Fluorescent Probe For Detection Research Articles

N-C QDs coated with a molecularly imprinted polymer as a fluorescent probe for detection of penicillin.

Many diseases are due to bacterial infections, which are treated by penicillin. Existing methods for penicillin detection have relatively high requirements for sample storage and processing, personnel professionalism, and instruments. Herein, water-soluble N-C quantum dots (QDs) from wheat straw were synthesized in a green way by using an efficient and simple method. The N-C QDs were modified with an imprinted layer by a gel-sol method. Penicillin selectively quenched the fluorescence emission of N-C QDs@MIP, and a linear relationship was obtained in the concentration range of 1.0 × 10-6-15.2 × 10-6 mol L-1. The reliability of the sensor in real sample analysis was satisfactory with results in the range of 93.6%-100%, and the sensor showed good reproducibility and long-term stability. The study provides a simple strategy to fabricate N-C QDs@MIP with a highly selective recognition ability and opens an avenue to develop highly efficient sensing probes for the detection of antibiotics in biological applications.

A deep-red xanthene-based highly sensitive fluorescent probe for detection of hypochlorite.

As an oxidant, deodorant and bleaching agent, the hypochlorous acid (HClO) and hypochlorite (ClO- ) are widely used in corrosion inhibitors, textile dyes, pharmaceutical intermediates and in our daily lives. However, excess usage or aberrant accumulation of ClO- leads to tissue damage or some diseases and even cancer. Therefore, it is necessary to develop a fluorescent probe that specifically identifies ClO- . In this article, we synthesized a deep-red xanthene-based fluorescent probe (XA-CN). The strong electron deficient group dicyano endows the probe XA-CN deep-red fluorescent emission with high solubility, selectivity and sensitivity for ClO- detection. Studies showed that the probe demonstrated turn-off fluorescence (643 nm) at the presence of ClO- in dimethylsulfoxide/phosphate-buffered saline 1:1 (pH9) solution with a limit of detection of 1.64 μM. Detection mechanism investigation revealed that the electron deficient group -CN and the hydroxyl group was oxidized into aldehyde or carbonyl groups at the presence of ClO- , resulting ultraviolet-visible absorption of the probe blue shifted and turned-off fluorescence. Furthermore, XA-CN was successfully used for the detection of ClO- in tap water samples.

Preparation of carbon quantum dots and their application in the detection of vitamin B2.

A novel metal-doped carbon quantum dot, zinc-chlorine co-doped carbon quantum dots (Zn/Cl-CQDs), has been developed for the fluorescent probe detection of vitamin B2 and the analysis of the correlation properties of this carbon quantum dot and vitamin B2. Stability experiments demonstrate that Zn/Cl-CQDs possess good fluorescence properties under alkaline conditions. However, when vitamin B2 is added into Zn/Cl-CQDs, the fluorescence intensity decreases sharply, indicating that the fluorescence sensor shows rapid and sensitive detection of vitamin B2 under the static quenching. Lastly, the use of Zn/Cl-CQDs in the detection of vitamin B2 tablets and vitamin B2-rich fruits resulted in recovery rates of 98.2% and 100.6%, respectively. Therefore, this method can be well applied to the detection and analysis of vitamin B2, and has great development prospects in the pharmaceutical industry and food monitoring fields.

A Benzil- and BODIPY-Based Turn-On Fluorescent Probe for Detection of Hydrogen Peroxide.

