Emission Fluorescent Probe Research Articles

Monitoring of mercury ion in environmental media and biological systems using a red emissive fluorescent probe with a large Stokes shift

The development of practical fluorescent probe for detecting toxic mercury ions (Hg2+) is desirable for environmental assurance and public health. In this study, a new red emissive fluorescent probe (KJL) was designed and synthesized for monitoring trace Hg2+ both in vitro and in vivo with distinct features including ideal response rate (within 4 min), red emission (596 nm), large Stokes shift (162 nm), highly sensitivity (LOD = 4.79 nM) and excellent specificity. KJL also validated the good capability for accurately monitoring trace Hg2+ levels in actual samples (faucet water, drinking water, river water, lake water, urine and serum) and possessed the eye-catching ability in visualization of Hg2+ under environmental/biological conditions, which revealed the great potential of this red-emitting fluorescent probe for practical applications in complex environmental and biological systems.

3‐Hydroxy‐2‐naphthohydrazide: A Commercially Available Compound for Fluorescence Sensing of Ortho‐Vanillin and Vanillin

ABSTRACTVanillin and ortho‐vanillin are the most important flavoring additives used in the food industry at a large scale. Herein, the aggregation‐induced emission (AIE) behavior of commercially available 3‐hydroxy‐2‐naphthohydrazide (3HN) was explored and applied for the detection of vanillin and ortho‐vanillin. The weakly fluorescent 3HN in DMSO showed fluorescence enhancement at 500 nm with the increase in HEPES or PBS buffer (pH 7.4) fractions in DMSO. The 3HN in DMSO containing 30% HEPES buffer is used as Probe 1 for the selective detection of ortho‐vanillin. Probe 1 showed a new fluorescence emission at 415 nm for ortho‐vanillin without altering the probe emission at 500 nm. With high specificity, Probe 1 can detect ortho‐vanillin down to 0.3 μM. In contrast, 3HN in DMSO containing 20% PBS buffer is used as Probe 2 for the selective turn‐off detection of vanillin. The green fluorescence emission of Probe 2 at 500 nm is selectively quenched by vanillin with a detection limit of 0.8 μM. Finally, the analytical novelty of the developed probes was examined by quantifying ortho‐vanillin and vanillin in spiked food samples with good recovery percentages.

A responsive aggregation-induced emission fluorescent probe for the detection of cysteine in food, serum samples and oxidative stress environments

Heavy metal ions tend to accumulate through the food chain and may cause many serious diseases. As an antioxidant, cysteine (Cys) plays a crucial role in regulating redox homeostasis. In addition, Cys is also widely used in the food industry. Therefore, the development of a convenient, sensitive, and practical tool for detecting Cys is of great significance for investigating the physiological and pathological functions of Cys induced by heavy metal ions. In this paper, a fluorescent probe NYVB with aggregation-induced emission (AIE) activities has been designed and synthesized, which featured good advantages in Cys detection, including favorable selectivity, desirable sensitivity, wide linear range, and low detection limit. The prepared solid-state sensor enabled the ratiometric visual detection of Cys. Probe NYVB has been successfully implemented for testing Cys in real food samples and serum samples with satisfactory recoveries. In addition, probe NYVB has been successfully employed for detecting endogenous and exogenous Cys in SKOV3 cells. More excitingly, probe NYVB has also been used to track the detection of Cys in H2O2, Hg2+, or Cu2+-induced redox imbalance. Overall, probe NYVB will open up a new avenue for studying Cys in the amelioration of heavy metal toxicity and has practical applications.

Near-infrared multi-functional aggregation-induced emission fluorescent probe for detection of viscosity and peroxynitrite and its imaging application

