Water-soluble Fluorescent Probe Research Articles

Water-Soluble Small Organic Fluorophores for Oncological Theragnostic Applications: Progress and Development.

Cancer is one of the major noncommunicable diseases, responsible for millions of deaths every year worldwide. Though various cancer detection and treatment modalities are available today, many deaths occur owing to its late-stage detection and metastatic nature. Noninvasive detection using luminescence-based imaging tools is considered one of the promising techniques owing to its low cost, high sensitivity, and brightness. Moreover, these tools are unique and valuable as they can detect even the slightest changes in the cellular microenvironment. To achieve this, a fluorescent probe with strong tumor uptake and high spatial and temporal resolution, especially with highwatersolubility, is highly demanded. Recently, several water-soluble molecules with emission windows in the visible (400-700nm), first near-infrared (NIR-I, 700-1000nm), and second near-infrared (NIR-II, 1000-1700nm) windows have been reported in literature. This review highlights recently reported water-soluble small organic fluorophores/dyes with applications in cancer diagnosis and therapeutics. We systematically highlight and describe the key concepts, structural classes of fluorophores, strategies for imparting water solubility, and applications in cancer therapy and diagnosis, i.e., theragnostics. We discuss examples of water-soluble fluorescent probes based on coumarin, xanthene, boron-dipyrromethene (BODIPY), and cyanine cores. Some other emerging classes of dyes based on carbocyclic and heterocyclic cores are also discussed. Besides, emerging molecular engineering methods to obtain such fluorophores are discussed. Finally, the opportunities and challenges in this research area are also delineated.

Water-soluble, SDS-functionalized CdSe/CdS/ZnS quantum dots for uranium detection in aqueous environments

Water-soluble fluorescent probes for conveniently and rapidly monitoring the hazardous uranyl ions (UO22+) in nuclear wastewater are crucial for public nuclear security. Herein, we demonstrated a water-soluble CdSe/CdS/ZnS QDs probe by substituting hydrophilic dodecyl sodium sulfate (SDS) ligands for the original hydrophobic oleic acid ligands toward the rapid and accurate detection of trace UO22+ in aqueous environments. From this simple ligand exchange mothed, the as-prepared QDs probe exhibited a narrow full width at half maximum (FWHM) of 53 nm with an emission peak at 666 nm. Benefiting from dynamic and static fluorescence quenching interaction, this probe represented a high sensitivity (a detect limit of 15.4 nM), a high selectivity with comparison of presettable eight metal ions), a high environmental stability (a recovery rate of 81–94 %) and a rapid inspection ability (on the order of a few minutes). Therefore, this work provided a new approach for the determination of UO22+ in aqueous environments and then for the assurance of public nuclear security.

CdTe based water-soluble fluorescent probe for rapid detection of zilpaterol in swine urine and pork

Zilpaterol hydrochloride (zilpaterol) is used in animal feed as it can increase the lean meat mass. However, consuming zilpaterol-containing animal products may damage human health. Therefore, rapid detection of zilpaterol is attracting increasing research attention. This study aimed to developed a fast, accurate, and ultrasensitive fluorescence immunoassay based on CdTe quantum dots (QDs). A CdTe QD fluorescence sensor was synthesized from thioglycolic acid using a simple hydrothermal method. The morphology and structure of the CdTe QDs were characterized using transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy. The detection limits of our method in swine urine and pork samples were 0.5 μg/L and 1.2 μg/kg, respectively. A wide linear range of 0.1–10000 μg/L (R2 = 0.996) was achieved. Both within-run precision (CVw) and between-run precision (CVb) were ≤ 10 %. The method was then successfully applied for the analysis of zilpaterol contents in swine urine and pork samples.

Lignin based water-soluble fluorescent macromolecular probes for the detection of Fe3+ ion

