Patrick G Hartley and Hsin-Hui. Shen. 2012. “Nanocharacterization of lyotropic liquid crystalline systems.” In Self-Assem. Supramol. Archit., Pp. 97–127. John Wiley & Sons, Inc. Abstract
A review. The development of techniques for the characterization of the nanostructure of lyotropic liq. cryst. systems were crucial in enabling increased understanding of fundamental properties and efficacy in technol. applications. Provided is a review of a no. of commonly used and emerging nanocharacterization techniques, with a view to providing a resource for academic and industrial researchers joining the field. [on SciFinder(R)]
Roy E Hoffman, Abraham Aserin, and Nissim. Garti. 2012. “New insights into the microemulsion-based chromatographic NMR resolution mechanism and its application to fragrance/flavor molecules.” Journal of Magnetic Resonance, 220, Pp. 18–25. Abstract
The NMR chromatog. method is applied to a class of mols. with similar phys. properties. We correlate the sepn. ability of microemulsions to the phys. properties of the analyzed mols. Flavor and aroma compds. are very widespread. Compositional anal. is in many cases tedious. Any new method of anal. is always useful and challenging. Here we show a new application to a class of fragrance mols., with only a moderate variation in their chem. and phys. characteristics. Up to 11 selected compds. in one mixt. are resolved in one spectrum by NMR chromatog., despite the similarity of the compds. The differences between O/W and W/O microemulsions and their resoln. mechanism as applied to fragrance mols. are explained in terms of hydrophilicity and lipophilicity and effective crit. packing parameters of the microemulsions. The obsd. diffusion rates are shown to correlate with solvation parameters. These results can be used to est. the diffusion rates of mols. to be sepd., allowing selection of the microemulsion or NMR chromatog. solvent appropriate for each specific application. [on SciFinder(R)]
Debby P Chang and Tommy. Nylander. 2012. “Nonlamellar lipid liquid crystalline structures at interfaces.” In Self-Assem. Supramol. Archit., Pp. 289–318. John Wiley & Sons, Inc. Abstract
A review. Nonlamellar lipid-based liq. cryst. structures, such as cubic, hexagonal, and sponge phases, have potential as delivery systems in pharmaceutical, food, and cosmetic applications. This is due to the space-dividing nature of these phases, which features mono- or bicontinuous networks of both hydrophilic and hydrophobic domains. To utilize these nonlamellar liq. cryst. structures as delivery vehicles, it is crucial to understand how they interact with and respond to different types of interfaces. The progress in the area of liq. cryst. lipid-based nanoparticles opens up new possibilities for prepn. of well-defined surface films with well-defined nanostructure. Apart from the relevance to drug delivery, such studies create opportunities for new applications for functionalized and tunable surface coatings as well. This review will focus on recent progress in the formation of nonlamellar dispersion and its interfacial properties at the solid-liq. and biol. relevant interfaces. Various exptl. techniques on the study of interfacial interactions of these cryst. structures will be discussed. [on SciFinder(R)]
Marganit Cohen-Avrahami, Dima Libster, Abraham Aserin, and Nissim. Garti. 2012. “Penetratin-induced transdermal delivery from HII mesophases of sodium diclofenac.” Journal of Controlled Release, 159, 3, Pp. 419–428. Abstract
Penetratin, a cell penetrating peptide is embedded within a reversed hexagonal (HII) mesophase for improved transdermal delivery of sodium diclofenac (Na-DFC). The HII mesophase serves as the solubilization reservoir and gel matrix whereas penetratin is the transdermal penetration enhancer for the drug. The systems were characterized and the interactions between the components were detd. by SAXS, ATR-FTIR and SD-NMR. High affinity of Na-DFC to glycerol monooleate (GMO) was revealed, assocd. with increasing the order within the water channels. This affinity is enhanced upon heating and seems to be assocd. with GMO dehydration. Penetratin (PEN) is entrapped at the hydrophilic region of the HII mesophase, between the GMO headgroups, reducing the order of the system and decreasing the size of the hexagonal domains. The transdermal delivery rate of Na-DFC through porcine skin, from the HII mesophases, was enhanced by PEN and so also the cumulative transport crossing the skin. PEN induced accelerated drug diffusion through the stratum corneum, towards the different skin layers. The transdermal delivery enhancement is explained from the results of the ATR-FTIR anal. It seems that PEN accelerates the structural transition of skin lipids from hexagonal to liq. The disordering results in enhanced diffusion of Na-DFC through the stratum corneum, followed by enhanced overall penetration of the drug. [on SciFinder(R)]
