Activatable Probes Research Articles

Rational Design of an Activatable Near-Infrared Fluorogenic Platform for In Vivo Orthotopic Tumor Imaging and Resection.

Rational and effective design of a universal near-infrared (NIR) light-absorbed platform employed to prepare diverse activatable NIR fluorogenic probes for in vivo imaging and the imaging-guided tumor resection remains less exploited but highly meaningful. Herein, mandelic acid with a core structure of 4-hydroxylbenzyl alcohol to link recognition unit, a fluorophore and a quencher was employed to prepare activatable probes. We exemplified ester as carboxylesterase (CE)-recognized unit, ferrocene as quencher and phenothiazinium as NIR fluorophore to afford fluorogenic probes termed NBS-Fe-CE and NBS-C-Fe-CE. These probes enabled the conversion toward CE with significant fluorescence increases and successfully discriminate CE activity in cells. NIR light enhances the tumor penetration and enable imaging-guided orthotopic tumor resection. This specific case demonstrated that this platform can be effectively used to construct diverse NIR probes for imaging analytes in biological systems.

Rational Design of an Activatable Near‐Infrared Fluorogenic Platform for In Vivo Orthotopic Tumor Imaging and Resection

Rational and effective design of a universal near‐infrared (NIR) light‐absorbed platform employed to prepare diverse activatable NIR fluorogenic probes for in vivo imaging and the imaging‐guided tumor resection remains less exploited but highly meaningful. Herein, mandelic acid with a core structure of 4‐hydroxylbenzyl alcohol to link recognition unit, a fluorophore and a quencher was employed to prepare activatable probes. We exemplified ester as carboxylesterase (CE)‐recognized unit, ferrocene as quencher and phenothiazinium as NIR fluorophore to afford fluorogenic probes termed NBS‐Fe‐CE and NBS‐C‐Fe‐CE. These probes enabled the conversion toward CE with significant fluorescence increases and successfully discriminate CE activity in cells. NIR light enhances the tumor penetration and enable imaging‐guided orthotopic tumor resection. This specific case demonstrated that this platform can be effectively used to construct diverse NIR probes for imaging analytes in biological systems.

A mitochondria-targeted nitric oxide probe with large Stokes shift for real-time imaging and evaluation of inflammatory bowel disease in situ

BackgroundInflammatory bowel disease (IBD) is a prevalent inflammatory disorder, and the abnormal expression of nitric oxide (NO) produced by biocatalysis of iNOS enzyme in mitochondria is directly associated with the occurrence and progression of IBD. Activatable fluorescent probes offer promising tools for early diagnosis of IBD, however, inadequate biodistribution and limited targeting properties of these probes in vivo severely impede accurate diagnosis of IBD and real-time evaluation of inflammatory levels in situ. Therefore, it is necessary to designed a highly efficient fluorescent probe towards NO to overcome inadequate biodistribution and achieve accurate diagnosis and evaluation of IBD in situ. ResultsWe designed a highly efficient mitochondria-targeted “turn-on” NIR fluorescent probe Cy-OMe which has excellent targeting properties and imaging ability. The response mechanism is probe Cy-OMe rapidly undergoes N-nitrosation reaction resulting in turn-on NIR fluorescence signal when exposed to NO. Cy-OMe exhibits high sensitivity and specificity in detecting NO content in vitro, owing to its large Stokes shift. Furthermore, the probe Cy-OMe not only efficiently targets mitochondria but also enables precise assessment of fluctuations in endogenous NO concertation across various cell types. Importantly, by virtue of large Stokes shift and excellent mitochondrial targeting ability, Cy-OMe has the capability to specifically evaluate dynamic fluctuations of NO in lipopolysaccharide (LPS)‐stimulated IBD mouse models in situ and Cy-OMe was achieved high-contrast imaging and precision diagnosis of intestinal inflammation diseases. SignificanceCy-OMe can accurately assess fluctuations in NO levels and show high signal fidelity in the diseased intestine region, which has prospects in the non-invasive diagnosis of intestinal inflammation in vivo. At the same time, it is expected to serve as a potential diagnose platform for investigating the physiological processes underlying NO-related inflammatory diseases and promoting understanding of the pathological functions of NO across diverse inflammatory diseases.

