Peer Review Publications

Rivka Efrat, Zoya Abramov, Abraham Aserin, and Nissim. Garti. 2010. “Nonionic-Anionic Mixed Surfactants Cubic Mesophases. Part I: Structural Chaotropic and Kosmotropic Effect.” Journal of Physical Chemistry B, 114, 33, Pp. 10709–10716. Abstract
We prepd. and investigated cubic bicontinuous (V) phase from mixts. of nonionic monoolein (GMO) and anionic oleyl lactate (OL) surfactants in the presence of ethanol and water. The isotropic region and the compn. of the V phase in the pseudoternary phase diagram vary with the nature of the hydrophilic headgroups and their charge. We examd. three anionic species, acidic (HOL), partially neutralized (OL), and totally ionized (NaOL) forms. The largest swollen V region within the phase diagram was formed from the partially neutralized form. The V formation is dependent on the GMO/OL ratio. The largest isotropic region in the phase diagrams was found with GMO/OL at a 70:30 wt % ratio and in the presence of 5.0 and 38.5 wt % ethanol and water, resp. The structural effect of OL was detd. by small-angle X-ray spectroscopy, differential scanning calorimetry, and Fourier transform IR. The results revealed that the structure is curvature-dependent. Mesophases made from 90:10 wt % GMO/OL showed phase transition from gyroid (G) to diamond (D) symmetry. Prepns. made from 30:70 wt % GMO/OL exhibited coexistence of two mesophases, one (of low order) cubic and the other lamellar. Because of the overall gauche deformation growth, the hydrocarbon order decreased with the OL content increase. The GMO, sn2 and sn3 headgroups, and water structure vibration bands indicate a chaotropic effect as a result of the interdigitation of OL anions and Na+ and H+ counterions. [on SciFinder(R)]
Miri Klein, Abraham Aserin, Paul Ben Ishai, and Nissim. Garti. 2010. “Interactions between whey protein isolate and gum Arabic.” Colloids and Surfaces, B: Biointerfaces, 79, 2, Pp. 377–383. Abstract
In this study we have attempted to understand the nature of "charge interactions" between two neg. charged biopolymers (whey protein isolate, WPI and gum Arabic, GA) and, consequently, why their mixt. exhibits better interfacial activity. Surface tension ($\gamma$0) measurements indicated that at ca. 1 wt.% of the biopolymer mixt. (3:1 wt. ratio) the air/water surface is satd. At 5 wt.% the $\gamma$0 of the mixt. is lower than the calcd. co-operative value. The $\zeta$-potential measurements revealed that the isoelec. point of the WPI:GA 3:1 wt. ratio mixt. is 3.8. The $\zeta$-potential values up to pH 6 are below those calcd. Similarly, the elec. conductivities of the mixt. are lower than those calcd. All these measurements indicate: (1) partial charge neutralization in spite of the fact that both biopolymers are neg. or (2) partial charge-charge interactions between the two biopolymers. The thermal heating behavior of the frozen water in the aq. mixt. studied by DSC (heating cycle of the frozen sample) clearly indicates that the two biopolymers are interacting. We calcd. the enthalpy, the free energy and the chem. potential of the interactions. We found that the interactions of the biopolymers are rather weak. They are likely derived from some local pos. charged domains (pH 7) on the protein that neutralize some of the neg. charged GA. These interactions form weak charge adducts. These charge adducts are sufficient to improve its adsorption into the oil-water interface and enhance the emulsion stability. [on SciFinder(R)]
Miri Klein, Abraham Aserin, Inna Svitov, and Nissim. Garti. 2010. “Enhanced stabilization of cloudy emulsions with gum Arabic and whey protein isolate.” Colloids and Surfaces, B: Biointerfaces, 77, 1, Pp. 75–81. Abstract
Cloudy emulsions are oil-in-water (O/W) emulsions normally prepd. as concs., further dild., per request, into the final beverage. The cloudy emulsion provides flavor, color, and cloud (turbidity) to the soft drink. These systems are stabilized by emulsifiers and/or amphiphilic polysaccharides. Cloudy emulsions based on naturally occurring food grade emulsifiers were studied in the present work. Two charged natural biopolymers, whey protein isolate (WPI) and gum arabic (GA), are interacted in aq. soln. to form charge-charge interactions improving the emulsion stability. The emulsions were high sheared (Microfluidizer) and characterized by particle size distribution anal. (DLS), optical centrifugation (LUMiFuge), optical microscopy observations, and turbidity measurements. Emulsions obtained from 10 wt% of 3:1 wt. ratio WPI:GA, at pH 7 (10 wt% canola oil) show better stability than emulsions stabilized by GA or WPI alone. The droplet sizes were smaller than 1 $μ$m and did not grow significantly during 1 mo of incubation at 25 °C. The D-limonene-based emulsion droplets were larger (\textgreater2 $μ$m) than those made with vegetable oils immediately after prepn. and underwent significant droplet size increase (coalescence) within 1 mo (\textgreater8 $μ$m). The emulsion with turbidity suitable as a cloudy emulsion was composed of 3 wt% WPI:GA (3:1) and 20 wt% canola oil. [on SciFinder(R)]
