Rhodamine-based fluorescent sensor for mercury in buffer solution and living cells

A novel fluorescent sensor based on thiooxorhodamine B has been prepared to detect Hg²⁺ in aqueous buffer solution. It demonstrates high selectivity for sensing Hg²⁺ with about 383-fold enhancement in fluorescence emission intensity and micromolar sensitivity (K_d = 7.5 × 10⁻⁶ mol L⁻¹) in comparison with alkali and alkaline earth metal ions (K⁺, Na⁺, Mg²⁺, Ca²⁺) and other transition metal ions (Mn²⁺, Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Ag⁺, Pb²⁺, Cr³⁺, Fe³⁺). Meanwhile the distinct color changes and rapid switch-on fluorescence also provide ‘naked eyes’ detection for Hg²⁺ over a broad pH range. Moreover, such sensor is cell-permeable and can visualize the changes of intracellular mercury ions in living cells using fluorescence microscopy.     

A selective fluorescent chemosensor with 1, 2, 4-triazole as subunit for Cu (II) and its application in imaging Cu (II) in living cells

A chemosensor based on rhodamine B with 1, 2, 4-triazole as subunit was synthesized and characterized. It exhibits high selectivity and sensitivity for Cu²⁺ in ethanol/water (6:4, v:v) of pH 7.0 HEPES buffer solution and undergoes ring opening mechanism, and a 2:1 metal-ligand complex is formed. The chemosensor displays a linear response to Cu²⁺ in the range between 1.0 × 10⁻⁷ M and 1.0 × 10⁻⁶ M with a detection limit of 4.5 × 10⁻⁸ M. Its capability of biological application was also evaluated and the results show that this chemosensor could be successfully employed as a Cu²⁺-selective chemosensor in the fluorescence imaging of living cells.     

A naphthalimide-rhodamine ratiometric fluorescent probe for Hg based on fluorescence resonance energy transfer

On the basis of fluorescent resonance energy transfer from 1,8-naphthalimide to rhodamine B, a new fluorophore dyads (4) containing rhodamine B and a naphthalimide moiety was synthesized as a ratiometric fluorescent probe for detecting Hg²⁺ with a broad pH range 5.7-11.0. The selective fluorescence response of 4 to Hg²⁺ is due to the Hg²⁺-promoted desulfurization of the thiocarbonyl moiety, leading to the ring-opening of rhodamine B moiety of 4. When 4 was employed at 0.1 μM with the slit size being 20 nm/20 nm, a low level of Hg²⁺ (up to 3 × 10⁻⁸ M) can be detected using the system.     

A highly selective fluorescent sensor for Hg based on the water-soluble poly(p-phenyleneethynylene)

The conjugated polymer P-1 could be synthesized by the polymerization of 4,7-diethynyl-benzo[2,1,3]thiadiazole (M-1) and 1,4-bis[3′-(N,N-diethylamino)-1′-oxapropyl]-2,5-diiodobenzene (M-2) via Pd-catalyzed Sonogashira reaction. The water-soluble conjugated polyelectrolyte P-2 could be obtained by the reaction of P-1 with ethyl bromide. Both P-1 and P-2 can emit orange fluorescence. The responsive optical properties of P-1 and P-2 on Hg²⁺ were investigated by fluorescence spectra. Hg²⁺ can lead to nearly complete fluorescence quenching of P-1. On the contrary, Hg²⁺ can show the most pronounced fluorescence enhancement response of P-2 in aqueous solution without interference from those coexistent ions, such as K⁺, Mg²⁺, Pb²⁺, Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, Fe³⁺ and Zn²⁺. The results also exhibit that this kind of water-soluble conjugated polyelectrolyte can be used as a highly sensitive and selective fluorescence sensor for Hg²⁺ detection in water.     

HAI-178 antibody-conjugated fluorescent magnetic nanoparticles for targeted imaging and simultaneous therapy of gastric cancer

The successful development of safe and highly effective nanoprobes for targeted imaging and simultaneous therapy of in vivo gastric cancer is a great challenge. Herein we reported for the first time that anti-α-subunit of ATP synthase antibody, HAI-178 monoclonal antibody-conjugated fluorescent magnetic nanoparticles, was successfully used for targeted imaging and simultaneous therapy of in vivo gastric cancer. A total of 172 specimens of gastric cancer tissues were collected, and the expression of α-subunit of ATP synthase in gastric cancer tissues was investigated by immunohistochemistry method. Fluorescent magnetic nanoparticles were prepared and conjugated with HAI-178 monoclonal antibody, and the resultant HAI-178 antibody-conjugated fluorescent magnetic nanoparticles (HAI-178-FMNPs) were co-incubated with gastric cancer MGC803 cells and gastric mucous GES-1 cells. Gastric cancer-bearing nude mice models were established, were injected with prepared HAI-178-FMNPs via tail vein, and were imaged by magnetic resonance imaging and small animal fluorescent imaging system. The results showed that the α-subunit of ATP synthase exhibited high expression in 94.7% of the gastric cancer tissues. The prepared HAI-178-FMNPs could target actively MGC803 cells, realized fluorescent imaging and magnetic resonance imaging of in vivo gastric cancer, and actively inhibited growth of gastric cancer cells. In conclusion, HAI-178 antibody-conjugated fluorescent magnetic nanoparticles have a great potential in applications such as targeted imaging and simultaneous therapy of in vivo early gastric cancer cells in the near future.     