Viscosity and peroxynitrite (ONOO−) are two crucial elements that influence the operational status of biological processes within living organisms. Their abnormal changes cause metabolic disorders and even diseases. Therefore, it is important to develop a near-infrared (NIR) probe with aggregation-induced emission (AIE) feature that is capable of dual channel detection of both viscosity and ONOO−. Here, a new NIR fluorescent probe LY with large Stokes shift was synthesized in which triphenylamine was conjugated to a pyridinium phenylborate salt. Probe LY with the distorted intramolecular twisted intramolecular charge transfer (TICT) properties is sensitive to systemic viscosity and exhibits enhanced fluorescence emission with peak at the 704 nm. On the other hand, the probe is also susceptible to peroxynitrite-triggered borate oxidation, providing an AIE fluorescence-enhanced response at the 639 nm peak. Moreover, with excellent photochemical stability, lower cytotoxicity and a precise targeting ability for mitochondria, probe LY was used to visualize imaging changes in endogenous and exogenous cellular viscosity and peroxynitrite. The imaging results of the probe during ferroptosis confirmed that both the intracellular viscosity microenvironment and peroxynitrite were further overexpressed. Finally, in vivo imaging experiments showed that the occurrence of inflammation was accompanied by an increase in the viscosity and the release in peroxynitrite.

Cys fluorescent probe precisely modified by fluorine revealing oxidative stress mechanism in Parkinson's disease

Oxidative stress is considered the fundamental pathophysiological mechanism of neurodegenerative diseases such as Parkinson's. Nuclear factor erythroid 2-related factor 2 (Nrf2), as a critical transcription factor for antioxidant response, activating its regulation of biothiol level is deemed an essential pathway for disease mitigation. Cysteine (Cys), an abundant and active biothiol, is a crucial molecule in this antioxidant pathway. To further elucidate these regulatory mechanisms, a specific, rapid, blood-brain barrier-crossing Cys fluorescent probe was demanded. Therefore, we selected isophorone as the parent compound, with bromoacetyl ester as the site responsive to Cys. By introducing fluorine only at the ortho position of bromoacetyl ester, utilizing fluorine's strong electron-withdrawing ability to activate the electrophilicity of methylene and carbonyl groups, probe WSX-F achieved specific and rapid response to Cys. Meanwhile, fluorine lengthened the probe's fluorescence emission wavelength and improved lipophilicity. In situ probe imaging revealed that the activated antioxidant mechanism for Nrf2 will up-regulate the level of Cys cells and the brain in Parkinson's disease, and the differential distribution of Cys in the Parkinson's brain region. The research provided theoretical guidance for preventing and treating Parkinson's disease.

A novel red-to-near-infrared AIE fluorescent probe for detection of Hg2+ with large Stokes shift in plant and living cells

Due to the highly toxic nature of mercury ions to living organisms, accurately detecting Hg2+ in water samples and biological systems is of great significance. In this study, we designed and synthesized a novel red-to-near-infrared Aggregation-Induced Emission (AIE) fluorescent probe (named as DS) based Fluorene derivatives on specifically for Hg2+ detection. Probe DS can visually identify Hg2+ through an red-to-near-infrared fluorescence enhancement change, characterized by a large Stokes shift (130 nm) and AIE feature. This probe offers a fast response, high selectivity and sensitivity. The Hg2+-induced deprotection reaction of the thioketal mechanism was thoroughly investigated using nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS) and density functional theory (DFT) calculation. Additionly, dynamic light scattering (DLS) results indicated that the aggregation states changes of the molecular play a crucial role in the AIE fluorescence response of probe DS toward Hg2+. The red-to-near-infrared response with AIE feature not only avoids the interference of auto-fluorescence signals in complex environments, but also reduces the fluorescence quenching caused by probe molecular aggregation. This makes probe DS highly suitable for high-quality imaging detection of Hg2+ in aqueous environments. Furthermore, probe DS demonstrates the capability for visual fluorescence detection of Hg2+ concentrations in water sample, plant roots and living cells.

Amphiphilic AIE Fluorescent Probe: A Dual-Functionality Strategy for Efficient Antibacterial Therapy Fluorescence Bioimaging against Staphylococcus aureus.

