Fluorescent Probe Research Articles

Concanavalin a Grafted Nanoemulsions for Nasal Delivery: Preliminary Studies with Fluorescently Labelled Formulations

Nasal delivery is a non-invasive strategy for effective drug delivery. Nevertheless, in order to promote drug uptake by the nasal mucosa, it is fundamental to increase its residence time in the administration site. To this aim, nano-sized drug delivery systems are widely exploited. Within this context, the commercially available nanoemulsion for parenteral nutrition is a biocompatible, safe and clinically approved vehicle for drug delivery. Furthermore, the nanodroplet surface can be modified via a well-established protocol to graft Concavalin A, a lectin capable of improving the mucosal adhesion, by binding to the α-mannose and α-glucose residues of the mucosal glycocalyx. The obtained targeted formulation is able to induce haemagglutination, as opposite to non-modified nanoemulsion. Furthermore, the ConA grafting maintains the physicochemical properties of the nanodroplets (size~230 nm, Z < −35 mV) and does not interfere with the loading of the Rose Bengal fluorescent probe. Fluorescently labelled ConA grafted nanodroplets showed enhanced permeation and accumulation in ex vivo bovine nasal mucosa. This study is a proof of concept that Concanavalin A can be used to decorate the surface of nanodroplets, acting as a permeation promoter.

TDDFT elucidating the PET-Inhibition Mediated fluorescence enhancement in a Cysteine probe

TDDFT has been used to confirm the cysteine-sensing mechanism of a reported fluorescent probe (Talanta, 2020, 220, 12136). Frontier molecular orbital analysis showed that the probe underwent a PET process from quinazolinone to acryloyl, which made the fluorescence quenched together with nonplanar structure. Cysteine removed the acryloyl moiety and inhibited the PET process. The planar geometry of the probe-cysteine product enlarged the conjugated system and enhanced the green fluorescence of the fluorophore. Moreover, the charge redistribution also led to the excited-state proton transfer process, ultimately enhanced the fluorescence intensity and a notable Stocks shift.

Polysiloxane-Based Fluorescent Probes for Visualizing pH and Thiocyanate during Mitochondrial Autophagy.

Mitochondrial autophagy, known as mitophagy, is a vital cellular process that involves the selective degradation of damaged or dysfunctional mitochondria through autophagy, which is critical to the functional integrity of the entire mitochondrial network and determines the survival and death of cells. An abnormal pH may lead to an imbalance in mitochondrial homeostasis and the occurrence of mitochondrial autophagic acidification and dysfunction. SCN- is also an important anion in cellular metabolism, and its abnormal concentration may lead to mitochondrial damage. However, so far, there are few reports on the simultaneous realization of pH and SCN- detection in mitochondria. Therefore, to complement the blank in this area, we developed the polysiloxane-based fluorescent probe P0-CMN that is capable of simultaneously visualizing pH and SCN- fluctuation levels in mitochondria. The probe P0-CMN has the desired mitochondrial-targeting properties and sensitivity to pH and SCN-. It is able to simultaneously monitor pH and SCN- changes in mitochondria in a dual-channel mode. In addition, probe P0-CMN can visualize pH changes during mitochondrial autophagy. This work provides an effective strategy for the design of dual-responsive fluorescent probes and further broadens the application of polysiloxane fluorescent materials.

A novel ultra-long carbon-chain salamo-like fluorescent chemosensor with good flexibility: Synthesis, crystal structure, Pb2+ ion recognition and mechanism exploration

A novel ultra-long carbon-chain salamo-like fluorescent chemical probe DMS containing ten methylene groups (DMS, 6,6′-dimethoxy-2,2′-[1,10-(decanedioxy)bis(nitromethyldyne)]diphenol), was synthesized based on the 3‑methoxy salicylaldehyde unit, and its single crystals were obtained. The single crystal structure for the probe DMS molecule was determined. Research has shown that the fluorescent probe DMS can achieve efficient and selective recognition of Pb2+ ions, with a binding constant Ka = 1.42 × 104 M-1. The detection limit is as low as LOD = 1.31 × 10–7 M, and quantification limit is as low as LOQ = 4.36 × 10–7 M The possible identification mechanism of the fluorescent chemosensor DMS to Pb2+ions was analyzed and studied through fluorescence titration test, nuclear magnetic changes and Job′s plot exprements, DFT calculation et al. The results indicated that the fluorescent chemosensor DMS forms a coordination compound with Pb2+through 1:1 coordination, enhancing its fluorescence and resulting in the coordinated fluorescence enhancement effect.

