peroxynitrite fluctuations in Hela cells

Peroxynitrite (ONOO-), an endogenous reactive nitrogen species, plays an important role in maintaining intracellular homeostasis. Abnormal levels of ONOO- in cells could cause protein oxidation which is confirmed that related with Alzheimer's diseases, so accurate monitoring of ONOO- in cells is crucial. Herein, a novel fluorescent probe (XPC) based on dicyanomethylene-4H-benzothiopyran was developed by regulating its intramolecular charge transfer (ICT) effect to detect ONOO-. Once reaction with ONOO-, the fluorescence of XPC was turned on and the emission wavelength could reach up to 750 nm. Furthermore, XPC exhibited satisfactory performances for ONOO- such as large Stokes shift (200 nm), good sensitivity (Limit of detection = 13 nM), high selectivity to ONOO- over other a reactive nitrogen species (RNS)/reactive oxygen species (ROS). More importantly, XPC was successfully applied for monitoring the fluctuations of ONOO- in living cells.

A perylenemonoimide-based fluorescent probe: ultrasensitive and selective tracing of endogenous peroxynitrite in living cells

Peroxynitrite (ONOO-), a highly reactive species, plays a key role in various physiological and pathological processes. Herein, a red-emitting fluorescent reporter perylenemonoimide-boronate ester (PMI-BE) was synthesized and utilized for ultrasensitive detection of ONOO-. The unique feature of PMI-BE is its nanomolar sensitivity with high selectivity towards ONOO-. Moreover, PMI-BE also detects endogenously generated ONOO- in live cells.

Multi-engineered Graphene Extended-Gate Field-Effect Transistor for Peroxynitrite Sensing in Alzheimer's Disease

The expression of β-amyloid peptides (Aβ), a pathological indicator of Alzheimer's disease (AD), was reported to be inapparent in the early stage of AD. While peroxynitrite (ONOO-) is produced excessively and emerges earlier than Aβ plaques in the progression of AD, it is thus significant to sensitively detect ONOO- for early diagnosis of AD and its pathological research. Herein, we unveiled an integrated sensor for monitoring ONOO-, which consisted of a commercially available field-effect transistor (FET) and a high-performance multi-engineered graphene extended-gate (EG) electrode. In the configuration of the presented EG electrode, laser-induced graphene (LIG) intercalated with MnO2 nanoparticles (MnO2/LIG) can improve the electrical properties of LIG and the sensitivity of the sensor, and graphene oxide (GO)-MnO2/Hemin nanozyme with ONOO- isomerase activity can selectively trigger the isomerization of ONOO- to NO3-. With this synergistic effect, our EG-FET sensor can respond to the ONOO- with high sensitivity and selectivity. Moreover, taking advantage of our EG-FET sensor, we modularly assembled a portable sensing platform for wireless tracking ONOO- levels in the brain tissue of AD transgenic mice at earlier stages before massive Aβ plaques appeared, and we systematically explored the complex role of ONOO- in the occurrence and development of AD.

Precise Spatiotemporal Identification of Mitochondrial H2S Fluctuations through Exploiting an On-Demand Photoactivated Probe

Various signal molecules participate in complex biological processes in mitochondria. However, most currently available probes have problems in elucidating the functions of these active species in mitochondria due to the inability to light up these probes exclusively at the desired mitochondrial location, thereby compromising the specificity and accuracy. In this study, we present an on-demand photoactivation approach to the molecular design of optimized probes for precise spatiotemporal identification of mitochondrial H2S fluctuations. The designed probe with native yellow fluorescence can monitor the process into mitochondria but maintains nonfluorescent response to H2S during cellular delivery, providing the accurate timing of accumulation in mitochondria. On-demand photoactivation exclusively at the desired mitochondrial location affords a significant aggregation-enhanced and emissive response to H2S with lighting up red fluorescence at 690 nm, which is the only way to get such an emissive phenomenon and greatly improves the specificity and accuracy of targeting mitochondrial H2S. By using this photocontrolled fluorescence responsiveness to H2S, precise spatiotemporal identification of mitochondrial H2S fluctuations is successfully performed. Our work could facilitate advances toward interrogating the physiological and pathological consequences of mitochondrial H2S in various biological events.