Drug-resistant bacteria present a grave threat to human health. Fluorescence imaging-guided photodynamic antibacterial therapy holds enormous potential as an innovative treatment in antibacterial therapy. However, the development of a fluorescent material with good water solubility, large Stokes shift, bacterial identification, and high photodynamic antibacterial efficiency remains challenging. In this study, we successfully synthesized an amphiphilic aggregation-induced emission (AIE) fluorescent probe referred to as NPTPA-QM. This probe possesses the ability to perform live-bacteria fluorescence imaging while also exhibiting antibacterial activity, specifically against Staphylococcus aureus (S. aureus). We demonstrate that NPTPA-QM can eliminate S. aureus at a very low concentration (2 μmol L-1). Moreover, it can effectively promote skin wound healing. Meanwhile, this NPTPA-QM exhibits an excellent imaging ability by simple mixing with S. aureus. In summary, this research presents a straightforward and highly effective method for creating "amphiphilic" AIE fluorescent probes with antibacterial properties. Additionally, it offers a rapid approach for imaging bacteria utilizing red emission.

Engineering a far-red fluorescent probe for rapid detection of Hg(II) ions in both cells and zebrafish

Abnormal accumulation of mercury ions (Hg2+) in organisms can lead to severe central nervous system and other diseases. Therefore, the monitoring and detection of Hg2+ are of great significance for human health and environmental safety. Herein, we designed and synthesized a novel far-red to NIR emission fluorescent probe (Rho-Hg) based on rhodamine derivative as the fluorophore and thiospirolactone as the recognition site for turn-on detecting of Hg2+ in living cells and zebrafish. The probe Rho-Hg displayed superior sensitivity (detection limit = 17.5 nM), rapid response (<1 min), colorimetric change, high selectivity, and moderate pH stability. Leveraging this probe, we realized the real-time monitoring of Hg2+ in real samples, living cells and zebrafish. By fostering zebrafish embryos and larvae in Hg2+-containing nutrient solution, we noticed that Hg2+ was ingested into the zebrafish liver when zebrafish were grown up to 3 days old, and thus we successfully monitored the accumulation and changes of Hg2+ during zebrafish growth and development. Thus, the probe Rho-Hg could be a powerful tool for sensitive and real-time monitoring of Hg2+ in living systems.

Construction of a double-increasing emission fluorescent probe and its application in food detection of benzoyl peroxide and biosystem imaging

In this work, based on the Förster resonance energy transfer (FRET) mechanism strategy, a new dual-increasing emission proportional near-infrared (NIR) fluorescent probe Lay-1 was designed for fast benzoyl peroxide (BPO) detection in real food samples and biosystems. Specifically, it employed a naphthylimide derivative and a NIR fluorophore dicyanoisophorone derivative as the energy transfer donor and acceptor, respectively, and a phenylboronic acid (Ph-B(OH)2) as the responding group of BPO. In addition, the results exhibited that the fluorescence color of Lay-1 was changed from red to orange in the absence and the presence of BPO with a fast response time (∼120 s), high sensitivity, and an excellent limit of detection as low as 60.8 nM. Impressively, Lay-1 has been successfully used for BPO detection in real food samples and biosystems with satisfactory results. Therefore, Lay-1 can be a robust molecular tool to further investigate the physiological and pathological function of BPO.

A non-peptide-based chymotrypsin-targeted long-wavelength emission fluorescent probe with large Stokes shift and its application in bioimaging

As a hydrolase, chymotrypsin (CHT) is involved in many physiological activities, and its abnormal activity is closely related to diabetes, pancreatic fibrosis, chronic pancreatitis and pancreatic cancer. In this work, an innovative long-wavelength emission fluorescent probe TCF-CHT was designed and synthesized for the high specificity detection of CHT, which utilized TCF-OH and a mimetic peptide substrate 4-bromobutyryl as chromogenic group and recognition group, respectively. TCF-CHT exhibited excellent selectivity and eye-catching sensitivity (8.91 ng/mL) towards CHT, “off-on” long-wavelength emission at 670 nm and large Stokes shift (140 nm). Furthermore, the successful fulfillment and perfect performance in imaging endogenous CHT in complex organisms (P815 cells, HepG2 cells, zebrafish and tumor-bearing mice) verified its potential as a powerful tool for the recognition of CHT in complicated biological environments.