Dima Libster, Abraham Aserin, Idit Amar-Yuli, Tehila Mishraki, Yael Domovich-Eisenberg, Oded Livnah, and Nissim. Garti. 2010. “Crystallization of cyclosporin A in lyotropic reverse hexagonal liquid crystals.” CrystEngComm, 12, 7, Pp. 2034–2036. Publisher's Version Abstract
In this communication we demonstrate for the first time that lyotropic reverse hexagonal mesophase can serve as a crystn. medium for a hydrophobic peptide, resulting in high quality single crystals suitable for crystallog. anal. The obtained crystals of cyclosporin A enabled excellent X-ray data collection, diffracting to a resoln. limit of 1.0 \AA. Current findings open a new perspective in the field of crystn. of biol. macromols. in lyotropic mesophases. [on SciFinder(R)]
Tehila Mishraki, Dima Libster, Abraham Aserin, and Nissim. Garti. 2010. “Lysozyme entrapped within reverse hexagonal mesophases: Physical properties and structural behavior.” Colloids and Surfaces, B: Biointerfaces, 75, 1, Pp. 47–56. Abstract
A model protein (lysozyme) was incorporated into monoolein-based reverse hexagonal (HII) mesophase and its structure effects were characterized by small angle X-ray scattering, ATR-FTIR spectroscopy, and rheol. measurements. Modifications in mol. organization of the HII mesophases as well as the conformational stability of lysozyme (LSZ) as a function of pH and denaturing agent (urea) were clarified. Up to 3 wt. % LSZ can be solubilized into the HII. The vibration FTIR anal. revealed that LSZ interacted with OH groups of glycerol monooleate (GMO) in the outer interface region, resulting in strong hydrogen bonding between the surfactant and its environment. Simultaneously, the decrease in the hydrogen-bonded carbonyl population of GMO was monitored, indicating dehydration of the monoolein carbonyls. These mol. interactions yielded a minor decrease in the lattice parameter of the systems, as detected by small angle X-ray scattering. Furthermore, LSZ was crystd. within the medium of the hexagonal structures in a single crystal form. The $\alpha$-helix conformation of lysozyme was stabilized at high pH conditions, demonstrating greater helical structure content, compared to D2O soln. Moreover, the hexagonal phase decreased the unfavorable $\alpha$ → $\beta$ transition in lysozyme, thereby increasing the stability of the protein under chem. denaturation. The rheol. behavior of the hexagonal structures varied with the incorporation of LSZ, reflected in stronger elastic properties and pronounced solid-like response of the systems. The hydrogen bonding enhancement in the interface region of the structures was most likely responsible for these phenomena. The results of this study provided valuable information on the use of hexagonal systems as a carrier for incorporation and stabilization of proteins for various applications. [on SciFinder(R)]
Tehila Mishraki, Dima Libster, Abraham Aserin, and Nissim. Garti. 2010. “Temperature-dependent behavior of lysozyme within the reverse hexagonal mesophases (HII).” Colloids and Surfaces, B: Biointerfaces, 75, 2, Pp. 391–397. Abstract
This manuscript is the second part of a study on the structural behavior of lysozyme-loaded reverse hexagonal mesophases. In the current paper, th focus was mainly on the mutual temp.-dependency relationship between the protein and the mesophase. The conformational stability of the enzyme and the structural effects on the host system were characterized using small-angle X-ray scattering (SAXS), ATR-FTIR spectroscopy, fluorescence, and rheol. measurements. It was found that the mesophase does not change the solubilized lysozyme (LSZ) active site conformation. The obtained data suggested that LSZ embedment within the HII mesophase improved its thermal stability by hampering its helical structure destruction, apparently due to hydrogen bonding of the protein with monoolein polar heads. Examn. of the structural parameters of the hexagonal carrier revealed a strong thermal dependency. The lattice parameter of both empty and LSZ-loaded systems had a similar temp.-dependent behavior. However, comparing the domain size of the LSZ-loaded system to the empty system showed different trends. LSZ incorporation induced a decrease in crystal size and lower order at room temp. Nevertheless, an increase in domain size was triggered by the enzyme at elevated temps., in contrast to its decrease in the empty carriers. Rheol. measurements showed concn.-dependent elasticity in the presence of LSZ compared to the empty system, which took place in a concn.-dependent manner at all examd. temps. Up to 60 °C, the elasticity of the LSZ-loaded hexagonal systems decreased with temp. increase. This finding was interpreted in the context of weakening and/or cleaving of the monoolein hydroxyls' interactions with the protein, leading to partial reconstitution of the initially low domain size and elasticity decrease. However, in the range of 60-75 °C (in most systems), the prevailing effect was thermally induced dehydration of the monoglyceride hydrophilic heads, which imposed elasticity increase, owing to enhanced flow ability of the liq. cryst. structure. [on SciFinder(R)]
