A Dendron-Based Fluorescence Turn-On Probe for Tumor Detection

Specifically amplifying the emission signals of optical probes in tumors is an effective way to improve the tumor-imaging sensitivity and contrast. In this paper, the first case of dendron-based fluorescence turn-on probes mediated by a Förster resonance energy transfer (FRET) mechanism is reported. Dendrons up to the fourth generation with a hydrophilic oligo(ethylene glycol) scaffold are synthesized by a solid-phase synthesis strategy, and show precise and defect-free chemical structures. To construct the fluorescence turn-on probe, one Cy5.5 molecule is conjugated to the focal of a G3 dendron through a robust linkage and eight Black Hole Quencher 3 (BHQ-3) molecules are conjugated to its periphery through a PEG chain bearing a reductively cleavable disulfide linkage. By in vitro and in vivo experiments, it is demonstrated that the fluorescence of the dendron-based probe can be activated effectively and rapidly in the reductive environments of tumor cells and tissues, and the probe thus exhibits amplified tumor signals and weak normal tissue signals. Compared with the reported nanoscale turn-on probes, the dendron-based probe has several significant advantages, such as well-defined chemical structure, precisely controllable fluorophore/quencher conjugation sites and ratio, desirable chemical stability, and reproducible pharmacokinetic and pharmacological profiles, and is very promising in tumor detection.     

Cyclodextrins as Surfactants for Solubilization and Purification of Carbon Nanohorn Aggregates

Nano‐ to micrometer‐scale surface roughness contributes to the hydrophobicity of materials as discussed often in terms of superhydrophobicity. We report here that as little as 1 wt% of α, β, and γ‐cyclodextrins (CDs) can disperse carbon nanohorn aggregates (CNHa) as surfactants in water by binding on their pointed tips. The binding mode was visually demonstrated using single‐molecule atomic resolution real‐time electron microscopy (SMART‐EM). The SMART‐EM data provided an estimation of the equilibrium constant of the CD binding to be close to that of adamantane ammonium chloride to β‐CD. A qualitative study on the rate of decomplexation of α, β, and γ‐CDs from CNHa suggests a substantial mechanistic difference in their binding mode to the CNH tips. A sequence of α‐CD complexation and decomplexation allows us to purify CNHa by selectively removing graphitic ball‐shaped impurity (GB). Upon treatment with NaNH₂, the purified CNHa produce GB‐free amino‐CNHa where the tips are functionalized with NH₂ groups.     

Determination of N-nitrosamines by HPTLC with Fluorescence Detection — Use of Non-Ionic Surfactants as Enhancing Agents

JPC – Journal of Planar Chromatography – Modern TLC - The dansyl derivatives of N-nitrosodimethylamine, N-nitrosodi-ethylamine, and N-nitrosodibuthylamine have been separated by HPTLC...     

表面活性剂增溶比率荧光Zn2+检测方法研究

合成了一种新的Zn2+荧光检测试剂8-(2-(十八氨基)乙酰氨基)喹啉(AQZ-18)。通过自发荧光的非离子表面活性剂OP-10增溶AQZ-18,获得了一个与Zn2+结合后在320 nm和505 nm分别有两个荧光发射峰的溶液体系。短波长荧光峰来自OP-10,荧光峰强度不随Zn2+浓度变化;长波长荧光峰来自AQZ-18,荧光峰强度随Zn2+浓度增加而增强。利用上述两个荧光峰强度随Zn2+浓度变化时的比值变化建立了一种新的比率荧光Zn2+检测方法。研究表明,Zn2+与AQZ-18形成1∶1型基态配合物,其表观结合常数为1.1×106L/mol。常见金属离子对Zn2+荧光检测无干扰,Zn2+浓度在0～1.1×10-5mol/L范围内与荧光强度变化的比值呈良好的线性关系,相关系数(r2)为0.996 2,检出限为55 nmol/L。该方法可用于水样中Zn2+的检测。     

