Determination of polyphenol components in herbal medicines by micellar electrokinetic capillary chromatography with Tween 20

A simple and convenient method of micellar electrokinetic capillary chromatography (MEKC) using polyoxyethylene sorbitan monolaurate (Tween 20) to form single micelle and methanol as a buffer additive was introduced for the simultaneous determination of five polyphenols, including scopoletin, rutin, esculetin, chlorogenic acid and caffeic acid. A running buffer solution of pH 9.3, 20 mmol/L sodium tetraborate containing 64 mmol/L Tween 20 and 9% (v/v) methanol was adopted in the separation. Because rutin and esculetin were difficult to be separated by capillary zone electrophoresis (CZE) and SDS-based MEKC, Tween 20-based MEKC was adopted and the polyphenols were separated satisfactorily. The proposed method was used to determine the polyphenol components in the herbal medicine of Cortex fraxini. The separation mechanism of Tween 20-based MEKC for the polyphenols was discussed preliminarily.     

吐温80—AuCl4^—化学发光新体系测定痕量碘离子的研究

基于碘离子对吐温８０－ＡｕＣｌ４＾－体系化学发光的强烈抑制作用,提出了一种测定痕量碘离子的新的化学发光分析法。方法的线性范围和检测分别为１．２×１０＾－８￣１．０×１０＾－６ｇ／ｍＬ和５．１×１０＾－９ｇ／ｍＬ碘离子。拟定的方法体系简单,选择性好,加碘酱油和实际水样中碘离子的测定,结果满意。     

钙黄绿素荧光法测定痕量钇(Ⅲ)

研究了钙黄绿素荧光法测定Y(Ⅲ)。在pH 8.0的H3BO3-Na2B4O7缓冲溶液和表面活性剂Tween 80的存在下,痕量Y(Ⅲ)能与钙黄绿素反应形成配合物,使体系的荧光强度显著增加,体系的激发和发射波长分别为492和512nm,Y(Ⅲ)的质量浓度在0～2.0μg/mL范围内与△F成良好的线性关系,其线性回归方程为:△F=3.2648+2.384ρ(μg/mL),相关系数r=0.9961,检出限为0.023μg/mL。方法用于乙酸铈中痕量钇(Ⅲ)的测定,测定结果与ICP-AES法相符,加标回收率在96.3%～103.0%之间。     

Colon-specific devices based on methacrylic functionalized Tween monomer networks: Swelling studies and in vitro drug release

Colon-targeted delivery devices based on methacrylic functionalized Tween monomer networks, useful for 5-FU or Ferulic acid site-specific release, were synthesized. The basic design consists of methacrylic functionalized Tween monomer-based networks prepared with or without acrylic acid as co-monomer. The swelling behaviour and loaded drugs release from these gels was studied as a function of pH. The devices showed a strong pH-dependent swelling behaviour, allowing a maximum release at pH 7.4. The acrylic acid introduction increased the polymeric gels pores size, as evidenced by the loading efficiency increase, but also reduced the amount of released drug in basic media compared to analogous network not containing the co-monomer. This behaviour, already found in the matrix swelling, could be attributed to a slower hydrolysis kinetics of the ester bond in functionalized Tween monomers, which implies a reduced ability to absorb water from a basic medium, resulting in a lower capacity to release the loaded drug.Since our device possesses a maximum drug release in the media at pH 7.4, it could be used for colon-targeted drug delivery of both 5-FU and Ferulic acid.     

A mild and regioselective Ullmann reaction of indazoles with aryliodides in water

A mild and regioselective Ullmann reaction of indazoles with aryliodides has been developed as a general method for the synthesis of 1-aryl-1H-indazoles. Water was used as the solvent wherein Tween 20 (2% w/w) was added to form aqueous micelles to improve solubility of starting materials and accelerate reaction rate. This aqueous protocol allows the Ullmann reaction to proceed at a mild temperature (60 °C) within a short reaction time (2 h), which typically requires high temperatures (≥100 °C) and prolonged duration (≥24 h). The protocol demonstrated broad substrate scopes with good isolated yields and high regioselectivity (N-1 arylation over N-2 arylation) for 25 examples examined.     

Antibody-based surfaces: rapid characterization using two complementary colorimetric assays

Finding a general solution for optimizing the grafting of antibody on solid surfaces is difficult due to the variety of material, grafting principles and chemistries or surface formats available (beads, microplates, fibers, etc.). Pre-screening methods able to assess grafting efficiency (GE) and specific activity (SA) are required. In this context, we present here two colorimetric assays that can be used on a wide variety of surface format, chemistry, etc. The first one, ADECA (Amino Density Estimation by Colorimetric Assay) allows a rapid estimation of grafted antibodies and allows calculating the GE. The second one, A₂HRP (Antibody Anti-HorseRadish Peroxidase) provides a measure of the amount of active antibody, which, combined to ADECA, is used to determine the SA of grafted antibody. Analytical parameters (limit of detection, repeatability, linearity, etc.) of these two colorimetric assays are presented. Using two commercially available microplates, we demonstrated that, when used in parallel, these rapid and sensitive methods are well adapted to pre-screening of antibody grafting performances.     