A Cascade Activation Probe with Double-Enhanced Near-Infrared Imaging for Monitoring Peroxynitrite Fluctuations in Vivo.

Monitoring peroxynitrite (ONOO-) fluctuations is particularly important for assessing pathological progression and oxidative damage due to their crucial role in maintaining the redox balance of organisms. However, due to the lack of efficient tools for differentially monitoring ONOO- fluctuations at different concentration ranges in vivo, the precise detection of endogenous ONOO- fluctuations under pathological conditions in living systems remains challenging. Herein, we rationally designed a double-enhanced emission cascade activatable near-infrared (NIR) fluorescent probe (B-TCF) for the measurement of ONOO-, which consists of a borate ester response group and a malononitrile hemicyanine fluorophore. Especially, after sequential oxidative hydrolysis of the borate ester group and xanthene skeleton, B-TCF exhibited a sequentially double-enhanced NIR emission response at 776 and 625 nm for different ONOO- concentration ranges. Moreover, B-TCF revealed excellent and promising performance for ONOO- in terms of high selectivity, sensitivity, and reaction rate (k = 28.2 M-1 s-1). Motivated by the two-step emission signal enhancement and large wavelength shift in the NIR region, B-TCF enabled discriminative imaging of ONOO- with the low and high concentrations in living cells. Importantly, B-TCF was successfully applied for assessing the pathological progression of isoniazid and acetaminophen-induced liver damage in vivo by detecting the endogenous different ONOO- levels. Overall, this study not only demonstrates the first double-enhanced emission cascade activatable NIR fluorescent probe for measuring the dynamic variation of ONOO- in related diseases but also shows great potential as an effective molecular tool for evaluating the various stages of drug-induced liver damage.

Discovery of peroxynitrite elevation in zinc ion-induced acute lung injury with an activatable near-infrared fluorogenic probe

Particulate matter derived from environmental pollution might contain zinc ions (Zn2+), and inhaling these particles exacerbates lung tissue's inflammatory response, impairing lung function and increasing the risk of acute lung injury (ALI). Zn2+ is known to contribute to oxidative stress, leading to elevated levels of reactive oxygen species such as peroxynitrite (ONOO-), which play a key role in the pathogenesis of ALI. Herein, a novel near-infrared fluorogenic probe, DCI-BT, was prepared for the specific detection of ONOO- based on the strategy of oxidative hydrolysis of imine to break into aldehyde. The response of DCI-BT to ONOO- was found to be extremely fast, and the addition of ONOO- would enhance its fluorescence intensity. Cell experiments showed that DCI-BT could efficiently indicate the changes in cellular ONOO- levels. Furthermore, employing DCI-BT, the Zn2+-induced endogenous ONOO- production in cells was successfully visualized, confirming that prolonged exposure to Zn2+ triggered cellular oxidative stress. Finally, the application of DCI-BT in the mice model of ALI was evaluated, and the results revealed that it had good biosafety and could effectively track the changes in ONOO- levels in the Zn2+-induced ALI model. Therefore, DCI-BT held promise as a valuable chemical tool for diagnosing and treating environmentally induced oxidative stress-related diseases.

Detection of carboxylesterases by an activatable NIR fluorescence probe with high selectivity in living systems

Carboxylesterases (CEs) have attracted increasingly attention in the physiological and pathological processes of many diseases such as diabetes, hepatocellular carcinoma (HCC) and drug metabolism. Selective detection of CEs activity is imperative to evaluate the pathophysiological process of CEs-related disease. Herein, a selective near-infrared (NIR) fluorescent probe (DCM-CE) with high selectivity is reported. DCM-CE was composed of dicyanoisophorone-based fluorophore and carbamate unit which is a highly selective identification group for CEs. DCM-CE exhibited good sensitivity for CEs detection at physiological pH and temperature. Furthermore, DCM-CE featured large Stokes shift (175 nm) and good at tracking the drug-induced trace change of CEs activity in HepG2 cells with little effect on cell viability. Moreover, DCM-CE was applied to monitor the activity of CEs in living mice. Taken all together, DCM-CE had extensive potential application value in detecting CEs for evaluating related diseases.