Raffaele. Mezzenga. 2012. “Physics of self-assembly of lyotropic liquid crystals.” In Self-Assem. Supramol. Archit., Pp. 1–20. John Wiley & Sons, Inc. Abstract
A review. Reviewed are recent advances in the understanding of self-assembly principles in lipid-based lyotropic lipid crystals, from the original rationalization achieved using the crit. packing parameter up to recent, more sophisticated thermodn. approaches, such as the SCF theory, which can be efficiently used to minimize the total free energy of a lipid-water system and identify stable mesophases. Highlighted is the importance of reversible hydrogen bonding as one of the key parameters ruling the self-assembly in these systems and examine the implications this may have also in real applications. The current understanding on the dynamics of phase transitions are finally discussed and the status of the art on current atomistic approaches to investigate the relaxation dynamics in these systems is reviewed. [on SciFinder(R)]
Perla Relkin and Marc. Anton. 2012. “Protein- and lipid-based nano- and mirco-capsules, as food micronutrient carriers.” In Nanotechnol. Solubilization Delivery Foods, Cosmet. Pharm., Pp. 125–149. DEStech Publications, Inc. Abstract
A review. Com. available food ingredients, such as proteins, satd. or polyunsatd. lipids and polysaccharides have nutritional and structure-forming properties at different scale levels. They belong to classes of biodegradable and biocompatible biomaterials which are the focus of intensive research studies thanks to their potentiality to be used as bioactive matrix carriers. This chapter will be concerned with physicochem. and structural properties of protein and lipoprotein assemblies naturally present in food or induced by thermomech. treatments; and with the description of exptl. design and formulation of nutrient-rich products. In the first part, we will focus on the structural properties, from nano- to microsize level, of casein micelle heat-induced proteins aggregates, and of natural egg lipoproteins in relation to their property of protecting nutrients or bioactive compds. (vitamins, unsatd. fatty acids, antioxidants, aroma compds.) and stabilizing emulsions. In the second part we will draw attention to the relation between their protective and carrying properties with the structure and dynamics, at different scales, of such complex food matrixes. In conclusion, the trends in research concerning the delivery of nutrients in complex food will be debated. [on SciFinder(R)]
Anan Yaghmur and Michael. Rappolt. 2012. “Recent advances in the characterization of lipid-based nanocarriers.” In Nanotechnol. Solubilization Delivery Foods, Cosmet. Pharm., Pp. 187–208. DEStech Publications, Inc. Abstract
A review. Soft self-assembled lipidic systems with well-defined nanostructures have become increasingly important in the development of pharmaceutical, food, and cosmetic delivery systems. They have key roles in overcoming the insufficiency of bioavailability and other obstacles in drug delivery systems, such as severe side effects and the toxicity of poorly water-sol. bioactive mols. In particular, self-assembled nanostructures of naturally occurring surfactant-like lipids represent an interesting family of nanocarriers. This family of biodegradable and biocompatible materials displays structures closely related to those obsd. in biol. membranes and enables the formation of efficient delivery systems. The optimal utilization of these nanostructured objects requires a full understanding of their physicochem. properties and detailed characterization of their structures. Their stability after administration is a key issue in the development of excipients with a good performance and a significant redn. of unwanted side effects. This chapter summarizes recent studies of the possibility of utilizing soft lipidic self-assembled systems as drug and food nanocarriers. The scope covers recent investigations that have attempted to shed light on the formation of delivery systems based on microemulsions, and different nanostructured aq. dispersions. It highlights also some recent advances in the characterization of these complex soft nanoobjects. The main focus is placed on the recent developments in the field of small-angle scattering methods, dynamic light scattering (DLS), electron microscopy (tilt-angle cryo-TEM, and cryo-FESEM), and NMR (NMR) techniques. [on SciFinder(R)]
