Bifunctional Fluorescent Probe Research Articles

Simultaneous targeting and monitoring of free antigen and in-situ membrane antigen in prostate cancer cells via an aggregation-induced emission-based bifunctional probe

The precise clinical diagnosis of prostate cancer still presents inherent challenges, and usually a monitoring of multiple biomarkers is required. In this study, a new aggregation-induced emission (AIE)-based bifunctional strategy was developed for the simultaneous detection of prostate cancer-specific in situ membrane antigens (PSMA) and free antigens (PSA). First, a bifunctional fluorescent probe with double sensing sites (a PSA-specific sensing site and a PSMA-targeted ligand) was constructed. In the presence of PSA, it specifically binds to the PSA-specific sensing site of the probe, resulting in the restoration of the fluorescence signal, enabling linear sensing of PSA. For the detection of PSMA, the PSMA-targeted ligand modified on the probe can specifically recognize PSMA, inducing the aggregation of the AIE material and resulting in an enhanced fluorescence signal. Moreover, a liposome-based artificial cell was developed to simulate the real prostate cancer cell, and it was used to investigate the feasibility of monitoring the two types of antigens. Utilizing this bifunctional fluorescent strategy, a dual-analysis of free serum antigen biomarker of PSA and in-situ membrane antigen of PSMA was achieved. The assay exhibited a wide linearity range for PSA detection from 0.0001 to 0.1 μg/mL, with a low limit of detection (LOD) of 6.18 pg/mL. For PSMA, the obtained LOD is 8.79 pg/mL, with a linearity range from 0.0001 to 0.1 μg/mL. This strategy allows us to simultaneously assess the levels of two types of biomarkers in living human prostatic cancer cells, providing a highly accurate and selective tool for early screening and monitoring of prostatic cancer.

Novel coumarin-based ratiometric bifunctional fluorescent probe mimicking a set-reset memorized device

A novel coumarin-based fluorescent sensor CHE, incorporating 2-hydrazinylbenzothiazole and coumarin aldehyde, has been developed that demonstrated a preferential detection of Hg2+ and Ag+ in presence of interferences. Compared to previously prevalent intensity-based fluorescent probes, CHE exhibited a ratiometric fluorescence response to Hg2+ and Ag+, and further accurately differentiated Hg2+ and Ag + using the differential extractive ability of EDTA when interacting with ion-CHE complexes. Sensing mechanism was investigated and elucidated. The chemosensor CHE was successfully applied to detect Hg2+ and Ag+ in six distinct samples with satisfactory results. Additionally, combinatorial logic circuits were constructed utilizing three distinct logic gates (NOT, OR, and INH) based on the sensor's differential output signals in response to Hg2+/Ag+ and other cations. Interestingly, utilizing the reversible and reproducible switching behavior of the EDTA interaction with Hg2+, a conceptual 'Write–Read–Erase–Read' memory function with multi-write capability was proposed, offering a novel perspective for molecular-based memory systems.

Bifunctional fluorescent probe for fluoride and copper(Ⅱ) based on perylene diimide derivative and its application in cell imaging

A bifunctional fluorescent probe P1 based on perylene diimide derivative (PDI) was developed, demonstrating high sensitivity and selectivity for the rapid detection of fluoride (F-) and copper (Cu2+). The fluorescence of P1 was quenched upon interaction with F- and enhanced upon interaction with Cu2+. The concentration ranges for fluorescent detection of F- and Cu2+ are 0 ∼ 4 × 10-5 M and 0 ∼ 2.4 × 10-5 M, respectively. The stoichiometry of the complex formed between Cu2+ and P1 or F− and P1 was 1:1. The probe displays detection limits of 0.16 and 0.21 μM and binding constants (Ksv) of 3.92 × 104 and 1.72 × 104 M−1 for the detection of F- and Cu2+, respectively. The sensing mechanism and binding mode of P1 with F- and Cu2+ were investigated. The fluorescence quenching/enhancement of P1 was controlled by a photoinduced electron-transfer (PET) process. Furthermore, the ability of the probe to detect intracellular F- and Cu2+ was assessed using cell imaging techniques.