Solubilization Enhancing Effect of A-B-Type Silicone Surfactants in Microemulsions

We report a solubilization enhancing effect of A-B-type silicone surfactants in microemulsions. The effect of added long-chain silicone surfactants, Si₂₅C₃EO_51.6 (extended length≈21.8 nm) and Si₁₄C₃EO_15.8 (extended length≈8.5 nm) on the solubilization capacity of C₁₂EO₅ (extended length≈3 nm)/water/dodecane microemulsion was investigated at the hydrophile-lipophile balance temperature at which a microemulsion (surfactant) phase containing equal weights of oil and water touches the three-phase body. The addition of silicone surfactants exhibits an enormous increase of the swelling of the middle phase primarily with an associated increase in the structural length scale of the microemulsion. The solubilization power increases with increasing x₂ (mole fraction of silicone surfactants to the total surfactant) and going through a maximum it decreases, since a lamellar liquid crystal introduces in the multiphase region at low surfactant concentrations. The solubilization capacity reaches at the maximum to an almost equal level for different x₂ values, 0.02 for Si₂₅C₃EO_51.6 and 0.09 for Si₁₄C₃EO_15.8. The solubilization power of the lamellar phase shows a similar trend with lower magnitude.     

Solubilization Behaviors of Nonpolar Substrates Using Double Tailed Cationic Surfactants

A series of double hydrophobic tails of N-methyl diethanolammonium bromide cationic surface active agents were synthesized. Their chemical structures were elucidated using different analytical tools including elemental analyses, FTIR, mass fragmentation, and ¹H-NMR spectroscopy. Their surface parameters including critical micelle concentration (CMC), effectiveness (π _CMC ), efficiency (Pc ₂₀), maximum surface excess (Γ _max ), and minimum surface area (A _min ) were calculated. The behaviors of the synthesized molecules in their solutions were discussed based on the data of surface parameters, micellization and adsorption thermodynamics at 25°, 40°, and 55°C. The experimental data of surface activity showed that these molecules are tends to form micelles in the bulk of their solutions at lower temperatures. On contrarily, they prefer to adsorb at higher temperatures. The synthesized cationic surfactants were used as solubilizing agent for nonpolar substrate (paraffin oil) at 25°C. The results of solubilization measurements showed good ability for the used surfactants towards solubilizing paraffin oil in aqueous medium. The results showed that the chemical structure of the solubilizate plays an important rule in its solubilization. Several factors were found to influence the extent of solubilization including: number of alkyl chains within surfactant molecule, symmetry of molecules and chain length of hydrophobic parts. The results were rationalized by the Kraft point and HLB values of the used surfactants. Furthermore, solubilization curves showed the steady state solubilization of each surfactant used.     

荧光探针法研究双子型阳离子表面活性剂与明胶的相互作用

利用荧光探针法研究了双子型阳离子表面活性剂与明胶的相互作用,考察了此类表面活性剂的分子结构和明胶对临界胶团浓度(cmc)、胶团聚集数(N_agg)和胶团微极性的影响.结果表明,当双子型阳离子表面活性剂的疏水基增长时,cmc减少,N_agg增加,胶团的微极性降低;加入明胶后,双子型阳离子表面活性剂的N_agg减少,cmc和胶团微极性增加.     

Molecular-Thermodynamic Model of Solubilization in Direct Spherical Micelles of Nonionic Surfactants

Colloid Journal - A thermodynamic model has been formulated for the formation work of a molecular aggregate consisting of molecules of a nonionic surfactant and a solubilisate in a...     