Recent progress in the development of small-molecule double-locked logic gate fluorescence probes

Various bioactive substances are simultaneously involved in physiological processes, and research on the synergistic effect of them can promote the study of pathological mechanisms. To achieve this purpose, several small-molecule double-locked logic gate fluorescence probes have been developed recently. They overcome many shortcomings of the traditional "single-signal" fluorescent probes, with fluorescence that can be activated by two analytes of interest order-independently or order-dependently with one output. In this review, we summarize recently published small-molecule double-locked logic gate probes for the optical detection of two bioactive substances in living systems. We envision that this review will attract significant attention from researchers to exploit more powerful functional double-locked logic gate probes.

A large Stokes shift NIR fluorescent probe for visual monitoring of mitochondrial peroxynitrite during inflammation and ferroptosis and in an Alzheimer's disease model

The excessive formation of peroxynitrite (ONOO-) in mitochondria has been implicated in various pathophysiological processes and diseases. However, owing to short emission wavelengths and small Stokes shifts, previously reported fluorescent probes pose significant challenges for mitochondrial ONOO- imaging in biological systems. In this study, a near-infrared (NIR) fluorescent probe, denoted as DCO-POT, is designed for the visual monitoring of mitochondrial ONOO-, displaying a remarkable Stokes shift of 170 nm. The NIR fluorophore of DCO-CHO is released by DCO-POT upon the addition of ONOO-, resulting in off-on NIR fluorescence at 670 nm. This phenomenon facilitates the high-resolution confocal laser scanning imaging of ONOO- generated in biological systems. The practical applications of DCO-POT as an efficient fluorescence imaging tool are verified in this study. DCO-POT enables the fluorometric visualization of ONOO- in organelles, cells, and organisms. In particular, ONOO- generation is analyzed during cellular and organism-level (zebrafish) inflammation during ferroptosis and in an Alzheimer's disease mouse model. The excellent visual monitoring performance of DCO-POT in vivo makes it a promising tool for exploring the pathophysiological effects of ONOO-.

Recent Progress of Spectroscopic Probes for Peroxynitrite and Their Potential Medical Diagnostic Applications

Peroxynitrite (ONOO-) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases.

Activatable fluorescent probes for imaging and diagnosis of rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease that is primarily manifested as synovitis and polyarticular opacity and typically leads to serious joint damage and irreversible disability, thus adversely affecting locomotion ability and life quality. Consequently, good prognosis heavily relies on the early diagnosis and effective therapeutic monitoring of RA. Activatable fluorescent probes play vital roles in the detection and imaging of biomarkers for disease diagnosis and in vivo imaging. Herein, we review the fluorescent probes developed for the detection and imaging of RA biomarkers, namely reactive oxygen/nitrogen species (hypochlorous acid, peroxynitrite, hydroxyl radical, nitroxyl), pH, and cysteine, and address the related challenges and prospects to inspire the design of novel fluorescent probes and the improvement of their performance in RA studies.

Bioimaging of glutathione variation for early diagnosis of hepatocellular carcinoma using a liver-targeting ratiometric near-infrared fluorescent probe

Reliable biomarkers are crucial for early diagnosis of diseases and precise therapy. Biological thiols (represented by glutathione, GSH) play vital roles in the antioxidant defense system for maintaining intracellular redox homeostasis in organisms. However, the aberrant variation in the cellular concentration of GSH correlates with diverse diseases including cancer. Here, a ratiometric near-infrared fluorescent probe CyO-Disu is constructed for the specific sensing of GSH variation in live cells and mice models of hepatic carcinoma (HCC). CyO-Disu features three key elements, a response moiety of bis(2-hydroxyethyl) disulfide, a near-infrared fluorescence signal transducer of heptamethine ketone cyanine, and a targeting moiety of D-galactose. By virtue of its liver-targeting capability, CyO-Disu was utilized for evaluating GSH fluctuations in primary and metastatic hepatoma living cells. To evaluate the efficacy of CyO-Disuin vivo, orthotopic HCC and pulmonary metastatic hepatoma mice models were employed for GSH imaging using two-dimensional and three-dimensional fluorescence molecular tomographic imaging systems. The bioimaging results offered direct evidence that GSH displayed varied concentrations during the progression of HCC. Therefore, the as-synthesized probe CyO-Disu could serve as a potential powerful tool for the early diagnosis and precise treatment of HCC using GSH as a reliable biomarker.

