Multifunctional Fluorescent Probe Research Articles

N-doped carbon dots as the multifunctional fluorescent probe for mercury ion, glutathione and pH detection

Recently, carbon dots (CDs) have exhibited promising applications in the fluorescence detection of various ions and biomolecules. In this work, one kind of nitrogen-doped CDs (N-CDs) with high fluorescence intensity was synthesized, characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, Fourier-transform infrared, UV–vis absorption spectra, and fluorescence spectra. The results show that the spherical and uniform N-CDs (quantum yield: 60.2%) have remarkable fluorescence properties and photostability, which makes N-CDs can be utilized as an ‘on-off-on’ sensor for Hg2+ and glutathione (GSH). In addition, the pH-sensitive behavior of N-CDs makes it also applicable to H+ detection under acid conditions (pKa = 3.53). The linear range of the ‘turn-off’ sensor detecting Hg2+ was 0.014–50 μM, with a 0.014 μM limit of detection (LOD). GSH was detected by the fluorescence ‘turn-on’ method with a linear range of 0.125–60 μM and a LOD of 0.125 μM. The outstanding performance of N-CDs makes it potential applications in ecological pollution and biomolecule visualization monitoring.

A novel lipid droplets/lysosomes-targeting colorimetric and ratiometric fluorescent probe for Cu2+ and its application

A novel multifunctional fluorescent probe LL2 was prepared via a one-step condensation reaction between 3-formyl-N-butylcarbazole and 2-Hydroxy-1-naphthylhydrazone. LL2 can work as a colorimetric probe for Cu2+, and can also selectively recognize Cu2+ via ratiometric fluorescence signal. After the addition of Cu2+, the probe LL2 responded rapidly within 5 s and reached stability within 30 s. In natural light, when Cu2+ were added to the solution, the color of probe LL2 changed from yellowish to colorless, while there was a discernible fluorescence changed from green to blue under a 365 nm UV lamp. The ratiometric fluorescence intensity (F449/F510) showed a good linear relationship (R2 = 0.9902) with Cu2+ concentration in the concentration range of 0–5 μmol/L, and the minimum detection limit was 1.96 μM. Cell imaging experiments showed that LL2 could capture fluorescence signals in the green and blue channels of HepG2 cells through fluorescence confocal microscope, and successfully recognize exogenous Cu2+ in HepG2 cells. In addition, fluorescence co-localization experiments showed that LL2 could target both lipid droplets and lysosomes. Meanwhile, LL2 could be applied to filter paper strip assay and detection of Cu2+ in actual water samples. These results indicated that probe LL2 has a good capability for monitoring Cu2+ in environment and living cells.

An off-on-off fluorescence probe based on a pyrazole derivative for Al3+ and Fe3+ detection

A multifunctional fluorescence probe (L) was synthesized and used as a dual sensing platform for detecting Al3+ and Fe3+.

Multifunctional fluorescent Eu-MOF probe for tetracycline antibiotics and dihydrogen phosphate sensing and visualizing latent fingerprints.

The contamination of tetracycline antibiotics and dihydrogen phosphate (H2PO4 -) in food and the environment is one of the major concerns for human health. Herein, a water-stable carboxyl-functionalized europium metal-organic framework (Eu-MOF) was prepared and demonstrated, for the first time, as a dual-responsive fluorescent sensor of tetracycline antibiotics (oxytetracycline (OTC), tetracycline (TC), and doxycycline (DOX)) and H2PO4 - via fluorescent turn-on and turn-off, respectively. Eu-MOF presents a sensitive and selective detection of OTC with a rapid response time (1 min) and good anti-interference ability. The limits of detection (LODs) of 78 nm, 225 nm, and 201 nM were achieved for OTC, TC, and DOX, respectively. Coordination and hydrogen bonding led to energy and electron transfer from the TC to the MOF, contributing to the fluorescent enhancement mechanism. Moreover, Eu-MOF can effectively detect H2PO4 - via fluorescence turn-off with a LOD of 0.70 μM. The interactions between H2PO4 - and MOF interrupt the energy transfer from ligand to MOF, leading to fluorescence quenching. In addition, Eu-MOF was successfully applied to determine OTC and H2PO4 - in real samples, obtaining satisfactory recoveries and RSDs. More fascinating, Eu-MOF could be utilized to develop latent fingerprints on various surfaces, providing well-defined fluorescent fingerprint details in which the sweat pores can be seen with the naked eye.