Lignin is an abundant biomass material in the natural world, its application value and application scope ought to be enlarged. In this work, dealkalized lignin with good water-solubility was used to combine with water-insoluble boron-dipyrromethene (BODIPY) fluorophore to obtain readily water-soluble macromolecular probes. Firstly, a small molecular fluorescent BODIPY probe with two amino groups (-NH2) and another small molecular fluorescent probe with two chlorine groups (-Cl) were synthesized. Secondly, the small-molecular fluorescent probe with two -NH2 groups reacted with carbonyl groups in the lignin by Schiff base formation reaction. Meanwhile, the small-molecular fluorescent probe with two -Cl groups reacted with hydroxyl groups in the lignin by Williamson ether formation reaction. Eventually, two lignin-based fluorescent probes were obtained. The molecular weights of the two probes reached 22.4 kDa and 20.1 kDa. Moreover, these two fluorescent probes were readily soluble in H2O and DMF. Both of the fluorescent macromolecules have good recognition ability for Fe3+, with detection limits of 2.1 × 10−7 mol/L and 1.1 × 10−7 mol/L respectively. Fe3+ interacts with the fluorescent probe, and the imine bond (-CN-) reacts with Fe3+ to cause fluorescence response. The photo-induced electron transfer effect is enhanced, and the photo-induced electron transfer (PET) mechanism causes the fluorescent quenching. This work expands the application scope of lignin as a biomass material and lays a foundation for the development of lignin materials.

Visualization of production and remediation of acetaminophen-induced liver injury by a carboxylesterase-2 enzyme-activatable near-infrared fluorescent probe

Acetaminophen (APAP) overdose, also known as APAP poisoning, may directly result in hepatic injury, acute liver failure and even death. Nowadays, APAP-induced liver injury (AILI) has become an urgent public health issue in the developing world so the early accurate diagnosis and the revelation of underlying molecular mechanism of AILI are of great significance. As a major detoxifying organ, liver is responsible for metabolizing chemical substances, in which human carboxylesterase-2 (CES2) is present. Hence, we chose CES2 as an effective biomarker for evaluating AILI. By developing a CES2-activatable and water-soluble fluorescent probe PFQ-E with superior affinity (Km = 5.9 μM), great sensitivity (limit of detection = 1.05 ng/mL), near-infrared emission (655 nm) and large Stokes shift (135 nm), activity and distribution of CES2 in cells were determined or imaged effectively. More importantly, the APAP-induced hepatotoxicity and the underlying molecular mechanism of pathogenesis of AILI were investigated by measuring the "light-up" response of PFQ-E towards endogenous CES2 in vivo for the first time. Based on the superior performance of the probe PFQ-E for sensing CES2, we believe that it has broad potential in clinical diagnosis and therapy response evaluation of AILI.

Water-soluble fluorescent probe for specific detection of SO2 derivatives in food and cells

SO2, the fourth endogenous gaseous signaling molecule, plays an important role in cells. Besides, SO2 derivatives are used as preservatives in food and drinks. To understand the level of SO2 derivatives in body and food, we developed a FRET-based fluorescent probe CPO. CPO had high energy transfer efficiency and high selectivity toward SO2 derivatives. It could fast respond toward SO2 derivatives in an aqueous solution (3 min) and possessed a low detection limit (68 nM). Furthermore, the SO2 derivatives in tap water, sugar, vermicelli and cells were detected by probe CPO. In addition, probe CPO had a high colocalization coefficient (0.95) for lipid droplets.

Development of a Water-Soluble Fluorescent Probe Based on Natural Flavylium for Mercury(II) Ion Detection and Clinical Antidote Evaluation.

The health hazard posed by Hg2+ makes it imperative to develop a fast and convenient means for detecting Hg2+ in water samples and living objects. While fluorescence sensing technology is considered a promising candidate, the poor water solubility and fluorescence quenching in aqueous solutions of most existing probes limit their practical application. To overcome this, we developed a natural flavylium-inspired fluorescent probe with excellent water solubility. Our probe demonstrated outstanding performance of high sensitivity (LOD = 0.47 nM), fast response (<10 min), and great selectivity for Hg2+. Notably, we validated its applicability in real water, urine samples, and living cells. Furthermore, the probe was successfully applied to evaluate the effectiveness of antidotes for clinical Hg2+ poisoning.

Construction of a water-soluble fluorescent probe for copper (II) ion detection in live cells and food products.

The quality of wine can be affected by excess Cu2+ due to the occurrence of oxidation reactions or precipitation. Therefore, it is essential to use simple and effective testing methods to ensure the Cu2+ content in wine. In this work, we designed and synthesized a rhodamine polymer fluorescent probe (PEG-R). The water solubility of PEG-R was improved by the introduction of polyethylene glycol, which improved the performance and broadened its application in the food field. The PEG-R was characterized by high sensitivity, selectivity and fast response to Cu2+ and was able to complete the response process within 30s, with approximately 29-fold fluorescence enhancement of the probe after exposure to Cu2+, the limit of detection (LOD) was 1.295×10-6 M. The probe can be used for the determination of Cu2+ in living cells, zebrafish, white wine and food products, and it was made into practical gels and test strips.