重金属镉离子人工合成抗原的荧光特性分析

以1-(4-异硫氰苄基)乙烯基二胺-N,N,N′,N′-四乙酸为双功能螯合剂,偶联Cd2+与血清蛋白质分子, 合成了Cd2+人工抗原.利用荧光光谱分析了Cd2+人工合成抗原的荧光特性并得到合成反应的偶联比为11∶ 1～16∶ 1;通过荧光相图分析表明, Cd2+人工抗原合成过程中血清蛋白质的折叠状态符合"二态模型";偏振荧光光谱检测结果显示, Cd2+人工抗原合成中血清蛋白质色氨酸残基的微区构象发生一定变化,导致载体蛋白质构象改变.     

The Interactions Between Nonionic Surfactants and Cyclodextrins Studied by Fluorescence Measurements

The complex formation between some nonionic surfactants and -, - and -cyclodextrin was studied by fluorescence measurements. The relative fluorescence intensity of a solute containing a nonionic surfactant at a constant concentration far below the critical micelle concentration (CMC) are enhanced by the addition of cyclodextrins. Non linear type equations were derived to obtain stability constants by fluorescence measurements for inclusion complexes formed between cyclodextrins and the nonionic surfactants. In most cases 1 : 1- and 2 : 1-complexes (ratio of cyclodextrin to surfactant) are formed.     

Spectrofluorimetric Assay of Cationic Surfactants by Fluorescence Quenching of 9-Anthracenecarboxylic Acid

A new simple, selective and sensitive fluorescence quenching method was developed to determine cationic surfactants with the 9-anthracenecarboxylic acid (ACA). The fluorescence intensity of ACA was decreased by addition of trace amounts of cationic surfactants. Under optimum conditions, the ratio of fluorescence intensity in the absence and presence of cationic surfactants was proportional to the concentration of cationic surfactants over the range of 0.3–4.5 × 10⁻⁵ mol L⁻¹ for cetylpyridinium chloride (CPC) and 0.4–6.0 × 10⁻⁵ mol L⁻¹ for cetyl trimethyl-ammonium bromide (CTAB). The detection limits are 1.0 × 10⁻⁶ mol L⁻¹ for CPC and 1.2 × 10⁻⁶ mol L⁻¹ for CTAB, respectively. Based on this approach, this paper presents a new quantitative method for cationic surfactants assay.     

分子信标荧光探针用于抑癌基因ING1表达产物的定量测定

根据抑癌基因ING1基因的序列设计并合成了检测ING1转录产物的分子信标核酸探针,发展了一种快速测量从正常细胞系和鼻咽癌肿瘤细胞系提取的ING1转录产物的方法,所得结果与用逆转录结合PCR法(RT-PCR)得到的结果相吻合.并且,将能表达ING1基因的质粒转入肿瘤细胞进行培养后,再将分子信标转入肿瘤细胞,发现转导了质粒的肿瘤细胞比未转导质粒的肿瘤细胞内的荧光明显增强,从而进一步证实了所设计的分子信标核酸探针与ING1转录产物的结合.     

Effects of Mixed Anionic-Cationic Surfactants and Alcohol on Solubilization of Water-in-oil Microemulsions

The solubilization of water in w/o microemulsions formed with mixed-surfactants containing one anionic and one cationic surfactant and alcohol was studied as a function of alkyl chain length of oil (C6 to C16), mixed-surfactant (sodium dodecyl sulfate, SDS, and cetyltrimethylammonium bromide, CTAB, or cetylpyridinium bromide CPB), and alcohol (1-butanol, 1-pentanol, 1-hexanol). The results show that the solubilization of water in microemulsion systems increases significantly with the mixed-surfactants due to the synergistic effect resulting from the strong Coulombic interactions between cationic and anionic surfactants and the solubilizing efficiency increases as the chain length or concentration of alcohol increases. With increasing the oil chain length the solubilization for water increases, decreases, and has the chain length compatibility effect when the systems contain 1-hexanol, 1-butanol, 1-pentanol, respectively. The total solubilizing capacity increases as the surfactant concentration (keep the ratio of SDS to butanol constant) increases.     