Activatable Multiplexed 19F NMR Probes for Dynamic Monitoring of Biomarkers Associated with Cellular Senescence.

Simultaneous detection of multiple biomarkers is crucial to achieve specific and dynamic analysis of cellular senescence, given its intrinsic high heterogeneity. Current approaches for senescence detection largely rely on fluorescence imaging, but fluorescent probes inevitably suffer from issues including autofluorescence and spectral overlap when being applied for the simultaneous detection of multiple biomarkers. Herein, we report an alternative strategy and design activatable multiplexed senoprobes based on 19F NMR for dynamic monitoring of cellular senescence. Differing from previous approaches, our strategy has two unique advantages. First, this strategy utilizes the changes in the 19F chemical shift as the signal output, which features by its fingerprint and quantifiable characters, thereby significantly enhancing the detection throughput toward biomarkers with minimized spectral overlapping. Second, the background signal is minimized, benefiting from the extremely low abundance of F in biological samples, and the detection accuracy can thus be improved. As a proof of concept, two activatable 19F NMR molecular probes are synthesized that specially respond to two key senescence-associated biomarkers (β-gal and ROS) and have been successfully demonstrated for dynamical and quantitative assessment of the changes of these biomarkers in different cellular models of senescence, without causing obvious cytotoxicity. Owing to the flexible molecular design, this work may offer a useful platform to create diversified 19F NMR senoprobes for deep understanding of cellular senescence across a wide range of aging-related diseases.

Activatable Near-Infrared Fluorescence Probe for Hypochlorous Acid Detection in Early Diagnosis of Keloids.

Keloids represent pathologic conditions characterized by the presence of hyalinized collagen bundles and chronic inflammatory reactions. Recently, increased ROS production and disrupted apoptosis mechanisms in keloids have been reported, although the detailed mechanisms remain unclear. Herein, we developed a specific fluorescence probe, Pro-NBS, to investigate ClO- levels in keloids. The probe demonstrated high specificity for ClO- over other ROS and exhibited a strong linear detection relationship. Based on its performance, we focused on the TGF-β pathway in the development of keloids. ROS upregulation was observed in keloid-derived fibroblasts. Using ClO- as an intrinsic overexpression marker, our probe effectively distinguished between normal fibroblasts and keloid-derived fibroblasts both in vitro and in vivo. Furthermore, Pro-NBS showed potential for monitoring the progression and evaluating the systematic therapy of abnormal scarring or keloids.

Dual-Activated Photoacoustic Probe for Reliably Detecting Hydroxyl Radical in Ischemic Cardiovascular Disease in Mouse and Human Samples.

Cardiovascular disease (CVD) is a chronic disease characterized by the accumulation of lipids and fibrous tissue within the arterial walls, potentially leading to vascular obstruction and an increased risk of heart disease and stroke. Hydroxyl radicals play a significant role in the formation and progression of CVD as they can instigate lipid peroxidation, resulting in cellular damage and inflammatory responses. However, precisely detecting hydroxyl radicals in CVD lesions presents significant challenges due to their high reactivity and short lifespan. Herein, we present the development and application of a novel activatable optical probe, Cy-OH-LP, designed to detect hydroxyl radicals in lipid-rich environments specifically. Built on the Cy7 molecular skeleton, Cy-OH-LP exhibits near-infrared absorption and fluorescence characteristics, and its specific response to hydroxyl radicals enables a turn-on signal in both photoacoustic and fluorescence spectra. The probe demonstrated excellent selectivity and stability in various tests. Furthermore, Cy-OH-LP was successfully applied in an in vivo model to detect hydroxyl radicals in mouse models, providing a potential tool for diagnosing and monitoring AS. The biosafety of Cy-OH-LP was also verified, showing low cytotoxicity and no significant organ damage in mice. The findings suggest that Cy-OH-LP is a promising tool for the specific detection of hydroxyl radicals in lipid-rich environments, providing new possibilities for research and clinical applications in the field of oxidative stress-related diseases.

