Peer Review Publications

Axel Benichou, Abraham Aserin, and Nissim. Garti. 2007. “Oil-in-water-in-oil double emulsions stabilized with WPI-polysaccharide conjugates.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 297, 1-3, Pp. 211–220. Abstract
Protein/polysaccharide conjugates were used to stabilize oil-in-water (O/W) emulsions and oil-in-water-in-oil (O/W/O) double emulsions. By properly selecting the type of protein (WPI) and the polysaccharide (xanthan gum, fenugreek gum), and by using specific ratios of the two biopolymers and their soln. concns., amphiphilic biopolymer adducts were formed. A synergism in the emulsification properties was obsd. in WPI/polysaccharide conjugates compared to each of the biopolymers alone. Submicron droplets of oil-in-water were obtained by applying a high-pressure homogenization process during the first step of the double emulsion prepn. It was also demonstrated that double-emulsion globules could be formed with a very high yield of addendum entrapment (above 95%) during the second step of the emulsification process. The differentiation between the two types of oils, O1 (the inner) and O2 (the outer), in the double emulsions enabled high entrapment capacity of the addendum in the inner oil phase. In addn., when the inner oil phase (O1) was a 1:1 (wt./wt.) mixt. of MCT/triacetin and the external oil phase (O2) was a silicone oil, it was possible to slow the release of the entrapped matter while the soly. of the inner phase in the external oil phase remained const. The addendum soly. in the external oil phase was not a limiting factor in the release process. The presence of hydrophobic additives (i.e., 1% glycerol monooleate) in the inner oil phase helped to better control the transport to the external oil phase. In the best case, the addendum leakage to the external oil phase was only ∼0.2% during a period of 28 days at 25°. WPI/xanthan gum adducts served as thick and efficient barriers against release of flumethrin (a veterinary drug model) entrapped in the core of the O/W/O multiple globules. [on SciFinder(R)]
Axel Benichou, Abraham Aserin, Rachel Lutz, and Nissim. Garti. 2007. “Formation and characterization of amphiphilic conjugates of whey protein isolate (WPI)/xanthan to improve surface activity.” Food Hydrocolloids, 21, 3, Pp. 379–391. Abstract
Proteins, polysaccharides and their blends, as examples of natural biopolymers, may be considered as amphiphilic macromolecules that play an essential role in stabilizing food formulations (foams, emulsions and dispersions). Under specific compositions and conditions (protein-to-polysaccharide ratio, pH, ionic strength, temperature, mixing, processing steps) proteins and polysaccharides form water-soluble hybrids (complexes or conjugates), but not coacervates, with enhanced functional properties in comparison to the proteins and polysaccharides alone. Aqueous mixtures of WPI (4-10wt%) and xanthan gum (\textgreater 0.5wt%) form clear aqueous systems exhibiting new physicochemical properties such as rheological behavior, surface properties, surface density of charge (zeta potential), surface hydrophobicity and diffusion behavior. Electrostatic interactions and thermodynamic incompatibility in mixed biopolymer solutions were correlated to the functional properties (rheology, surface properties and surface hydrophobicity) of these adducts. Evidences for associative interactions between WPI and xanthan gum have been established by studying the rheological behavior, the surface hydrophobicity and the surface dynamic properties of the blends. The electrostatic and hydrophobic interactions form hybrids that can provide a synergistic effect on the emulsifying capabilities of the biopolymers and can increase the stability of emulsion droplets against coalescence and flocculation. (c) 2006 Elsevier Ltd. All rights reserved.