Visualizing HClO and ONOO− fluxes based on bifunctional fluorescent probe

Hypochlorous acid (HOCl) and peroxynitrite (ONOO−) are pivotal biomarkers of oxidative stress, intricately associated with diverse physiological and pathological processes. Nonetheless, due to the lack of methods to detect both HOCl and ONOO−, many of their roles remain obscure. In order to resarch the intrinsic interrelationship between HClO and ONOO− and the distribution of the two active substances within the cell, it is highly beneficial to develop fluorescence sensors capable of exhibiting distinct signals for HClO, ONOO−, and the combination of HClO/ONOO−. Here, we reasonably designed and constructed a new fluorescence sensor (DURC) with three different fluorescence signal outputs of blue, red and blue/red for HClO, ONOO−, and the combination of HClO/ONOO−, respectively. DURC exhibits high sensitivity in detecting HClO (58.6 nM) and ONOO− (89.3 nM). Moreover, DURC could effectively detects exogenous and endogenous HClO/ONOO− in living cells. Hence, this innovative fluorescent probe with a dual response capability can serve as a valuable tool for investigating the functions of HClO and ONOO−, as well as their involvement in physiological and pathological processes.

Bifunctional ratiometric fluorescent membrane containing pyrene-based probe for visual monitoring and efficient removal of Al3+

A bifunctional fluorescent pyrene-based probe, PYR, was designed by incorporating pyridine and phenolic hydroxyl moieties into pyrene fluorophore, which exhibited ratiometric fluorescent response toward Al3+. PYR underwent unique monomer-excimer conversion in ratiometric manner through the formation of a 2:1 coordination complex and accomplished with fluorescent color variation from green to blue. PYR displayed excellent selectivity, high sensitivity (LOD = 0.33 μM), rapid response (<45 s), and good cytocompatibility to Al3+. Notably, a fluorescent cellulose membrane decorated with PYR was successfully developed and applied for accurately quantify of Al3+ in diverse actual samples, and high-efficiency removal (∼96%) of Al3+ from water systems, with sustainable recycling performance up to 10 times. Bifunctional membranes also played an important role in reducing the LOD of Al3+ to 16 nM through the preconcentration process. Therefore, this study is crucial to the development of environmentally sustainable strategy for monitoring and removing pollution.

A Halloysite Nanotubes-based Probe for Efficient Fluorescence Detection and Adsorption Removal of Pb2+ in Water.

The detection and removal of Pb2+ is of utmost importance for environmental protection and human health due to its toxicity, persistent pollution, and bioaccumulation effects. To address the limitations associated with organic small molecule-based fluorescence probes such as poor water solubility and single functionality in detecting Pb2+, a fluorescence probe based on halloysite nanotubes was developed. This probe not only enables specific, rapid, and reliable detection of Pb2+ but also facilitates efficient removal of it from water. The development of this bifunctional fluorescent probe provides a valuable insight for designing more advanced probes targeting heavy metal ions.

A novel 2D Eu-MOF as a dual-functional fluorescence sensor for detection of benzaldehyde and Fe3.

Lanthanide metal-organic frameworks (Ln-MOFs) have unique advantages in sensing due to their excellent optical properties. In this study, we synthesized a dicarboxylic acid ligand with amide groups and successfully synthesized a novel two-dimensional (2D) MOF with the molecular formula C42H31EuN4O10 (Eu-MOF) by a solvothermal method. Single-crystal X-ray diffraction showed that amide groups are exposed on the outside of the two-dimensional coordination layer, with the possibility of recognizing specific molecules through hydrogen bonding interactions. The ligand's "antenna effect" enables Eu-MOF to emit a strong luminescence characterized by the "f-f" transition. Further studies have revealed that Eu-MOF could be used as a bifunctional fluorescent probe for the selective detection of benzaldehyde and Fe3+. The sensing mechanism has been analyzed in detail through powder X-ray diffraction (PXRD) analysis, UV-vis spectroscopy, fluorescence lifetime measurement, and density functional (DFT) theory calculation. This design and research can provide a reference for subsequent related work.