Microalbuminuria sensitive near‐infrared AIE probe for point‐of‐care evaluating kidney diseases

AbstractUrinary microalbumin (mALB) serves as an exceptionally sensitive indicator for the early detection of kidney damage, playing a pivotal role in identifying chronic renal failure and kidney lesions in individuals. Nevertheless, the current fluorescent methodologies for point‐of‐care (POC) diagnosis of mALB in real urine still exhibit suboptimal performance. Herein, the development and synthesis of QM‐N2, an albumin‐activated near‐infrared (NIR) aggregation‐induced emission (AIE) fluorescent probe, are presented. The strategic incorporation and positioning of quaternary ammonium salts within the quinoline‐malononitrile (QM) scaffold significantly influence solubility and luminescence characteristics. Specifically, the quaternary ammonium salt‐free variant, QM‐OH, and the quaternary ammonium salt integrated at the donor function group (DFG) site, QM‐N1, display limited solubility in aqueous solutions while demonstrating a distinct fluorescence signal. Conversely, the incorporation of quaternary ammonium salt at the conformational functional group (CFG) site in QM‐N2 imparts superior dispersibility in water and reduces the initial fluorescence. Furthermore, the integration of a well‐defined D‐π‐A structure within QM‐N2 enables itself with near‐infrared emission, which is crucial for mitigating interference from autofluorescence present in urine samples. Upon interaction with albumin, QM‐N2 forms a tight bond with the IIA site of the subdomain of human serum albumin (HSA), inducing alterations in protein configuration and constraining the intrinsic motion of fluorescent molecules. This interaction induces fluorescence, facilitating the sensitive detection of trace albumin. Ultimately, QM‐N2 is applied for POC testing of mALB using portable equipment, particularly in the diagnosis of mALB‐related diseases, notably chronic renal failure. This positioning underscores its potential as an ideal candidate for self‐health measurement at home or in community hospitals.

Design, Synthesis of Hydrogen Peroxide Response AIE Fluorescence Probes Based on Imidazo [1,2-a] Pyridine.

Hydrogen peroxide (H2O2), a significant member of reactive oxygen species, plays a crucial role in oxidative stress and cell signaling. Abnormal levels of H2O2 in the body can induce damage or even impair body function, leading to the development of certain diseases. Therefore, real-time monitoring of H2O2 in living cells is very important. In this work, the aggregation-induced emission fluorescence probe 2-(2-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) benzyl) oxy) phenyl) imidazo [1,2-a] pyridine (B2) was designed and synthesized, which enables the long-term tracing of H2O2 in living cells. The addition of H2O2 to probe B2 results in a dramatic fluorescence enhancement around 500 nm. Notably, B2 can visualize both exogenous and endogenous H2O2 in living cells. The synthesis method for B2 is simple, has a high yield, and utilizes readily available materials. It exhibits advantages such as low toxicity, photostability, and good biocompatibility. Consequently, the developed fluorescent probe in this study has great potential as a reliable tool for determining H2O2 in living cells.

Simultaneous two-color visualization of lipid droplets and lysosomes for cell homeostasis monitoring using a single fluorescent probe.

Lipid droplets (LDs) and lysosomes are vital organelles that play crucial roles in various physiological and pathological processes. However, simultaneous two-color visualization of these two organelles using a single probe for cell homeostasis monitoring remains a challenge due to the lack of rational design strategies. To address this issue, we have developed an aggregation-induced emission (AIE) fluorescent probe named TPE-NDI-Mor with an electron donor (D)-acceptor (A) structure, which can stain both LDs and lysosomes with high selectivity through green and red fluorescence imaging, respectively. A detailed mechanism study revealed that TPE-NDI-Mor, with a twisted intramolecular charge transfer (TICT) effect, shows a high affinity for a polar microenvironment. Additionally, the probe also demonstrates good stability, high anti-interference performance and a large Stokes shift, making it suitable for visualizing cell homeostasis and further disease diagnosis by tracking the dynamic changes of LDs and lysosomes.

Selectively lighting up glyoxal in living cells using an o-phenylenediamine fused hemicyanine.

Glyoxal (GL) is a reactive α-dicarbonyl compound generated from glycated proteins in the Maillard reaction. It has attracted particular attention over the past few years because of its possible clinical significance in chronic and age-related diseases. In this work, a reaction-based red emission fluorescent probe GL1 has been synthesized successfully by grafting an alkyl group onto an amino group to regulate its selectivity for GL. Under physiological conditions, the fluorescence intensity of GL1 at 640 nm obviously increased with the increase of GL concentration, and it exhibited high selectivity for GL over other reactive carbonyl compounds, as well as a lower detection limit (0.021 μM) and a larger Stokes shift (112 nm). At the same time, GL1 can selectively accumulate in mitochondria and can be used to detect exogenous and endogenous GL in living cells with low cytotoxicity.