Synthesis of a novel triphenylamine-based multifunctional fluorescent probe for continuous recognition applications

In this paper, a novel fluorescent probe, TPA-PAT, with continuous recognition based on triphenylamine was designed, synthesized, and characterized by NMR, IR, and fluorescence spectrophotometry techniques.

One step synthesis of highly photoluminescent red light-emitting carbon dots from O-phenylenediamine and 2,4-diaminophenol as fluorescent probes for the detection of pH and Cr(VI).

In this study, new red light-emitting carbon dots (R-CDs) that can selectively recognize Cr(VI) were prepared using a strategy that utilizes 2,4-diaminophenol to enhance the fluorescence of O-phenylenediamine based carbon dots. The results showed that 2,4-diaminophenol increased the quantum yield (QY) of the carbon quantum dots (CDs), and that the QY of the CDs increased from their original value of 8.7% to 20.1% (R-CDs). The R-CDs show sensitivity to acidic conditions and maintain good linearity between pH = 1.00-4.00, making them useful as pH probes. Furthermore, the prepared R-CDs possess good solubility in water and are responsive to changes in Cr(VI) concentrations in aqueous environments. The quenching of the R-CDs fluorescence was linearly correlated with the Cr(VI) concentration within a range of 0-20 μM, with a lower detection limit of 66 nM. The detection mechanism is attributed to the formation of hydrogen bonds between Cr(VI) and the R-CDs, resulting in the fluorescence quenching of the R-CDs. The R-CDs can be considered effective multifunctional fluorescent probes for both pH and Cr(VI) in aqueous environments. This study will provide new R-CD design strategies for probes that selectively identify specific target substances.

Unique development of a new dual application probe for selective detection of antiparallel G-quadruplex sequences.

G-Quadruplex (G4) structures play vital roles in many biological processes; consequently, they have been implicated in various human diseases like cancer, Alzheimer's disease etc. The selective detection of G4 DNA structures is of great interest for understanding their roles and biological functions. Hence, development of multifunctional fluorescent probes is indeed essential. In this investigation, we have synthesized a quinolinium based dual application probe (QnMF) that presents molecular rotor properties. This dual application molecular rotor is able to detect selectively antiparallel G4 sequences (22AG in 100 mM NaCl) through a turn-on response over other G4 topologies. The QnMF also contains a distinct fluorine-19 that undergoes a significant chemical shift in response to microenvironmental changes around the molecule when bound to G4 structures. The probe QnMF exhibits significantly brighter fluorescence emissions in glycerol (ε × ϕ = 2800 cm-1 M-1) and relatively less brighter fluorescence emissions in methanol (ε × ϕ = 40.5 cm-1 M-1). The restricted rotation inherent property of the QnMF molecular rotor is responsible for brighter fluorescence and leads to enhancement in the fluorescence upon binding to the G4 structure. Overall, the probe's dual detection method makes it useful for monitoring the G4 structures that are abundant and plays a vital role in living organisms.

A Zn-coordination polymer as a multifunctional fluorescent probe for the detection of V2O74-, Fe3+, and p-nitrotoluene.