Solvothermal synthesis of bifunctional carbon dots for tartrazine and Fe(III) detection from chamomile residue by ternary DES pretreatment.

A ternary deep eutectic solvent (DES) consisting of choline chloride, lactic acid, and urea in a molar ratio of 1:2:2 was used to pretreat chamomile residue, followed by carbon dots (CDs) preparation using a one-pot solvothermal method. The CDs prepared under the suitable conditions had a high quantum yield of 47.34% and could be used as a bifunctional fluorescent probe for the detection of tartrazine and Fe(III). The concentration of tartrazine or Fe(III) had a good linear relationship with the fluorescence intensity of CDs that the determination coefficient (R2) was 0.9957 and 0.9943, and the limit of detection (LOD) was 40nM and 119nM, respectively. After verifying the different fluorescence quenching mechanisms of CDs by these two substances, a quantitative analysis was performed on real samples with recoveries of 90.70%∼104.29%. Overall, this study provided a promising technology for chemical conversion from low-cost chamomile residue to attractive bifunctional fluorescent probe.

Two unique M-MOFs (M:Zn, Mn) based on various metal-oxygen chains for good sensitivity sensing and magnetic properties

In this paper, two novel two-dimensional MOFs were synthesized by solvothermal reaction of 2,4-di(2′,5′-dicarboxylphenyl)benzoic acid ligand and Zn(Ⅱ) and Mn(Ⅱ) metal ions: {[Zn2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (1), {[Mn2(HL)(H2O)(DMF)2]·(H2O)·(DMF)}n (2). Complexes 1 and 2 are unique two-dimensional skeletons with particular metal-oxygen chains in their structures. The solid-state luminescence spectrum of complex 1 shows that its maximum emission peak is 448 nm. Further fluorescence studies of complex 1 show that it can efficiently detect Fe3+ and Cr2O72− in aqueous solution with a detection limit of 4.1 × 10−4 M and 2.7 × 10−4 M respectively, and has good recycling performance, so it is a potential bifunctional fluorescent probe material. The mechanism of fluorescence sensing quenching was also investigated in detail. Furthermore, magnetic studies have shown that there is an antiferromagnetic interaction between Mn(II) ions of complex 2.

A dual-functional coumarin-based fluorescent probe for turn off detection of Cu2+ and ratiometric detection of H2S and its applications in environmental samples and bioimaging samples

Bifunctional fluorescent probe has excited extensive interest in view of its dual-emission detection mode, favorable efficiency and low cost. Herein, a novel coumarin-based dual responsive fluorescent probe NNH was synthesized for response to Cu2+ and H2S with different fluorescence signals. This probe displayed a significant “turn-off” fluorescence response to Cu2+, and the limit of detection (LOD) for Cu2+ was calculated to be 0.356 µM. On the other hand, NNH exhibited a ratiometric fluorescence response to H2S with highly sensitivity (detection limit 4.266 µM), and the fluorescence color change from orange to cyan in the presence of H2S. The sensing mechanisms of NNH between Cu2+ and H2S were approved by Job's plot, ESI-MS analysis, and density functional theory (DFT) calculations. Besides, NNH could be served as a sensing tool for Cu2+ and H2S in environmental samples and living zebrafish.

A Novel Dye-Modified Metal-Organic Framework as a Bifunctional Fluorescent Probe for Visual Sensing for Styrene and Temperature.