Neutrophil elastase-activated carbon dots for non-invasive early diagnosis of inflammatory bowel disease by near-infrared-II fluorescence imaging

Most near-infrared-II (NIR-II) fluorescent probes produce an “always-on” output with poor signal specificity for biomarkers. Neutrophil elastase (NE) is a critical factor in chronic inflammation or in the acute response to infection and injury, and NE activatable NIR-II fluorescent probes can aid in the early clinical diagnosis of inflammatory bowel disease (IBD). In this paper, we synthesized OPDG-PFA@PEI carbon dots (CDs) through a two-step reaction of solvothermal/surface covalent bond modification, which can “turn on” specific NIR-II fluorescence signals related to the level of NE produced by neutrophils and target sites of inflammation effectively, thus realizing the monitoring of in-situ NE in cells and in vivo. OPDG-PFA@PEI CDs fluorescent nanoprobe show high-performance real-time non-invasive NIR-II fluorescence imaging for early diagnostic evaluation of IBD in mouse models of DSS-induced IBD, providing a promising approach for the development of clinical non-invasive and more convenient early diagnosis of IBD.

Smart molecular probes with controllable photophysical property for smart medicine

AbstractPrecision medicine calls for advanced theranostics that integrate controllable diagnostic and therapeutic capabilities into one platform for disease treatment in the early stage. Phototheranostics such as fluorescence imaging (FLI), photoacoustic imaging (PAI), photodynamic therapy (PDT), and photothermal therapy (PTT) have attracted considerable attention in recent years, which mainly employ different excited‐state energy dissipation pathways of a chromophore. According to the Jablonski diagram, FLI is related to the radiative process, PAI and PTT are derived from the nonradiative thermal deactivation, and PDT originates from the triplet state energy, in which these processes are usually competitive. Therefore, it is critically important to precisely tune the photophysical energy transformation processes to realize certain diagnosis and treatment properties in optimal state for boosting biomedical applications. Currently, there are mainly two strategies including chemical structure and aggregate behavior changes that relate to the regulation of excited state energy dissipation. In this review, we will discuss the recent advances of smart molecular probes that the photophysical properties can be regulated by external triggers and their applications in biomedical fields. We will summarize the development of activatable phototheranostic molecular probes in response to stimuli such as reactive oxygen species, pH, light, hypoxia, enzyme and gas. The assembly and disassembly of molecular aggregates that greatly affect the photophysical energy transformation processes will also be highlighted. This review aims to provide valuable insights into the development of more accurate diagnostic and therapeutic systems, thereby advancing the emerging field of smart medicine.

An activatable near-infrared fluorescent probe with large Stokes shift for visualizing peroxynitrite in Alzheimer’s disease models

Alzheimer’s disease (AD), characterized by its incurable nature and prevalence among the elderly, has remained a focal point in medical research. Increasing evidence suggests that peroxynitrite (ONOO−) serves as a crucial biomarker for the diagnosis of AD. In this study, we present a novel, easily available, high-yield, and cost-effective near-infrared (NIR) fluorescent probe, CDCI-ONOO. This probe utilizes a coumarin-dicyanoisophorone conjugate as the fluorophore and diphenylphosphinic chloride as the recognition site, enabling the detection of ONOO− both in vitro and in vivo. Upon interaction with ONOO−, CDCI-ONOO exhibits a distinct maximum emission peak at 715 nm with a substantial Stokes shift of 184 nm. The probe demonstrates excellent selectivity and sensitivity (LOD = 144 nM), along with noticeable colorimetric and fluorescence changes after the reaction. Comprehensive analyses using high-performance liquid chromatography (HPLC), high-resolution mass spectrometry (HRMS), and density functional theory (DFT) calculations confirm that the reaction with ONOO− restores the initially quenched Intramolecular Charge Transfer (ICT), resulting in the formation of CDCI-OH, a product that emitting fluorescence in the near-infrared region. Furthermore, we demonstrated the successful application of CDCI-ONOO for ONOO− detection in neuronal cells and imaging of ONOO− in the brains of mice. These findings underscore the potential of CDCI-ONOO as a near-infrared fluorescent probe for in vivo ONOO− detection, offering a significant avenue for advancing our understanding of AD pathology and diagnosis.

