Significant effect of surfactant micelles on pH dependent fluorescent off-on-off behavior of Salicylaldehyde-2,4-Dinitrophenylhydrazone

The fluorescence response to pH of 2,4 dinitrophenolhydrazone in 1:1 CH₃OH:H₂O and micellar mediums—negatively charged sodium dodecylsulphate (SDS), positively charged cetyltrimethyl ammonium bromide (CTAB) and neutral Triton X-100 (TX-100), is reported. At pH 4.0 the fluorescence of the molecule can be switched “on” by selecting CTAB as the solvent. At pH 6.0 if the medium is TX-100 the fluorescence is “off”, but remains “on” for the other three solvents. At pH 8.0, fluorescence is “on” in the solvents except CTAB. SDS and TX-100 switch the fluorescence “on” at pH 13.0 but for the other two solvents the fluorescence is “off”.     

Thioflavin T Displays Enhanced Fluorescence Selectively Inside Anionic Micelles and Mammalian Cells

Thioflavin T (ThT) has been widely employed to detect amyloid fibrils in tissues and recently in presence of SDS micelles. However, the contribution of membranes or micelles to ThT fluorescence has never been investigated. In this paper, we show for the first time that the anionic micellar microenvironment of SDS has a profound impact on the absorption and fluorescence spectra of ThT in sharp contrast to cationic (CTAB) and neutral micelles (Triton X-100 & Tween 20). Unlike CTAB or Triton X-100 or Tween 20 micelles, formation of SDS micelles shifts the λ_max for ThT absorption from 412 nm in buffer to 428 nm inside the micelle, with a 28% increase in the peak molar absorptivity and a ∼13 fold increase in ThT fluorescence (λ_max = 489 nm). Extending these observations to cell plasma membranes, we show that ThT can quickly enter and appear selectively fluorescent inside mammalian cells like BHK21 and HT29, against a dark background owing to negligible fluorescence from free ThT in aqueous medium. The above results suggest that ThT can be a useful probe for live cell imaging and for selectively labeling micelles on the basis of the charge in the polar headgroup. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of surfactants on the aggregation of pyronin B and pyronin Y in aqueous solution

Molecular dynamics of pyronin B (PyB) and pyronin Y (PyY) in aqueous solution containing different surfactants were investigated by using absorption and fluorescence spectroscopy techniques. First, the interactions of PyB and PyY with the negatively charged surfactant sodium dodecyl sulphate (SDS) were investigated in the below and above critical micelle concentration (cmc). The H-aggregate formation of the dye compounds was observed for below the cmc of SDS surfactant. The absorbance of H-aggregate absorption band of PyB and PyY decreased according to the aggregate-monomer equilibrium by increasing SDS surfactant concentration towards the cmc. Therefore, equilibrium constants of the aggregate formation and oscillator strengths of monomer and aggregate of the dye compounds were calculated from spectral studies. Moreover, aggregate formation dynamics was discussed in terms of thermodynamic functions by using temperature studies. The interactions of PyB and PyY with the positively charged hexadecyltrimethylammonium bromide (CTAB) and neutral Triton X-100 (TX-100) were also studied and it was observed that there was no aggregate formation on the absorption and fluorescence spectra for below and above the cmc.     

Spectrophotometric and spectrofluorimetric investigation of different equilibria of a recently synthesized Schiff base with the aid of chemometric methods

In this study ground and excited states acidic dissociation constants of a recently synthesized Schiff base was obtained in a DMF:water mixture of 30:70 (v/v) using absorption and fluorescent spectra of the Schiff base in different pH values with the aid of chemometric methods. In addition, the fluorescent of the two kinds of tautomers of this Schiff base was investigated and the rate of tautomerization was obtained using rank annihilation factor analysis (RAFA). The effect of different kinds of surfactants such as sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and Triton X-100 on fluorescence spectrum of the Schiff base in a DMF:water mixture of 2:98 (v/v) was investigated. CTAB increased the fluorescence intensity of the Schiff base while SDS and Triton X-100 had no significant effect on it. β-Cyclodextrin increased the fluorescence intensity of the Schiff base. Also the sensing behavior of this Schiff base toward metal ions was studied in DMF and ethanol by fluorescence spectroscopy. The Schiff base showed prominent fluorescent signal in the presence of Zn²⁺, whereas other metal ions failed to induce response and ground-state dissociation constant of the complex was determined by direct fluorimetric titration as a function of Zn²⁺ concentration.     