Tumor inflammation-specific self-amplifying fluorescent molecular probes induce an anti-tumor immune response

Tumor inflammation-specific self-amplifying fluorescent molecular probes induce an anti-tumor immune response

A colorimetric fluorescent probe for reversible detection of HSO3−/H2O2 and effective discrimination of HSO3−/ClO− and its application in food and bioimaging

In view of the significant role of reactive sulfur species (RSS) and reactive oxygen species (ROS) in maintaining the redox homeostasis of organisms, we proposed a colorimetric fluorescent probe (HTN) for reversible detection of HSO3−/H2O2 and effective discrimination of HSO3−/ClO−. C = C is the active site for the Michael addition of HSO3− and the oxidation of ClO−. When HTN interacts with HSO3− and ClO−, it exhibits fluorescence quenching. The addition of oxidizing H2O2 to the system can restore the conjugate structure of the addition product of HSO3− (HTN-HSO3−) and the fluorescence recovery, but it cannot restore the structure of the oxidation product of ClO− (HTN-ClO−). By studying the change of the reversibility/non-reversibility of the probe structure with the addition of H2O2, the purpose of reversible detection of HSO3−/H2O2 and distinguishing HSO3−/ClO− is achieved. In addition, HTN can not only be used as a fluorescent ink to detect HSO3− on the test paper, but also has excellent detection effect on HSO3− and ClO− in real food samples and water samples. Meantime, HTN has good biocompatibility and can target mitochondria to achieve reversible detection of HSO3−/H2O2 and effective discrimination of HSO3−/ClO− in living cells. Therefore, HTN has great potential as a molecular tool for studying redox homeostasis in the interaction network of complex living systems.

Ratiometric fluorescence probe based on boric acid-modified carbon dots and alizarin red for sensitive and rapid detection of glyphosate.

Bycombining boric acid-modified carbon dots (p-CDs) and alizarin red (ARS), a double emission probe p-CDs@ARS with fluorescence at 410nm and 600nm is designed for the detection of glyphosate. When Cu2+ is added, it binds with ARS to cause ARSreleasefrom p-CDs@ARS, which decreases the fluorescence at 600nm. However, in the presence of glyphosate, glyphosate competes to thebinding ofCu2+, releasing ARS to bind with p-CDs again. Therefore, the fluorescence of 600nm recovers. Based on this, the fluorescence of 410nm and 600nm act as the reference and response signal, respectively,achieving the ratiometric fluorescence detection of glyphosate. The linear range of glyphosate detection is 0.5-50µM with a limit of detection at 0.37µM which is well below the maximum residue limit for glyphosate in food. When the probe is used to detect the glyphosate residue in Pearl River water and cucumber, the detection results are well consistent with those detected by HPLC. The established method based on p-CDs@ARS has the advantages that the assembly of ratiometric fluorescence probe is simple, and the detection speed is fast. Additionally, a typical INHIBIT logical system has been successfully constructed based on glyphosate, Cu2+, and the fluorescence signal of p-CDs@ARS.

Changes in early endosomes in rat hippocampal CA1 neurons after transient global cerebral ischaemia.