Faced with rising threats of terrorism, environmental and health risks, achieving sensitive and selective detection of peroxide-based explosives (PEs) has become a global focus. In this study, a turn-on fluorescent probe (BOD) based on benzil (H2O2-recognition element) and 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivative (fluorophore) was developed to sensitively and specifically detect hydrogen peroxide (H2O2). The synthesized BOD had a very weak fluorescence due to intramolecular donor-excited photo-induced electron transfer (d-PET) effect; however, it could emit a strong fluorescence since H2O2 selectively oxidized the benzil moiety and released free BODIPY fluorophore (BOD-COOH). As a result, the proposed BOD detected H2O2 in linear detection ranged from 25 to 125 µM with a detection limit of 4.41 µM. Meanwhile, the proposed BOD showed good selectivity toward H2O2, which is not affected by other common reactive oxygen species (ROS) and ions from explosive residues. In addition, a blue shift from 508 to 498 nm was observed in the absorption spectra upon addition of H2O2. More importantly, the BOD was successfully applied for rapid detection of H2O2 vapor with good sensitivity (down to 7 ppb), which holds great potential for practical use in public safety, forensic analysis and environmental monitoring.

Development of a fluorescent multiplexed lateral flow immunoassay for the simultaneous detection of crustacean allergen tropomyosin, sarcoplasmic calcium binding protein and egg allergen ovalbumin in different matrices and commercial foods

A quantum dot (QD) based multiplexed lateral flow immunoassay (xLFIA) for the simultaneous detection of egg allergen ovalbumin, crustacean allergen tropomyosin (TM) and sarcoplasmic calcium binding protein (SCP) was developed in this study. QD-labeled rabbit anti-ovalbumin, SCP and TM antibodies were applied as fluorescent detection probes. The chromatography system was optimized to reduce the mutual interference of different test lines. Visual and instrumental detection limits of the xLFIA were 0.1 and 0.05 μg/mL for SCP, both 0.05 μg/mL for ovalbumin and both 0.5 μg/mL for TM. As low as 0.10 % crab powder, 0.01 % egg white powder and 0.05 % shrimp powder could be detected in all three model foods using xLFIA. Besides, the xLFIA detection results of 23 of 28 commercial foods were consistent with ingredient labels. These findings indicate that the developed xLFIA is a practical tool for point-of-care detection of egg and crustacean allergens in processed and commercial foods.

Construction of a super large Stokes shift near-infrared fluorescent probe for detection and imaging of superoxide anion in living cells, zebrafish and mice

As one of the major reactive oxygen species (ROS), superoxide anion (O2•−) is engaged in maintaining redox homeostasis in the cell microenvironment. To identify the pathological roles in related disorders caused by abnormal expression of O2•−, it is of great significance to monitor and track the fluctuation of O2•− concentration in vivo. However, the low concentration of O2•− and the interference caused by tissue autofluorescence make the development of an ideal detection methodology full of challenges. Herein, a “Turn-On” chemical response near-infrared (NIR) fluorescence probe Dcm-Cu-OTf for O2•− detection in inflamed models, was constructed by conjugating the NIR fluorophore (dicyanisophorone derivative) with an O2•− sensing moiety (trifluoromethanesulfonate). Dcm-Cu-OTf exerted about 140-fold fluorescence enhancement after reacting 200 μM O2•− with an excellent limited of detection (LOD) as low as 149 nM. Additionally, Dcm-Cu-OTf exhibited a super large Stokes shift (260 nm) and high selectivity over other bio-analytes in stimulated conditions. Importantly, Dcm-Cu-OTf showed low toxicity and enabled imaging of the generation of O2•− in the Lipopolysaccharide (LPS)-stimulated HeLa cells, zebrafish, and LPS-induced inflamed mice. The present study provided a potential and reliable detection tool to inspect the physiological and pathological progress of O2•− in living biosystems.