A transition metal coordination polymer, [Zn(tpba)(bqdbc)0.5]n (1), was successfully designed and synthesized based on 2,2'-biquinoline-4,4'-dicarboxylic acid (H2bqdc) and 4-(2,2';6',2'-terpyridin)-4'-yl)benzoic acid (Htpba). Compound 1 is initially constructed from the 1D chain of tpba- and bqdc2- and further connected by π⋯π interactions, forming a 2D layered structure. Notably, compound 1 showed good fluorescence stability ranging from pH 1 to 13 in an aqueous solution. It was found that compound 1 could not only detect V2O74- ions with high selectivity and recyclability but also serve as an excellent selective sensing material for Fe3+ among some cations. More crucially, it is the first time that a luminescent coordination polymer has been used to detect V2O74- ions in aqueous solution. The detection of nitrotoluene (p-NT) demonstrated that compound 1 could also behave as a functional probe with high selectivity, sensitivity, and recyclability; and the detection limit of p-NT was 50.9 nM. Meanwhile, the luminescence sensing mechanisms for different analytes were speculated in detail.

A novel dehydroabietic acid-based multifunctional fluorescent probe for the detection and bioimaging of Cu2+/Zn2+/ClO.

A multifunctional dehydroabietic acid-based fluorescent probe (CPS) was designed and synthesized by introducing the 2,6-bis(1H-benzo[d]imidazol-2-yl)phenol fluorophore. The probe CPS could selectively recognize Cu2+, Zn2+ and ClO- ions from other analytes, and it showed fluorescence quenching behavior toward Cu2+ and a ratiometric response to Zn2+ and ClO- by changing from green fluorescence to blue and cyan, respectively. The detection limits toward Cu2+, Zn2+ and ClO- ions were 3.8 nM, 0.253 μM and 0.452 μM, respectively. In addition, CPS presented many fascinating merits, such as high selectivity, a short response time (15-20 s), a wide pH range (3-10) and high photostability. The sensing mechanisms of CPS were verified by 1H-NMR, ESI-MS, FT-IR and Job's plot methods. Meanwhile, CPS exhibited satisfactory detection performance in water samples. More importantly, the probe could be applied as a promising tool for visual bioimaging of three ions in living cells and zebrafishes.

A new intramolecular proton transfer (ESIPT)‐based fluorescent probe for selective visualization of cyanide ion

AbstractFluorescent probes for detection of CN− still have many limitations, such as small Stokes shift, irreversible, and background interference, which hamper their applications for on‐site detection and bioimaging of CN−. In this work, we design a new CN−‐activatable fluorescent probe (named AHMM) containing an ESIPT (excited‐state intramolecular proton transfer) and hydrogen bond features, which show a large Stokes shift (225 nm) and molecular structural reversible detection. The probe AHMM exhibits an excellent selectivity for CN− without any interference from other anions in aqueous DMSO system. Furthermore, the mechanism of the interaction of AHMM with CN− is concluded by various experiments. The limit of detection of AHMM for CN− is calculated as low as 4.47 × 10−8 M, lower than the concentration of CN− deemed acceptable by WHO (World Health Organization). AHMM can recognize CN− in tap water quantitatively and on‐site by a smartphone APP. Moreover, food samples such as almond and cassava including CN− are visualized by fluorescence imaging. In addition, the probe shows practical applications of CN− imaging in cells and mice. This concept can be applied for designing multifunctional fluorescent probes with ESIPT and reversible characteristics for detection of CN−.

Theoretical investigation on FRET strategy of ratio metric fluorescent probe sensing hydrogen sulfide

The level of hydrogen sulfide (H2S) in human body is related to many diseases, such as Alzheimer's disease, Down syndrome, etc. Therefore, the detection of H2S level in biological systems is very important and has attracted great attention from scientific and clinical researchers. Understanding the design and working mechanism of fluorescent probes for H2S level detection is important for building new highly efficient fluorescent probe. The mechanisms of a recently reported efficient small molecule fluorescent probe based on the Fluorescence Resonance Energy Transfer (FRET) were investigated thoroughly in this work. The theoretical results would provide the insights for designing new efficient and multi-functional fluorescent probe applicable in the biological systems.