Ido Nir, Abraham Aserin, Dima Libster, and Nissim. Garti. 2010. “Solubilization of a Dendrimer into a Microemulsion.” Journal of Physical Chemistry B, 114, 50, Pp. 16723–16730. Abstract
The present work investigates, for the first time, a system comprising a dendrimer incorporated into the water core of water-in-oil (W/O) microemulsion (ME). A second generation (G-2) poly(propyleneimine) dendrimer (PPI) was solubilized into W/O ME composed of AOT (sodium bis(2-ethylhexyl)sulfosuccinate), heptane, and water. Such a model system possessing the benefits of both dendrimers and ME, can potentially offer superior control of drug administration. The localization of PPI within the system, its specific interactions with the components of the carrier, and its effect on the ME structure was explored by SAXS, DSC, ATR-FTIR, and elec. cond. measurements. Considerable water binding by PPI, accompanied by partial dehydration of AOT polar heads, was detected by ATR-FTIR and DSC anal., suggesting that PPI acted as a "water pump". In addn., SAXS measurements showed periodicity increase and disordering of the droplets. Hence, localization of PPI within the core and interfacial regions of the droplets was assumed. Direct electrostatic interactions between PPI and the sulfonate group were not noticed, since the dendrimer mols. were mostly not protonated in the current basic environment at pH 12. However, slight hydrogen bonding between PPI and the S=O groups allowed the dendrimer to behave as a "spacer" between sodium and sulfonate ions. This affected the elec. cond. behavior of the system, revealing that PPI favored the percolation process. Most likely, PPI decreased the rigidity of the interfacial layer, facilitating the diffusion of sodium ions through the channels. The characterized model system can be advantageously utilized to design specific delivery vehicles, allowing administration of dendrimers as a therapeutic agent from host MEs. [on SciFinder(R)]
Shoshana Rozner, Deborah E Shalev, Alexander I Shames, Maria Francesca Ottaviani, Abraham Aserin, and Nissim. Garti. 2010. “Do food microemulsions and dietary mixed micelles interact?” Colloids and Surfaces, B: Biointerfaces, 77, 1, Pp. 22–30. Abstract
Using microemulsions (ME) as delivery vehicles requires understanding whether water-insol. mols. are delivered by an interaction of the ME system with the dietary mixed micelles (DMM) in the small intestine to give new mixed micelles, or by alternate paths. Dild. DMM and ME systems were mixed at various wt. ratios to address this question. The individual and mixed systems were characterized by phys. techniques that address this interaction from different aspects. This research showed that increased DMM concn. in ME/DMM mixed systems caused: (1) increased conformational order of the acyl chains and perturbed hydrogen bonds between the ethoxylate headgroups (based on ATR-FTIR results); (2) significant increase in microviscosity (from 1.7 to 3.3 ns) (based on EPR results); (3) increased diffusivity of the surfactant mols. compared to their diffusivity in pure ME droplets, and decreased diffusivity of the taurochenodeoxycholate mols. compared to their diffusivities in pure DMM micelles (based on PGSE-NMR results); (4) formation or modification of intramol. interactions (based on NOESY-NMR results); (5) decreased av. droplet diam. and increased droplet d. per unit area compared to pure ME systems (based on DLS and cryo-TEM results); and (6) fluorescence resonance energy transfer between two dyes (diphenylhexatriene and Nile Red), which were solubilized in each system sep. (based on fluorescence resonance energy transfer results). These results show that DMM and ME interact to create ME-DMM mixed micelles, providing a potential pathway for delivering solubilized mols. [on SciFinder(R)]
Doron Yariv, Rivka Efrat, Dima Libster, Abraham Aserin, and Nissim. Garti. 2010. “In vitro permeation of diclofenac salts from lyotropic liquid crystalline systems.” Colloids and Surfaces, B: Biointerfaces, 78, 2, Pp. 185–192. Abstract
