Development of an ICT-based ratiometric fluorescent hypochlorite probe suitable for living cell imaging

We have judiciously constructed a novel ICT-based ratiometric OCl(-) probe capable of ratiometric imaging in the live cells based on the new OCl(-)-promoted de-diaminomaleonitrile reaction.     

Development of FRET-based ratiometric fluorescent Cu2+ chemodosimeters and the applications for living cell imaging

Coumarin-rhodamine-based compounds 1a,b were rationally designed and synthesized as novel FRET ratiometric fluorescent chemodosimeters. Ratiometric chemodosimeters 1a,b exhibit several favorable features, including a large variation in the emission ratio, well-resolved emission peaks, high sensitivity, high selectivity, low cytotoxicity, and good cell membrane permeability. Importantly, these excellent attributes enable us to demonstrate ratiometric imaging of Cu(2+) in living cells by using these novel ratiometric fluorescent chemodosimeters.     

Development of a near-infrared fluorescent probe for imaging of endogenous Cu+ in live cells

We have constructed a novel NIR fluorescent turn-on Cu(+) probe suitable for imaging endogenous Cu(+) ions in living cells based on a tricarbocyanine scaffold and a high affinity Cu(+) receptor.     

A selective fluorescent probe for carbon monoxide imaging in living cells

A genetically encoded fluorescent probe is capable of selectively detecting carbon monoxide inside living cell. The probe, named COSer (CO sensor), consists of a circularly permuted yellow fluorescent protein (cpYFP) inserted into the regulatory domain of the bacterial CO-sensing protein, CooA, which gives the probe its selective CO-binding property.     

Development of an oxidative dehydrogenation-based fluorescent probe for Cu and its biological imaging in living cells

Based on a boron dipyrromethene (BODIPY) derivative containing an N, O and S tridentate ligand, a Cu²⁺ fluorescent probe BTCu was developed. The detection mechanism was verified as Cu²⁺-promoted oxidative dehydrogenation of an amine moiety, leading to a formation of a fluorescent Cu⁺-Schiff base complex. Free BTCu exhibited a maximum absorption wavelength at 496 nm, and a very weak maximum emission at 511 nm. Upon addition of various metals ions, it showed large fluorescence enhancement toward Cu²⁺ (417-fold in MeCN and 103-fold in MeCN/HEPES solution, respectively) with high selectivity. The detection limits are as low as 1.74 × 10⁻⁸ M and 4.96 × 10⁻⁸ M in the two different solutions, respectively. And BTCu could work in a wide pH range with an extraordinary low pK_a of 1.21 ± 0.06. Using fluorescence microscopy, the probe was shown to be capable of penetrating into living cells and imaging intracellular Cu²⁺ changes.     

Highly green fluorescent Nb2C MXene quantum dots for Cu2+ ion sensing and cell imaging

Niobium carbide MXene quantum dots (Nb₂C MQDs) derived from 2D Nb₂CT_x (MXene) are the rising-star material recently. Herein, a sulfur and nitrogen co-doped Nb₂C MQDs (S, N-MQDs) were synthesized through a hydrothermal method. The obtained Nb₂C MQDs have excellent green fluorescence with a quantum yield (QY) of 17.25%. In addition, they exhibited excitation-dependent photoluminescence, anti-photobleaching and dispersion stability. They emit light at 520 nm when excited at 390 nm. The Nb₂C MQDs could be successfully applied to copper ion detection with detection limit of 2 μmol/L and Caco-2 cells imaging.     

A fluorescent chemosensor for Cu2+ ions and its application in cell imaging

A new on-off fluorescent probe 1 for Cu²⁺ based on Schiff base compound was designed and synthesized by one-step reaction. The single probe 1 exhibited strong green fluorescence emission. A fluorescence quenching effect and faint color change were observed as soon as the Cu²⁺ was added to the probe system in H₂O/EtOH (v/v = 8:2, HEPES buffer, 0.05 M, pH = 7.4) solution. Other common metal cations did not cause the changes in the fluorescence and color of the probe 1. The optical properties were studied by the fluorescence emission and UV–Vis spectra. Meanwhile, the geometry optimizations of probe 1 and the [1-Cu²⁺] coordination complexes were also carried out by DFT using the Gaussian 09 program, in which the B3LYP function was used. Based on experimental measurement and theoretical analysis, we can know that the combination ratio of the probe and Cu²⁺ is 2:1 and the limit of detection (LOD) is as low as 5.3 × 10^?9 M Besides, the probe 1 was also used to analyze the Cu²⁺ in living cells.     

