Protein detection and quantitation by tetraphenylethene-based fluorescent probes with aggregation-induced emission characteristics

Three functionalized derivatives of tetraphenylethylene (TPE), namely, 1,2-bis(4-methoxyphenyl)-1,2-diphenylethene (1), 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethene (2), and 1,2-bis[4-(3-sulfonatopropoxyl)phenyl]-1,2-diphenylethene sodium salt (3), were synthesized and their fluorescence properties were investigated. All the TPE molecules are nonluminescent in the solution state but are induced to emit efficiently by aggregate formation. This novel process of aggregation-induced emission (AIE) is rationalized to be caused by the restriction of intramolecular rotations of the dye molecules in the aggregate state. The possibility of utilizing the AIE effect for protein detection and quantification is explored using bovine serum albumin (BSA) as a model protein, with salt 3 being found to perform as a stable, sensitive, and selective bioprobe.     

Facile fabrication of aggregation-induced emission based red fluorescent organic nanoparticles for cell imaging

A cyano-substituted diarylethlene derivative aggregation-induced emission （ALE） dye with two amino end-groups and 4,4＇-（hexafluoroisopropylidene）diphthalic anhydride were facilely incorporated into red fluorescent organic nanoparticles （FONs） via room temperature anhydride ring-opening polymerization under an air atmosphere. These obtained RO-HFDA FONs were characterized by a series of techniques including gel permeation chromatography, Fourier transform infrared spectroscopy, size distribution and zeta potential measurements, UV-Vis absorption spectrum, fluorescent spectroscopy and transmission electron microscopy. Biocompatibility evaluation and cell uptake behavior of RO-HFDA FONs were further investigated to explore their potential biomedical application. We demonstrated that such FONs showed high water dispersibility, stable uniform spherical morphology （150-200 nm）, broad excitation band （350-605 nm）, intense red fluorescence （627 nm） and excellent biocompatibility, making them promising for cell imaging applications.     

Water-soluble NIR fluorescent probes based on squaraine and their application for protein labeling.

Water-soluble near-infrared (NIR) fluorescent labeling probes, named KSQ-3 and -4, which are based on a squaraine backbone, were synthesized and applied to biological labeling. The presented results demonstrate that the large, planar and hydrophobic squaraine dye becomes fully soluble in aqueous solution by the introduction of several sulfo group terminated alkyl substituents. Especially KSQ-4, which is substituted with four sulfo groups, exhibited perfect water solubility and significant fluorescence emission at the NIR region (817 nm) in the presence of bovine serum albumin (BSA). BSA was covalently labeled with KSQ-4, and the conjugate showed a strong absorption peak at 787 nm, which indicates compatibility with commercially available NIR laser diodes used for exciting the fluorophore. Furthermore, strong fluorescence emission was observed at 812 nm (phi = 0.08).     

A novel "turn-on" fluorescent chemosensor for the selective detection of Al3+ based on aggregation-induced emission

A water-soluble, 'turn-on' fluorescent chemosensor based on aggregation-induced emission (AIE) has been developed. It exhibits rapid response, excellent selectivity, and sensitivity to Al(3+).     

A multifunctional aggregation-induced emission (AIE)-active fluorescent chemosensor for detection of Zn2+ and Hg2+

An aggregation-induced emission (AIE)-active fluorescent chemosensor based on a tetraphenylethene (TPE) unit has been successfully designed and synthesized. Interestingly, the luminogen could detect Zn²⁺ selectively in a THF solution with the detection limit of 1.24 × 10⁻⁶ mol L⁻¹. Meanwhile, the luminogen could also detect Hg²⁺ selectively in a THF-water mixture with the water content of 90%, and the detection limit was 2.55 × 10⁻⁹ mol L⁻¹. Furthermore, the solid-state mechanochromic fluorescence behavior of the luminogen was investigated systematically. Indeed, the AIE-active luminogen also exhibited reversible mechanofluorochromic phenomenon involving fluorescent color change from blue to green, and powder X-ray diffraction results indicated that the switchable morphology conversion between crystalline and amorphous states was responsible for this mechanochromism phenomenon.     

Sugar-bearing tetraphenylethylene: novel fluorescent probe for studies of carbohydrate-protein interaction based on aggregation-induced emission

Neutral sugar-bearing tetraphenylethenes (TPE) are designed and prepared as "turn-on" luminescent sensors for lectins and glycosidases based on aggregation-induced emission. Through aggregation derived from carbohydrate-lectin binding, multivalent mannosyl-bearing TPE shows a good selectivity and sensitivity to Con A by switching on the fluorescence of water-soluble tetraphenylethylene-based glyco-conjugates in aqueous solution. Meanwhile, cellobiosyl-bearing TPE can be used to investigate enzymatic hydrolysis based on emission enhancing by glycosidase-induced aggregation.     