Shape and Structure Formation of Mixed Nonionic–Anionic Surfactant Micelles

Aqueous solutions of a nonionic surfactant (either Tween20 or BrijL23) and an anionic surfactant (sodium dodecyl sulfate, SDS) are investigated, using small-angle neutron scattering (SANS). SANS spectra are analysed by using a core-shell model to describe the form factor of self-assembled surfactant micelles; the intermicellar interactions are modelled by using a hard-sphere Percus–Yevick (HS-PY) or a rescaled mean spherical approximation (RMSA) structure factor. Choosing these specific nonionic surfactants allows for comparison of the effect of branched (Tween20) and linear (BrijL23) surfactant headgroups, both constituted of poly-ethylene oxide (PEO) groups. The nonionic–anionic surfactant mixtures are studied at various concentrations up to highly concentrated samples (ϕ ≲ 0.45) and various mixing ratios, from pure nonionic to pure anionic surfactant solutions. The scattering data reveal the formation of mixed micelles already at concentrations below the critical micelle concentration of SDS. At higher volume fractions, excluded volume effects dominate the intermicellar structuring, even for charged micelles. In consequence, at high volume fractions, the intermicellar structuring is the same for charged and uncharged micelles. At all mixing ratios, almost spherical mixed micelles form. This offers the opportunity to create a system of colloidal particles with a variable surface charge. This excludes only roughly equimolar mixing ratios (X≈ 0.4–0.6) at which the micelles significantly increase in size and ellipticity due to specific sulfate–EO interactions.     

Nonionic surfactant‐capped gold nanoparticles for selective enrichment of aminothiols prior to CE with UV absorption detection

In this study, we describe the use of Tween 20‐capped gold nanoparticles (AuNPs) as selective probes for the extraction of aminothiols from an aqueous solution. Tween 20 molecules noncovalently attached to the surface of AuNPs to form Tween 20–AuNPs were used for the selective extraction of aminothiols through the formation of Au–S bonds. After extraction and centrifugation, the aminothiols were detached from the surface of the AuNPs by adding DTT in a high concentration. We used this probe in combination with CE and UV absorption detection. On‐line concentration and separation of the released aminothiols were performed by using 1.6% v/v poly(diallyldimethylammonium chloride) as an additive in CE. Under optimal extraction and stacking conditions, the LOD at a S/N of 3 were 28, 554, and 456 nM for glutathione (GSH), cysteine (Cys), and homocysteine (HCys), respectively. In comparison with the normal injection without the extraction procedure, approximately 2280‐, 998‐, and 904‐fold improvements in the sensitivity were observed for GSH, Cys, and HCys, respectively. We have validated the application of our method on the basis of the analysis of GSH and HCys in human urine samples. It is believed that this approach has significant potential to be extended to clinical diagnosis.     

Kinetic Effects in non Ionic Micellar Solutions

The elimination reaction between 2-(p-nitrophenyl)ethyl bromide and OH^- ions was studied in nonionic aqueous micellar solutions of two esters of long chain fatty acids and sorbitan polyethylene glycol, Tween 20 (monolaurate) and Tween 80 (monooleate). The equilibrium binding constants of the 2-(p-nitrophenyl)ethyl bromide molecules to the nonionic micellar aggregates were obtained by spectroscopic measurements. The experimental kinetic data were quantitatively rationalized by the treatment of first-order reactions based on the pseudophase model. Results from this work and from previous studies show that, whereas the presence of cationic and sulfobetaine micelles accelerates the reaction, the presence of nonionic micelles inhibits the reaction.     

Group-specific enzyme-linked immunosorbent assay for fenitrooxon and 3-methyl-4-nitrophenol in water samples based on a polyclonal antibody

Fenitrooxon [O,O-dimethyl-O-(4-nitro-m-tolyl)phosphate] is the major metabolite of the organophosphorus insecticide fenitrothion, and 3-methyl-4-nitrophenol is its major degradation product. In the present study, we describe the development of an indirect competitive enzyme-linked immunosorbent assay (ELISA) for the detection of these compounds in water samples based on a group-specific polyclonal antiserum generated with a “bifunctional hapten”, which has two functions: the conventional function of producing an antibody against an antigen and a unique function of promoting the production of the antibodies in rabbit. For application to water samples, the influence of several factors such as organic solvent, pH, and detergent was studied. Under optimized conditions, the quantitative working range of the fenitrooxon ELISA was 0.71-27 ng ml⁻¹ with a limit of detection (LOD) of 0.32 ng ml⁻¹, and the fenitrooxon concentration giving 50% reduction of the maximum signal (IC₅₀) was 4.2 ng ml⁻¹. The quantitative working range of the 3-methyl-4-nitrophenol ELISA was 0.67-27 ng ml⁻¹ with a LOD of 0.38 ng ml⁻¹ and an IC₅₀ of 3.7 ng ml⁻¹. No significant matrix effect originating from the water sample (river water, tap water, purified water, and bottled water) was shown by addition of Tween 20 to the assay buffer. Water samples spiked with each of these compounds at 1, 5, 10, and 20 ng ml⁻¹ were directly analyzed without extraction and clean-up by the proposed ELISA. The mean recovery was 100.9%, and the mean coefficient of variation (CV) was 7.7% for the fenitrooxon ELISA and for the 3-methyl-4-nitrophenol ELISA, the mean recovery was 97.6%, and the mean CV was 7.2%. The proposed ELISA allows precise and accurate determination of these compounds in water at such low levels.