Near-infrared Fluorescent Probe Research Articles

A novel “AND” logic platform based on ICT and FRET for constructing near-infrared dual-locked fluorescence probe

In this study, a new “AND” logic platform based on intramolecular charge transfer (ICT) and Förster resonance energy transfer (FRET) is developed for constructing a near-infrared dual-locked fluorescence probe with high resistance to pH in biological environments. Using esterase and glutathione (GSH) as representative activators, the developed dual-locked probe BBQ650-SS-ClHC-E discriminates cancer cells from normal cells. The esterase substrate in the probe blocks the ICT process, while the GSH substrate acts as a linker to connect the fluorescence part with the quencher part to induce the FRET process. The fluorescence activation at 732 nm operates as an “AND” logic that depends on the “ICT-on” and “FRET-off” states in the presence of both esterase and GSH. BBQ650-SS-ClHC-E can successfully discriminate HeLa, 4T1, and RAW264.7 cancer cells from HFL1 normal cells and 4T1 tumor-bearing cells in living mice. This new platform can be used to develop dual-locked fluorescence probes.

Monitoring the fluctuation of hydrogen peroxide with a near-infrared fluorescent probe for the diagnosis and management of kidney injury

Kidney injury has become an increasing concern for patients because of environmental hazards and physiological factors. However, the early diagnosis of kidney injury remains challenging. Studies have shown that oxidative stress was closely related to the occurrence and development of kidney injury, in which abnormal hydrogen peroxide (H2O2) production was a common characteristic. Consequently, monitoring H2O2 level changes is essential for the diagnosis and management of kidney injury. Herein, based on fluorescence imaging advantages, a near-infrared fluorescent probe DHX-1 was designed to detect H2O2. DHX-1 showed high sensitivity and selectivity toward H2O2, with a fast response time and excellent imaging capacity for H2O2 in living cells and zebrafish. DHX-1 could detect H2O2 in pesticide-induced HK-2 cells, revealing the main cause of kidney injury caused by pesticides. Moreover, we performed fluorescence imaging, which confirmed H2O2 fluctuation in kidney injury caused by uric acid. In addition, DHX-1 achieved rapid screening of active compounds to ameliorate pesticide-induced kidney injury. This study presents a tool and strategy for monitoring H2O2 levels that could be employed for the early diagnosis and effective management of kidney injury.

Dual NIR-channel fluorescent probe for detecting ONOO− in vitro and vivo

As one of endogenous reactive oxygen species (ROS), peroxynitrite (ONOO−) performs various functions in both pathological and physiological mechanisms. In this work, an optical and near-infrared (NIR) fluorescent probe (NX), which based on 3-dihydro-1H-xanthene and 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) group was designed and prepared to detect ONOO−. This probe revealed an obvious optical and a fluorescent response when ONOO− was present and it exhibited higher selectivity over other ROS. Especially, the dual NIR fluorescence changes at 660 and 800 nm allowed quantitative detection of ONOO− in the range of 15–40 μM, and the detection limit was 82 nM. Finally, the probe was effectively employed to visualize exogenous and endogenous ONOO− in HepG2 cells and zebrafish, respectively. All the results indicated the dual NIR-channel probe could serve as a potent detecting tools in studying ONOO− in vitro and in vivo.

Novel Iminocoumarin-substituted Tetraphenylethylene-based Near-infrared Fluorescent Probe for Ratiometric Detection of F- and H2S.

An iminocoumarin and tetraphenylethylene compound that exhibits aggregation-induced emission (AIE) and a significant Stokes shift (Δλ = 135nm) in THF was created via the Knoevenagel condensation method. TPICBT could also be used as a ratiometric near-infrared fluorescent probe for the naked color identification of F- and H2S. It showed a large red shift (˃ 90nm), good selectivity, and anti-interference. Test strip detection and cell imaging had both been accomplished using the probe. In addition, the probe could conveniently detect H2S produced during food spoilage without laboratory instruments.