Transient global ischaemia in rodents causes selective loss of hippocampal CA1neurons, but the potential involvement of endocytic pathways has not been fully explored. The aim of this study was to investigate the changes in early endosomes in the CA1 subfield after ischaemia and reperfusion. A four-vessel occlusion (4-VO) model was established in Wistar rats to induce 13 minutes of global cerebral ischaemia. Neuronal death was detected by Fluoro-Jade B (FJ-B) staining at various intervals after reperfusion, and intracellular membrane changes in ischaemic neurons were revealed using DiOC6(3), a lipophilic fluorescent probe. Ras-related protein Rab5 (Rab5) immunostaining was performed to detect changes in early endosomes in ischaemic neurons. Western blot analysis was used to confirm the morphological observations on Rab5 in the CA1 hippocampal subfield. FJ-B staining confirmed progressive neuronal death in the CA1 subfield in ischaemic rats after reperfusion. DiOC6(3) staining revealed abnormally increased membranous components in ischaemic CA1 neurons. Specifically, early endosomes, as labelled by Rab5 immunostaining, significantly increased in number and size in CA1 neurons at 1.5 and 2 days post-reperfusion, followed by rupture at day 3 and a decrease in staining intensity at day 7 post-reperfusion. Western blot analysis confirmed a significant upregulation of Rab5 protein levels at day 2, which returned to near control levels by day 7. Our study revealed significant changes in the dynamics of early endosomes in CA1 neurons after ischaemia-reperfusion injury. The initial increase in the area fraction of early endosomes in CA1 neurons may reflect an upregulation of endocytic activity, whereas the fragmentation and reduction of early endosomes at the later stage may indicate a failure of adaptive mechanisms of ischaemic neurons against ischaemia-induced death. Understanding the temporal dynamics of early endosomes provides critical insights into the cellular mechanisms that govern fate of CA1 hippocampal neuronsl after ischaemia/reperfusion.

Biocompatibility evaluation and imaging application of a new fluorescent chemodosimeter for the specific detection of mercury ions in environmental and biological samples

Mercury is widely distributed in the natural environment and living environment, and as a heavy metal element with significant toxicity mercury ions pose a threat to agriculture and the food chain, thus consequently the residue and bioaccumulation of mercury ions will cause numerous and serious diseases, such as neurological abnormalities, gingivitis and tremor. Therefore, the development of a responsive and accurate fluorescent probe or sensor with excellent biocompatibility for mercury ions is crucial and marketable in the health and environmental protection. In this study, a novel fluorescent probe named BE-Hg has been innovatively proposed for the dynamic monitor of mercury ions. The probe showed excellent spectral performance in vitro experiments with detection limit as low as 1.18 nM, while it was applied to monitor environmental water samples with recovery as high as 93 %. Moreover, our group evaluated the probe safety using fluorescence-labeled tissue, organ and organ system including liver, heart, blood vessel and immune system in zebrafish for the first time. Note that the probe is proved with good biocompatibility by the cytotoxicity test, behavioral test, hepatotoxicity test, cardiotoxicity test, blood vessel toxicity test and immunotoxicity test with 15 indicators. In addition, the probe owns the ability to detect Hg2+ in live cells and zebrafish models. Thus it is expected to be a tool for the detection of mercury ions in water environments and organisms. In addition, behavioral test, hepatotoxicity test, cardiotoxicity test, blood vessel toxicity test and immunotoxicity test can be used to evaluate the biocompatibility of fluorescent probe, which provide a reliable safeguard for the research and development of probe.

A highly specific two-photon fluorescent probe for real-time monitoring of acetylcholinesterase in neurogenic disorders in vivo

Acetylcholinesterase (AChE) hydrolyses choline into thiocholine, which is essential for cholinergic neurons to revert to their resting state following activation. Abnormal changes in AChE activity can directly affect nervous system function. Thus, the specific detection of AChE activity is urgently needed for elucidating the function of the nervous system and diagnosing AChE-related diseases. Current methods for detecting AChE activity have several limitations, including strong background interference and poor tissue penetration. Thus, we designed and synthesized a two-photon (TP) excited fluorescent probe, WZ-AChE, for the specific detection of AChE. Briefly, a carbamate bond was chosen to specifically recognize AChE, which can also be cleaved by AChE. The product, WZ, released strong deep red fluorescence signal under TP excitation at 800 nm. Our results showed that WZ-AChE can detect AChE activity in PC12 cells with both superior sensitivity and selectivity. In addition, we successfully applied WZ-AChE to a C. elegans Parkinson's disease (PD) model and a mouse model of depression. The findings revealed that AChE activity was greater in both disease models than in the control group. To summarize, a novel tool was created to investigate the mechanisms underlying PD and depression.