Axel Benichou, Abraham Aserin, and Nissim. Garti. 2007. “W/O/W double emulsions stabilized with WPI-polysaccharide complexes.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 294, 1-3, Pp. 20–32. Abstract
A synergism in the emulsification properties was seen in WPI/polysaccharide complexes in comparison to each of the biopolymers alone and it was found also to depend on surface properties of the complexes that is strongly affected by the WPI/polysaccharide ratio. It was also demonstrated that the galactose/mannose ratio and the overall no. of galactose residues available on the polysaccharide surface, increasing with the mol. wt. of the mol., strongly influence the surface properties of the blend. At pH below the isoelec. point of WPI/xanthan gum, an increase in the thermal stability of the complex was obsd. and was attributed to strong interactions existing between the biopolymer mols. These adducts served also as thick and efficient barriers against release of Vitamin B1 entrapped in the core of the W/O/W multiple globules. [on SciFinder(R)]
Rivka Efrat, Abraham Aserin, Ellina Kesselman, Dganit Danino, Ellen J Wachtel, and Nissim. Garti. 2007. “Liquid micellar discontinuous cubic mesophase from ternary monoolein/ethanol/water mixtures.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 299, 1-3, Pp. 133–145. Abstract
In constructing the phase diagram of glycerol monooleate (GMO)/EtOH/H2O mixts. the authors detected, in addn. to the well-characterized regions of lamellar and cubic bicontinuous liq. crystals, 3 addnl. isotropic transparent regions that were not previously well-defined; a large isotropic region denoted in early studies as the L1-phase, an isotropic region with characteristics similar to the sponge L3-phase, and a 3rd isotropic region which had not been characterized previously. The present study deals with efforts to characterize this unique isotropic region. The isotropic region is an island located within a 2 phase region connecting the 3 isotropic regions of the cubic, lamellar, and micellar phases. The authors termed this phase I2 (QL) phase or the QL phase, which stands for cubic liq. mesophase. This phase is a totally transparent and nonbirefringent fluid (completely pourable). It is stable even after over 9 mo of storage at room temp. The fluid is of low viscosity and almost Newtonian. The new phase shows many characteristic features of an ordered phase. Small-angle x-ray scattering measurements (SAXS), SAXS-synchrotron temp.-dependent measurements, and cryogenic-TEM (cryo-TEM) observation reveal that the phase has a cubic symmetry. The SAXS diffractions indicate formation of a somewhat less ordered discontinuous cubic micellar mesophase. The cryo-TEM images provide strong evidence for ordered domains with cubic symmetry. Complementary measurements confirm that the phase is a unique case of a micellar cubic phase. The authors expect that the fluidic ordered mesostructure will have future applications as a liq. vehicle for the solubilization of nutraceuticals, cosmetoceuticals, and pharmaceuticals. [on SciFinder(R)]
Rivka Efrat, Abraham Aserin, Deborah E Shalev, Roy E Hoffman, and Nissim. Garti. 2007. “Effect of drug solubilized in a novel cubic nanostructure.” In Abstracts of Papers, 233rd ACS National Meeting, Chicago, IL, United States, March 25-29, 2007, Pp. COLL–196. American Chemical Society. Abstract
The binary phase diagram of GMO/water reveals the formation of two major lyotropic mesophases that have been extensively studied. Adding short-chain alc. (ethanol, propanol and butanol) to a mixt. of various compns. formed one large isotropic micellar phase (the L phase) and two small confined lyotropic regions termed the L3 sponge phase and the QL (micellar cubic). The QL phase is a new mesostructure. It was shown that while the cubic phase is highly viscous the QL phase is fluid and, it displays unique phys. properties. It is fully transparent (not tinted), non-birefringent, and very stable at room temp. (samples were stored for over 8 mo with no phys. changes). The phases were investigated by cryo-TEM, SAXS and self-diffusion NMR. The structure it has primitive cubic symmetry and is discontinuous micellar phases rather than a bicontinuous one. The QL phase was further dispersed in water contg. amphiphilic copolymer (Pluronic 127) to form cubic nanoparticles that we termed micellosomes. The effect of solubilization of water-insol. drugs like, diclofenc (DCF), at different concns. (0.1, 1, 3, and 10 wt%) in the QL phase was investigated by SAXS, rheol. measurements, and NMR (self-diffusion and relaxation) measurements. The rate of percutaneous penetration through rat skin of these structures is significantly higher than that of the com. drug. The compn. that shows the best penetration was QL with 1 wt% DCF. [on SciFinder(R)]
Nissim Garti and Rivka. Efrat. 2007. “Micellar cubic structures, QL, and micellosomes for improved solubilization and bioavailability on nutraceuticals.” In Abstracts of Papers, 233rd ACS National Meeting, Chicago, IL, United States, March 25-29, 2007, Pp. AGFD–127. American Chemical Society. Abstract