A highly sensitive "switch-on" fluorescent probe for protein quantification and visualization based on aggregation-induced emission

A highly sensitive and water-soluble "switch-on" fluorescent probe with aggregation-induced emission characteristics was developed for protein quantification and visualization. It offers a rapid, economic and effective way for the assay of complete serum proteins and disease-marker proteins.     

A design of fluorescent probes for superoxide based on a nonredox mechanism

Fluorometric detection of O2-* is performed based on desulfonylation of 3 to the corresponding fluoresceins 4 through nucleophilic substitution, and this fluorescing process is quite specific toward O2-* over H2O2, t-BuOOH, NaOCl, 1O2, HO*, NO*, and ONOO-. Furthermore, effects of glutathione, cytochrome P450 reductase/NADPH, and diaphorase/NADH are relatively small on the fluorescing process of probe 3 with X = Y = F, which is useful to detect O2-* released from neutrophils stimulated by phorbol myristate acetate with satisfactory sensitivity.     

Leek-derived codoped carbon dots as efficient fluorescent probes for dichlorvos sensitive detection and cell multicolor imaging

A biomass nitrogen and sulfur codoped carbon dots (NS-Cdots) was prepared by a simple and clean hydrothermal method using leek, and was employed as efficient fluorescent probes for sensitive detection of organophosphorus pesticides (OPs). The leek-derived NS-Cdots emitted blue fluorescence, but was quenched by H₂O₂. Due to acetylcholinesterase/choline oxidase–based cascade enzymatic reaction that produces H₂O₂ and the inhibition effect of OPs on acetylcholinesterase activity, a NS-Cdots-based fluorescence “off-on” method to detect OPs-dichlorvos (DDVP) was developed. More sensitivity and wider linear detection range were achieved from 1.0 × 10⁻⁹ to 1.0 × 10⁻³ M (limit of detection = 5.0 × 10⁻¹⁰ M). This developed method was applied to the detection of DDVP in Chinese cabbage successfully. The average recoveries were in the range of 96.0~104.0% with a relative standard deviation of less than 3.3%. In addition, the NS-Cdots fluorescent probes were also employed successfully in multicolor imaging of living cells, manifesting that the NS-Cdots fluorescent probes have great application potential in agricultural and biomedical fields.

Graphical Abstract

     

Colorimetric and ratiometric fluorescent chemosensor based on diketopyrrolopyrrole for selective detection of thiols: an experimental and theoretical study

A colorimetric and ratiometric fluorescent thiol probe was devised with diketopyrrolopyrrole (DPP) fluorophore. The probe gives absorption and emission at 523 and 666 nm, respectively. In the presence of thiols, such as cysteine, the absorption and emission band shifted to 479 and 540 nm, respectively. Correspondingly, the color of the probe solution changed from purple to yellow, and the fluorescence changed from red to yellow. The emission intensity at 540 nm was enhanced by 140-fold. The Stokes shift of probe 1 (107 nm) is much larger than the unsubstituted DPP fluorophore (56 nm). Mass spectral analysis demonstrated that besides the expected Michael addition of thiols to the C═C bonds, the CN groups of the malonitrile moieties also react with thiols to form 4,5-dihydrothiazole structure. Probe 1 was used for fluorescence imaging of intracellular thiols. In the presence of thiols, both the green and red channel of the microscopy are active. With removal of the intracellular thiols, signal can only be detected through the red channel; thus, ratiometric bioimaging of intracellular thiols was achieved. The ratiometric response of probe 1 was rationalized by DFT calculations. Our complementary experimental and theoretical studies will be useful for design of ratiometric/colorimetric molecular probes.     

A ratiometric fluorescent chemosensor for Al in aqueous solution based on aggregation-induced emission and its application in live-cell imaging

A ratiometric fluorescent chemosensor 1 was developed for the detection of Al³⁺ in aqueous solution based on aggregation-induced emmision (AIE). The chemosensor showed the fluorescence of its aggregated state and Al³⁺-chelated soluble state in the absence and in the presence of Al³⁺, respectively, and resulted in a fluorescence ratio (I₄₆₁/I₅₃₇) response to Al³⁺ in neutral aqueous solution at a detection limit as low as 0.29 μmol L⁻¹. The method was also highly selective to Al³⁺ over other physiological relevant metal ions investigated in this study. Taking advantage of its AIE characteristics, the chemosensor was successfully applied on test papers for simple and rapid detection of Al³⁺. Moreover, the application of 1 for the imaging of Al³⁺ in living cells by ratiometric fluorescence changes was also achieved.     

