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)]

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)]

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)]

A review on phytosterol vegetable oil organogels, phospholipid microemulsion organogels, wax-based organogels, and 12-hydroxystearic acid vegetable oil organogels. [on SciFinder(R)]

A review on fundamental concepts that are pertinent to understanding surfactants. It also describes self-assembled aggregate structures of surfactants. [on SciFinder(R)]

A review. Transdermal delivery has lately emerged as a valuable alternative method to improve bioavailability and increase pharmaceutical efficacy of various drugs. Transdermal administration can potentially minimize side effects as well as first-pass metab. It has been used successfully for hormone replacement therapy, smoking cessation, and pain management. However, there have been challenges in the expanding use of the technol. to numerous types of pharmaceuticals, including extremely hydrophilic or lipophilic drugs, peptides, proteins, and other macromols. In this context, colloidal drug carriers, and in particular lyotropic liq. crystals (LLCs), seem to be promising candidates as the vehicles of unconventional delivery for various drugs. Such vehicles can provide enhanced drug soly., relative protection of the solubilized drugs, and controlled release of drugs, while avoiding substantial side effects. Exhibiting interesting properties for a topical delivery system, LLCs were considered and have been studied as delivery vehicles of pharmaceuticals via the skin and mucosa. This review focuses on lyotropic non-lamellar lyotropic mesophases (hexagonal and cubic) and their nano-dispersions as topical delivery vehicles. Recent advances in transdermal and mucosal drug delivery via LLC carriers are demonstrated and discussed. [on SciFinder(R)]

The incorporation of dendrimer into three lyotropic liq. cryst. (LLCs) mesophases is demonstrated for the first time. A second generation (G2) of poly(propylene imine) dendrimer (PPI) was solubilized into lamellar, diamond reverse cubic, and reverse hexagonal LLCs composed of glycerol monooleate (GMO), and water (and D-$\alpha$-tocopherol in the HII system). The combination of PPI with LLCs may provide an advantageous drug delivery system. Cross-polarized light microscope, small-angle X-ray scattering (SAXS), and attenuated total reflectance Fourier transform IR (ATR-FTIR) were utilized to study the structural behavior of the mesophases, the localization of PPI within the system, and the interactions between the guest mol. and the system's components. It was revealed that PPI-G2 functioned as a "water pump", competing with the lipid headgroups for water binding. As a result, L$\alpha$→HII and Q224→HII structural shifts were detected (at 10 wt % PPI-G2 content), probably caused by the dehydration of monoolein headgroups and subsequent increase of the lipid's crit. packing parameter (CPP). In the case of HII, as a result of the balance between the dehydration of the monoolein headgroups and the significant presence of PPI within the interfacial region, increasing the quantity of hydrogen bonds, no structural transitions occurred. ATR-FTIR anal. demonstrated a downward shift of the H-O-H (water), as a result of PPI-G2 embedment, suggesting an increase in the mean water-water H-bond angle resulting from binding PPI-G2 to the water network. Addnl., the GMO hydroxyl groups at $\beta$- and $\gamma$-C-OH positions revealed a partial interaction of hydrogen bonds with N-H functional groups of the protonated PPI-G2. Other GMO interfacial functional groups were shown to interact with the PPI-G2, in parallel with the GMO dehydration phenomenon. In the future, these outcomes can be used to design advanced drug delivery systems, allowing administration of dendrimers as a therapeutic agent from LLCs. [on SciFinder(R)]