Water soluble β-CD-PMAA/PMAm/PHEMA-Coumarin macromolecular fluorescent probes prepared via RAFT method and their sensing ability to Fe3+/Fe2+ and Cu2+ ions

Developing water-soluble fluorescent probes has important scientific and practical significance. In this work, coumarin derivatives bearing -OH were obtained through the classical Knoevenagel reaction firstly. Secondly, -CC- on allyl bromide was introduced into coumarin by Williamson ether formation method. Thirdly, hydrazine hydrate was added to the coumarin derivatives, a polymerizable small molecular coumarin fluorophore containing probe was obtained successfully. And, the -COOH on di-thioester underwent an esterification reaction with –OH groups on β-cyclodextrin(β-CD) to prepare oligomer based reversible addition-fragmentation chain transfer(RAFT) reagents. Finally, three copolymer probes β-CD-PMAA-Coumarin, β-CD-PMAm-Coumarin, and β-CD-PHEMA-Coumarin were prepared via RAFT polymerization, in which CC-coumarin was used as the functional monomer and methacrylamide(MAm)/methacrylic acid (MAA)/hydroxyethyl methacrylate (HEMA) as the main monomers. The MALDI-TOF mass tests showed that the macromolecular level probes were successfully prepared. These polymer probes have molecular weights up to 5.4 kDa and have narrow molecular weight distributions (PDI≤1.31). With the assistance of water-soluble long-chained PMAm/PMAA/PHEMA and hydrophilic β-CD, the coumarin containing macromolecular fluorescent probes could be dissolved in water readily. These water soluble polymer fluorescent probes could recognize Fe3+/Fe2+ and Cu2+ ions with high sensitivity. The detection limit of Fe3+ could be as low as 0.34 μM. This study successfully developed a promising technique for producing highly selective, fully water-soluble fluorescent macromolecular probes.

A turn-on fluorescent probe for sensing N2H4 in living cells, zebrafishes and plant root with a large turn-on fluorescence signal

Hydrazine (N2H4) plays an important role in industrial production, but it is highly toxic, leaking or exposing it will pollute the environment and cause serious harm to human beings. Therefore, it is necessary to use a simple and effective method to detect N2H4 in environmental systems and organisms. Herein, a novel water-soluble fluorescent probe based on coumarin fluorophore, 2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)isoindoline-1,3-dione (C-Z1), is reported. The fluorescence intensity of the probe at 530 nm was enhanced gradually with the addition of N2H4, and the maximum enhancement was about 28 times. The probe has good selectivity and sensitivity, the detection limit of hydrazine hydrate is 1.48 × 10−7 M, and the response mechanism of the probe is proved by theoretical calculation and experiment. C-Z1 has been shown to detect N2H4 in a variety of environmental samples, including water, soil, air, cells, zebrafish and plants. In addition, C-Z1 can be made into test strips for easy portability and used for rapid quantitative detection of N2H4 in the field by its distinct change in fluorescence color. Thus, C-Z1 has great potential for the analysis and detection of environmental contaminants.

Terpyridine-Zn(II) based water-soluble fluorescent probes for selective detection of pyrophosphate ions in aqueous medium and its bioimaging application in living cells

Pyrophosphate (PPi) is a key biomarker for various cellular processes and human diseases and thus the development of receptors to bind selectively with PPi ions and facilitate the monitoring of intracellular PPi concentration in living cells is highly imperative. In the present study, novel water-soluble terpyridine-Zn(II) complexes-based fluorescent probes [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 have been designed and synthesized for the selective and sensitive detection of pyrophosphate (PPi) ions in aqueous environment as well as in living cells. The selectivity investigations of both the fluorescent probes towards different anions in HEPES buffer (pH = 7.4) showed highly selective binding towards PPi ions even in the presence of other concomitant nucleotides. Both the probes [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 have exhibited linear fluorescence enhancement upon the addition of different concentrations of PPi and this enhancement in the intensity could be attributed to the photoinduced electron transfer (PET) inhibition process. This proposed binding mechanism was demonstrated using fluorescence and NMR spectroscopic titrations and also the interaction of [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 probes with PPi ions was examined in detail using density functional theory (DFT) analysis. The Job’s plot has shown the binding of complexes between [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 and PPi in 1:2 stoichiometry and the probes have shown excellent binding affinity towards PPi ions with binding constants of 7.72 × 105 M−2 and 6.74 × 104 M−2, respectively. Noticeably, both the probes exhibited promising sensitivity towards PPi with detection limits as low as 0.47 nM and 0.17 nM, respectively. Cytotoxicity studies of [TPD-Zn2]Cl4 and [TPTBr-Zn2]Cl4 revealed that both the probes are biocompatible and subsequently their diagnostic efficacy as bioimaging probes was demonstrated through monitoring the intracellular PPi concentrations in breast cancer cells (MCF-7).