Fluorescent Probes for the Detection of Bone Metabolism

AbstractThe skeleton plays a significant role in human health. Comprehensive and non‐invasive visualization of the bone is in high demand to detect bone‐related diseases. Clinically, conventional imaging techniques continue to face challenges in terms of limited imaging sensitivity, extended acquisition durations, and the inherent presence of ionizing radiation. These factors collectively hinder their capacity to furnish real‐time spatial insights into cellular activity. Recently, Numerous innovative imaging methodologies employing diverse types of probes have emerged to enhance the clinical detection of bone. In vivo imaging of bone contribute to continuously detecting bone metabolism and growth, diagnosing bone metastases, visualizing medication delivery to bones. Fluorescent probes in dynamic detection of bone metabolism several inherent advantages. First, Fluorescent probes present lower potential long‐term toxicity than radioactive isotope labels. Second, fluorescent dyes used in in vitro imaging are more cost‐effective and come in a more compact size. Next, Near‐infrared (NIR) dyes have deeper tissue penetration capability and lower tissue autofluorescence. However, bone‐imaging fluorescent probes highly depend on phosphonate‐related ligands. These ligands have multiple side effects in clinic and long half‐live of them also exacerbates clearance concerns. This review aims to conclude and analyse the recently reported fluorescent probes for the precise detection of bone. Firstly, we outline the fundamental design mechanism of bone fluorescent probes and describe diverse bone‐targeting moieties, emphasizing the targeting ligands, signal moieties, and functionalities of these probes. Secondly, we discuss the recent promising bone fluorescent probes for the precise and sensitive detection of bone. Finally, we offer our insights on potential future advancements in this field. We anticipate that this review will inspire creative ideas for designing and creating innovative bone‐targeting probes, with applications in bone imaging, pharmaceutical screening, and assessing therapeutic outcomes.

Synthesis of novel coordination polymer Cd-MOF and fluorescent probe detection of Fe3+, Cr2O72−, and ceftriaxone sodium (CRO)

In this contribution, Cd-MOF (1) complex with stable fluorescence properties was constructed by using 3dpu (N, N' -bis(3-pyridyl) urea) and H2IPA (isophtalic acid) as the organic ligands and Cd(NO3)2·4H2O as the metal nodes. The structure of the complex 1 was characterized by infrared spectroscopy, single crystal X-ray diffraction, powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), ultraviolet-visible spectroscopy, SEM and ICP-MS. The Cd-MOF with Cd cluster as the node, and 3dpu and IPA2− as linkers, exhibited excellent thermal and chemical stabilities. It was extended to the three-dimensional supramolecular framework by π - π stacking interaction and hydrogen bonding interaction. Importantly, complex 1 can be used as excellent fluorescent sensors toward Fe3+, Cr2O72−, and CRO (ceftriaxone sodium) with a low limit of detection and a high quenching constant, and have good anti-interference and recyclable characteristics. In addition, complex 1 has the advantages of high sensitivity and selectivity for detecting CRO in simulated human urine.

Direct immersion single-drop microextraction combined with fluorescence detection using an optical probe. Application for highly sensitive determination of rhodamine 6G

The use of an optical probe for fluorescence detection combined with direct immersion single-drop microextraction has been demonstrated as an innovative approach. The optical probe served both as a drop holder for extractant and as a measuring device which made it possible to eliminate the use of cuvettes. A laser and a light emitting diode (LED) were tested as possible light sources. Both of them showed comparable results. However, given the much smaller half-band width of the laser radiation, its use has proven to be preferable since background correction can be eliminated. Direct immersion single-drop microextraction of an ionic association complex of rhodamine 6G with picric acid with subsequent fluorescent detection (λex was 532 nm and 525 nm for laser and LED, respectively; λem was 560 nm for both laser and LED) was used a model system to evaluate the new approach. The extractant phase was a 55 μL amyl acetate microdrop fixed in the optical part of the probe. LOD, LOQ and linear calibration range were found as 0.14, 0.48 and 0.5–10 nmol L−1, and 0.15, 0.50 and 0.5–5 nmol L−1 for laser and LED light sources, respectively. The accuracy of the method was assessed by analyzing real water samples.