DNA-lipid interactions have important implications for biol. functions, gene therapy and biotechnol. In the present work, the authors exploit hydrogen bonding and ionic interactions between lipids and DNA to control the entrapment, the binding and the release properties of DNA confined within the water channels of reverse hexagonal columnar phases. Two lipid formulations were considered, consisting of glycerol monooleate/tricaprylin and glycerol monooleate/oleyl amine/tricaprylin, yielding the nonionic and cationic-based systems, resp. In the presence of water, or water-DNA dil. solns., both formulations led to the formation of reverse hexagonal columnar mesophases. To study the confinement of DNA in the reverse hexagonal mesophases, and to understand its interactions with the nonionic and cationic lipid formulations, the authors relied on small-angle x-ray scattering (SAXS) and attenuated total reflectance-Fourier transform IR (ATR-FTIR) spectroscopy. The release of the DNA from these hosting systems in excess water was monitored by UV spectrophotometry and single mol. at. force microscopy (AFM). In the case of the nonionic columnar system, DNA confined within the water cylinders, was stabilized by hydrogen bonding with the lipid polar heads, as revealed by the dehydration of the glycerol monooleate polar headgroups and a decrease in the water channel diam. The diffusion of DNA out of the mesophase water channels was found to occur in 3 steps correlated with the different contour lengths of the DNA fragments generated enzymically from the same pristine DNA macromol. In contrast, the presence of a low dose of cationic surfactants in the formulation enabled strong electrostatic interactions with the DNA mols., swelling the water cylinders and entirely suppressing the release of DNA. These results show that lipidic mesophases constitute an appealing, fully biocompatible carrier, allowing a fine control on the encapsulation and delivery of DNA in excess water environment. [on SciFinder(R)]

Four lipophilic food volatile mols. of different chem. characteristics, phenylacetaldehyde, 2,6-dimethyl-5-heptenal, linalool, and trans-4-decenal, were solubilized into binary mixts. of monoolein/water, facilitating the formation of reverse hexagonal (HII) mesophases at room temp. without the need of solvents or triglycerides. Some of the flavor compds. are important building blocks of the hexagonal mesostructure, preventing phase transition with aging. The solubilization loads were relatively high: 12.6, 10.0, 12.6, and 10.0 wt% for phenylacetaldehyde, 2,6-dimethyl-5-heptenal, linalool, and trans-4-decenal, resp. Phenylacetaldehyde formed mixts. of lamellar and cubic phases. Linalool, 2,6-dimethyl-5-heptenal, and trans-4-decenal induced structural shift from lamellar directly to HII mesophase, remaining stable at room temp. Lattice parameters were found to increase with water content and to decrease with temp. and/or food volatile content. trans-4-decenal produces more stable HII mesophase compared to linalool-loaded mesophase. At 40-60 °C, depending on the chem. structure and on the solubilization location of the food volatile compds., the HII mesophase transforms to isotropic micellar phase, facilitating the release of the food volatile compds. Mol. interactions suggest the existence of two consecutive stages in the solubilization process. [on SciFinder(R)]

A review. Recently, self-assembled lyotropic liq. crystals (LLCs) of lipids and water have attracted the attention of both scientific and applied research communities, due to their remarkable structural complexity and practical potential 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. Among the studied lyotropic mesophases, reverse hexagonal LLC (HII) of monoolein/water were not widely subjected to practical applications since these were stable only at elevated temps. Lately, we obtained stable HII mesophases at room temp. by incorporating triacylglycerol (TAG) mols. into the GMO/water mixts. and explored the phys. properties of these structures. The present feature article summarizes recent systematic efforts in our lab. to utilize the HII mesophases for solubilization, and potential release and crystn. of biomacromols. Such a concept was demonstrated in the case of two therapeutic peptides-cyclosporin A (CSA) and desmopressin, as well as RALA peptide, which is a model skin penetration enhancer, and eventually a larger macromol.-lysozyme (LSZ). In the course of the study we tried to elucidate relationships between the different levels of organization of LLCs (from the microstructural level, through mesoscale, to macroscopic level) and find feasible correlations between them. Since the structural properties of the mesophase systems are a key factor in drug release applications, we investigated the effects of these guest mols. on their conformations and the way these mols. partition within the domains of the mesophases. The examd. HII mesophases exhibited great potential as transdermal delivery vehicles for bioactive peptides, enabling tuning the release properties according to their chem. compn. and phys. properties. Furthermore, we showed a promising opportunity for crystn. of CSA and LSZ in single crystal form as model biomacromols. for crystallog. structure detn. The main outcomes of our 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 and crystn. medium for biomacromols. [on SciFinder(R)]