Picomolar detection of As(III) ions by using hydrothermal synthesis of functionalized polymer dots as a highly selective fluorescence sensor

Arsenic is a toxic and ubiquitous metalloid that leads to a widespread health risk to human beings and other living organisms. In this paper, a novel water-soluble fluorescent probe based on functionalized polypyrrole dots (FPPyDots) was designed and applied to determine As(III) selectively and sensitively in aqueous media. FPPyDots probe was synthesized by using a hydrothermal method, via the facile chemical polymerization of pyrrole (Py) and cysteamine (Cys) and then functionalized with ditheritheritol (DTT). To investigate the chemical composition, morphology, and optical properties of the resultant fluorescence probe various characterization techniques including FTIR, EDC, TEM, Zeta potential, UV–vis, and fluorescence spectroscopies were used. The Stern-Volmer equation was used for calibration curves and show a negative deviation with the two linear concentration ranges of 270–2200 pM and 2.5–22.5 nM with an excellent limit of detection (LOD) of 110 pM. FPPyDots exhibit high selectivity to As(III) ions over various transition and heavy metal ions interferences. The performance of the probe has also been perused concerning the pH effect. Finally, to illustrate the applicability and reliability of the FPPyDots probe, the As(III) traces were identified in water real samples and compared with ICP-OES analysis.

A hemicyanine-based fluorescent probe for ratiometric detection of ClO- and turn-on detection of viscosity and its imaging application in mitochondria of living cells and zebrafish

A water-soluble fluorescent probe 1 based on chromene-hemicyanine has been developed, that exhibits ratiometric fluorescent response toward hypochlorite (ClO-) with the LOD (0.082 μM), and “turn-on” response to viscosity changes. Due to low cytotoxicity and good biocompatibility, probe 1 used to monitor hypochlorous acid and viscosity in mitochondria of living cells and zebrafish.

FRET-based fluorescent probe with favorable water solubility for simultaneous detection of SO2 derivatives and viscosity

The intracellular viscosity is an important parameter of the microenvironment and SO2 is a vital gas signal molecule. At present, some dual-response fluorescence probes for simultaneous measurements of viscosity and SO2 derivatives (HSO3−/SO32−) possessed poor water solubility. In this work, we developed a water-soluble fluorescence probe CIJ (0.0864 g/100 mL of water at 20 °C) for simultaneous measurements of viscosity and SO2 derivatives. CIJ exhibited a sensitive fluorescence enhancement to environmental viscosity from 0.97 to 28.04 cP based on a twisted intramolecular charge transfer mechanism and was applied to effective measurement of viscosity in vitro and in vivo. CIJ could also respond to SO2 derivatives with a low detection limit (44 nM) and a fast response time (5 min) based on the nucleophilic addition reaction. Furthermore, CIJ was applied to monitor SO2 derivatives in ratiometric response manner in living cells.

Design of a selective and water-soluble fluorescent probe targeting Tau fibrils for intracellular and in vivo imaging

Tau protein has attracted much research interest in recent years. Development of effective techniques for in vivo imaging of Tau protein with high sensitivity and selectivity is of great importance. Herein, we rationally designed two novel, Tau-selective and AIE-active fluorescent probes (JL-3 and JL-6). Triphenylamine (TPA) as the AIE group, was first linked with a -CN group and N, N’-dimethylaminobenzene by π-π conjugation to form a D-A-D structure. Then, a hydrophilic unit was conjugated to increase probe hydrophilicity. The AIE-activity and water-solubility characteristics contributed to larger Stokes shift and quantum yields, decreased background fluorescence and therefore enhanced the signal-to-noise ratio of the detection. An excellent discrimination between Tau and β-amyloid (Aβ) aggregates (4.3- and 3.5- times higher Tau-over-Aβ) was obtained on JL-3 and JL-6. Taking JL-3 as the example, an excellent linear relationship between Tau concentrations from 50 nM to 5 μM and fluorescence was obtained (detection limit, 14.9 nM). Finally, JL-3 demonstrated a remarkable capacity for bioimaging in living cells, brain tissues and transgenic mice. Collectively, our results illustrated the potential of the developed probes as Tau-specific fluorescent dyes for both in vitro and in vivo applications.