Dima Libster, Abraham Aserin, and Nissim. Garti. 2012. “Recent developments in lyotropic liquid crystals as drug delivery vehicles.” In Self-Assem. Supramol. Archit., Pp. 219–256. John Wiley & Sons, Inc. Abstract
A review. Recently, self-assembled lyotropic liq. crystals (LLCs) of lipids and water have attracted the attention of both the scientific and the applied research communities due to the remarkable structural complexity and practical potential of these nanostructures in diverse applications. The phase behavior of mixts. of glycerol monooleate (monoolein, GMO) was particularly well studied due to the potential utilization of these systems in drug delivery systems, food products, and encapsulation and crystn. of proteins. The present chapter summarizes structural features of LLCs and recent systematic efforts to utilize these for solubilization and the potential release of drugs and biomacromols. One of the most interesting applications is the implementation of cell-penetrating peptides in the reversed hexagonal mesophase to enhance the skin-penetrating pattern of a model drug (sodium diclofenac). Liq. crystal vehicles were shown to allow "on demand" targeted release, based on controlling the polymorphism of lyotropic liq. cryst. mesophases. Novel liq. cryst. matrix-gold nanorod hybrid materials were reported to induce light-triggered phase transition of liq. cryst. phases. Hydrophobized gold nanorods (GNRs) have been incorporated within the LLCs, composed of phytantriol and water, to provide remote heating, and trigger the phase transitions on irradn. at close to their resonant wavelength. A new pathway to pH-responsive LLCs, enabling the controlled release of hydrophilic drugs diffusing through the water channels of the mesophases, was also investigated. The system is capable of self-assembling into a reverse bicontinuous cubic phase of Im3m symmetry at pH 7 and transforming into a reverse columnar hexagonal phase at pH 2. Lyotropic liq. crystals were shown to entrap several nucleotides into cubic and lamellar monoolein-based mesophases in order to protect them and enable their release. DNA (DNA) within two types of reverse columnar hexagonal mesophases was studied, one based on pure nonionic lipids and the other decorated by cationic lipids to induce opposite charges at the surfaces of the water channels of the mesophases. This provided new opportunities in the design technologies for DNA transfection and for gene delivery. The main outcomes of the described research demonstrated that control of the phys. properties of hexagonal LLC on different length scales is key for rational design of these systems as delivery vehicles for both low-mol.-wt. therapeutics and biomacromols. [on SciFinder(R)]
Alejandro D Rey and EE Herrera-Valencia. 2012. “Rheological theory and simulation of surfactant nematic liquid crystals.” In Self-Assem. Supramol. Archit., Pp. 21–77. John Wiley & Sons, Inc. Abstract
Presented a comprehensive review of rheol. theory, modeling, and simulation of surfactant nematic liq. cryst. phases, including calamitic and discotic micellar solns. and wormlike micelles. A review of verifiable rheol. liq. crystal models for lyotropic nematics highlighting the mechanisms that control orientation behavior under shear, anisotropic viscoelasticity, and non-Newtonian behavior. Since defects and textures are essential characteristics of these materials that affect the flow properties, an in-depth review of phys. and rheophys. defects is presented, including defect nucleation and coarsening processes. The theory for micellar nematics is applied to textures, flow birefringence, phase transition under shear, orientation fluctuations, and flow alignment, and the predictions are compared with exptl. data. The theory is finally applied to transient shear flows of wormlike micellar nematic solns., and the predicted banded textures and transient stress responses are compared to rheol. expts. The predictions provide a new way to ext. addnl. information from exptl. rheol. data and allow to distinguish the role of liq. cryst. properties such as viscoelastic anisotropy, flow alignment, coupling between orientation kinematics, and flow kinematics. The rheol. predictions show a strong similarity with other nematic materials, including low-molar-mass thermotropes and lyotropic nematic polymers. [on SciFinder(R)]