Nickel(II)-induced excimer formation of a naphthalene-based fluorescent probe for living cell imaging

Ni(2+)-induced intramolecular excimer formation of a naphthalene-based novel fluorescent probe, 1-[(naphthalen-3-yl)methylthio]-2-[(naphthalen-6-yl)methylthio]ethane (L), has been investigated for the first time and nicely demonstrated by excitation spectra, a fluorescence lifetime experiment, and (1)H NMR titration. The addition of Ni(2+) to a solution of L (DMSO:water = 1:1, v/v; λ(em) = 345 nm, λ(ex) = 280 nm) quenched its monomer emission, with subsequent enhancement of the excimer intensity (at 430 nm) with an isoemissive point at 381 nm. The fluorescence lifetime of free L (0.3912 ns) is much lower than that of the nickel(2+) complex (1.1329 ns). L could detect Ni(2+) as low as 1 × 10(-6) M with a fairly strong binding constant, 2.0 × 10(4) M(-1). Ni(2+)-contaminated living cells of plant origin could be imaged using a fluorescence microscope.     

Synthesis, crystal structure and living cell imaging of a Cu(2+)-specific molecular probe

We report the development of a rhodamine chromene-based fluorescence probe to monitor the intracellular Cu(2+) level in living cells. The new fluorescent probe exhibits a fluorescence response towards Cu(2+) under physiological conditions with high sensitivity and selectivity, and facilitates the naked-eye detection of Cu(2+). The fluorescence intensity was significantly increased by about 40-fold with 10 equiv. of added Cu(2+).     

A naphthalene-based Al3+ selective fluorescent sensor for living cell imaging

An efficient fluorescent Al(3+) receptor, N-(2-hydroxy-1-naphthalene)-N'-(2-(2-hydroxy-1-naphthalene)amino-ethyl)-ethane-1,2-diamine (L) has been synthesized by the condensation reaction between 2-hydroxy naphthaldehyde and diethylenetriamine. High selectivity and affinity of L towards Al(3+) in ethanol (EtOH) as well as in HEPES buffer at pH 7.4, makes it suitable to detect intracellular Al(3+) with fluorescence microscopy. Metal ions, viz. Li(+), Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Ag(+), Cd(2+), Hg(2+) and Pb(2+) do not interfere. The lowest detection limit for Al(3+) is 3.0 × 10(-7) M and 1.0 × 10(-7) M in EtOH and HEPES buffer respectively.     

A coumarin-based fluorescent probe for selective detection of Cu2+ in water

Fluorescent Red GK, a commercially available coumarin-based dye, was developed as a “turn-off” fluorescent probe for detection of Cu²⁺ in aqueous solution. It exhibited high selectivity and sensitivity at room temperature. Upon addition of Cu²⁺, the strong fluorescence of Fluorescent Red GK was severely quenched and its color changed from orange to colorless under illumination with a UV lamp; the color of the solution also changed from pink to colorless. So, it can be used as a specific colorimetric and fluorescent probe for Cu²⁺ with a detection limit as low as 0.0634?μM.     

Luminescent CdSe-ZnS quantum dots as selective Cu2+ probe

Luminescent CdSe-ZnS quantum dots (QDs) were modified with bovine serum albumin (BSA) and used as selective copper ion probe. The fluorescence of the water-soluble QDs can be quenched only by Cu²⁺ and Fe³⁺ in physiological buffer solution. Approximate concentrations of other physiologically important cations, such as Zn²⁺, Na⁺ and K⁺ etc. have no effect on the fluorescence. Adding F⁻ to form the colorless complex FeF₆³⁻ can eliminate the interference of Fe³⁺. The detection limit of Cu²⁺ ions was 10 nM. The results can be explained in terms of strong binding of Cu²⁺ onto the surface of CdSe resulting in a chemical displacement of Cd²⁺ ions and the formation of CuSe on the surface of the QDs.     