Rapidly responsive and highly selective NIR fluorescent probe for detecting hydrogen sulfide in food samples and living cells

Hydrogen sulfide (H2S) is a pungent gas that is one of the key mediators of signal transduction in biological systems, and its presence is related to the freshness of some protein foods. Using phenothiazine derivatives as fluorophores and 2, 4-dinitrobenzene sulfonate (DNBS) fragments as reaction groups, a near-infrared (NIR) probe WX-HS for H2S identification was designed. With the addition of H2S, WX-HS appeared a strong fluorescence signal at 660 nm with short reaction time (90 s) and high sensitivity, and fluorescence state change from non-fluorescent to orange-red. In addition, WX-HS could effectively detect H2S produced during food oxidation. Based on its low cytotoxicity, the WX-HS probe further enabled the detection and imaging of H2S in A549 cells.

Combined strategies for optimizing BODIPY-based near-infrared fluorescent probe targeting Aβ oligomers

Recently, some near-infrared fluorescent (NIRF) probes targeting a toxic form of Aβ aggregate, “Aβ oligomer”, have been developed as useful imaging tools in various situations. However, the general strategy for their development has not been established, hampering the appearance of new candidates. In this study, we improved the Aβ oligomer-targeting probe based on a strategic approach. Seven candidates were newly designed by modifying the structure of our previously developed NIRF probe, BAOP-16, according to combined three strategies, and their characteristics were evaluated. The results of computational analysis, photophysical evaluation, and in vitro assays with Aβ species demonstrated that our strategies improved some characteristics of BAOP-16, and a promising candidate, BAOP-24, was successfully developed. Furthermore, the data from in vivo NIRF imaging suggested that BAOP-24 can detect Aβ oligomers in vivo. We believe that insights from this study will help advance the development of imaging probes targeting Aβ oligomers.

A near-infrared lysosomal probe for dynamic sulfur dioxide monitoring in inflammation

Inflammation is a complex physiological response involving various cellular and molecular events. Sulfur dioxide (SO2), recognized as both an endogenous signaling molecule and anti-inflammatory agent, plays a crucial role in modulating inflammation and maintaining cellular homeostasis. To gain deeper insights into the dynamics of inflammation-related processes, real-time monitoring of SO2 concentrations within cellular organelles is imperative. Here, we developed a near-infrared fluorescent probe, R2, equipped with lysosomal targeting features. R2 effectively monitors dynamic SO2 concentration changes during inflammation. The fluorescence intensity at 703 nm of R2 shows a strong linear correlation with the concentration of SO2, displaying a rapid response time to SO2 within 10 s and maintaining excellent photostability. The successful application of R2 in elucidating dynamic SO2 concentration changes in lysosomal during cellular and rat inflammatory processes underscores its significant potential as a tool for understanding the pathogenesis of inflammation-related diseases.

Near-infrared fluorescent probe to track Cys in plant roots under heavy metal hazards and its application in cells and zebrafish

Heavy metals, including Hg2+, Cr6+ and Cd2+, have always been a major issue in environmental pollution, leading to abnormal changes in the levels of biologically active molecules including Cys in plants, seriously affecting all aspects of the growth and development of plants. This makes it essential to develop a simple and practical method to study the potential impact of heavy metals on plants. In this paper, our research group has developed near-infrared fluorescent probe WRM-S, which has the advantages of fast response, sensitivity to Cys, and successfully applying it to cells and zebrafish. Moreover, it combined the close relationship between heavy metal stress on plants and Cys, using Cys as the detection target, monitoring the internal environment changes of two plants under Hg2+, Cr6+, and Cd2+ stress in the environment, and then conducting 3D imaging. The results indicated that the probe has strong penetration ability in plant tissues, and revealed abnormal changes in plant Cys levels caused by heavy metal stress-induced cellular oxidative stress or cytotoxicity. Thus, the in-situ imaging detection of this probe provides a direction for the physiological dynamics research of plant environmental stress.