Evaluation of peroxynitrite fluxes in inflammatory mice with a ratiometric fluorescence probe

Inflammation is a critical physiological process in the human body, which is closely related to numerous disorders and cancers. ONOO^- is generated and functionalized in the inflamed process, but the roles of ONOO^- are still blurred. To illuminate the roles of ONOO^-, we fabricated an intramolecular charge transfer (ICT)-based fluorescence probe, HDM-Cl-PN, for the ratiometric determination of ONOO^- in the inflamed mouse model. The probe displayed a gradual fluorescence increase at 676 nm and a fluorescence drop at 590 nm toward 0-10.5 μM ONOO^-, and the ratio of 676 nm fluorescence and 590 nm fluorescence varied from 0.7 to 24.7. The significantly changed ratio and favorable selectivity ensure the sensitive detection of subtle changes in cellular ONOO^-. Thanks to the excellent sensing performance, HDM-Cl-PNin vivo ratiometrically visualized ONOO^- fluctuations in the LPS-triggered inflammatory process. Overall, this work not only expatiated the rational design for a ratiometric ONOO^- probe but also built a bridge to investigate the connections between ONOO^- and inflammation in living mice.

THQ-Xanthene: An Emerging Strategy to Create Next-Generation NIR-I/II Fluorophores

Near-infrared fluorescence imaging is vital for exploring the biological world. The short emissions (<650 nm) and small Stokes shifts (<30 nm) of current xanthene dyes obstruct their biological applications since a long time. Recently, a potent and universal THQ structural modification technique that shifts emission to the NIR-I/II range and enables a substantial Stokes shift (>100 nm) for THQ-modified xanthene dyes is established. Thus, a timely discussion of THQ-xanthene and its applications is extensive. Hence, the advent, working principles, development trajectory, and biological applications of THQ-xanthene dyes, especially in the fields of fluorescence probe-based sensing and imaging, cancer theranostics, and super-resolution imaging, are introduced. It is envisioned that the THQ modification tactic is a simple yet exceptional approach to upgrade the performance of conventional xanthene dyes. THQ-xanthene will advance the strides of xanthene-based potentials in early fluorescent diagnosis of diseases, cancer theranostics, and imaging-guided surgery.

Fluorescent Detection of Peroxynitrite Produced by Myeloid-Derived Suppressor Cells in Cancer and Inhibition by Dasatinib

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells that expand dramatically in many cancer patients. This expansion contributes to immunosuppression in cancer and reduces the efficacy of immune-based cancer therapies. One mechanism of immunosuppression mediated by MDSCs involves production of the reactive nitrogen species peroxynitrite (PNT), where this strong oxidant inactivates immune effector cells through destructive nitration of tyrosine residues in immune signal transduction pathways. As an alternative to analysis of nitrotyrosines indirectly generated by PNT, we used an endoplasmic reticulum (ER)-targeted fluorescent sensor termed PS3 that allows direct detection of PNT produced by MDSCs. When the MDSC-like cell line MSC2 and primary MDSCs from mice and humans were treated with PS3 and antibody-opsonized TentaGel microspheres, phagocytosis of these beads led to production of PNT and generation of a highly fluorescent product. Using this method, we show that splenocytes from a EMT6 mouse model of cancer, but not normal control mice, produce high levels of PNT due to elevated numbers of granulocytic (PMN) MDSCs. Similarly, peripheral blood mononuclear cells (PBMCs) isolated from blood of human melanoma patients produced substantially higher levels of PNT than healthy human volunteers, coincident with higher peripheral MDSC levels. The kinase inhibitor dasatinib was found to potently block the production of PNT both by inhibiting phagocytosis in vitro and by reducing the number of granulocytic MDSCs in mice in vivo, providing a chemical tool to modulate the production of this reactive nitrogen species (RNS) in the tumor microenvironment.