Fluorescence Spectroscopic Studies on Comicellization of Anionic Surfactants

The intrinsic fluorescence of linear alkylbenzene sulphonate (LAS) has been exploited to show that sodium oleate (Na Ol) and sodium laurate (Na L) comicellize with LAS. It is also shown that comicellization occurs only at concentrations close to the critical micelle concentration (CMC) of Na Ol and Na L. ¹³C NMR results indicated that in LAS/Na Ol mixed micelles, the oleate molecule loops back and adopts a bent conformation.     

Study of Crown Ether Surfactants with Pyrene Fluorescence Probe

Both C₁₀H₂₁-18-crown-5 and C₁₀H₂₁-15-crown-5 were successfully synthesized and exhibited the distinctive characteristics of surfactants. Fluorescence of pyrene was used as a sensitive probe to study the micelle formation of the crown ether surfactant. The variation of the intensity ratio (I₁/I₃) of the first and third vibrational fluorescence bands of pyrene was employed to determine the critical micellar concentration (CMC). Both CMC and cloud points were found to depend on the kinds of cations and the ionic strength in solution. The quenching of pyrene fluorescence is also investigated for some cations under micelle and non-micelle circumstances.     

Water Soluble Cruciforms: Effect of Surfactants on Fluorescence

Brighten up! Adding surfactants to aqueous solutions of three different water‐soluble cruciforms (XF) improves their fluorescence quantum yields. Additionally, changes are observed in the emission wavelength of the XF around the critical micelle concentration (cmc) of the surfactant.

     

Mechanism of the Micellar Solubilization of Curcumin by Mixed Surfactants of SDS and Brij35 via NMR Spectroscopy

The micellar solubilization mechanism of curcumin by mixed surfactants of SDS and Brij35 was investigated at the molecular scale by NMR spectroscopy. Through the investigation of the micelle formation process, types and structures of mixed micelles and solubilization sites, the intrinsic factors influencing the solubilization capacity were revealed. For systems with α_SDS = 0.5 and 0.2, the obtained molar solubilization ratios (MSRs) are consistent with the MSR_ideal values. However, for α_SDS = 0.8, the solubilization capacity of curcumin is weakened compared to the MSR_ideal. Furthermore, only one single mixed SDS/Brij35 micelles are formed for α_SDS = 0.5 and 0.2. However, for α_SDS = 0.8, there are separate SDS-rich and Brij35-rich mixed micelles formed. In addition, NOESY spectra show that the interaction patterns of SDS and Brij35 in mixed micelles are similar for three systems, as are the solubilization sites of curcumin. Therefore, for α_SDS = 0.5 and 0.2 with single mixed micelles formed, the solubility of curcumin depends only on the mixed micelle composition, which is almost equal to the surfactant molar ratio. Although curcumin is solubilized in both separate micelles at α_SDS = 0.8, a less stable micelle structure may be responsible for the low solubility. This study provides new insights into the investigation and application of mixed micelle solubilization.     

Solubilization of Celecoxib in Microemulsions Based on Mixed Nonionic Surfactants and Peppermint Oil

U-type microemulsions formulated with water, mixed nonionic surfactants, and peppermint oil were used to solubilize celecoxib. Microemulsion dilution and interfacial factors contributing to the celecoxib solubilization were evaluated. Celecoxib solubilization capacity decreases with the increase in the water content. Electrical conductivity, dynamic viscosity, and SAXS measurements reveal the structural transition occurring in the microemulsion region. It was found that below 0.25 aqueous phase volume fraction the water-in-oil microemulsions are present, the transition between the water-in-oil to bicontinuous and then to oil-in water microemulsions occur at 0.30 and 0.8 aqueous phase volume fraction, respectively. The results demonstrate that the solubilized drug affects the transition from bicontinuous to water-in-oil microemulsions. The solubilized drug increases the hydrodynamic radius of the oil-in-water microemulsion droplets measured by dynamic light scattering.