Activity-based NIR specific fluorescent probe reveals the abnormal elevation of prolyl endopeptidase in hippocampus during Alzheimer's disease progression

Although prolyl endopeptidase (PREP) has become one of the important proteins to investigate the pathogenesis of Alzheimer's Disease (AD), the activity of PREP in the brain of AD patients is still controversial. This study aims to construct a novel enzyme-activated near-infrared (NIR) fluorescence probe for in-situ detection and imaging of PREP in brain, as well as to reveal the relationship between the activity variation of PREP and the development of AD. For these purposes, based on PREP's unique endopeptidase activity catalyzing prolyl-bond hydrolysis and cleavage, four probes deriving from a good NIR fluorophore (ACM) were designed and synthesized. Observations indicated that the Z-GP-ACM exhibited superior selectivity and sensitivity in detecting PREP. In addition, molecular thermodynamic/kinetic calculations and enzymatic kinetics studies also showed that Z-GP-ACM was an excellent substrate for PREP. Subsequent experiments demonstrated that Z-GP-ACM can be used to measure and image endogenous PREP in living cells and mouse brain. We also revealed for the first time that PREP activity was abnormally increased in hippocampus of AD mice during the disease progression. All these results highlighted that Z-GP-ACM could be a promising tool for exploring the biological functions of endogenous PREP in living systems.

A Near-Infrared Fluorescent Probe with Large Stokes Shift for Sensitive Detection of Hydrogen Sulfide in Environmental Water, Food Spoilage, and Biological Systems.

Hydrogen sulfide (H2S) is an important endogenous gas transmitter that plays a critical role in various physiological and pathological processes and can also cause a negative impact on foodstuffs. In this study, we designed and synthesized a simple, easily available, high-yield, and low-cost near-infrared (λem = 710 nm) fluorescent probe, DEM-H2S, with a substantial Stokes shift (205 nm) for the detection of H2S. DEM-H2S features high selectivity and sensitivity (LOD = 80 nM) toward H2S, accompanied by a noticeable color change. Upon interaction with H2S, DEM-H2S exhibits a restored ICT (Intramolecular Charge Transfer) process, thereby manifesting near-infrared fluorescence. DEM-H2S has been successfully utilized to detect H2S in actual water samples and to monitor the spoilage of food items, such as pork, shrimp, and eggs. Furthermore, DEM-H2S enables the imaging of endogenous and exogenous H2S in living MCF-7 cells and zebrafish. Hence, DEM-H2S provides an attractive method for the detection of H2S in environmental, food, and biological systems, holding potential value in physiological and pathological research.

Iterative Design of Near-Infrared Fluorescent Probes for Early Diagnosis of Alzheimer's Disease by Targeting Aβ Oligomers.

Amyloid-β oligomers (AβOs), crucial toxic proteins in early Alzheimer's disease (AD), precede the formation of Aβ plaques and cognitive impairment. In this context, we present our iterative process for developing novel near-infrared fluorescent (NIRF) probes specifically targeting AβOs, aimed at early AD diagnosis. An initial screening identified compound 18 as being highly selective for AβOs. Subsequent analysis revealed that compound 20 improved serum stability while retaining affinity for AβOs. The most promising iteration, compound 37, demonstrated exceptional qualities: a high affinity for AβOs, emission in the near-infrared region, and good biocompatibility. Significantly, ex vivo double staining indicated that compound 37 detected AβOs in AD mouse brain and in vivo imaging experiments showed that compound 37 could differentiate between 4-month-old AD mice and age-matched wild-type mice. Therefore, compound 37 has emerged as a valuable NIRF probe for early detection of AD and a useful tool in exploring AD's pathological mechanisms.

