Amphotropic Liquid Crystals

Blunh, Dirk; Praefcke, Klaüs; Vill, V.

doi:10.1002/9783527620593.ch6

Cited by 21 publications

(11 citation statements)

References 155 publications

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“…In a recent study on carbohydrate-based nonionic gemini surfactants, Pestman et al (13) demonstrated that the aggregation state, which for conventional single-tailed surfactants is almost exclusively micellar (14), could be changed to vesicular simply by connecting the headgroups via an alkyl spacer. We have subsequently replaced the amide linking groups for amines afforded gemini surfactants with pH-titratable headgroups (15).…”

Section: Introductionmentioning

confidence: 99%

pH-Dependent Aggregation Behavior of a Sugar-Amine Gemini Surfactant in Water: Vesicles, Micelles, and Monolayers of Hexane-1,6-bis(hexadecyl-1′-deoxyglucitylamine)

Bergsma

Fielden

Engberts

2001

Journal of Colloid and Interface Science

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The pH-dependent aggregation behavior of one representative of a recently described series of sugar-amine gemini surfactants has been investigated. The surface tension (γ ) and turbidity of hexane-1,6-bis(hexadecyl-1 -deoxyglucitylamine) drop steeply between pH 5.5 and 4.0, consistent with a vesicle-to-micelle transition. The critical micelle concentration (cmc) at low pH (3.0) was determined by surface tension measurements to be 1 × 10 −3 M. This value is high, as γ is at the cmc (57 mN m −1 ). The area per headgroup (A h ) extracted from the slope of the curve of γ vs concentration below the cmc is 109Å2 . In an attempt to obtain a reasonable estimate of the headgroup area at higher pH, surface pressure vs area measurements were performed on a monolayer supported on pure water (pH 6), providing an A h of ca. 69Å 2 . The dependence of A h on pH is consistent with the proposed vesicle-to-micelle transition. Measurements of the gel-to-liquid crystalline phase transition using differential scanning calorimetry at a range of pHs revealed a drop in both the phase transition temperature and the transition enthalpy with decreasing pH. The pH dependence of the aggregation behavior can thus be summarized as follows: (1) pH 7.5-5.5, bilayer vesicles; (2) pH 5.5-4.0, a "drop region" where aggregate morphology is sensitive to small changes in pH; and (3) pH < 4.0, micelles. C 2001 Academic Press

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Section: Introductionmentioning

confidence: 99%

pH-Dependent Aggregation Behavior of a Sugar-Amine Gemini Surfactant in Water: Vesicles, Micelles, and Monolayers of Hexane-1,6-bis(hexadecyl-1′-deoxyglucitylamine)

Bergsma

Fielden

Engberts

2001

Journal of Colloid and Interface Science

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“…In one case, polylysine was functionalized with glucitylamido groups, for which there are no known receptors, solely to increase solubility and decrease the strength of binding to DNA [36]. In the case of simple sugar amphiphiles bearing a single monosaccharide or disaccharide residue and a single alkyl tail, micelles are almost exclusively formed [38]. The presence of micelles in a transfection mixture at physiological pH is considered to be undesirable due to potential toxicity problems [21], so a way of changing the aggregation state to bilayer vesicles was necessary.…”

mentioning

confidence: 99%

Sugar‐based tertiary amino gemini surfactants with a vesicle‐to‐micelle transition in the endosomal pH range mediate efficient transfection in vitro

Fielden¹,

Perrin²,

Kremer³

et al. 2001

European Journal of Biochemistry

127

119

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Novel reduced sugar gemini amphiphiles linked through their tertiary amino head groups via alkyl spacers of 4 or 6 carbons, and with varying (unsaturated) alkyl tail lengths of 12–18, have been synthesized and tested for transfection in vitro in an adherent Chinese hamster ovary cell line (CHO‐K1). Transfection efficiencies peaked at 2.7 times that of the commercial standard Lipofectamine Plus/2000 for pure solutions of the compound bearing unsaturated (oleyl) alkyl tails. For those compounds bearing saturated alkyl tails, transfection efficiency peaked at a tail length of 16, at a level similar to Lipofectamine Plus/2000. All of the amphiphiles formed bilayer vesicles at physiological pH. Some of the amino groups at the surface were protonated, and vesicles therefore bore a positive charge. Increased protonation with reduced pH resulted in greatly increased monomer solubility and a morphology change from vesicle to micelle at characteristic pH values, dependent on the tail length. For the compounds promoting high transfection efficiency, this characteristic pH was within the range found in the endosomal compartment (7.4–4.0). Formation of mixed micelles between gemini surfactant and membrane phospholipids at reduced pH may therefore provide a method of endosome rupture and subsequent escape of entrapped DNA, thus discarding the need for extra fusogenic or endosomolytic agents. The positive charge on the vesicles at physiological pH drives the colloidal association with DNA. Small angle X‐ray scattering measurements indicate that lamellar aggregates are formed, which have a d spacing of 48–54 Å. Preliminary differential scanning calorimetric measurements suggest that reduction of pH causes a disordering of the hydrocarbon region of the DNA–surfactant complex.

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“…Carbohydrate liquid crystals are a special type of liquid crystals, because they have different rules and different applications from the classical and monophilic liquid crystals. Compared to synthetic liquid crystal polymer matrices, carbohydrates liquid crystals have some interesting advantages, such as, easy accessibility, very common materials, non-toxicity and degradability, high diversities of structures, chirality, low melting temperatures, good solubility in water and in organic solvents, clearly defined thermotropic and lyotropic mesophase behavior, etc.. Glycolipids form a special class of liquid crystal mesophases because they obey different rules compared to the classical monophilic liquid crystals and give a variety of interesting applications [3][4][5]. The high diversity of carbohydrate mesogens has been described where hundreds of different compounds can be formed, e.g.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of cyanoethyl konjac glucomannan and its liquid crystalline behavior in an ionic liquid

Shen

Zhang

et al. 2011

J Polym Res

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Cyanoethyl konjac glucomannan (CKGM) products with various degree of substitution (DS) were synthesized, and their chemical structure was characterized by infrared spectroscopy and 1 H and 13 C NMR spectroscopy. Direct evidence of the formation of liquid crystalline phase of cyanoethyl KGM (DS02.10) solution in 1-allyl-3-methylimidazolium chloride (AMIMCl), a room temperature ionic liquid, was confirmed by using polarized optical microscopy (POM). The mesophase and anisotropic phase of cyanoethyl KGM solutions and the phase transition boundaries were investigated by steady shear and dynamic sweep measurements. The crystalline state of the cyanoethyl KGM powder and solution were studied by wide X-ray diffraction.

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Amphotropic Liquid Crystals

Cited by 21 publications

References 155 publications

pH-Dependent Aggregation Behavior of a Sugar-Amine Gemini Surfactant in Water: Vesicles, Micelles, and Monolayers of Hexane-1,6-bis(hexadecyl-1′-deoxyglucitylamine)

pH-Dependent Aggregation Behavior of a Sugar-Amine Gemini Surfactant in Water: Vesicles, Micelles, and Monolayers of Hexane-1,6-bis(hexadecyl-1′-deoxyglucitylamine)

Sugar‐based tertiary amino gemini surfactants with a vesicle‐to‐micelle transition in the endosomal pH range mediate efficient transfection in vitro

Synthesis of cyanoethyl konjac glucomannan and its liquid crystalline behavior in an ionic liquid

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