A fluorescent platform integrated with a “one-pot” nicking endonuclease signal amplification and magnetic separation for simultaneous detection of tumor markers

Although Enzyme-linked immunosorbent assay (ELISA) has been widely used for biomedical research, simultaneous sensitive and cost-effective detection of multiple biomarkers is challenging. Herein, we proposed a “one-pot” nicking endonuclease signal amplification (NESA)-based fluorescent aptasensor for simultaneous detection of carcinoembryonic antigen (CEA) and alpha fetoprotein (AFP). Firstly, two aptamers were synchronously immobilized on the surface of magnetic nanoparticles (MNPs) by coupling with two complementary DNA (cDNA). CEA and AFP specifically recognized the aptamers and then the released cDNA (ssDNA) from the double-strands (dsDNA) triggers NESA, further breaking two detection probes which were labeled with the fluorescent dye (FAM and ROX) and its quencher (BHQ1 and BHQ2) at the same time. Then, the fluorescence signal of FAM and ROX were restored separately. The results indicated that the fluorescence intensity at the emission wavelength of 518 nm and 610 nm had a positive correlation with CEA and AFP concentrations, respectively. Under the optimum conditions, wider liner range of 1–500 ng mL−1 to CEA and 5–800 ng mL−1 to AFP of this fluorescent aptasensor were successfully obtained, achieving a detection limit of CEA and AFP were 0.7 ng mL−1 and 2 ng mL−1, respectively. Hence, it turned out that the aptasensor strategy can be a promising candidate for developing a newly fluorescence assay for the simultaneous quantitative detection of multiple tumor markers in matrix samples by changing the corresponding sequences of aptamer and fluorescent signal probe, which has great potential for the screening of early cancer.

Novel anti-CEA affibody for rapid tumor-targeting and molecular imaging diagnosis in mice bearing gastrointestinal cancer cell lines.

Gastrointestinal cancer is a common malignant tumor with a high incidence worldwide. Despite continuous improvements in diagnosis and treatment strategies, the overall prognosis of gastrointestinal tumors remains poor. Carcinoembryonic antigen (CEA) is highly expressed in various types of cancers, especially in gastrointestinal cancers, making it a potential target for therapeutic intervention. Therefore, the expression of CEA can be used as an indication of the existence of tumors, chosen as a target for molecular imaging diagnosis, and effectively utilized in the targeted therapy of gastrointestinal cancers. In this study, we report the selection and characterization of affibody molecules (ZCEA539, ZCEA546, and ZCEA919) specific to the CEA protein. Their ability to bind to recombinant and native CEA protein has been confirmed by surface plasmon resonance (SPR), immunofluorescence, and immunohistochemistry assays. Furthermore, Dylight755-labeled ZCEA affibody showed accumulation within the tumor site 1 h post injection and was continuously enhanced for 4 h. The Dylight755-labeled ZCEA affibody exhibited high tumor-targeting specificity in CEA+ xenograft-bearing mice and possesses promising characteristics for tumor-targeting imaging. Overall, our results suggest the potential use of ZCEA affibodies as fluorescent molecular imaging probes for detecting CEA expression in gastrointestinal cancer.

Influence of cell-wall permeability on starch digestion in sweet potato cells

This study aims to evaluate the effects of cell-wall permeability on starch digestibility in sweet potato (SP) cells. Intact cells were separated from purple, red, and white SP tubers, which differ in terms of cell-wall composition and structure, and used as whole SP food models. Purple SP cells exhibited markedly higher polyphenol content but lower starch crystallinity than red and white SP cells. Thermal analysis showed that the gelatinization enthalpy of starch considerably increased due to cell wall damage and the damaged cells of purple SP increased more. The purple SP cell wall dissolved the least pectin and had the lowest permeability for amylase-sized fluorescence probes after cooking, indicating it had stronger thermal stability and resistance to amylase penetration. Among the three cell samples, purple SP cells had the highest starch digestibility (93.95%) when the cell walls were damaged; however, when cell walls remained intact, the starch digestibility (75.95%) of purple SP cells was significantly lower. Therefore, cell-wall permeability mainly controls starch digestion within SP tubers. More polyphenols may enhance cell-wall stability and barrier amylase capacity. This study provides novel insights into the function of the cell wall, which protects starchy plants from the action of amylase.