A novel fluorescent probe (C460@Tb-MOFs) was designed and synthesized by encapsulating the fluorescent dye 7-diethylamino-4-methyl coumarin (C460) into a terbium-based metal-organic framework using a simple ultrasonic impregnation method. It is impressive that this dye-modified metal-organic framework can specifically detect styrene and temperature upon luminescence quenching. The sensing platform of this material exhibits great selectivity, fast response, and good cyclability toward styrene detection. It is worth mentioning that the sensing process undergoes a distinct color change from blue to colorless, providing conditions for the accurate visual detection of styrene liquid and gas. The significant fluorescence quenching mechanism of styrene toward C460@Tb-MOFs is explored in detail. Moreover, the dye-modified metal-organic framework can also achieve temperature sensing from 298 to 498 K with high relative sensitivity at 498 K. The preparation of functionalized MOF composites with fluorescent dyes provides an effective strategy for the construction of sensors for multifunctional applications.

Bifunctional fluorescent probe for the recognition of hydrazine and bisulfite in lipid droplets

Bifunctional fluorescent probes for recognizing different substances have important research significance due to the wide variety of analytes. Here, a triphenylamine structural fluorescent probe (TPA-CHO) for the recognition of hydrazine (N2H4) and bisulfite (HSO3-) in environment and lipid droplets based on aldehyde group sensing site was developed. The probe can detect those analytes with low detection limits and distinguishable color change (0.24 µM, red to green for N2H4; 1.71 µM, red to blue for HSO3-). The reaction mechanism indicates that after reacting with N2H4 and HSO3-, the production of hydrazone or hydroxy methanesulfonate group leads to a different molecular length and intramolecular charge transfer degree and then induces color-differentiated fluorescence emission. This structural design strategy for bifunctional fluorescent probes provides essential ideas for the design of single-molecule dual-analyte target probes.

Construction of bifunctional fluorescent probe for two-step cascade recognition of hydrogen sulfide and biothiols in biological system

Hydrogen sulfide (H2S) and biothiols play close interrelated roles in complex physiological and pathological events. Differentiating H2S and biothiols is highly significant to dissect their interplaying roles in biological system. Herein, a bifunctional fluorescent probe, OY, that could differentiate H2S and biothiols has been rationally constructed. Probe OY possessed two different recognition sites for detecting H2S and biothiols respectively, so as to avoid two analytes competing for one recognition site. Moreover, optical studies revealed that probe OY was able to selectively detect H2S and biothiols in red and blue fluorescence channels correspondingly. Furthermore, the sensing reaction of probe OY to H2S is much faster than that to biothiols. Therefore, probe OY was capable of detecting H2S and biothiols in two-step cascade mode in distinct fluorescence channels, which will dramatically mitigate potential crosstalk detection between H2S and biothiols. Practical application demonstrated that probe OY could be utilized for differentiating H2S and biothiols in living cells. Also, the variations of H2S and biothiols concentrations during non-enzymatical production of H2S were monitored. In addition, probe OY was used to track dynamic levels of H2S and biothiols in crop plant tissues which cultivated under different concentration of atmospheric H2S.

TDDFT study on the simultaneous sensing mechanism for peroxynitrite and glutathione by a bifunctional fluorescent probe

Using time-dependent density functional theory (TDDFT) method, the response mechanism of a reported bifunctional fluorescent probe for simultaneous recognition of peroxynitrite and glutathione (Chem. Commun. 2018, 54, 11336) was theoretically studied. Calculated vertical excitation energies based on the ground-state and excited-state geometries were consistent with the corresponding experimental ultraviolet–visible and fluorescence spectra. In the ground state, electron delocalization in the probe was limited because its geometry was restrained by steric hindrance. Frontier molecular orbital analysis has shown that the probe should undergo photoinduced electron transfer (PET) from the benzothiazole moiety to the maleimide moiety after excitation. The nonplanar structure together with PET led to fluorescence quenching of the probe. The probe could be dealkylated by peroxynitrite anion. The resulting intramolecular hydrogen bond increasesd the planarity of the molecule, while also gave rise to an excited-state proton-transfer process. Moreover, the addition reaction between the probe and glutathione inhibited the PET process. These two analytes together contributed to the fluorescence enhancement of the final product. This theoretical sensing mechanism for peroxynitrite and glutathione may potentially be important for the design and enhancement of novel probes.