Metal-enhanced fluorescent probes based on silver nanoparticles and its application in IgE detection

In this paper, a novel metal plasmon coupled with an aptamer–nucleotide hybridized probe was fabricated and applied for protein detection. The specific aptamer and single-strand oligonucleotide were chemically bound to silver nanoparticles (AgNPs), and Cy5-labeled, complementary single-strand oligonucleotides were hybridized with the particle-bound oligonucleotides. The hybridized DNA duplexes were regarded as rigid rods that separated the fluorophore Cy5 and the surface of AgNPs to reduce the competitive quenching. Using a model system comprising human immunoglobulin E (IgE) as the analyte and goat antihuman IgE as immobilized capture antibody on glass slides, we demonstrate that the detection performance of the synthetic probe was superior to the aptamer-based fluorescent probes. The results showed a good linear correlation for human IgE in the range from 10 ng/ml to 6.25 μg/ml. The detection limit obtained was 1 ng/ml, which was 50 times lower than that using Cy5 oligonucleotide/aptamer hybrid duplex (Probe2) due to the metal-enhanced fluorescence effect. This new strategy opens the possibility for the preparation of high-sensitivity detection probes based on metal nanoparticles.     

Linear Schiff-base fluorescence probe with aggregation-induced emission characteristics for Al detection and its application in live cell imaging

A simple Schiff-base derivative with salicylaldehyde moieties as fluorescent probe 1 was reported by aggregation-induced emission (AIE) characterization for the detection of metal ions. Spectral analysis revealed that probe 1 was highly selective and sensitive to Al³⁺. The probe 1 was also subject to minimal interference from other common competitive metal ions. The detection limit of Al³⁺ was 0.4 μM, which is considerably lower than the World Health Organization standard (7.41 μM), and the acceptable level of Al³⁺ (1.85 μM) in drinking water. The Job's plot and the results of ¹H-NMR and FT-IR analyses indicated that the binding stoichiometry ratio of probe 1 to Al³⁺ was 1:2. Probe 1 demonstrated a fluorescence-enhanced response upon binding with Al³⁺ based on AIE characterization. This response was due to the restricted molecular rotation and increased rigidity of the molecular assembly. Probe 1 exhibited good biocompatibility, and Al³⁺ was detected in live cells. Therefore, probe 1 is a promising fluorescence probe for Al³⁺ detection in the environment.     

11-Mercaptoundecanoic acid functionalized gold nanoclusters as fluorescent probes for the sensitive detection of Cu2+ and Fe3+ ions

Metal ions are physiologically essential,but excessive metal ions may cause severe risk to plants and animals.Here,we prepared gold nanoclusters(Au NCs) protected by 11-mercaptoundecanoic acid(11-MUA),which have excellent fluorescence properties for the detection of metal ions.The results showed that the copper ions(Cu~(2+)) and iron ions(Fe~(3+)) in the solution have obvious quenching effect on the fluorescence intensity of Au NCs.The detection range of Fe~(3+) was 0.8–4.5 mmol/L(R~2= 0.992) and 4.5–11.0 mmol/L(R~2= 0.997).And Cu~(2+) has a lower linear range(0.1–1.0 mmol/L,R2= 0.993).When EDTA was added into the reaction system,it was observed that the quenching effect of Cu~(2+) and Fe~(3+)on Au NCs showed different phenomenon.Then,the effect of metal ions on the fluorescence of Au NCs was investigated.The selective detection of Cu~(2+) was achieved by EDTA masking of Fe~(3+).In addition,we realized the metal ions detection application of Au NCs in the serum     

Designing of naphthalene based acylhydrazone derivative as a selective fluorogenic sensor for strong volatile acids based on aggregation-induced emission