Tetrahedral DNA-Based Ternary Recognition Ratiometric Fluorescent Probes for Real-Time In Situ Resolving Lysosome Subpopulations in Living Cells via Cl-, Ca2+, and pH.

Lysosomes are multifunctional organelles vital for cellular homeostasis with distinct subpopulations characterized by varying levels of Cl-, Ca2+, and H+. In situ visualization of these parameters is crucial for lysosomal research, yet developing probes that can simultaneously detect multiple ions remains challenging. Herein, we developed a lysosome-targeting ternary recognition ratiometric fluorescent probe based on tetrahedral DNA nanostructures (TDNs) to analyze lysosome subpopulations by Cl-, Ca2+, and pH. The TDN probe is assembled from four single-stranded DNAs, each end-modified with responsive fluorophores (Pr-Cl for Cl-, Pr-Ca for Ca2+, and Pr-pH for pH) or a reference fluorophore (Cy5). The fluorophores are integrated at the vertices of the rigid TDN to minimize mutual interference, and their fixed stoichiometry establishes a robust ternary recognition ratiometric fluorescence sensor for in situ resolution of lysosome subpopulations in living cells. Accordingly, a rise in lysosome subpopulations 2/6 characterized by low [Cl-], medium/high [Ca2+], and high pH was observed in the Niemann-Pick disease model cells but seldom observed in the control group. Conversely, there was a marked decline in the fraction of subpopulations 1/4/5 characterized by high [Cl-], medium to low [Ca2+], and pH. These changes were substantially reversed upon treatment. The probe holds great promise for studying lysosome subpopulations and the diagnosis and treatment of related diseases.

Highly fluorescent nitrogen doped carbon dots as analytical probe for sensitive detection of curcumin through smartphone integrated 3D-printed platform: A new horizon in food safety

COVID-19 pandemic has significantly influenced the dietary habits of humans, emphasizing the incorporation of natural ingredients to enhance immunity towards viral and bacterial infections. Curcumin (Cur), a widely used traditional medicine in various Asian countries and a natural coloring agent, has gained popularity, leading to surge in its usage specially in post COVID-19 era. This surge has led to increased scrutiny of the potential side effects of excessive Cur use, with recent reports suggesting it may result in inactivation of DNA and reduce adenosine triphosphate levels, leading to health risks. In this work, we synthesized highly fluorescent nitrogen-doped carbon dots with a photoluminescence quantum yield of 72.9 % for the sensitive and selective detection of Cur. The developed fluorescent probe exhibits excellent sensory response towards Cur within a concentration range of 0.081–51.45 µM, achieving an ultra-low detection limit of 15.91 nM. The sensor was successfully tested on real food samples like ginger powder, turmeric powder, and curry powder, demonstrating good recovery rates. To assess the practicality of the sensor system, we developed a 3D-printed smartphone-integrated device platform for curcumin detection through fluorescence image analysis. This developed platform exhibited promising results, achieving a limit of detection (LoD) of 132.28 nM across a curcumin concentration range of 0.13–54.00 µM. This device platform holds significant potential for the development of efficient sensors for real-time detection of Cur in food samples.