Bifunctional Fluorescent Probes for the Detection of Mustard Gas and Phosgene

Mustard gas [sulfur mustard (SM)] and phosgene are the most frequently used chemical warfare agents (CWAs), which pose a serious threat to human health and national security, and their rapid and accurate detection is essential to respond to terrorist attacks and industrial accidents. Herein, we developed a fluorescent probe with o-hydroxythioketone as two sensing sites, AQso, which can detect and distinguish mustard gas and phosgene. The dual-sensing-site probe AQso reacts with mustard gas to form a cyclic product with high sensitivity [limit of detection (LOD) = 70 nM] and is highly selective to SM over phosgene, SM analogues, active alkylhalides, acylhalides, and nerve agent mimics, in ethanol solutions. When encountering phosgene, AQso rapidly converts to cyclic carbonate, which is sensitive (LOD = 14 nM) and highly selective. Their sensing mechanisms of AQso to mustard gas and phosgene were well demonstrated by separation and characterization of the sensing products. Furthermore, a facile test strip with the probe was prepared to distinguish 2-chloroethyl ethyl sulfide (CEES) and phosgene in the gas phase by different fluorescence colors and response rates. Not using the complicated instrument, the qualitative and quantitative detection of CEES or phosgene can be achieved only by measuring the red-green-blue (RGB) channel intensity of the test strip after being exposed to CEES or phosgene gas by the smartphone with an RGB color application.

Rational construction of sulfur dioxide and viscosity bifunctional fluorescent probe and its applications in water, food and bioimaging

Abnormal sulfur dioxide (SO2) and microenvironmental viscosity are detrimental to human health, so the effective monitoring of these indicators in relevant foods and organisms is of great significance. The dual-functional fluorescent probes that are sensitive to active sulfur and microenvironment at the subcellular organelle level can link the spatiotemporal changes of different species, which are crucial for understanding complex biological processes. In this work, a high-performance bifunctional red fluorescent probe named Probe 2 was rationally designed and constructed by screening different electron-donating groups. The probe exhibits good chromogenic and turn-on fluorescence responses to SO2 and viscosity, and can target mitochondria well. The probe has been successfully applied for accurate and rapid determination of sulfite content in water and food samples with good recovery (93.2–98.1 % and 94.2–100.4 %). Furthermore, Probe 2 enables real-time tracking and dual-color fluorescence imaging of SO2 and viscosity in cells and zebrafish, especially its high sensitivity to changes in these two parameters during mitochondrial dysfunction and apoptosis.

Construction of a bi-functional ratiometric fluorescent probe for detection of endoplasmic reticulum viscosity and ONOO- in cells and zebrafish

Viscosity and ONOO- are two important factors that affect the physiological activities and functions of endoplasmic reticulum (ER). Therefore, the detection of changes in viscosity and ONOO- levels is important to the study of related physiological and pathological processes. In this work, a new bi-functional fluorescent probe WND-1 for simultaneous detection of ER viscosity and ONOO- fluctuations in different channels was developed. The novel probe has good viscosity responsiveness. With the increase of viscosity, the ratio of fluorescence intensity (I638/I453) showed a good linear correlation with viscosity log values. In addition, the probe also has the ability to specifically detect ONOO- changes, and its limit of detection (LOD) value was 0.93 μM. WND-1 also has the advantages of high anti-interference, low cytotoxicity, good ER localization and rapid response. Notably, it not only can be used for ratiometric fluorescence detection of viscosity in cells and zebrafish, but also can simultaneously detect viscosity and ONOO- in different channels. Additionally, with WND-1, we also found that ONOO- could induce an increase in viscosity in the ER. This may help to facilitate the study of related physiopathological processes.