Rigidify styryl-pyridinium dyes to benzo[h]coumarin-based bright two-photon fluorescent probes for cellular bioimaging.

Fluorescence imaging of organelles at the cellular level is important for studying biological processes. The development of a highly emissive fluorescent probe that operates under a suitable excitation light source is a key step in high-quality fluorescence imaging. For long-term, high-fidelity fluorescence imaging of mitochondria-related cellular processes using two-photon microscopy and stimulated emission depletion microscopy, we developed a new benzocoumarin-based cationic fluorescent probe (BS-CN) that is far-red emitting, water-soluble, photostable, and very bright in cells. BS-CN showed a remarkably high quantum yield of 0.35 and a large two-photon excited fluorescence action cross-section of 76 GM, enabling the long-term tracking of mitochondria in live cells. In addition, BS-CN exhibited a certain affinity for RNA and stained nucleoli in fixed cells. A comparative assessment of the photophysical properties and bioimaging performance of benzo[h]coumarin-pyridinium and the structurally similar styryl-pyridinium (BS-MN) clearly indicated the importance of structural rigidity for fluorescence efficiency.

Preparation of Tetrandrine Nanocrystals by Microfluidic Method and Its In Vitro and In Vivo Evaluation.

The anti-hepatocellular carcinoma effects of TET are acknowledged, but its application is hindered by its poor water solubility and low bioavailability. Conventional methods for nanocrystal preparation are laborious and lack control. To address these limitations, we propose employing the microfluidic method in the preparation of TET nanocrystals, aiming to enhance the aforementioned constraints. The objectives of this study were to prepare TET nanocrystals (TET-NC@GL) using a Y-microfluidic method with glycyrrhetinic acid (GL) as a stabilizer. The optimal preparation prescription was determined through a single-factor test and Box-Behnken response surface method. Additionally, the nanocrystals prepared with the commonly used stabilizer polyvinylpyrrolidone K30 (PVPK30), known as TET-NC@PVPK30, were characterized and evaluated for their toxicity to HepG2 cells. Hybridized nanocrystals (TET-HNC@GL and TET-HNC@PVPK30) were synthesized using a water-soluble aggregation-induced emission (AIE) fluorescent probe (TVP). Qualitative and quantitative cellular uptake experiments were conducted using these hybridized nanocrystals. Conducting in vivo pharmacokinetic assays evaluates the relative bioavailability of nanocrystals. The results indicated that TET-NC@GL, optimized using the response surface method, had a particle size of 136.47 ± 3.31nm and a PDI of 0.219 ± 0.002. The administration of TET-NC@GL significantly enhanced the cell inhibition rate compared to the TET group and the TET-NC@PVPK30 group (P < 0.01). Moreover, the qualitative and quantitative cellular uptake results revealed a significant enhancement in cellular uptake in the TET-HNC@GL administration group compared to the TET-HNC@PVPK30 group (P < 0.01). In vivo pharmacokinetic results showed that the bioavailability of TET-NC@GL group was 3.5 times higher than that of the TET group. The results demonstrate the successful preparation of TET-NC@GL nanocrystals.

A near-infrared aggregation-induced emission photosensitizer targeting mitochondria for depleting Cu2+ to trigger light-activated cancer cells oncosis

Abnormally high levels of copper in tumors stimulate malignant proliferation and migration of cancer cells, which proposes a formidable challenge for the thorough therapy of malignant tumors. In this work, we developed a reliable, mitochondria-targeted near-infrared aggregation-induced emission fluorescent probe, TTQ-Th, whose thiourea moiety specifically could recognize mitochondria even both upon loss of mitochondrial membrane potential or in fixated cells, and can capture copper overexpressed by tumor cells, leading to severe copper deficiency. In parallel, TTQ-Th can generate sufficient reactive oxygen species (ROS) upon photoexcitation, while copper deficiency inhibits expression of related copper-based enzymes, resulting in a decline in ATP production. Such energy deficiency, combined with reduced MMP and elevated oxidative stress can lead to critical cell oncosis. Both in vitro and intracellular experiments can illustrate that the elevated ROS has remarkable damage to tumor cells and contributes to the elimination of the primary tumor, while copper deficiency further hinder tumor cell migration and induces G0/G1 cell cycle arrest in a dose-dependent manner, which is an efficacious strategy for the treatment of malignant tumors.