Activatable near-infrared fluorescence probe for real-time imaging of PD-L1 expression in tumors.

In clinical practice, determining programmed death-ligand 1 (PD-L1) expression is crucial for selecting patients and monitoring immune checkpoint blockade therapies. Currently, PD-L1 expression is quantified using immunohistochemistry (IHC). However, IHC-based methods do not capture the heterogeneous and dynamic nature of PD-L1 expression. Thus, there is a pressing need for a rapid and efficient method for monitoring PD-L1 expression both in vitro and in vivo, which would considerably aid in prognosis and treatment selection. In this study, we present for the first time an activatable near-infrared (NIR) fluorescence imaging probe (Q-Atezol) for the real-time monitoring of PD-L1 expression in vitro and in vivo. The ability of Q-Atezol to detect PD-L1 expression quickly and in real-time was evaluated in both tumor spheroid and lung cancer xenograft models. An always-on optical probe (ON-Atezol) was synthesized and tested for comparison. In vivo NIR fluorescence imaging studies were conducted on A549 and H1975 tumor-bearing mice, and their tumor-to-background ratios (TBRs) were analyzed. The quenched NIR fluorescence of Q-Atezol is activated upon binding to PD-L1 proteins on the surface of cancer cells, thereby enabling PD-L1 detection in the three-dimensional (3D) tumor spheroids without a washing step. Notably, PD-L1-positive H1975 tumors were clearly visualized with a high TBR 6 hours after Q-Atezol injection, whereas ON-Atezol treatment could not detect H1975 tumors even 24 hours post-injection. The activatable fluorescence probe Q-Atezol demonstrated great potential as an exceptional sensor for assessing PD-L1 expression in 3D cell structures and for in vivo applications.

Conditionally restricted detection of nitrite under acidic conditions by activatable fluorescent probes

As a commonly used food additive, excessive nitrite intake seriously affects people’s health in daily life. As the stomach is the main organ involved in nitrite intake, achieving fast and in situ detection of nitrite in the stomach is of great significance for avoiding the hazards caused by nitrite. However, owing to the poor stability or low sensitivity of existing fluorescent probes under acidic conditions, their application for nitrite detection within the stomach remains challenging. To solve this problem, we developed novel probes specifically designed to maintain stability and demonstrate high sensitivity to nitrite under acidic conditions. Utilizing the optimized probe (DHUROS-11), nitrite levels in environmental and real samples were successfully quantified. Notably, tracing of nitrite within the stomach of mice in real time was realized by using DHUROS-11 as the probe.

Regiospecific Coelenterazine Analogs for Bioassays and Molecular Imaging.

Bioluminescence (BL) generated by luciferase-coelenterazine (CTZ) reactions is broadly employed as an optical readout in bioassays and in vivo molecular imaging. In this study, we demonstrate a systematic approach to elucidate the luciferase-CTZ binding chemistry with a full set of regioisomeric CTZ analogs, where all the functional groups were regiochemically modified. When the chemical structures were categorized into Groups 1-6, the even-numbered Groups (2, 4, and 6) of the CTZ analogs are found to be exceptionally bright with NanoLuc enzyme. A CTZ analogue M2 was the brightest with NanoLuc and the reason was deciphered by a computational analysis of the binding modes. We also report that (i) the regioisomeric CTZ analogs collectively create unique intensity patterns according to each marine luciferase, (ii) the quantitative structure-activity relationship analysis revealed the roles of respective functional groups of CTZ analogs, and (iii) the regioisomeric CTZ analogs also exert red shifts of the BL spectra and color variation: that is, the λmax values are near 500 nm with NanoLuc, near 530 nm with ALuc16, and near 570 nm with RLuc86SG. The advantages of the regioisomeric CTZ analogs were finally demonstrated using (i) a dual-luciferase system with M2-specific NanoLuc and native CTZ-specific ALuc16, (ii) an estrogen activatable single-chain BL probe by imaging, and (iii) BL imaging of live mice bearing tumors expressing NanoLuc and RLuc8.6SG. This study is the first systematic approach to elucidate the regiochemistry in BL imaging studies. This study provides new insights into how CTZ analogs regiochemically work in BL reporter systems and guides the specific applications to molecular imaging.