A highly-efficient exciplex-based multifunctional fluorescent film probe to aniline and N-methylphenethylamine vapors

Exciplexes are often mentioned in the research of organic light-emitting diode (OLED), but there are nearly no reports using the ready-made exciplexes as fluorescent probes directly. In this work, F1 based on the fluorescent exciplex composed of 4, 4′, 4″- tris (N-carbazolyl) triphenylamine (TCTA) and 1- phenyl- 1H- benzo[d]imidazole −1, 3, 5- triazine (PIM-TRZ) is firstly applied as fluorescent film probe to organic amine vapors. The F1 film can accurately identify aniline (AN) and N-methylphenethylamine (MPEA, a simulant of methamphetamine) vapors, as well as roughly distinguish aliphatic and aromatic amine vapors easily by different output signals: the AN vapor causes an instantaneous and entire fluorescence quenching, MPEA vapor leads to the fluorescence quenching of the F1 film along with obvious red-shifted photoluminescence (PL) spectrum, the common aliphatic amine vapors bring the emergence of emission peak of TCTA, and the common aromatic amine vapors only result in partial fluorescence quenching of the F1 film. To the best of our knowledge, it is the first multifunctional fluorescent probe to highly identify AN and MPEA vapors simultaneously among various amines. Hereby, the study provides both promising accurate fluorescent multifunctional probe to AN and MPEA and new strategy for the construction of fluorescent sensors to organic amine vapors. Moreover, the new application of fluorescent exciplex is explored.

Selective fluorescent sensing and photocatalytic properties of a new 2D Co coordination polymer based on 1,1′-di(p-carbonylbenzyl)-2,2′-biimidazoline

A stable 2D Co coordination polymer [Co(DCB)(BIMBP)]n (1) was advisably designed and synthesized (H2DCB and BIMBP are 1,1′-di(p-carbonylbenzyl)-2,2′-biimidazoline and 4,4′-bis(imidazol-1-ylmethyl)biphenyl). Profiting by the excellent luminescence performance and high stability in water, complex 1 is a latent multi-functional fluorescent probe toward Fe3+, Cr2O72− and CrO42−, and nitrofurantoin (NFT) in aqueous medium. The quenching constant (KSV) values of complex 1 are 1.56 × 104 M−1 for Fe3+, 1.45 × 104 M−1 for Cr2O72−, 1.19 × 104 M−1 for CrO42−, and 4.80 × 103 M−1 for NFT, respectively. Furthermore, complex 1 is an effective and stable photocatalyst and displays outstanding photocatalytic degradation of Rhodamine B (RhB) and methylene blue (MB) in water solution. The maximum degradation rate can reach 91.3 % for MB and 90.6 % for RhB in 80 min.

A dual-site multifunctional fluorescent probe for selective detection of endogenous H2O2 and SO2 derivatives based on ICT process and its bioimaging application

In this paper, we reported a coumarin-based fluorescent probe for selective detection of H2O2/SO2 derivatives via ICT process. To the best of our knowledge, it was few reported with the same probe to enable visual detection of H2O2/SO2 derivatives in vivo and in vitro. H2O2 and SO32− were selectively sensed over other analytes, and the probe displayed 20-fold and 220-fold relative fluorescence intensity respectively, as well as the good linear relationship and the excellent detection limits of 2.7 * 103 nM and 19.3 nM. Furthermore, the probe was successfully used for fluorescence imaging of the HeLa cells and the mice to monitor exogenous and endogenous H2O2 and SO32−, suggesting its potential biomedical application for investigation and detection the intermediate indicator of oxidative stress in vitro and in vivo.