识别细胞内金属离子的有机荧光探针研究进展

金属离子广泛存在于组织细胞和体液中,在人体的生理和病理中发挥着十分重要的作用。金属离子的浓度必须精确控制在一定的范围内,某些离子浓度的微弱变化都将引发人体的疾病。由于细胞是生命活动的基本单位,因此研究各种金属离子对生物体的影响,通过对活体细胞内金属离子的荧光显微成像进行细胞内离子的可视化定量和定性分析引起了人们的极大关注。就近年来人们对识别细胞内金属离子的有机荧光探针与细胞成像研究领域的进展进行了评述。     

Covalently cross-linked multilayer thin films composed of diazoresin and brilliant yellow for an optical pH sensor

The multilayered thin films composed diazoresin (DR) and brilliant yellow (BY) were fabricated by a layer-by-layer (LbL) deposition technique, and the ionic bonds between diazonium ion in DR and sulfonate residues in BY were converted to covalent bonds by UV light irradiation. The cross-linking between BY and DR prevented BY from desorption even in a pH 13 solution. The cross-linked (DR/BY)₁₀DR film exhibited pH-dependent absorption spectra in pH 9-13, and the response was repeatable and quick. The pH response time of the films was within a few seconds upon change from pH 9.0 to 13.0, and ca. 40 s upon change from pH 13.0 to 9.0.     

A fluorescent color/intensity changed chemosensor for Fe by photo-induced electron transfer (PET) inhibition of fluoranthene derivative

A fluorescent color/intensity changed fluoranthene derivative chemosensor for Fe³⁺ has been prepared and confirmed by ¹H-NMR, ¹³C-NMR, HRMS, and crystal data, which displays a high selectivity and antidisturbance for Fe³⁺ among environmentally and biologically relevant metal ions. Fluorescence studies show that fluorescent emission peak blue shifts about 100 nm with fluorescent intensity enhancing 75-fold, indicating a Fe³⁺-selective dual-emission behavior. Further study demonstrates the detection limit on fluorescence response of the sensor to Fe³⁺ is down to 10⁻⁷ M range. The fluorescence signals of chemosensor can be restored with o-phenanthroline, showing the binding of chemosensor and Fe³⁺ is really chemically reversible.     

A highly selective fluorescent probe for real-time imaging of UDP-glucuronosyltransferase 1A8 in living cells and tissues

Uridine diphosphate(UDP)-glucuronosyltransferases(UGTs)are enzymes involved in the biotransformation of important endogenous compounds such as steroids,bile acids,and hormones as well as exogenous substances including drugs,environmental toxicants,and carcinogens.Here,a novel fluorescent probe BDMP was developed based on boron-dipyrromethene(BODIPY)with high sensitivity for the detection of UGT1A8.The glucuronidation of BDMP not only exhibited a redemission wavelength(lex/lem=500/580 nm),but also displayed an excellent UGT1A8-dependent fluorescence signal with a good linear relationship with UGT1A8 concentration.Based on this perfect biocompatibility and cell permeability,BDMP was successfully used to image endogenous UGT1A8 in human cancer cell lines(LoVo and HCT15)in real time.In addition,BDMP could also be used to visualize UGT1A8 in tumor tissues.These results suggested that BDMP is a promising molecular tool for the investigation of UGT1A8-mediated physiological function in humans.     

A turn-on fluorescent sensor for imaging labile Fe(3+) in live neuronal cells at subcellular resolution

An eye for an iron: A highly sensitive, selective and reversible turn-on Fe(3+) sensor for imaging labile Fe(3+) in live cells at subcellular resolution is reported. The sensor can respond to changes in intracellular Fe(3+) levels and was used to image endogenous chelatable Fe(3+) in live human neuroblastoma SH-SY5Y cells, with two Fe(3+) pools being identified in mitochondria and endosomes/ lysosomes for the first time.     