Dual-Locked Enzyme-Activatable Bioorthogonal Fluorescence Turn-On Imaging of Senescent Cancer Cells.

Bioorthogonal pretargeting optical imaging shows the potential for enhanced diagnosis and prognosis. However, the bioorthogonal handles, known for being "always reactive", may engage in reactions at unintended sites with their counterparts, resulting in nonspecific fluorescence activation and diminishing detection specificity. Meanwhile, despite the importance of detecting senescent cancer cells in cancer therapy, current methods mainly rely on common single senescence-associated biomarkers, which lack specificity for differentiating between various types of senescent cells. Herein, we report a dual-locked enzyme-activatable bioorthogonal fluorescence (DEBOF) turn-on imaging approach for the specific detection of senescent cancer cells. A dual-locked bioorthogonal targeting agent (DBTA) and a bioorthogonally activatable fluorescent imaging probe (BAP) are synthesized as the biorthogonal pair. DBTA is a tetrazine derivative dually caged by two enzyme-cleavable moieties, respectively, associated with senescence and cancer, which ensures that its bioorthogonal reactivity ("clickability") is only triggered in the presence of senescent cancer cells. BAP is a fluorophore caged by trans-cyclooctane (TCO), whose fluorescence is only activated upon bioorthogonal reaction between its TCO and the decaged tetrazine of DBTA. As such, the DEBOF imaging approach differentiates senescent cancer cells from nonsenescent cancer cells or other senescent cells, allowing noninvasive tracking of the population fluctuation of senescent cancer cells in the tumor of living mice to guide cancer therapies. This study thus provides a general molecular strategy for biomarker-activatable in vivo bioorthogonal pretargeting imaging with the potential to be applied to other imaging modalities beyond optics.

Quenched Zwitterionic Cyclic Arg-Gly-Asp-Containing Pentapeptide Probe for Real-Time Brain Tumor Imaging.

The efficacy of glioblastoma treatment is closely associated with complete tumor resection. However, conventional surgical techniques often result in incomplete removal, leading to poor prognosis. A major challenge is the accurate delineation of tumor margins from healthy tissues. Imaging-guided surgery, particularly using fluorescent probes, is a promising solution for intraoperative guidance. The recently developed 'always-on' types of targeted fluorescence probes generate signals irrespective of their presence in tumor cells or in blood circulation, hampering their effectiveness. Here, we propose a novel activatable fluorescence imaging probe, Q-cRGD, that targets glioma cells via the specific binding of the cyclic Arg-Gly Asp-containing pentapeptide (cRGD) to integrins. The Q-cRGD probe was synthesized by conjugating a near-infrared (NIR) dye to a tryptophan quencher via a disulfide linkage, including a cRGD-targeting ligand. This activatable probe remained inactive until the redox-responsive cleavage of the disulfide linkage occurred within the target cell. The zwitterionic nature of NIR dyes minimizes nonspecific interactions with serum proteins, thereby enhancing the tumor-to-background signal ratio (TBR). An in vivo fluorescence imaging study demonstrated a TBR value of 2.65 within 3 h of the intravenous injection of Q-cRGD, confirming its potential utility in imaging-guided brain cancer surgery.

Dipeptidylpeptidase-4-targeted activatable fluorescent probes visualize senescent cells.