Fluorescence Characteristics of some Flavones Probes in Different Micellar Media

The fluorescence characteristics of five hydroxiflavones (HFs) (some typical models of flavonols), (3 - HF, 6 - HF, 7-HF, 3, 6 - diHF and 3, 7-diHF) in the micellar media of non-ionic surfactant (Triton X-100), anionic surfactant (SDS) and the block copolymer Pluronic F127, have been investigated by means of UV–Vis and steady-state and time resolved fluorescence spectroscopies. Attention is paid to both excited-state intra-molecular proton transfer (ESIPT) as well as ground-state intermolecular proton transfer. The influence of the -OH groups as well as the effect of temperature on the dual fluorescence emission, the Normal and Tautomer emissions, are also investigated. The fluorescence quantum yield of the HFs in mentioned micellar media has been also determined. The results are discussed with relevance to the local environment of HFs as sensitive fluorescence probe in biological membrane systems.     

Micellar effects on the molecular aggregation and fluorescence properties of benzazole-derived push-pull butadienes

The absorption and fluorescence spectral behaviour of 1-(2-benzoxazolyl)-4-(p-dimethylaminophenyl)buta-1,3-diene and its benzothiazolyl analogue (abbreviated as BODB and BTDB, respectively) have been investigated in dioxane-water mixtures and micellar environments using steady-state techniques. In water, water-rich mixtures or premicellar solutions, BODB and BTDB tend to form molecular aggregates labelled as H-aggregates. These aggregates dissociate on adding surfactants forming micellized monomers. In all micellar media the fluorescence quantum yield is greatly enhanced along with a large hypsochromic shift. Also, in TX-100, CTAB and SDS both dienes show dual emission from the locally excited (LE) and intramolecular charge transfer (ICT) states. For BTDB in TX-100 and DODB in all solutions, the LE fluorescence predominates, while for BTDB in CTAB and SDS, the ICT fluorescence is the predominant. The fluorescence shifts suggest that the fluorescing molecules penetrate the core of the micellar unit in TX-100, whereas in CTAB and SDS they occupy the interfacial region. The binding constants and the micelle properties (such as polarity and CMC) have been determined using both dienes as probes.     

FT-EPR study of photoionization in micellar solutions

Fourier Transform EPR (FT-EPR) was used to study the formation and decay of free radicals produced by photoionization of phenothiazine (PTH) solubilized in aqueous SDS and Triton X-100 micellar solutions in the absence and presence of electron acceptors. CIDEP spectra produced by PTH photoionization in micellar solution differ from those found in homogeneous solution. The effect is attributed to changes in relative importance of single-photon, singlet excited state, and biphotonic, triplet excited state, photoionization. With quinone acceptors present in the bulk aqueous phase, photoionization of PTH in SDS, results in instantaneous formation of quinone anion radicals that carry the spin polarization of the precursor hydrated electrons. If the acceptor is anchored in the micelle, electron capture cannot compete with electron escape into the aqueous phase. Instead, anion radicals are formed primarily by reductive quenching of³PTH*. This process gives rise to a spectrum that is attributed to long-lived spin-correlated radical pairs, [PTH⁺…Q^?].     