Polar lipid mols. such as glycerol monooleate (GMO) and polar solvent (usually water) can spontaneously organize in high order at the long-range distances while in the short-range, at at. distances, they are disordered. Liq. cryst. mesophases with a long-range order in one dimension are lamellar phases (L$\alpha$ ) while those showing two dimensional long-range order are known as hexagonal phases (HI and H2 for normal and reverse hexagonal) and those with three dimension long-range orders are lyotropic cubic phase (C). Hydrophobic effect with a variety of intra- and intermol. interactions, in combination with a no. of geometric packing constraints, are responsible for the degree of order. Addn. of guest mols. (solubilizates) to the liq. crystals can alter the structure according to specific mol. interaction between the GMO and the guest compd. that contributes to the surface area species. In our recent studied we have discovered that ternary blends of GMO, water and cosolvent can form unique structures. The focus of this presentation is on a new mesophase that was formed as a result of phase transformations. The new structure was eluted from lamellar, cubic, and hexagonal isotropic liq. phases in ternary systems. The new phase, termed by us the QL mesophase, is very unique since it is transparent liq. phase with long-range order. The QL phase was studied by small-angle X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), self-diffusion NMR, DSC and cond. methods. The unique rheol. properties of a system totally fluid and yet non Newtonian will be discussed in view of the suggested structure of micellar discontinuous cubic phase. Microstructure data as well as solubilization data of several nutraceuticals mols. and their bioavailability advantages will be presented. [on SciFinder(R)]
Anna Kogan, Inna Popov, Vladimir Uvarov, Shmuel Cohen, Abraham Aserin, and Nissim. Garti. 2007. “Microemulsion-facilitated crystallization of carbamazepine.” Journal of Dispersion Science and Technology, 28, 7, Pp. 1008–1019. Abstract
The crystn. patterns of carbamazepine pptd. from a confined microemulsion reservoir were studied by DSC, TGA, Powder XRD, single crystal XRD, SEM, and optical microscopy. The results suggest that interfacial fast nucleation and slow growth from O/W microemulsion leads to a selective, large, and better-ordered single crystals of dihydrate form with primitive monoclinic unit cell with parameters a = 10.16 {\AA
Anna Kogan, Abraham Aserin, and Nissim. Garti. 2007. “Improved solubilization of carbamazepine and structural transitions in nonionic microemulsions upon aqueous phase dilution.” Journal of Colloid and Interface Science, 315, 2, Pp. 637–647. Abstract
Solubilization capacity and structural transformations in nonionic microemulsions characterized by a large continuous isotropic region forming dilutable self-assembled nanodroplets contg. solubilized carbamazepine, were studied along diln. lines 73 and 82 (70 and 80% surfactant and 30 and 20% of oil phase, resp.). The prepns. were based on pharma-grade ingredients, water, R-(+)-limonene, ethanol, propylene glycol, and Tween 60. Solubilization capacity (SC) of the drug was dependent on the microstructure of the microemulsion and on the surfactant-to-oil phase wt. ratio. The SC in the conc. (reversed micelles) was 15 times higher than its soly. in the oil. Transition of the W/O microemulsion to a bicontinuous phase and to O/W droplets were identified by elec. cond., viscosity, SAXS, and SD-NMR measurements. Once the system is dild. to 90% aq. phase, the SC is 10 and 16-fold higher, along diln. lines 73 and 82, resp., than in pure water. Being solubilized, carbamazepine serves as a cosurfactant therefore it affects the curvatures of the microstructures and consequently the boundaries of the structural regions and the transition points between the different phases. Dilutable microemulsions are promising new carbamazepine vehicles for oral intake. [on SciFinder(R)]
Rachel Lutz, Abraham Aserin, Ellen J Wachtel, Einav Ben-Shoshan, Dganit Danino, and Nissim. Garti. 2007. “A Study of the Emulsified Microemulsion by SAXS, Cryo-TEM, SD-NMR, and Electrical Conductivity.” Journal of Dispersion Science and Technology, 28, 8, Pp. 1149–1157. Abstract
A H2O-in-oil microemulsion was further dispersed in an aq. phase contg. Pluronic F127 as a steric stabilizer, to form a specific type of double emulsion termed emulsified microemulsion (EME). The inner microemulsion phase was made from glycerol-monooleate (GMO), R(+)-limonene, EtOH and glycerol. SAXS (small x-ray scattering), PGSE-NMR (pulse gradient spin echo-NMR), elec. cond., and cryo-TEM (cryogenic-TEM) imaging techniques were used to confirm the existence of inner W/O nano-droplets after 2nd emulsification step and upon EME aging. Spherical globules of EME without long-range internal order were obsd. by the SAXS measurements and the cryo-TEM images. The av. globule size of ∼200-300 nm remained intact for at least 6 mo. [on SciFinder(R)]
Dima Libster, Abraham Aserin, and Nissim. Garti. 2007. “Advanced nucleating agents for polypropylene.” Polymers for Advanced Technologies, 18, 9, Pp. 685–695. Abstract