Aptamer functionalized fluorescent probe for detection of thrombin in human serum via static quenching

Thrombin plays a pivotal role in blood coagulation, wound healing, and tumor metastasis. In this study, we developed a fluorescent probe (Apt15@QDs) by functionalizing quantum dots (QDs) with an aptamer 15 to specifically recognize thrombin. The aptamer Apt15 binds specifically to thrombin by adopting a G-quadruplex conformation, resulting in the formation of a binary complex that quenches the fluorescence of the probe. Analysis using the classical fluorescence quenching equations Stem-Volmer and Lineweaver-Burk revealed that the mechanism of quenching is static in nature. The established method was successfully applied for detecting thrombin in human serum samples. As shown from the results, the established method exhibited high sensitivity, with a limit of detection (LOD) of 8 nM, and possessed a wide linear range within the concentration span of 20 to 200 nM. Additionally, this method circumvented the need for intricate experimental procedures. Furthermore, it offered a short analysis time, obviated the requirement for additional reagents, and proved suitable for high-throughput analysis of biological samples. This study presents a sensitive, straightforward, and rapid approach for detecting thrombin in complex biological matrices.

Recent Research Progress in Fluorescent Probes for Detection of Amyloid-β In Vivo.

Alzheimer's disease (AD) is a neurodegenerative disease. Due to its complex pathological mechanism, its etiology is not yet clear. As one of the main pathological markers of AD, amyloid-β (Aβ) plays an important role in the development of AD. The deposition of Aβ is not only related to the degeneration of neurons, but also can activate a series of pathological events, including the activation of astrocytes and microglia, the breakdown of the blood-brain barrier, and the change in microcirculation, which is the main cause of brain lesions and death in AD patients. Therefore, the development of efficient and reliable Aβ-specific probes is crucial for the early diagnosis and treatment of AD. This paper focuses on reviewing the application of small-molecule fluorescent probes in Aβ imaging in vivo in recent years. These probes efficiently map the presence of Aβ in vivo, providing a pathway for the early diagnosis of AD and providing enlightenment for the design of Aβ-specific probes in the future.

Theoretical investigation on a simple turn on fluorescent probe for detection of biothiols based on coumarin unit.

The discovery of a simple and efficient detection method for biothiols would be scientifically significant due to the crucial role of them in various physiological processes. Recently, a simple fluorescent probe, DEMCA-NBSC, based on coumarin fragments, was developed by Ding et al., and provided an efficient way for real-time sensing of biothiols both in vivo and vitro. Theoretical insights to the fluorescence sensing mechanism of the probe were provided in this work. Details of the electron transfer process in the probe under optical excitation and the fluorescent character of the probe were analyzed using a quantum mechanical method. All these theoretical results could inspire the development of a highly convenient and efficient fluorescent probe to sense biothiols both in vivo and vitro.

A highly sensitive and selective Cd-MOF fluorescent probe for the detection of His, NB, TC and PTH and its applications in real samples

A novel metal–organic framework (MOF) with the formula of [Cd(CIA)(4,4′-BB)·H2O]·H2O (Cd-MOF) (H2CIA = 5-methoxyisophthalic acid, 4,4′-BB: 4,4′-bis((1H-imidazol-1-yl)methyl)-1,1′-biphenyl) has been designed and synthesized through solvothermal reaction. The structure was characterized by TG, IR, PXRD, elemental analysis, single-crystal X-ray diffraction and XPS. The coordination pattern of the fully deprotonated ligand (CIA) in Cd-MOF is μ2-к1: к0: к2. The complex is found to be a three-dimensional reticular material with good thermal stability. Further study revealed that Cd-MOF has good fluorescence performance and can be used as a fluorescent probe for sensitive detection of histidine (His), nitrobenzene (NB), tetracycline (TC) and pyrimethanil (PTH) in water. Four cycles experiments can be achieved with a low detection limit. The detection limits were 0.3 µM (His), 0.05 µM (NB), 0.2 µM (TC) and 0.01 µM (PTH), respectively. To verify the feasibility of detecting PTH in real samples, we further explored it in water samples and apple peels. The spiked recoveries were 95.3–99.4 % and 97.2–101.2 %, respectively. Finally, the fluorescence quenching mechanism of Cd-MOF in His, NB, TC and PTH detection is discussed in detail.