Development of the near-infrared fluorescence probe for detection of ONOO− and its application in vitro and vivo

Diabetes has become one of the most common endocrine and metabolic diseases threatening human health, which can induce mitochondrial dysfunction and exacerbate the excessive production of reactive oxygen species (ROS). Among them, ONOO− level fluctuation was closely related to diabetes. Hence, it is of great significance to develop a near-infrared fluorescence probe for visualizing ONOO− level fluctuations in diabetes. In this paper, we constructed a fluorescence probe YBL with dicyano-isophorone derivative as fluorophore and diphenyl phosphate as ONOO− response site, which can detect ONOO− with the low detection limit (39.8 nM) and exhibit excellent selectivity and sensitivity. The probe YBL has been applied to monitor intracellular ONOO− level fluctuations. Meanwhile, the image results showed that high sugar promoted the increase of ONOO− level in cells. More important, the probe YBL can be used for imaging in mice, and the results showed that content of ONOO− was increased in diabetic mice. Therefore, the probe YBL provided a tool for understanding diabetes progression by imaging ONOO−.

Near-infrared fluorescent probe with large Stokes shift and long emission wavelength for rapid diagnosis of lung cancer via aerosol inhalation delivery

Near-infrared fluorescent probe with large Stokes shift and long emission wavelength for rapid diagnosis of lung cancer via aerosol inhalation delivery

Near-infrared colorimetric fluorescent probe for detecting HSO3− and its practical application

A colorimetric near-infrared fluorescent probe was designed and synthesized in this paper. The probe XCCC was obtained by simple condensation of 6-(diethylamino)-2,3-dihydro-1H-xanthene-4-carbaldehyde and 3-cyanoacetyl indoles. XCCC detects HSO3− through 1, 4-nucleophilic addition reaction, with obvious near-infrared fluorescence quenching (λem = 696 nm), and the solution color changes from pink to pale yellow under natural light to realize naked eye recognition. In addition, XCCC has a super large Stokes shift value (196 nm) by calculation. The sensitivity of XCCC and HSO3− in the concentration range of 0 ∼ 60 μM is excellent, and the LOD value is as low as 11.4 nM. It is very fast for XCCC to detect HSO3− in real time (30 s), and the reversible cycle of HSO3−- H2O2 is realized (5 times). In practical application, XCCC successfully detected HSO3− qualitatively and quantitatively in actual water samples. Furthermore, we made XCCC into fluorescent test strips to qualitatively detect HSO3− in red wine. In particular, XCCC was used to realize exogenous cell imaging of HSO3− with different concentrations and reversible cell imaging of HSO3−-H2O2 in A549 cells. It shows that probe XCCC has a potential application prospect in food samples and life systems.

Design and synthesis of hemicyanine-based NIRF probe for detecting Aβ aggregates in Alzheimer’s disease

Alzheimer’s disease (AD), a progressive neurodegenerative disorder, has garnered increased attention due to its substantial economic burden and the escalating global aging phenomenon. Amyloid-β deposition is a key pathogenic marker observed in the brains of Alzheimer’s sufferers. Based on real-time, safe, low-cost, and commonly used, near-infrared fluorescence (NIRF) imaging technology have become an essential technique for the detection of AD in recent years. In this work, NIRF probes with hemicyanine structure were designed, synthesized and evaluated for imaging Aβ aggregates in the brain. We use the hemicyanine structure as the parent nucleus to enhance the probe’s optical properties. The introduction of PEG chain is to improve the probe’s brain dynamice properties, and the alkyl chain on the N atom is to enhance the fluorescence intensity of the probe after binding to the Aβ aggregates as much as possible. Among these probes, Z2, Z3, Z6, X3, X6 and T1 showed excellent optical properties and high affinity to Aβ aggregates (Kd = 24.31 ∼ 59.60 nM). In vitro brain section staining and in vivo NIRF imaging demonstrated that X6 exhibited superior discrimination between Tg mice and WT mice, and X6 has the best brain clearance rate. As a result, X6 was identified as the optimal probe. Furthermore, the docking theory calculation results aided in describing X6′s binding behavior with Aβ aggregates. As a high-affinity, high-selectivity, safe and effective probe of targeting Aβ aggregates, X6 is a promising NIRF probe for in vivo detection of Aβ aggregates in the AD brain.