Sensing of Micellar Microenvironment with Dual Fluorescent Probe, Triazolylpyrene (TNDMBPy)

We report a dual fluorescent triazolylpyrene ( ^TNDMB Py) as an efficient fluorescent light-up probe of various micellar microenvironments. The absorption spectra of ^TNDMB Py in an aqueous solution of varying surfactant concentration, CTAB, SDS and TX-100 showed that as the surfactant concentration was increased the absorbance increased with no shift in wavelength maxima. The increase of absorbance in each surfactant solution with increase in surfactant concentration was due to the enhanced solubilization of ^TNDMB Py in surfactant solutions. Our investigations based on steady state and time resolved fluorescence techniques showed that the probe reports the microenvironment of ionic surfactant solutions (CTAB and SDS) via dual emission (LE and ICT) at low surfactant concentration. The ICT band showed a blue shifting pattern with enhanced intensity that disappeared as the concentration of surfactant increases (> 1 mM for CTAB and > 3 mM for SDS). In non-ionic surfactant (Triton X-100) solution, the fluorophore showed dual emission with dominant ICT behaviour over LE emission at low concentration (up to 0.35 mM). In reverse micelle we observed a blue shifted ICT band with no LE band with increasing molar concentration of water. We found 100 nm blue shifting when we moved from R?=?0 to R?=?7, where R is the molar ratio of water to TX-100 (R?=?[H2O]/[TX-100]). The blue shifting of ICT band is because of the movement of the probe from hydrophilic core to hydrophobic core (surface) of the reverse micelle. Thus from the steady-state fluorescence study it was observed that the ICT band of the probe, ^TNDMB Py was more influenced by the micellar environment in comparison to the LE band. This difference in behaviour of the fluorophore is probably because of varying extent of hydrophobic/hydrogen bonding interactions experienced by the probe and its relative disposition inside the various micellar nanocores.      

取代3H-吲哚分子在Triton X-100反胶束中的光谱性质和存在状态研究

用光谱法研究了荧光分子2-(对-己基胺基)苯基-3, 3-二甲基-5-乙酯基-3H-吲哚基-甲基-二-十八烷基碘化铵(A)与Triton X-100/正庚烷/正己醇/水反胶束间的相互作用。分别测定了A在Triton X-100反胶束体系中所处环境的微极性、各向异性参数和pH效应,此外还通过红外吸收光谱考察了水在反胶束中的状态。由以上实验结果得到了有关Triton X-100反胶束的结构信息,初步推测了A在该体系中的大致位置。     

1H NMR探究空间效应对表面活性剂复配体系中协同作用的影响

通过核磁共振氢谱（¹H NMR）实验测量了温度为298.0 K时3种表面活性剂——十六烷基三甲基溴化铵（CTAB）、辛基苯基聚氧乙烯醚（TX-100）和十二烷基硫酸钠（SDS）组成的复配体系CTAB/TX-100、SDS/TX-100和CTAB/TX-100/SDS中各组分的化学位移,得到了各混合体系中CTAB、TX-100和SDS的临界胶束浓度（CMC）.对不同体系中各组分CMC随摩尔分数的变化曲线进行比较,发现了空间效应对表面活性剂复配体系中协同作用的影响在一定的情况下并不逊于静电相互作用：表面活性剂分子的截面积越大,对体系中其他组分的协同作用越强;当组分间存在弱的静电相互作用时,空间效应对协同作用起到更主要的影响.     

Triton X-100微乳液中铈与L-色氨酸荧光反应的研究与应用

研究了Triton X-100微乳液(Triton X-100-M)对荧光法测定L-色氨酸的增敏作用。在酸性条件中Ce4+可将色氨酸氧化为强荧光性物质,以此为基础建立了分析色氨酸的新方法。与Triton X-100胶束相比,Triton X-100微乳液对荧光法测定L-色氨酸具有更好的增敏作用,在该介质中测定灵敏度提高了225倍。实验中对影响荧光测定的各种因素进行了优化,同时考察了共存离子的干扰并做了回收试验,对荧光增敏机理也进行了初步探讨。试验结果表明：在优化条件下,色氨酸浓度在0.1～1.0 μg·mL-1范围内与荧光强度成线形关系,其线性方程为F=342.37+30.45c,r=0.998 4,检出限为0.09 μg·mL-1。在优化参数条件下,对实际样品进行分析,结果令人满意。     

Surfactant fluorescence in the study of aggregation and clouding

The intrinsic fluorescence of Triton X-114 and Igepal CO-630 was used to monitor the aggregation behavior of micellar solutions of these surfactants. The response to changes in surfactant concentration, increases in temperature up to and beyond the cloud point, and addition of an ionic surfactant (SDS) was monitored. The intrinsic fluorescence was used to measure aggregate anisotropy as a function of SDS concentration and temperature. Relative aggregate abundance showed a minimum at the CMC, confirming the existence of premicellar assemblies. Structural differences in the hydrophobic portions of the two nonionic surfactants led to vastly different packing in their aggregates. The addition of SDS produced smaller, more closely packed micelles.     