Lanthanide coordination polymers used for fluorescent ratiometric sensing of H2O2 and glucose

Scheme 1. Schematic description of the preparation of GOx@Tb-ATA/GDP CPs and detection of glucose. • The dual-emission multi-functional probes based on Ln CPs were facilely prepared by self-assembly. • The ratiometric fluorescence method based on double ligand Ln 3+ coordination polymers for H 2 O 2 detection was realized. • By integrating GOx through the adaptive inclusion property of CPs in the self-assembly process, a simple, highly selective and sensitive one-pot retiometric glucose assay was developed. A dual-emission lanthanide coordination polymers (Ln CPs) were facilely prepared by self-assembly of guanine diphosphate (GDP) and 2-aminoterephthalic acid (ATA) with Tb 3+ , termed as Tb-ATA/GDP CPs. GDP played as the antenna ligand to sensitize the luminescence of Tb 3+ , and ATA served as a fluorescent auxiliary ligand for the ratiometric assay. The obtained Tb-ATA/GDP CPs exhibited both blue-emission of ATA at 430 nm and characteristic green-emission of Tb 3+ under a single excitation wavelength. Upon addition of H 2 O 2 , the fluorescence of Tb 3+ could be selectively quenched and that of ATA slightly enhanced. The fluorescence intensity ratio at 430 nm and 549 nm (I 430 /I 549 ) increased linearly with increasing the concentration of H 2 O 2 in the range of 0.005–20 μM and 120–500 μM, and the detection limit was 3.42 nM. Furthermore, by integrating the glucose oxidase (GOx) through the adaptive inclusion ability of Ln CPs, GOx@Tb-ATA/GDP CPs were facilely obtained. Based on their high affinity to oxidize glucose and the fluorescence response to the generated H 2 O 2 , a simple, highly selective and sensitive one-pot ratiometric glucose assay was developed. This work will facilitate the design and construct of multi-functional fluorescent probes based on the Ln CPs, and exploit their applications in bio-sensing and environmental analysis.

An ultra-sensitive fluorescent sensor based on Zn-MOF for selective detection of riboflavin in food

Riboflavin can not only promote cell metabolism, but also prevent cardiovascular diseases. People usually need to obtain riboflavin from food or medicine, so the determination of riboflavin is significant for safety and quality control. An ingenious zinc-based metal-organic framework (Zn-MOF) was synthesized which can be used for rapid fluorescence detection of riboflavin with an ultralow detection limit of 2 ​× ​10−8 ​mol/L. The quenching mechanism is mainly attributed to the fluorescence resonance energy transfer and the absorption competition. In addition, this Zn-MOF can be used as a multifunctional fluorescence probe to specifically recognize acetylacetone and Cr2O72−/CrO42−. Most importantly, it has been applied to the quantitative analysis of milk and energy drinks with satisfactory recovery (100.71%–103.42%). It is the first attempt to use MOF as fluorescence probe to determine riboflavin without additional surface modification and functionalization, which provides a promising functional platform for detecting riboflavin in food industry.

Bifunctional ratiometric fluorescent probe for sensing anthrax spore biomarker and tetracycline at different excitation channels

Multifunctional fluorescent probes have received increasing attention for the sake of atom economy and high-density integration. Herein, CdTe quantum dots (QDs) modified with Eu3+ were synthesized as the bifunctional ratiometric fluorescent probe for sensing two hazardous substances tetracycline (TC) and anthrax spore biomarker 2,6-dipicolinic acid (DPA) at different excitation channels, based on the discrepant excitation wavelengths of Eu3+ and the fluorescence quenching of CdTe QDs after interaction with them. Both DPA and TC enhanced the red emission of Eu3+ via antenna effect but caused the green emission of CdTe QDs to quench. Interestingly, the excitation wavelengths of Eu3+ after coordinating with DPA and TC were 275 and 386 nm, respectively. On this basis, CdTe QDs-Eu3+ achieved the bifunctional ratiometric detection of DPA (λex = 275 nm) and TC (λex = 386 nm) with different excitation channels. Both DPA and TC were selectively detected by CdTe QDs-Eu3+ with rapid response (DPA-1 min, TC-1 min) and high sensitivity (DPA-LOD 0.3 μM, TC-LOD 2.2 nM). CdTe QDs-Eu3+ were applied to analyzing DPA and TC in food, biological and environmental samples. Satisfactory spiked recoveries (80.0–119.0 %) and relative standard deviations (0.5–8.4 %) were obtained for measuring DPA and TC in these samples.