Synthesis and biological evaluation of indane-based fluorescent probes for detection of amyloid-β aggregates in Alzheimer’s disease

In this article, the development of fluorescent imaging probes for the detection of Alzheimer's disease (AD)-associated protein aggregates is described. Indane derivatives with a donor-π-acceptor (D-π-A) structure were designed and synthesized. The probes were evaluated for their ability to bind to β-amyloid (Aβ) protein aggregates, which are a key pathological hallmark of AD. The results showed that several probes exhibited significant changes in fluorescence intensity at wavelengths greater than 600 nm when they were bound to Aβ aggregates compared to the Aβ monomeric form. Among the tested probes, four D-π-A type indane derivatives showed promising binding selectivity to Aβ aggregates over non-specific proteins such as bovine serum albumin (BSA). The molecular docking study showed that our compounds were appropriately located along the Aβ fibril axis through the hydrophobic tunnel structure. Further analysis revealed that the most active compound having dimethylaminopyridyl group as an election donor and dicyano group as an electron acceptor could effectively stain Aβ plaques in brain tissue samples from AD transgenic mice. These findings suggest that our indane-based compounds have the potential to serve as fluorescent probes for the detection and monitoring of Aβ aggregation in AD.

A new hydrazone linkage-based covalent organic framework for ratiometric fluorescent probe detection of hypochlorite

A new hydrazone-linked covalent organic framework (TFTH-COF) was synthesized and characterized. TFTH-COF has porous crystalline framework structure with high thermal stability. TFTH-COF exhibited highly selective fluorescence blue-shift response towards hypochlorite (ClO−) in ethanol and accompanied by the obvious color change under both day light and UV light. TFTH-COF has the ratiometric fluorescence sensing ability for hypochlorite with high sensitivity. The ratiometric fluorescence intensity of TFTH-COF presented a linear change against hypochlorite concentration with a low detection limit of 0.417 μM. The results of XPS, FT-IR and fluorescence lifetime indicated the formation of hydrogen bond between the O and N atoms of hydroxyl and amine of TFTH-COF with hypochlorite. The DFT calculation further confirmed the formation of hydrogen bond and resulted in the change of fluorescence spectra. Its practical application ability was confirmed by good recovery rate of TFTH-COF in the quantitative detection of hypochlorite in 84 disinfectants and water samples. Moreover, TFTH-COF can also identify hypochlorite through fluorescent test strips by the naked eye. This work sheds light on the fabrication of COFs as ratiometric fluorescence probes for easily-operable, instantaneous and accurate detection and identification of different analytes.

The Green Synthesis of Carbon Quantum Dots through One-step Hydrothermal Approach by Orange Juice for Rapid, and Accurate Detection of Dopamine.

In the current study, the fluorescent Carbon quantum dots (CDs) were synthesized through one-step hydrothermal approach by orange juice without any additional agents. The as-prepared green-CDs (GCDs) were quasi-spherical shape ranged from 2 to 8nm with an average diameter of 5nm, and emitted bright blue fluorescent (FL) under ultraviolet light irradiation (Uv). Different detailed analyses proved that the as-prepared GCDs had good morphologies, various functional groups, high water solubility, great optical features, and excellent stability towards diverse environmental conditions. The results indicated that the as-prepared GCDs can detect different concentrations of dopamine from 1 to 100 µM based on the quenching of their native fluorescent. Furthermore, the good linear relationship was obtained for dopamine in the broad range of concentrations from 1 to 100 µM with the limit of detection (LOD) of 0.81 µM. In addition, the as-prepared GCDs can be applied as a fluorescent probe for detection of dopamine in the different real samples.

Facile synthesis and modifying of Nitrogen-doped graphene quantum dots (N-doped GQDs) as fluorescent probes for detection of nitrite ions

Modifying of graphene quantum dots (GQDs) by adding heteroatoms to them improves their structural and optical properties and also makes them applicable in different areas. In this work, we synthesized nitrogen- doped GQDs (N-GQDs) by green method. They were used as fluorescence probes for the recognition and determination of nitrite. The reaction between the nitrogen groups of N-GQDs sensors and the analyte caused quenching fluorescence to increase linearly with increasing nitrite concentration due to an electron transfer mechanism. Under the ideal tested conditions, the response of N-GQDs to nitrite showed a concentration range of 0.3–1400 µM and R2 = 0.9956 with a LOD of 0.1 µM, with (S/N = 5).