Effectiveness factor for spatial gradient sensing in living cells

We consider the steady-state pattern of messenger molecules produced in the membrane of a cell perceiving and responding to an extracellular gradient of chemoattractant, which directs cell movement towards the chemoattractant source. Specifically, we analyze the undesirable effect of lateral diffusion in blurring the intracellular messenger profile. The concept of an effectiveness factor, akin to the analysis of reactions in porous catalysts, is applied to the spatial gradient sensing problem, with the distinction that slow, not fast, diffusion is required for effective gradient sensing. Analytical effectiveness factor expressions are derived for ideal geometries and then generalized to arbitrary cell shapes. In the case of mouse fibroblasts responding to gradients of platelet-derived growth factor, we conclude that the cell morphology and orientation with respect to the gradient can dictate whether messenger diffusion obliterates gradient sensing or has very little effect. The analysis outlined here allows the effect of intracellular messenger diffusion on spatial gradient sensing to be quantified for individual cells.     

4-Amino-1,8-naphthalimide-based fluorescent sensor with high selectivity and sensitivity for Zn2 + imaging in living cells

A new 4-amino-1,8-naphthalimide-based fluorescent sensor with iminodiacetic acid as receptor, was synthesized and characterized. Under physiological pH conditions, it demonstrates high selectivity and sensitivity for sensing Zn^2 + with about 50-fold enhancement in fluorescence intensity. The fluorescent sensor exhibited a characteristic emission band of 4-amino-1,8-naphthalimide with a green color centered at ~ 550 nm and was successfully applied to image Zn^2 + in living cells. Upon sensing of Zn^2 + the fluorescence emission spectrum is “switched on” demonstrating the suppression of PET from the receptor to the fluorophore.     

Carbon dots-based fluorescence sensor for two-photon imaging of pH in diabetic mice

Herein, a reversible pH fluorescent sensor was developed using caffeic acid as the precursor by one-step solvothermal synthesis method. The carbon dots-based sensor (CA-CDs) exhibited pH-dependent increase in fluorescence intensity and showed linear relationship in the range of pH 6.60 and 8.00. Notably, the fluorescence sensor has a reversible response to pH change. Finally, the CA-CDs has been successfully applied for two-photon imaging of the pH in liver and kidney of diabetic mice. Imaging results showed that the pH value in kidney of diabetic mice was lower than that of the normal mice, while the pH value in liver of diabetic mice was almost the same as that of the normal mice. The present study provides a simple analytical method for pH detection suitable for in vivo.     

Reduced texaphyrin: A ratiometric optical sensor for heavy metals in aqueous solution

We report here a water-soluble metal cation sensor system based on the as-prepared or reduced form of an expanded porphyrin, texaphyrin. Upon metal complexation, a change in the redox state of the ligand occurs that is accompanied by a color change from red to green. Although long employed for synthesis in organic media, we have now found that this complexation-driven redox behavior may be used to achieve the naked eye detectable colorimetric sensing of several number of less-common metal ions in aqueous media. Exposure to In(III), Hg(II), Cd(II), Mn(II), Bi(III), Co(II), and Pb(II) cations leads to a colorimetric response within 10 min. This process is selective for Hg(II) under conditions of competitive analysis. Furthermore, among the subset of response-producing cations, In(III) proved unique in giving rise to a ratiometric change in the ligand-based fluorescence features, including an overall increase in intensity. The cation selectivity observed in aqueous media stands in contrast to what is seen in organic solvents, where a wide range of texaphyrin metal complexes may be prepared. The formation of metal cation complexes under the present aqueous conditions was confirmed by reversed phase high-performance liquid chromatography, ultra-violet-visible absorption and fluorescence spectroscopies, and high-resolution mass spectrometry.     

The use of magnesium silicate (talc) in a potentiometric sensor for hydrogen ions

The construction and analytical evaluation of a pH sensor based in a matrix containing 20% of [(Mg₆Si₈O₂₀)](OH)₄, a magnesium silicate, talc and 30% graphite dispersed in an epoxy resin (50%) is described. The data obtained from various acid–base titrations were compared with those using a glass electrode in the same conditions. The proposed electrode presented a linear response in the 1–12 pH range with a slope of −39.9±0.3 mV/pH (at 25 °C) and ca. 15 s of response time. The lifetime of this electrode was higher than 8 months (ca. 1500 determinations) and it showed a good performance for pH determination and end-point indication in the potentiometric titrations of acids and bases.     

Synthesis of a highly selective bis-rhodamine chemosensor for naked-eye detection of Cu ions and its application in bio-imaging

A bis-rhodamine based fluorescent chemosensor for naked-eye detection of Cu²⁺ with enhanced sensitivity as compared to mono-rhodamine derivative has been synthesized, and its selectivity for Cu²⁺ in the presence of other competitive metal ions (Li⁺, Na⁺, K⁺, Cs⁺, Mg²⁺, Ca²⁺, Sr²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺), and application in bio-imaging are demonstrated.