A near-infrared fluorescent probe for differentiating cancer cells from normal cells and early diagnosis of liver cirrhosis

BackgroundCirrhosis represents the terminal stage of liver disease progression and timely intervention in a diseased liver can enhance the likelihood of recovery. Viscosity, a crucial parameter of the cellular microenvironment, is intricately linked to the advancement of cirrhosis. However, viscosity monitoring still faces significant challenges in achieving non-invasive and rapid early diagnosis of cirrhosis. Near-infrared (NIR) fluorescence imaging has the advantages of high sensitivity, non-destructive detection, and ignoring background fluorescence interference, plays an important role in diagnosing and treating various biological diseases. Hence, monitoring cellular viscosity changes with NIR fluorescence probe holds great significance in the early diagnosis of cirrhosis. ResultsIn this study, the NIR fluorescence probe based on the intramolecular charge transfer (TICT) mechanism was developed for imaging applications in mouse model of liver cirrhosis. A molecular rotor-type viscosity-responsive probe was synthesized by linking dioxanthracene groups via carbon-carbon double bonds. The probe demonstrated remarkable sensitivity, high selectivity and photostability, with its responsiveness to viscosity largely unaffected by factors such as polarity, pH, and interfering ions. The probe could effectively detect various drug-induced changes in cellular viscosity, enabling the differentiation between normal cells and cancerous cells. Furthermore, the enhanced tissue penetration capabilities of probe facilitated its successful application in mouse model of liver cirrhosis, allowing for the assessment of liver disease severity based on fluorescence intensity and providing a powerful tool for early diagnosis of cirrhosis. SignificanceA NIR viscosity-sensitive fluorescent probe was specifically designed to effectively monitor alterations in cellular and organ viscosity, which could advance the understanding of the biological characteristics of cancer and provide theoretical support for the early diagnosis of cirrhosis. Overall, this probe held immense potential in monitoring viscosity-related conditions, expanding the range of biomedical tools available.

Construction of a Near-Infrared Fluorescent Probe for Dynamic Monitoring and Early Diagnosis of Heart Failure.

Cardiac hypertrophy characterized by abnormal cardiomyocyte viscosity is a typical sign of heart failure (HF) with vital importance for early diagnosis. However, current biochemical and imaging diagnostic methods are unable to detect this subclinical manifestation. In this work, we developed a series of NIR-I fluorescence probes for detecting myocardial viscosity based on the pyridazinone scaffold. The probes showed weak fluorescence due to free intramolecular rotation under low-viscosity conditions, while they displayed strong fluorescence with limited intramolecular rotation in response to a high-viscosity environment. Among them, CarVis2 exhibited higher stability and photobleaching resistance than commercial dyes. Its specific response to viscosity was not influenced by the pH and biological species. Furthermore, CarVis2 showed rapid and accurate responses to the viscosity of isoproterenol (ISO)-treated H9C2 cardiomyocytes with good biocompatibility. More importantly, CarVis2 demonstrated excellent sensitivity in monitoring myocardial viscosity variation in HF mice in vivo, potentially enabling earlier noninvasive identification of myocardial abnormalities compared to traditional clinical imaging and biomarkers. These findings revealed that CarVis2 can serve as a powerful tool to monitor myocardial viscosity, providing the potential to advance insights into a pathophysiological mechanism and offering a new reference strategy for early visual diagnosis of HF.

Near-Infrared Ratiometric Fluorescent Probe for Detecting Endogenous Cu2+ in the Brain.