In the present study, a cognitive self-assembled fluorescent chemosensor, (2-hydroxy-naphthalene-1-ylmethylene)-hydrazide (NIZ) was presented which disclosed sensitive and selective trace quantity detection of strong volatile acids both in binary solvent mixture [2:8 (v/v) THF/water] and solid state (thin film) based on aggregation-induced emission (AIE) characteristics. In molecularly dissolved state, NIZ participated in the excited-state intramolecular proton transfer (ESIPT), where the dynamic flexibility during a fast photoinduced process debilitated the consumed excited energy nonradiatively and enabled NIZ to be completely nonluminescent in THF (φ_f = 0.39%). However, vigorous rigidification of molecular framework upon exercising different noncovalent forces obstructed all possible intramolecular motions via restricted intramolecular rotation (RIR), where delimited ESIPT upon prompting the molecules into self-assembly resulted dramatically augmented emission intensity (φ_f = 29.8%) impregnated with AIE behavior in THF/water. Subsequently, spontaneously evolved green emissive fluorescent nanoaggregates were primarily employed as a fluorescent chemosensor for aqueous phase recognition of strong acids where protonation-induced destruction of aggregated morphology due to reasonable interaction between NIZ and analytes led to a selective fluorescence quenching towards trifluoroacetic acid [(HTFA); detection limit (DL) = 41.74 nM], hydrochloric acid [(HCl); DL = 47.47 nM] and nitric acid [(HNO₃); DL = 50.17 nM). Importantly, the ready-made cost-effective test kits of NIZ exhibited a selective fluorogenic response towards vapors from HNO₃, HTFA and HCl in the rapid fashion where DLs were as low as 0.88, 1.39 and 4.57 ppm respectively to demonstrate the “in-the field” monitoring of air quality. Finally, the reversible “ON-OFF” fluorogenic response from NIZ inspired us to device a “use” and “throw” security marker upon alternative presence of HTFA and triethylamine (TEA) to augment the day-to-day practical applications.     

Synthesis and mechanism study of two similar colorimetric fluorescent probes for specific detection of bisulfite and hypochlorite

Research on Chemical Intermediates - Based on coumarin structure, two fluorescent probes (L1 and L2) were constructed for specific detection of bisulfite (HSO3?) and hypochlorite...     

A ratiometric fluorescent probe for palladium detection based on an allyl carbonate group functionalized hemicyanine dye

A novel ratiometric fluorescent probe for palladium species was synthesized based on an allyl carbonate group, a novel reaction site, and a hemicyanine dye. The probe displays relatively rapid response, high selectivity, and anti-disturbance toward palladium in HEPES buffers without additional reagents. The detection mechanism, palladium triggers the cleavage of allyl carbonate in the probe and then decarboxylation of the product to induce the ratiometric fluorescence response, was verified using UV–vis and mass spectrometry analysis. The probe was successfully applied for ratiometric fluorescent detection of palladium in tap water, river water, and in fetal bovine serum.     

基于香豆素与胍的荧光探针的合成及对Co2+、Fe3+的识别研究(英文)

本论文设计合成了基于1,3-二氨基胍盐酸盐、氨基胍盐酸盐的新型香豆素类荧光探针L1、L2。通过紫外-可见、荧光光谱的变化研究探针L1、L2对金属离子的识别效应。利用Job’s plot曲线确定探针L1与Co²⁺形成了1∶2的配合物,探针L2和Fe³⁺形成了3∶1的配合物,且表现为明显的荧光增强。探针L1对Co²⁺的检出限可达到10^-6mol/L,探针L2对Fe³⁺的检出限可达到10^-7mol/L。两种高灵敏度荧光探针有望应用于生物和环境监测领域。     

Dual recognition strategy for ultra-sensitive fluorescent detection of Hg2+ at femto-molar level based on aptamer functionalized sulfur quantum dots

In the present study, a dual recognition strategy for ultrasensitive detection of Hg²⁺ was successfully developed for the first time based on aptamer functionalized sulfur quantum dots (Apt-SQDs). The developed Apt-SQDs not only retained the good fluorescence properties of quantum dots but also overcame the problem of poor selectivity of SQDs for heavy metal ions. This system used the dual recognition strategy, including the combination of S_x^2? and Hg²⁺ and T-Hg²⁺-T structures to excellently identify and capture Hg²⁺, and an ultrahigh sensitivity fluorescent aptasensor was fabricated. The fluorescent aptasensor had a good response to Hg²⁺ at concentrations ranging of 10^?15 to 10^?7 M with an ultralow limit of detection of 0.3 fM, and the response to other metal ions was far less than that to Hg²⁺. It was successfully applied to detect Hg²⁺ in nearby environmental water samples (tap water, lake water and river water) with a good recovery rate. Moreover, portable test papers that would be useful for Hg²⁺ monitoring in environmental water were designed. The dual recognition strategy not only achieves ultrasensitive fluorescent detection of Hg²⁺ but also provides a new insight into the further expansion of the application of SQDs.     

N-aryl-9-amino-substituted acridizinium derivatives as fluorescent "light-up" probes for DNA and protein detection

[reaction: see text] N-Arylamino-substituted acridizinium (benzo[b]quinolizinium) derivatives are almost nonfluorescent in water or organic solvents; however, upon addition of calf thymus DNA or bovine serum albumin the fluorescence intensity increases by a factor of 10 to 50. Thus, these dyes exhibit ideal properties to be used as DNA- and protein-sensitive "light-up probes".