An ultrasensitive and visual ratio fluorescence sensing platform for tannic acid in water based on boric acid functionalized lanthanide MOF

Tannic acid (TA) is a natural polyphenol that is widely used as a preservative and antioxidant in foods, beverages, health products and pharmaceuticals. In this study, a novel Eu-MOF skeleton was prepared using a simple solvothermal strategy and used as a ratio-metric fluorescence sensor for the ultra-sensitive detection of TA. The constructed Eu-MOF has excellent fluorescence properties and high stability in the aqueous phase. With the introduction of TA, a special covalent structure is formed between the o-diphenol group of TA and the boric acid hydroxyl group in ligand of the MOF, resulting in a gradual decrease in the red emission of Eu-MOF at 614 nm and a basically invariable blue emission at 420 nm. As the concentration of TA increased, the color of the system also changes from red to blue, thus achieving rapid and sensitive detection with a low limit of detection (LOD) of 75.6 nM through a ratiometric fluorescence strategy. What is more, Eu-MOF fluorescent probe combined with smart phone color detector is used to visually detect TA. The propose method is successfully applied in the target analysis in tea and beverage samples and the recovery is 95.6∼110.0 %, which is proved to be an effective strategy for the food safety and healthy monitoring.

Aggregation-Induced Emission Luminogen: Role in Biopsy for Precision Medicine.

Biopsy, including tissue and liquid biopsy, offers comprehensive and real-time physiological and pathological information for disease detection, diagnosis, and monitoring. Fluorescent probes are frequently selected to obtain adequate information on pathological processes in a rapid and minimally invasive manner based on their advantages for biopsy. However, conventional fluorescent probes have been found to show aggregation-caused quenching (ACQ) properties, impeding greater progresses in this area. Since the discovery of aggregation-induced emission luminogen (AIEgen) have promoted rapid advancements in molecular bionanomaterials owing to their unique properties, including high quantum yield (QY) and signal-to-noise ratio (SNR), etc. This review seeks to present the latest advances in AIEgen-based biofluorescent probes for biopsy in real or artificial samples, and also the key properties of these AIE probes. This review is divided into: (i) tissue biopsy based on smart AIEgens, (ii) blood sample biopsy based on smart AIEgens, (iii) urine sample biopsy based on smart AIEgens, (iv) saliva sample biopsy based on smart AIEgens, (v) biopsy of other liquid samples based on smart AIEgens, and (vi) perspectives and conclusion. This review could provide additional guidance to motivate interest and bolster more innovative ideas for further exploring the applications of various smart AIEgens in precision medicine.

Enhanced Real‐Time Monitoring of Catalytic Therapy Efficacy with Dual‐Channel MRI and Fluorescent Platform

AbstractCatalytic therapies, such as chemodynamic therapy and ferroptosis, harness the tumor microenvironment to enhance the specificity and penetration of treatments, thus improving targeted tumor therapy. Despite these advancements, treatment effectiveness varies due to individual differences, making precise monitoring of drug activity and dosage essential to optimize therapy. Traditional imaging strategies, which monitor metal ion release or reactive oxygen species production, frequently fail to well correlate with therapeutic outcome. Herein, this study have developed an integrated self‐monitoring catalytic therapy platform that combines palladium‐ and manganese‐based nanoparticles (PdMn NPs) with caspase‐3 activated probe (Casp probe). Dual‐channel MRI and fluorescent probe, responsive to both low pH and caspase‐3 activity, significantly enhances the accuracy of real‐time therapeutic evaluations, allowing for early reporting treatment response (in 6 h), earlier than tumor volume reduction (8 days). This approach improves the assessment of therapeutic outcomes and aligns with the shift toward individualized cancer treatment protocols.

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.

Stimuli-Induced Fluorescence Switching in Azine-Containing Fluorophores Displaying Resonance-Stabilized ESIPT Emission.

This article reports the synthesis, along with structural and photophysical characterization of 2-(2'-hydroxyphenyl)benzazole derivatives functionalized with various azaheterocycles (pyridine, pyrimidine, terpyridine). These compounds show dual-state emission properties, that is intense fluorescence both in solution and in the solid-state with a range of fluorescent color going from blue to orange. Moreover, the nature of their excited state can be tuned by the presence of external stimuli such as protons or metal cations. In the absence of stimuli, these dyes show emission stemming from anionic species obtained after deprotonation (D* transition), whereas upon protonation or metal chelation, ESIPT process occurs leading to a stabilized and highly emissive K* transition. With the help of extensive ab initio calculations, we confirm that external stimuli can switch the nature of the transitions, making this series of dyes attractive candidates for the development of stimuli-responsive fluorescent ratiometric probes.