In this paper the authors examd. feasible correlations between the structure of different lyotropic mesophases and transdermal administration of three diclofenac derivs. with varying degrees of kosmotropic or chaotropic properties, solubilized within the mesophases. It was found that the most chaotropic deriv. of diclofenac di-Et amine (DEA-DFC) interacted with the polar heads of glycerol monooleate (GMO), thus expanding the water-lipid interface of the lamellar and cubic mesophases. This effect was detected by an increase in the lattice parameter of both mesophases, enhanced elastic properties, and increased solid-like response of the systems in the presence of DEA. Potassium diclofenac (K-DFC), a less chaotropic salt, had less pronounced effect on the structural features of the mesophases. Kosmotropic Na+ salt (Na-DFC) had only minor influence on both lamellar and cubic structures. The locus of solubilization of the mols. with the host mesophases was correlated with their delivery. It was suggested that transdermal delivery of kosmotropic Na-DFC was accelerated by the aq. phase and less constrained by the interaction with monoglyceride. The chaotropic cations (K+ and DEA+), presumably entrapped in the water-lipid interface, interacted with monoglyceride headgroups, which is likely to be the key cause for their sustained administration. [on SciFinder(R)]
I Amar-Yuli, A Aserin, and N Garti. 2009. “Coenzyme Q10: functional benefits, dietary uptake and delivery mechanisms.” Woodhead Publishing Series in Food Science, Technology and Nutrition, 177, Designing Functional Foods, Pp. 676–700. Abstract
A review. Coenzyme Q10, present in all cells and membranes, is essential for electron transport in the mitochondrial respiratory chain, antioxidant defense, and other functions of great importance for cellular metab. The essential advantages of CoQ10, combined with its poor and slow absorption, generated the need to develop new technologies for delivery. Therefore, much effort has been expended to design delivery vehicles that can improve its aq. soly. and overall bioavailability for oral and topical administration. This chapter summarizes the findings available today concerning CoQ10 chem. characteristics, human functionalities, its impact on human diseases, and new techniques developed to enhance its delivery. [on SciFinder(R)]
Orit Amsalem, Idit Yuli-Amar, Abraham Aserin, and Nissim. Garti. 2009. “Phospholipids embedded fully dilutable liquid nanostructures. Part 1: Compositions and solubilization capacity.” Colloids and Surfaces, B: Biointerfaces, 73, 1, Pp. 15–22. Abstract
The use of phospholipids (PL) as surfactants in micellar systems and microemulsions offers many advantages as drug delivery vehicles. PL are commonly used in combination with other non-food surfactants with cosolvents and cosurfactants to form a cascade of delivery structures. The authors incorporated phosphatidylcholine (PC) in a unique U-type water-dilutable phase diagrams exhibiting large isotropic regions of nanostructures. The nanometric liq. structures were prepd. from food-grade emulsifiers. The authors formed water-free concs. with PC that are fully dild. with water to form a variety of unusually structured nanodroplets. Due to the uniqueness of their compn., the designed concs. derived from the nature of the oil phase, type of surfactants, and cosurfactants were characterized and found to be direct micelles (rather than inverse micelles), with the surfactant headgroups convexed toward the hydrophilic phase away from the micelle's core, even in the absence of water. The concs. tend to self-assemble upon adding water to form O/W microemulsions even with small amts. of water (water-poor compns. of 0-20% water). Upon further diln. with water the swollen micelles retain the oil as the inner phase. Multi-component compns. with two types of hydrophilic surfactants were investigated. The most significant enhancement in the total isotropic region was obtained by decreasing the triacetin and PC content in the system. The authors explored, by varying the nature of the headgroups and the nature and length of the lipidic (lipophilic) tails of the PL, the diln. capabilities of each of the systems. [on SciFinder(R)]
Idit Amar-Yuli, Dima Libster, Abraham Aserin, and Nissim. Garti. 2009. “Solubilization of food bioactives within lyotropic liquid crystalline mesophases.” Current Opinion in Colloid & Interface Science, 14, 1, Pp. 21–32. Abstract