Anan Yaghmur and Otto. Glatter. 2012. “Self-assembly in lipidic particles.” In Self-Assem. Supramol. Archit., Pp. 129–155. John Wiley & Sons, Inc. Abstract
A review. The present contribution summarizes our previous investigations on the formation of emulsions, whose particles consist of a self-assembled inverted-type liq. cryst. phase or an inverted-type microemulsion. In this context, the main focus was on replacing either the dispersed oil droplets in normal O/W emulsions, or the kinetically stabilized internal W/O emulsion in double W/O/W emulsions, by an inverted-type liq. cryst. phase or an inverted-type microemulsion system. Owing to the physico-chem. properties of their internal nanostructures, these unique aq. dispersions are superior to conventional emulsions and double emulsions. They are attractive as nanonreactors and as host systems for solubilizing active mols. (drugs, flavors, and vitamins) in the cosmetics, pharmaceutical, and food industries. This chapter describes the effect of varying temp. and solubilizing oil on the reversible structural transitions of the internal nanostructures of these lipidic dispersions. [on SciFinder(R)]
Idit Amar-Yuli, Abraham Aserin, and Nissim. Garti. 2012. “Synthesis and alignment of nanostructured materials using liquid crystals.” In Self-Assem. Supramol. Archit., Pp. 193–218. John Wiley & Sons, Inc. Abstract
A review. Liq. crystal (LC) science and technol. have made important contributions to nanoscience and nanotechnol. in areas such as medical diagnostics, drug delivery, and in high-tech devices. The major nanotechnol. contribution is their capability to provide new preparative procedures, self-assembly, and alignment of nanoscale materials with controlled uniform size, shape, and dimensionality. The self-assembly of the liq. cryst. systems, particularly the lyotropic LC type, enables the integration of lipophilic and hydrophilic reagents that meet to react at the interface. Therefore the reaction and the products properties are governed by the host liq. cryst. medium and by the external conditions (e.g., light, heat, chem. environment, and elec. and magnetic field), which directly affect the LC hosting system. This review attempts to give an overview of current research in the fields of prepn., self-assembly, and alignment of nanomaterials using mainly lyotropic LCs and partially thermotropic LCs as direct and reverse templates. [on SciFinder(R)]
Shifra Rokach, Maria Francesca Ottaviani, Alexander I Shames, Ido Nir, Abraham Aserin, and Nissim. Garti. 2012. “W/O Microemulsions as Dendrimer Nanocarriers: An EPR Study.” Journal of Physical Chemistry B, 116, 41, Pp. 12633–12640. Abstract
A complex system, based on a dendrimer solubilized in the aq. core of water-in-oil microemulsion, may combine the advantages of both dendrimers and microemulsions to provide better control of drug release. We report for the first time the use of EPR technique to det. the effect of solubilized dendrimer on the structure of the microemulsion. The solubilized poly(propyleneimine) (PPI-G2) interacts with sodium bis(2-ethylhexyl) sulfosuccinate (AOT). EPR anal. provided information on polarity, microviscosity, and mol. order of the systems. Polarity and microviscosity increased from unloaded water-in-oil microemulsion to the system loaded with 0.2 wt. % PPI-G2, but remained unchanged with higher PPI-G2 loads. The degree of order also increased with 0.2 wt. % PPI-G2 with only minor addnl. increase with larger quantities (25 wt. %) of PPI-G2. Variations in pH only slightly affected the structure of microemulsion in the absence and presence of the loaded dendrimers. Aliph. oils with longer lipophilic chains enhanced the structural order of the microemulsion. On increasing water content, polarity and degree of order increased. PPI-G2 dendrimer in small loads is attracted by the neg. charged AOT and thus intercalates in the interface of the droplets. Yet, at higher PPI-G2 loads, the excess mols. are solubilized in the water core. [on SciFinder(R)]