K562细胞摄取光敏剂ZnPcS2P2的测定及药代动力学

通过荧光分析方法，比较了2．0％SDS(Wt％)，1．5％Triton X-100(φ为体积百分比V／V)及DMF等不同溶剂对K562细胞内摄取的两亲性酞菁锌ZnPcS2P2提取效率，结果表明Triton X-100具有较高的一次提取率。以1．5％Triton X-100为提取剂，获得了K562细胞摄取ZnPcS2P2及ZnPcS2P2-低密度脂蛋白(LDL)复合物的动力学曲线。结果显示，K562细胞对ZnPcS2P2-LDL的最大摄取量是ZnPcS2P2的两倍，表明LDL是有效的靶向载体。     

表面活性剂单体引起的细胞膜失稳

表面活性剂常用于细胞裂解、脂质体外排与膜组分搜集等.但在临界成胶束浓度以下,它如何以单体状态与生物膜作用的机制与调控仍存在很多疑问.本文研究了表面活性剂带电性对膜失稳的影响.石英电子微天平检测发现非离子型Triton X-100产生了最显著的磷脂膜结构三维再组装.荧光显微观测表明膜表面生成了非稳的出芽微泡,在机械扰动下可发生解离.该表面活性剂溶液环境中的体外细胞也出现了活力丧失.但是,离子型CTAB与SDS却无法触发相似的膜失稳与细胞失活效应.分析认为,由于不存在后两者体系中的单体间静电排斥, Triton X-100更易高效地插入生物膜,从而诱导膜结构再组装.研究深化了表面活性剂与生物膜作用机制的理解,对表面活性剂在生物医药、膜组分萃取等领域的深化应用提供了指导与帮助.     

Phenol and anisol fluorescence quenching in aqueous micellar solutions

Phenol and anisol fluorescence quenching in aqueous micellar solutions is investigated on addition of H ₂ O ₂. It is established that the efficiency of interaction of the phenol molecule in water with hydrogen peroxide is higher than of anisol. In the phenol-H ₂ O ₂ system, the buildup of phenol fluorescence occurs in the presence of an anionic-reagent detergent. A decrease in the efficiency of phenol fluorescence quenching by hydrogen peroxide in aqueous solutions in the presence of CTAB and triton X-100 micelles is observed. The micellar media increase the efficiency of interaction of anisol with a quencher in comparison with phenol. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 73–79, April, 2006.     

Synthesis of Novel Fluorescent Cyclohexenone Derivatives and their Partitioning Study in Ionic Micellar Media

An approach is demonstrated toward the synthesis of four novel cyclohexenone derivatives (CDs) via a convenient route of Michael addition of ethyl acetoacetate. The molecular structures of CDs were confirmed by means of FT-IR, ¹H NMR, EIMS, UV and also by X-ray single crystal structure analysis. CDs are strongly fluorescent compounds and their fluorescent spectra exhibits intense violet fluorescence. To model the binding to biological membranes the behavior of CDs in micellar solutions of a cationic surfactant, cetyltrimethylammonium bromide (CTAB) and an anionic surfactant, sodium dodecylsulfate (SDS) has also been examined. The characteristics of partition and binding interactions of CDs with CTAB and SDS were investigated by UV-Visible and fluorescence spectroscopic techniques. Higher values of all mentioned interactions in case of CTAB, compared to SDS, indicate that there are greater interactions between the CDs and CTAB than with SDS.     