In an attempt to form H-II mesophases at room temperature we prepared lyotropic liquid crystals with two surfactants of the same lipophilic tails (glycerol monooleate, GMO, and oleyl lactate, OL) but differing in the size and charge of the headgroups. Increasing OL concentration significantly affected the hydration of the headgroups and subsequently the lipids packing. At low OL content the cubic mesophase was formed, while at higher OL contents the formation of hexagonal mesophase was favored. It was assumed that OL competed on the water binding, tuning the headgroups' curvature and the packing parameter inducing the formation of reverse hexagonal mesophase. It was detected that cubic mesophase transformed upon heating to hexagonal structures. The hexagonal mesophases, which were formed both immediately after preparation and after aging, remained stable at elevated temperatures. alpha-Chymotrypsinogen was solubilized into the obtained LLCs at relatively high concentration (up to 1 wt%). The lattice parameter of the host LLCs exhibited a decrease as a function of the protein content. This process was assigned to partial dehydration of the GMO polar moieties in favor to CTA hydration. Generally speaking, the present study indicated that adding anionic to nonionic lipid is highly beneficial to gain additional compositional and structural characteristics of LLCs. (C) 2011 Elsevier B.V. All rights reserved.

Provided are homogeneous liq. systems substantially 1H-NMR inactive and/or devoid of protons and are capable of enhancing the diffusion sepn. of a mixt., the system is substantially devoid of at least one NMR active nucleus present in the mixt. Further provided are methods of using the homogeneous liq. systems for enhancing the diffusion sepn. of a mixt. and/or generating a diffusion ordered spectrum of a mixt. and/or minimizing the peak width in a liq. state diffusion ordered spectrum of a mixt. [on SciFinder(R)]

Silica is used as an important component for NMR "chromatog.". In this study the effect of the binding strength to silica of a variety of compds. on their diffusion rate is measured for the first time. Over two orders of magnitude of diffusion difference enhancement was obtained in the presence of silica for some compds. An explanation of the enhancement is given that also allows one to predict the "chromatog." behavior of new compds. or mixts. The binding strength is divided into categories of weakly bound, singly bound and multiply bound. Carboxylates, sulfonates, and diols are found to be particularly strongly bound and to diffuse up to 21/2 orders of magnitude more slowly in the presence of silica. [on SciFinder(R)]

NMR spectroscopy is an excellent tool for structural anal. of pure compds. However, for mixts., it performs poorly because of overlapping signals. Diffusion ordered NMR spectroscopy (DOSY) can be used to sep. the spectra of compds. with widely differing mol. wts., but the sepn. is usually insufficient. NMR chromatog. methods were developed to increase the diffusion sepn. but these usually introduced solids into the NMR sample that reduce resoln. Using nanostructured dispersed media, such as microemulsions, eliminates the need for suspensions of solids and brings NMR chromatog. into the mainstream of NMR anal. techniques. DOSY was used in this study to resolve spectra of mixts. with no increase in line-width as compared to regular solns. Components of a mixt. are differentially dissolved into the sep. phases of the microemulsions. Several examples of previously reported microemulsions and those specifically developed for this purpose were used here. These include a fully dilutable microemulsion, a fluorinated microemulsion, and a fully deuterated microemulsion. Log(diffusion) difference enhancements of up to 1.7 orders of magnitude were obsd. for compds. that have similar diffusion rates in conventional solvents. Examples of com. pharmaceutical drugs were also analyzed via this new technique, and the spectra of up to six components were resolved from one sample. [on SciFinder(R)]

The potential of reverse hexagonal mesophases based on monoolein (GMO) and glycerol (as cosolvent) to facilitate the solubilization of proteins, such as insulin was explored. HII mesophases composed of GMO/decane/water were compared to GMO/decane/glycerol/water and GMO/phosphatidylcholine (PC)/decane/glycerol/water systems. The stability of insulin was tested, applying external phys. modifications such as low pH and heat treatment (up to 70°), in which insulin is known to form ordered amyloid-like aggregates (that are assocd. with several neurodegenerative diseases) with a characteristic cross $\beta$-pleated sheet structure. The impact of insulin confinement within these carriers on its stability, unfolding, and aggregation pathways was studied by combining SAXS, FTIR, and AFM techniques. These techniques provided a better insight into the mol. level of the component interplay in solubilizing and stabilizing insulin and its conformational modifications that dictate its final aggregate morphol. PC enlarged the water channels while glycerol shrank them, yet both facilitated insulin solubilization within the channels. The presence of glycerol within the mesophase water channels gave stronger hydrogen bonds with the hosting medium that enhanced the thermal stability of the protein and remarkably affected the unfolding process even after heat treatment (at 70° for 60 min). [on SciFinder(R)]