2012. Cocoa Butter and Related Compounds., Pp. 528 pp. AOCS Press.
Idit Amar-Yuli, Abraham Aserin, and Nissim. Garti. 2012. “Interfacial reactivity at liquid crystal interfaces.” In Nanotechnol. Solubilization Delivery Foods, Cosmet. Pharm., edited by I. Amar-Yuli, Pp. 209–225. USA: DEStech Publications, Inc. Abstract
A review. Liq. crystal (LC) science and technol. have made important contributions to nanoscience and nanotechnol. in areas such as medical diagnostics, drug-delivery, and high-tech devices. Their main nanotechnol. contribution is their ability to provide new synthetic procedures and the self-assembly of nanoscale materials with controlled uniformity of size, shape, and dimensionality. The self-assembly of the liq. cryst. systems, particularly of the lyotropic LC type, enables the incorporation of lipophilic and hydrophilic reagents that meet to react at the interface. Therefore the properties of reactions and products are governed by the host system and by the external conditions which directly affect the LC host or template. This article attempts to present an overview of current research in the fields of synthesis and self-assembly of nanomaterials using mainly lyotropic LCs, and partially thermotropic LCs, as direct and reverse templates. [on SciFinder(R)]
Shmaryahu Ezrahi, Dima Libster, Abraham Aserin, Rivka Efrat, and Eran Tuval. 2012. “Microemulsions - characterization and selected applications.” In Nanotechnol. Solubilization Delivery Foods, Cosmet. Pharm., edited by Nissim. Garti and I. Amar., Pp. 51–80. DEStech Publications, Inc. Abstract
A review. First the definition of microemulsions is referred. The differences between microemulsions, emulsions and nanoemulsions are demonstrated. A simple presentation of the mechanism of microemulsion stability is then given., followed by a discussion of microstructures, a characterization of microemulsions,and a brief description of their phase behavior. After that, applications of. microemulsions are discussed, with a focus on the important topic of solubilization of bioactives. Obviously the description of this application was not meant to be all-inclusive. Rather, it was delved into selected microemulsion systems which mainly were investigated in the authors' lab. [on SciFinder(R)]
N. Garti and I. Amar-Yuli. 2012. Nanotechnologies for solubilization and delivery in foods, cosmetics and pharmaceuticals. Lancaster, Pa: DEStech Publications.
Liron Bitan-Cherbakovsky, Dima Libster, Maria Francesca Ottaviani, Abraham Aserin, and Nissim. Garti. 2012. “Structural Behavior and Interactions of Dendrimer within Lyotropic Liquid Crystals, Monitored by EPR Spectroscopy and Rheology.” Journal of Physical Chemistry B, 116, 8, Pp. 2420–2429. Abstract
Micro- and macrostructural behaviors of three different lyotropic liq. crystals (LLCs) loaded with a dendrimer, namely second generation poly(propylene imine) (PPI-G2), were studied by rheol. and ESR (EPR). The three mesophases were L$\alpha$, Q224, and HII composed of glycerol monooleate (GMO) and water-PPI-G2 soln. (and d-$\alpha$-tocopherol (vitamin E) in the case of HII). We characterized the impact of PPI-G2 interactions with the components of the host mesophases on their structural characteristics on different length scales. The incorporation of PPI-G2 within the L$\alpha$ and HII systems induced the formation of more elastic hexagonal systems with a solid-like behavior, while in the Q224 system a different trend with a liq.-like behavior was obsd. As a result, the dendrimer induced a remarkable change in both the structural and viscoelastic properties of the systems. Hence, the microenvironment in the interface region within the systems was monitored by computer-aided EPR using 5-doxylstearic acid (5-DSA) as a pH-dependent probe. The microviscosity ($\tau$) and order (S) of systems were sensitive to the PPI-G2 presence: when PPI-G2 concn. increased, $\tau$ and S increased in both the L$\alpha$ and Q224 systems. In the HII systems two trends were obsd., reflecting a decrease in $\tau$ and S up to 10 wt.% PPI-G2 and subsequently their increase at higher dendrimer concns. PPI-G2 interacted strongly with the GMO hydroxyl groups in the L$\alpha$ phase, with the water mols. in the Q224 systems. In the HII mesophase strong interactions with both the water and GMO hydroxyl mols. were detected. [on SciFinder(R)]
Edmund Co and Alejandro G Marangoni. 2012. “Structured organogels based on vegetable oils and surfactants - structures, characteristics and applications.” In Nanotechnol. Solubilization Delivery Foods, Cosmet. Pharm., Pp. 227–301. DEStech Publications, Inc. Abstract
A review on phytosterol vegetable oil organogels, phospholipid microemulsion organogels, wax-based organogels, and 12-hydroxystearic acid vegetable oil organogels. [on SciFinder(R)]