Rational design of a rapidly responsive and highly selective fluorescent probe for SO2 derivatives detection and imaging

Sulfur dioxide (SO2) is emerging as a double-edged molecule, while plays vital roles in food and biological system. However, the fast, highly sensitive, and versatile fluorescent probe still remains a tough challenge among current reports. Herein, we developed a novel aggregation-induced emission (AIE) fluorescent probe TPE-PN for specifically sensing SO2 derivatives with high sensitivity (150 nmol/L) and rapid response time (10 s) based on intramolecular charge transfer (ICT) mechanism. And the fluorescence at 575 nm decreased tremendously with 31-fold after the probe was treated with HSO3−. Employing the probe, the accurate analysis of HSO3− was successfully realized in food samples, cells, plant tissues, and zebrafishes. Furthermore, we successfully demonstrate the eruption of SO2 derivatives within plant during drought and salt stress processes. Therefore, probe TPE-PN illustrates significant potential for applications in food analysis and monitoring of SO2 derivatives levels in biological systems under stress conditions.

A Label-Free Aptasensor for Turn-On Fluorescent Detection of Aflatoxin B1 Based on an Aggregation-Induced-Emission-Active Probe and Single-Walled Carbon Nanohorns.

The determination of the aflatoxin B1 (AFB1) content has received widespread attention in the context of food safety, which is a global public health issue. Accordingly, a label-free and turn-on fluorescent AFB1 determination method is developed herein with an ss-DNA aptamer as the recognition element, 4, 4-(1E,1E)-2, 2-(anthracene-9, 10-diyl) bis(ethene-2, 1-diyl) bis(N, N, N-trimethylbenzenaminium iodide) (DSAI) as the aggregation-induced emission (AIE) fluorescent probe, and single-walled carbon nanohorns (SWCNHs) as the selective part with a fluorescence quenching effect. In the presence of AFB1, the AFB1-specific aptamer undergoes a structural transformation and switches from being a random helix to a folded structure. DSAI's fluorescence is protected as a result of the resistance of the transformed aptamer adsorbed on the SWCNHs' surface. Because DSAI's fluorescence is not quenchable, the fluorescence intensity is calculated as a function of the AFB1 concentration. By simply mixing DSAI, aptamer, AFB1 samples, and SWCNHs, the method can be carried out in 2 h, with a limit of detection (LOD) of 1.83 ng/mL. It has a high selectivity in the presence of other mycotoxins, and its performance is confirmed in soybean sauce with a known concentration of AFB1. The LOD was 1.92 ng/mL in the soy sauce samples and the recovery ranged from 95 to 106%, implying that the presented aptasensor has great potential for food analysis.

Identification and quantification of compounds with Angiotensin-converting enzyme inhibitory activity in licorice by UPLC-MS.

Licorice is a famous medicine-food herb for treating cardiovascular diseases in many compound prescriptions. Angiotensin-converting enzyme (ACE) is a key target of cardiovascular diseases. Despite its significance, there is limited scientific investigation regarding the ACE inhibitory effects of licorice. In this study, we used an activity-guided approach with an aggregation-induced emission (AIE) fluorescent probe to identify compounds with ACE-inhibitory activity in licorice. Nine components of licorice were found to have ACE inhibitory activity, in which 46 compounds were identified by using UPLC-QTOF-MS. Seven active compounds were found in this study. Among them, licochalcone B had best ACE inhibitory activity (IC50=0.24μM). Finally, an UPLC-Q-MS method was established to quantify the five major active compounds in three batches of licorice. The findings of this study offer valuable insights into the potential of licorice as a source of ACE inhibitors and its relevance in the development of related products.