Kill three birds with one stone: Zr-MOF-mediated composite multi-functional materials to enhance the efficiency for fluorescent and colorimetric dual-signal readout bioassay

In this work, we report a fluorescent and colorimetric dual readout bioassay for deoxynivalenol detection to ensure public food safety. A multifunctional fluorescent and colorimetric signal probe was constructed to develop the bioassay for deoxynivalenol detection based on the characteristics of Zr-MOF (PCN-224; i.e., high porosity, a large surface area, and excellent fluorescence quenching performance). Platinum nanoparticles (Pt NPs) were grown in situ outside, while glucose oxidase was stored inside (PPG). Glucose oxidase and Pt NPs are both enriched by Zr-MOF, achieving the first signal amplification, and cascade catalysis by the glucose-TMB system for colorimetric signal readout leads to the second signal amplification. PPG was quenched through the spontaneous formation of ZrOP bonds with fluorescent DNA to achieve a highly sensitive fluorescent readout. The self-supplied H2O2 in the colorimetric detection further improved the self-accuracy of the dual-mode analysis strategy (the accuracy of independent signal readout modes from two different signal transduction mechanisms). This multifunctional PPG probe avoids the time-consuming assembly of different probes and reduces error accumulation from uncontrollable factors in complex experimental procedures. It allows for the sensitive and accurate detection of deoxynivalenol with excellent limits of detection (5.3 pg/mL for the fluorescent assay and 34 pg/mL for the colorimetric method). Overall, this work demonstrates a viable approach for the construction of a dual-signal biosensing platform based on multifunctional MOF probes for biological analysis.

A multifunctional fluorescent probe for dual-color visualization of intracellular mitochondria and lipid droplets and monitoring of SO2 in vivo

Mitochondria and lipid droplets (LDs) are organelles involved in intracellular lipid and energy metabolism, and their complicated interplays are critical for maintaining cellular homeostasis. However, the fluorescent probes capable of simultaneously and discriminatively visualizing mitochondria and LDs are severely insufficient, which greatly limits the investigation of the interaction between two organelles in cells. In addition, abnormal SO2 levels can have harmful effects on living organisms. Monitoring the changes of SO2 levels in vivo is of great significance for biological and medical research. In this work, a SO2-dependent strategy was proposed for the first time to construct the new functional fluorescence conversion probe MLD-SO2 for two-color visualization of mitochondria and LDs. Under normal physiological conditions, the cationic form enabled the probe to selectively target the mitochondria and emit red fluorescence. In addition, based on SO2-driven nucleophilic addition reaction, the probe MLD-SO2 was converted to the neutral lipophilic structure in the presence of SO2, which targeted to LDs and displayed a strong blue emission. Importantly, mitochondria and LDs could be visualized simultaneously in the red and blue emission channels under the appropriate amount of SO2 exposure. Furthermore, the probe MLD-SO2 has been successfully employed to monitor the SO2 changes in zebrafish and mung bean sprouts. The remarkable imaging performances render the novel probe MLD-SO2 as a powerful tool for deciphering the interactions between mitochondrial and LDs and monitoring SO2 in different organisms.

Application of Near‐Infrared Fluorescence Imaging in Thrombosis Detection

AbstractIn recent years, researchers have developed a variety of near infrared (NIR) fluorescent probes to achieve visual detection of thrombotic plaques in vivo. In this review, after clarifying the advantages of NIR probes in sensing thrombus in vivo, the structures and design strategies underlying always‐on and turn‐on NIR thrombus probes are discussed. Subsequently, by summarizing and classifying the biomarkers overexpressed in thrombus, we highlight the recent advances in thrombus NIR fluorescent probes in biomedical applications. Furthermore, specific issues and opportunities in this field are explored at the end of the review, which will facilitate the inventive design of new multifunctional fluorescent probes and actively promote their future clinical translation.