Effect of temperature on the phase behavior and microstructure of aggregates in SDS/Triton X-100/aH2O systems

The phase behavior and microstructure of a system containing polyoxyethylene tert-octylphenyl (Triton X-100), sodium dodecyl sulfate (SDS) and water were investigated using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and small-angle X-ray diffraction (XRD). Phase-behavior study revealed that lamellar and hexagonal phases occurred in different compositions, and that lyotropic liquid crystal phases tended to form an H phase with increased Triton X-100 content. The effects of temperature on the phase behavior and microstructure of lyotropic liquid crystals were also studied. Heating induced a change from hexagonal to lamellar phase and from gel to hexagonal phase. POM and small-angle X-ray diffraction (SXRD) revealed that the phase-transition temperature of LLCs increased with increased Triton X-100 content, as further supported by DSC data.     

Photophysics of 2-(4′-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethylaminophenyl)imidazo[4,5-b]pyridine in Micelles: Selective Dual Fluorescence in Sodium dodecylsulphate and Triton X-100

The photophysical behavior of 2-(4′-N,N-dimethylaminophenyl)imidazo[4,5-b]pyridine (DMAPIP-b) has been studied in nonionic triton X-100 (TX-100), cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecylsulfate (SDS) micelles using steady state and time resolved fluorescence techniques. The molecule emits both normal and TICT fluorescence in SDS and TX-100 but emits only normal fluorescence in CTAB. This difference in behavior of the fluorophore is due to varying extent of hydrogen bonding experience by it in different micelles. Of the three possible monocations, only two kinds of monocations, MC1 (formed by protonation of pyridine ring nitrogen) and MC2 (formed by the protonation of imidazole nitrogen) are present in all the micelles (Scheme 1). DFT calculations performed on the monocations reveal that MC1 and MC2 are more stable than MC3, the monocation formed by the protonation of dimethylamino nitrogen.      

Light scattering and fluorescence probe studies on micellar properties of Triton X-100 in KCl solutions

The effect of KCl on micelle formation and structure of Triton X-100 (TX-100) was investigated by using combined static and dynamic light scattering measurements, together with the fluorescence probe technique. An analysis of the light scattering data, including hydrodynamic radius and micellar aggregation number, accounted for both micelle growth and hydration. Fluorescence studies using pyrene as a probe were carried out to determine the critical micelle concentration (CMC) as a function of solution composition. In addition, with the aim of gaining information on the possible changes in the micro-environmental properties of TX-100 micelles, fluorescence probe studies, including intermolecular pyrene excimer formation and fluorescence polarization of coumarin 6 associated with micelles, were carried out. It was found that the addition of electrolyte induces a decrease in the CMC and an increase in both aggregation number and hydration. However, complementary data of partial specific volume and cloud point of the surfactant suggested that the main contribution to micellar hydration is due to water mechanically trapped in the micelle. Fluorescence measurements do not indicate changes in the micellar micropolarity, probably due to modifications of the solubilization site of the probe caused by the micellar growth. Both pyrene excimer formation and fluorescence polarization of coumarin 6 revealed an increase in microviscosity with electrolyte addition, which is consistent with increased micellar hydration.     

荧光层析法研究由胶束溶液分离出的两种抗菌素

喹诺酮药物是一类重要的化学合成抗菌素 ,其临床应用正在不断扩大[1] 。氧氟沙星 (OFLX)和环丙沙星 (CPLX)结构非常相似。本文采用胶束薄层色谱法分离了两种药物。加入 1%氨水的 0 0 0 15mol·L-1十六烷基三甲基溴化铵 (CTAB)和 1%十二烷基磺酸钠 (SDS)的等体积水溶液作为展开剂 ,聚酰胺薄膜作为固定相。考查了CTAB浓度 ,SDS浓度及氨水对氧氟沙星和环丙沙星Rf 值的影响。在选定条件下 ,Rf 值分别为 0 87和 0 76 ,在激发波长为 2 80nm处对其进行了荧光测定。测定了该方法的稳定性和灵敏度。本文首次使用胶束溶液分离了氧氟沙星和环丙沙星