Senescent cells promote cancer development and progression through chronic inflammation caused by a senescence-associated secretory phenotype (SASP). Although various senotherapeutic strategies targeting senescent cells have been developed for the prevention and treatment of cancers, technology for the invivo detection and evaluation of senescent cell accumulation has not yet been established. Here, we identified activatable fluorescent probes targeting dipeptidylpeptidase-4 (DPP4) as an effective probe for detecting senescent cells through an enzymatic activity-based screening of fluorescent probes. We also determined that these probes were highly, selectively, and rapidly activated in senescent cells during live cell imaging. Furthermore, we successfully visualized senescent cells in the organs of mice using DPP4-targeted probes. These results are expected to lead to the development of a diagnostic technology for noninvasively detecting senescent cells invivo and could play a role in the application of DPP4 prodrugs for senotherapy.

Rational design of an activatable dual-color fluorogenic probe for revealing the interaction of adenosine-5′-triphosphate and peroxynitrite in pyroptosis associated with acute kidney injury

ATP and ONOO- play unique roles in various biological events and exhibit notable interactions. To date, there is no available chemical tool for investigating the correlation between ATP and ONOO- concentrations in pyroptosis associated with acute kidney injury (AKI). Herein, we designed a novel dual-color near-infrared fluorescent (NIRF) probe P2 for simultaneous visualization of ATP and ONOO- both in vitro and in vivo. Unlike previously reported single-site fluorescent probes, P2 enabled concurrent imaging of ATP and ONOO- in two distinct fluorescence channels, with emission wavelengths centered at 585 and 690 nm, which greatly reduced spectral cross-talk. Employing a HK-2 pyroptosis model, a significant interaction between ATP and ONOO- was unveiled. Elevated ONOO- production was found to correlate with decreased ATP levels; conversely, an increase in ATP levels was associated with rapid ONOO- scavenging. Remarkably, P2 allowed the assessment of cellular hypoxia by monitoring ATP and ONOO- concentrations. The commercial ONOO--scavenger uric acid showcased a protective effect on HK-2 cells via inhibition of the cellular pyroptosis pathway. Furthermore, P2 was successfully employed for imaging of ATP and ONOO- in the AKI mice model. Our findings confirmed that renal ischemia-reperfusion triggered a rise in ONOO- levels, concurrent with a decline in ATP levels. Surprisingly, the cells exhibited a compensatory recovery of ATP levels as the reperfusion time was prolonged. These results suggested the newly devised P2, as a pivotal chemical tool for the simultaneous monitoring of ATP and ONOO-, might open new avenues for disease diagnosis and treatment.

Activatable Fluorescent Probe for Studying Drug-Induced Senescence In Vitro and In Vivo.

Aging represents a significant risk factor for compromised tissue function and the development of chronic diseases in the human body. This process is intricately linked to oxidative stress, with HClO serving as a vital reactive oxygen species (ROS) within biological systems due to its strong oxidative properties. Hence, conducting a thorough examination of HClO in the context of aging is crucial for advancing the field of aging biology. In this work, we successfully developed a fluorescent probe, OPD, tailored specifically for detecting HClO in senescent cells and in vivo. Impressively, OPD exhibited a robust reaction with HClO, showcasing outstanding selectivity, sensitivity, and photostability. Notably, OPD effectively identified HClO in senescent cells for the first time, confirming that DOX- and ROS-induced senescent cells exhibited higher HClO levels compared to uninduced normal cells. Additionally, in vivo imaging of zebrafish demonstrated that d-galactose- and ROS-stimulated senescent zebrafish displayed elevated HClO levels compared to normal zebrafish. Furthermore, when applied to mouse tissues and organs, OPD revealed increased fluorescence in the organs of senescent mice compared to their nonsenescent counterparts. Our findings also illustrated the probe's potential for detecting changes in HClO content pre- and post-aging in living mice. Overall, this probe holds immense promise as a valuable tool for in vivo detection of HClO and for studying aging biology in live organisms.