Xanthene-based Hg2+ fluorescent probe for detection of Hg2+ in water/food samples, as well as imaging of live cells, zebrafish and tobacco seedlings

In this paper, an Hg2+ detection probe, HOS, was prepared with a xanthene as the parent fluorophore. Hg2+-initiated thioacetal deprotection reaction is the detection mechanism of this probe. After testing, the probe HOS was able to accurately determine Hg2+ with a detection limit of 36 nM. It was successfully applied to the detection of Hg2+ in different water samples and shrimp samples, meanwhile, the filter paper strips prepared by HOS were obviously changed from light yellow to dark yellow under daylight, and from green to yellow under 365 nm UV light. Furthermore, probe HOS enabled Hg2+ bioimaging experiments on HepG2 cells, zebrafish and tobacco seedlings under laser confocal microscopy.

Fluorescence Sensing Mechanisms of Versatile Graphene Quantum Dots toward Commonly Encountered Heavy Metal Ions.

Graphene quantum dots (GQDs) have received tremendous attention as fluorescent probes for detection of diverse heavy metal ions (HMIs). Nevertheless, the fluorescence sensing mechanisms of versatile GQDs with respect to different HMIs remain elusive. Herein, the fluorescence sensing behaviors and mechanisms of GQDs with amino and carboxyl groups toward commonly encountered Cr6+, Fe3+, Cu2+, Cr3+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, and Hg2+ under different pH conditions are systemically explored. The results show that the fluorescence of GQDs can be enhanced by Zn2+/Cd2+ and quenched by other HMIs at pH 5.8, while it can be enhanced by HMIs except Cr6+/Fe3+/Cu2+ at pH 2.0. Systematic studies verify that the fluorescence quenching/enhancing is mediated by the synergistic effect of the inner filter effect (IFE) and the photoinduced electron transfer (PET) or metal orbital-controlled chelation-quenched/enhanced fluorescence (CHQF/CHEF) effect. The strong and weak IFEs of Cr6+/Fe3+ and Cr3+/Cu2+, respectively, are one of the reasons for the fluorescence quenching, while other HMIs have no IFE. Moreover, the PET effect caused by the interaction of GQDs with Hg2+ at pH 5.8 and the CHQF/CHEF effect caused by the interaction of GQDs with other HMIs are also crucial for fluorescence quenching/enhancing. The findings suggest that the pH condition, the existing forms of functional groups on GQDs, and the complexation states of HMIs in aqueous systems dominate the PET and CHQF/CHEF effects. The elucidating of the fluorescence sensing mechanisms of GQDs toward different HMIs paves the way for developing versatile sensing platforms for monitoring of HMI contamination.

Discovery of a minimalistic DIE-based fluorescent probe for detection of parallel G-quadruplex forms

G-quadruplexes (G4s) are considered to be involved in some key biological processes, leading to the development of a large number of G4 fluorescent probes, which offer possibilities to study G4 dynamics as well as their biological roles. However, the structures of G4s show high polymorphism, which can be classified into parallel, hybrid and antiparallel forms, and the probes targeting a certain topology are limited. In this study, we have developed a minimalistic fluorescent probe by exploiting the disaggregation-induced emission (DIE) principle. The further studies demonstrated that this probe exhibited promising selectivity toward parallel DNA and RNA G4 forms in vitro. Moreover, it was found that this probe could be applied to map the RNA G4s that always form into parallel topologies in live cells, which distinguished it from other reported DIE-based probes that often targeted the mitochondrial or nuclear DNA G4s. To the best of our knowledge, this was the first DIE-based fluorescent probe for mapping cellular RNA G4s.