A dual-response triphenylamine-based fluorescent probe for selective sensing of copper(II) and nitric oxide in live cells

The development of bifunctional fluorescent probes for rapid and sensitive detection of copper(II) and nitric oxide (NO) in vivo is of significant importance to better understand their roles in human health. In this paper, a novel dual-response triphenylamine-based fluorescent probe, BQ, was developed for the detection of Cu2+ and NO in live cells. The sensing mechanism of the probe towards Cu2+can be attributed to the photoinduced electron transfer (PET) process of BQ-Cu2+, resulting in the remarkable quenching of the fluorescence emission. Meanwhile, the addition of NO can make the fluorescent wavelength of the probe red shift due to the intramolecular charge transfer (ICT) effect of BQ-NO, and the sensing mechanisms of BQ towards Cu2+ and NO have been further confirmed by 1H NMR and the high resolution mass spectrometry (HR-MS) analysis and the density functional theory (DFT) theoretical computation. Furthermore, BQ has the obvious advantages of high sensitivity, rapid fluorescent response, and reliability at physiological pH towards Cu2+ and NO. It is noteworthy that BQ can be used as a sensor for the detection of Cu2+ and NO in live RAW 264.7 cells by fluorescence imaging.

A novel bifunctional fluorescent probe for selectively sensing Hg2+ or ClO− and its application in living cell imaging

A new triazole compound, 2H-1,2,3-triazole-4,5-dicarboxylate containing double ester groups was firstly synthesized by one-step reaction and further combined with rhodamine B to generate a novel “turn-on” fluorescent probe L2 characterized by 1H NMR, 13C NMR, and HRMS techniques, respectively. The structural properties, quantum chemical parameters, and physiochemical parameters of the compound L2 were investigated using the computational chemistry method. The probe L1 showed good selectivity and sensitivity to Hg2+ in DMF/Tris-HCl (1:1, v/v, pH = 6.0, 20 μM) solution and to ClO− in MeOH (20 μM) solution. The spectral sensing behaviors of L1 toward 19 kinds of metal ions and 14 kinds of anions were respectively determined by fluorescence spectra and UV absorption spectra. A new emission peak appeared at 585 nm in the presence of Hg2+ and 576 nm in the presence of ClO− respectively. Meanwhile, the fluorescence intensity enhanced significantly along with naked-eye sensitive color changes, which indicated that the spiro-ring moiety of rhodamine was converted to the open-ring state in the presence of Hg2+ and formed the new complex as 1:2 M ratios confirmed by using MS, Job's plot, 1H NMR titrations, and TD-DFT calculation. Moreover, the limits of detection (LOD) for Hg2+ and ClO− were calculated as 4.73 nM and 0.21 μM based on the 3σ/k method, respectively. In addition, the results of the biological activity assay revealed that L1 showed less low cytotoxicity to HeLa cells. Furthermore, the probe L2 was successfully used for bioimaging Hg2+ and ClO− in HeLa cells, thereby indicating its great potential for the micro-detection of Hg2+ and ClO− in vivo.

TDDFT study on the ESPT and ICT mechanism of a bifunctional fluorescent probe for detecting fluoride and sulphite

TDDFT method was applied to study the excited-state mechanism of a reported fluorescent probe for fluoride and sulfite. Theoretical results showed the excitation of the probe molecule involved an intramolecular charge transfer process. Based on potential energy scanning and frontier orbital analysis, the excited-state proton-transfer process of the fluoride-probe product resulted in the significant red-shifted fluorescence. In contrast, the intramolecular charge transfer process was inhibited by sulfite anions. Due to the curtailing of the conjugated system, a blue-shifted emission was observed in the fluorescence spectrum. By exploiting the difference in fluorescence wavelengths,fluoride and sulfite anions could be recognized.