A new fluorescent and colorimetric probe for Cu2+ in live cells

Based on a change in structure between spirocyclic (non-fluorescent) and ring-open (fluorescent) forms of rhodamine-based dyes, a new fluorescent and colorimetric Cu(2+) probe was designed and synthesized. Upon treatment with Cu(2+), the weakly fluorescent probe exhibited a strong fluorescence response with high selectivity. In addition, the turn-on fluorescent probe upon the addition of Cu(2+) was applied in live cell imaging.     

A FRET-based fluorescent probe for imaging H2S in living cells

A FRET-based fluorescence probe was developed for selective detection of H₂S in aqueous buffer and inside living cells. For this probe, the FRET probe could be cleaved by H₂S, and the fluorescence of FRET donor is released. The probe is highly selective to H₂S over other biologically relevant species to give color change for naked eye observation. Confocal imaging indicated that the probe could monitor intracellular H₂S level changes.     

一种罗丹明类Cu~(2+)荧光探针化合物的合成及性能研究

以罗丹明B、水合肼和咔唑为原料,合成了一种新型的荧光增强型Cu2+荧光探针,即4-(N-咔唑基)苯亚甲基罗丹明B腙(CPMRH)。用FTIR、1H NMR和13C NMR对其分子结构进行了表征,并通过荧光光谱对探针的识别性能进行了研究。研究结果表明:探针CPMRH对水溶液中的Cu2+具有良好的选择识别性,且基本不受其他金属离子的影响;探针与Cu2+络合显示粉红色,可以作为一种裸眼检测的试剂用于溶液中Cu2+的检测;当λex=520 nm时,Cu2+水溶液与探针作用可显示橙红色荧光。且Cu2+浓度在1×10-5-5×10-5mol·L-1的范围内,探针的荧光强度与Cu2+浓度呈现出较好的线性关系;Cu2+的最低检出限为5.25×10-7mol·L-1;Job’s曲线表明,探针CPMRH与Cu2+的络合比为1∶1。     

A ratiometric fluorescent probe for imaging hydroxyl radicals in living cells

A novel fluorescent probe, the detection mechanism of which is based on the 'on-off' switching of a FRET triggered by the *OH-induced cleavage of a DNA strand, has been developed for the ratiometric imaging of *OH.     

Development of a hypoxia-selective near-infrared fluorescent probe for non-invasive tumor imaging

A near-infrared fluorochrome, GPU-311, was designed, synthesized and evaluated for its application in non-invasive imaging of tumor hypoxia. Efficient synthesis was achieved by nucleophilic substitution and click chemistry ring using the bifunctional tetraethylene glycol linker 2 containing thiol and azide groups for the conjugation of the propargylated nitroimidazole 1 and the heptamethine cyanine dye 3 bearing a 2-chloro-1-cyclohexenyl ring. GPU-311 exhibited long excitation and emission wavelength (Ex/Em=785/802?nm) and a decent quantum yield (0.05). The water solubility and hydrophilicity of GPU-311 increased. After in vitro treatment of SUIT-2/HRE-Luc pancreatic cancer cells with GPU-311, a higher level of fluorescence was observed selectively in hypoxia than in normoxia. However, in vivo fluorescence imaging of a mouse xenograft model after GPU-311 administration revealed inadequate accumulation of GPU-311 in tumors due to its rapid elimination through the liver.     

A novel fluorescent probe with a large Stokes shift for real-time imaging mitochondria in different living cell lines

Fluorescent dyes with large Stokes shift play a key role in avoiding self-quenching and scattered light of dyes in the process of biological imaging. In this work, a novel mitochondria-targetable fluorescent dye (PI-C2) with large Stokes shift (e. g. Maximum value is 219 nm in DMSO) have been developed. Compared to the commercial mitochondria probes MTR and MTG (Less than 30 nm in various solution), the newly constructed PI-C2 has a much larger Stokes shift in various solutions (169–219 nm in various solutions). Furthermore, the probe can successfully be applied for sensing mitochondria, and exhibited excellent photostability in different living cell lines. The novel fluorescent platform with the large Stokes may be extended to construct powerful fluorescent probes with large Stokes shift for detecting a wide variety of biomolecules in mitochondria.