Copper participates in a range of critical functions in the nervous system and human brain. Disturbances in brain copper content is strongly associated with neurological diseases. For example, changes in the level and distribution of copper are reported in neuroblastoma, Alzheimer's disease, and Lewy body disorders, such as Parkinson disease and dementia with Lewy bodies (DLB). There is a need for more sensitive techniques to measure intracellular copper levels to have a better understanding of the role of copper homeostasis in neuronal disorders. Here, we report a reaction-based near-infrared (NIR) ratiometric fluorescent probe CyCu1 for imaging Cu2+ in biological samples. High stability and selectivity of CyCu1 enabled the probe to be deployed as a sensor in a range of systems, including SH-SY5Y cells and neuroblastoma tumors. Furthermore, it can be used in plant cells, reporting on copper added to Arabidopsis roots. We also used CyCu1 to explore Cu2+ levels and distribution in post-mortem brain tissues from patients with DLB. We found significant decreases in Cu2+ content in the cytoplasm, neurons, and extraneuronal space in the degenerating substantia nigra in DLB compared with healthy age-matched control tissues. These findings enhance our understanding of Cu2+ dysregulation in Lewy body disorders. Our probe also shows promise as a photoacoustic imaging agent, with potential for applications in bimodal imaging.

Construction of a pH- and viscosity-switchable near-infrared fluorescent probe and its imaging application

Viscosity is a parameter used to measure the fluidity of liquids and a key indicator in evaluating the states of body fluid in biological tissues and lesions. Most traditional detection methods have many drawbacks such as a short emission wavelength and interference by background fluorescence. Inspired by the multiple double bond structure of retinal, a novel pH and viscosity dual-response fluorescent probe (Rh-TR) was constructed in this study. Rh-TR exhibited two emission signals centered at 510 and 660 nm. As the pH of the phosphate-buffered saline increased, the fluorescence at 510 nm increased by about 124-fold, while the change in fluorescence at 660 nm was not obvious. When detecting the change in viscosity using the probe, the fluorescence at 510 nm decreased by about 85 %, while the fluorescence at 660 nm increased by over 20-fold. The probe also showed high selectivity and little toxicity. As demonstrated by the biological imaging experiment, the probe successfully imaged changes in the pH and viscosity of cells and in a live animal model of zebrafish. Considering the unique structure of Rh-TR with retinal and its pH- and viscosity-switchable spectral property, the probe may find further application in detecting viscosity-related diseases and industrial detection.

Novel Near-Infrared Fluorescent Probe for Hepatocyte Growth Factor in Vivo Imaging in Surgical Navigation of Colorectal Cancer.

Despite recent advancements in colorectal cancer (CRC) treatment, the prognosis remains unfavorable primarily due to high recurrence and liver metastasis rates. Fluorescence molecular imaging technologies, combined with specific probes, have gained prominence in facilitating real-time tumor resection guided by fluorescence. Hepatocyte growth factor (HGF) is overexpressed in CRC, but the advancement of HGF fluorescent probes has been impeded by the absence of effective HGF-targeting small-molecular ligands. Herein, we present the targeted capabilities of the novel V-1-GGGK-MPA probe labeled with a near-infrared fluorescent dye, which targets HGF in CRC. The V-1-GGGK peptide exhibits high specificity and selectivity for HGF-positive in vitro tumor cells and in vivo tumors. Biodistribution analysis of V-1-GGGK-MPA revealed tumor-specific accumulation with low background uptake, yielding signal-to-noise ratio (SNR) values of tumor-to-colorectal >6 in multiple subcutaneous CRC models 12 h postinjection. Quantitative analysis confirmed the probe's high uptake in SW480 and HT29 orthotopic and liver metastatic models, with SNR values of tumor-to-colorectal and -liver being 5.6 ± 0.4, 4.6 ± 0.5, and 2.1 ± 0.3, 2.0 ± 0.5, respectively, enabling precise tumor visualization for surgical navigation. Pathological analysis demonstrated the excellent tumor boundaries discrimination capacity of the V-1-GGGK-MPA probe at the molecular level. With its rapid tumor targeting, sustained tumor retention, and precise tumor boundary delineation, V-1-GGGK-MPA merges as a promising HGF imaging agent, enriching the toolbox of intraoperative navigational fluorescent probes for CRC.