A water-soluble fluorescent pH probe and its application for monitoring lysosomal pH changes in living cells.

Intracellular pH plays a crucial role in many cellular processes, and abnormal intracellular pH has been linked to common diseases such as cancer and Alzheimer's. To address this issue, a water-soluble fluorescent pH probe was designed based on the protonation/deprotonation of the 4-methylpiperazin-1-yl group, using dicyanoisophorone as the fluorophore. In the neutral form of the probe, fluorescence is quenched due to charge transfer from the 4-methylpiperazin-1-yl group to the fluorophore upon excitation. Under acidic conditions, protonation of the 4-methylpiperazin-1-yl group inhibits the photoinduced electron transfer process, leading to an increase in fluorescence intensity. Density-functional theory calculations also verified the fluorescence OFF-ON mechanism. The probe exhibits high selectivity, photostability, fast response to pH changes, and low cytotoxicity to cells. Additionally, the probe selectively accumulates in lysosomes, with a high Pearson coefficient (0.95) using LysoTracker Green DND-26 as a reference. Notably, the probe can monitor lysosomal pH changes in living cells and track pH changes stimulated by chloroquine. We anticipate that the probe has potential for diagnosing pH-related diseases.

Probing fluctuations in sulfur dioxide and viscosity levels during mitochondrial dysfunction using a dual-response fluorescent probe with good water solubility.

Mitochondrial dysfunction is associated with increased viscosity and reactive oxygen species (ROS) levels. As an effective antioxidant, sulfur dioxide (SO2) can actively scavenge excess ROS to regulate the redox state and protect cells from oxidative stress. However, few studies have evaluated the connection between viscosity and SO2 during mitochondrial dysfunction. Herein, a water-soluble fluorescent probe (MBI) is designed and synthesized for dual-detecting SO2 and viscosity. The probe rapidly detects SO2 within 12 s based on Michael's addition reaction. Meanwhile, increasing viscosity further inhibits the intramolecular rotation, causing the probe to show a greatly enhanced fluorescence. Probe MBI possesses mitochondria targeting capability due to its quaternary ammonium salt. More importantly, probe MBI successfully supports SO2 and viscosity imaging in living cells and can effectively monitor them during mitochondrial dysfunction and cell apoptosis.

A water soluble fluorescent probe for selective and sensitive detection of picric acid – a nitroexplosive

Novel water soluble fluorescent probe for picric acid detection.

Water-soluble fluorescent probes for differentiating cancer cells and normal cells by tracking lysosomal viscosity.

Lysosomal viscosity is a significant parameter of lysosomes and closely related to various diseases. Herein, two fluorescent probes, Lyso-vis-A and Lyso-vis-B, were developed, which demonstrate diverse advantages, including great water solubility, lysosome targeting ability and viscosity sensitivity. In particular, Lyso-vis-A exclusively showed fluorescence response toward viscosity but was not influenced by pH changes, rendering it a selective lysosomal viscosity probe. Furthermore, Lyso-vis-A was successfully applied to monitor lysosomal viscosity variations in living cells and differentiate cancer cells and normal cells.

Fluorescent azamonardine probe for “turn-off” detection of chromium (VI) and “turn-on” detection of ascorbic acid based on inner filter effect

In this study, a facile water-soluble fluorescent azamonardine probe is directly prepared by the reaction of dopamine and resorcinol under alkaline conditions (pH 11.0). Under the excitation light of 420 nm, it emits fluorescence at 460 nm. Since chromium(VI) (Cr6+) has absorbance from 300 to 450 nm, fluorescence of this probe gets decreased in the presence of Cr6+ based on the inner filter effect. It is worth noting that Cr6+ can be reduced to Cr3+ by ascorbic acid (AA) and the inner filter effect is inhibted in the presence of both AA and Cr6+. Accordingly the fluorescence is turned on again. Therefore this probe is utilized in fluorescent “turn-off” detection of Cr6+ in the range of 15–600 μM and “turn-on” detection of AA in the range of 0.2–1.5 mM. It has high selectivity in Cr6+ and AA detection towards other metal ions or other substances such as glutathione or cysteine. Meanwhile, when it is utilized to detect Cr6+ in lake water and AA in serum sample, the calculated average recoveries are from 97.4% to 103.8% and from 98.8% to 101.5%, with the relative standard deviations (RSDs) lower than 5%.