A review. Liq. crystals are widely utilized as model systems to mimic biol. processes where the phase behavior of lipids plays a mediating role. In various foods and pharmaceutical and biotech. applications, the liq. cryst. phases formed by surfactants in an aq. medium represent useful host systems for drugs, amino acids, peptides, proteins and vitamins. Various biol. active food additives are sol. in neither aq. nor oil phase and require environmental protection against hydrolysis or oxidn. Lyotropic liq. crystals meet these requirements mainly due to their high solubilization capacities for hydrophilic, lipophilic and amphiphilic guest mols. Moreover, recent studies demonstrated controlled and/or sustained release of solubilized mols. from different liq. cryst. matrixes. This paper surveys the solubilization of hydrophilic, lipophilic and amphiphilic guest mols. for food applications and illustrates the corresponding structural transformations. Recent developments in liq. crystal characterization methods are discussed. [on SciFinder(R)]
Liron Bitan-Cherbakovsky, Idit Yuli-Amar, Abraham Aserin, and Nissim. Garti. 2009. “Structural Rearrangements and Interaction within HII Mesophase Induced by Cosolubilization of Vitamin E and Ascorbic Acid.” Langmuir, 25, 22, Pp. 13106–13113. Abstract
We investigated the effect of ascorbic acid (AA) cosolubilized with vitamin E (VE) on reverse hexagonal (HII) mesophase. The HII phase comprises monoolein (GMO)/D-$\alpha$-tocopherol (VE) in a ratio of 90/10 by wt. and 12.5 wt% water. The macrostructural characteristics of this system were detd. by polarized light microscopy and small-angle X-ray scattering measurements. We used differential scanning calorimetry and attenuated total reflectance Fourier transform IR to characterize the microstructure, the vibration of the functional groups, and the location of the AA guest mol. AA was incorporated to the system in two steps: 1-4 wt% AA and 5-6 wt% AA. We compared this system to one contg. tricaprylin as the oil phase, as previously reported. These measurements revealed that AA is localized first in the water rich-core and in the interface, and acts as a chaotropic mol. that decreases the water m.p. When a larger quantity of AA (5-6 wt%) is added, the system is satd., and the AA is located in the inner cylinder and manifested by more moderate distortion. The addn. of AA also causes alteration in the behavior of the GMO hydrocarbon chains and makes them more flexible. Further addn. of AA caused the GMO hydrocarbon chain to be more solvated by the VE hydrocarbon chain and enabled addnl. migration of VE; hence a decrease in the hydrophobic melting temp. occurred (similar to tricaprylin). Increasing the amt. of AA weakened the bonding between the GMO and water and created new bonds between AA and GMO and AA with water. [on SciFinder(R)]
Rivka Efrat, Ellina Kesselman, Abraham Aserin, Nissim Garti, and Dganit. Danino. 2009. “Solubilization of Hydrophobic Guest Molecules in the Monoolein Discontinuous QL Cubic Mesophase and Its Soft Nanoparticles.” Langmuir, 25, 3, Pp. 1316–1326. Abstract
Hydrophobic bioactive guest mols. were solubilized in the discontinuous cubic mesophase (QL) of monoolein. Their effects on the mesophase structure and thermal behavior, and on the formation of soft nanoparticles upon dispersion of the bulk mesophase were studied. Four additives were analyzed. They were classified into two types based on their presumed location within the lipid bilayer and their influence on the phase behavior and structure. Differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), polarized light microscopy, cryogenic-transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used for the anal. We found that carbamazepine and cholesterol (type I mols.) likely localize in the hydrophobic domains, but close to the hydrophobic-hydrophilic region. They induce strong perturbation to the mesophase packing by influencing both the order of the lipid acyl chains and interactions between lipid headgroups. This results in significant redn. of the phase transition enthalpy, and phase sepn. into lamellar and cubic mesophases above the max. loading capacity. The inclusion of type I mols. in the mesophase also prevents the formation of soft nanoparticles with long-range internal order upon dispersion. In their presence, only vesicles or sponge-like nanoparticles form. Phytosterols and coenzyme Q10 (type II mols.) present only moderate effects. These mols. reside in the hydrophobic domains, where they cannot alter the lipid curvature or transform the QL mesophase into another phase. Therefore, above max. loading, excess solubilizate ppts. in crystal forms. Moreover, when type II-loaded QL is dispersed, nanoparticles with long-range order and cubic symmetry (i.e., cubosomes) do form. A model for the growth of the ordered nanoparticles was developed from a series of intermediate structures identified by cryo-TEM. It proposes the development of the internal structure by fusion events between bilayer segments. [on SciFinder(R)]
Nissim. Garti. 2009. “Preface.” Journal of Thermal Analysis and Calorimetry, 14, 1, Pp. 1–2.