The present short review aims to summarize advanced nucleating agents for polypropylene (PP). Reviewing the relevant literature, we focused on powerful nucleators that are capable of significantly increasing the crystn. temp. of the polymer at very low working concns. and also serving as clarifying agents. The nucleation mechanism and efficiency of these compds. are discussed in detail. The nucleating agents were divided into groups according to their tendency to induce monoclinic ($\alpha$), hexagonal ($\beta$), or orthorhombic ($\gamma$) PP cell geometries. The major $\alpha$-nucleators and clarifiers are sorbitol-based compds. that speed-up the polymer crystn. due to gelation phenomena and induction of epitaxial crystn. by the metal salts of substituted arom. heterocyclic phosphate. Among $\beta$-nucleators, N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide was found to be very efficient and its nucleation ability was highly concn. dependent. In addn., it was shown that nucleation efficiency of a nucleator can be significantly increased by a new dispersion method comprising its solubilization in a microemulsion. Moreover, the nucleator (HPN-68) increased the $\gamma$-modification present in the polymer. [on SciFinder(R)]
Dima Libster, Abraham Aserin, Ellen Wachtel, Gil Shoham, and Nissim. Garti. 2007. “An HII liquid crystal-based delivery system for cyclosporin A: Physical characterization.” Journal of Colloid and Interface Science, 308, 2, Pp. 514–524. Abstract
In the present study we demonstrate that large quantities of cyclosporin A and three dermal penetration enhancers (phosphatidylcholine, ethanol, or Labrasol) can be solubilized into reverse hexagonal (HII) liq. cryst. structures composed of monoolein, tricaprylin, and water. The microstructural characteristics of these complex multi-component systems were elucidated by rheol., SAXS, and DSC measurements. Addn. of up to 20 wt% phosphatidylcholine improved significantly the elastic properties of the systems (lower values of tan $δ$ ) and increased the thermal stability of the mesophases enabling us to solubilize up to 6 wt% cyclosporin A and two other enhancers (Labrasol and ethanol) to obtain stable mesophases at physiol. temp. Rheol. measurements revealed that solubilization of cyclosporin A alone has a destabilizing effect on the reverse hexagonal phases: it caused a deterioration in the elastic properties of the systems, leading to more liq.-like behavior and resulting in very short relaxation times (0.04-0.1 s). Labrasol, solubilized at high concns. (up to 12 wt%) into the liq. crystals, also demonstrated a destabilizing effect on the HII structure: the decreasing elasticity of the system was attributed to Labrasol's presumed locus at the interface and its ability to bind water, as shown by DSC measurements. Ethanol had a destabilizing effect similar to that of Labrasol, yet the effect appeared to be more pronounced, probably due to its higher water-binding capability. [on SciFinder(R)]
Shoshana Rozner, Abraham Aserin, Ellen J Wachtel, and Nissim. Garti. 2007. “Competitive solubilization of cholesterol and phytosterols in nonionic microemulsions.” Journal of Colloid and Interface Science, 314, 2, Pp. 718–726. Abstract
It is well documented that phytosterols inhibit the uptake of exogenic cholesterol and do not interfere with cholesterol synthesis or cause side effects. The mechanism by which phytosterols interfere with cholesterol absorption is not completely clear and there are at least three hypotheses for their beneficial activity. Among these is that of competitive solubilization of phytosterols and cholesterol in dietary mixed micelles. In the present study we investigated the competitive solubilization of phytosterols (approx. 50% $\beta$-sitosterol) and cholesterol in a nonionic microemulsion system constructed as a model for the dietary mixed micelles. We studied the effect of the competitive solubilization of cholesterol and phytosterols on the structural transformations and phys. properties of the microemulsion and evaluated the locus of the solubilizates within the nanodroplets of each sterol sep. and when they are loaded together at different wt. ratios along one diln. line. Our results show that chem. and structural differences between cholesterol and phytosterols significantly influence the solubilization capacity of the nonionic microemulsion. Cholesterol, being more amphiphilic, is solubilized more efficiently at the W/O microemulsion interface, while in the O/W microemulsion phytosterols are dissolved somewhat more efficiently in the droplet core. [on SciFinder(R)]
Aviram Spernath, Abraham Aserin, Lior Ziserman, Dganit Danino, and Nissim. Garti. 2007. “Phosphatidylcholine embedded microemulsions: Physical properties and improved Caco-2 cell permeability.” Journal of Controlled Release, 119, 3, Pp. 279–290. Abstract
The present study evaluates the effect of a solubilized model drug, diclofenac sodium salt (diclofenac), in our unique new U-type microemulsion system embedded with phosphatidylcholine (PC) in terms of microstructure transformations, phys. properties of the system (viscosity, elec. cond.), droplet sizes and shapes, and nucleation and growth of the droplets. The phys. properties are correlated to the permeability of diclofenac through Caco-2 monolayer cells. The major findings reported are: (1) systems that are rich in surfactant and contain minimal oil phase form a microemulsion that enables high solubilization of diclofenac (20% diclofenac in the oil and surfactant conc. can be fully dild. with water); (2) PC presence at the interface does not affect the size of the O/W droplets, while the presence of diclofenac at the interface decreases the O/W droplet size by an av. of 50%; (3) diclofenac seems to increase incorporation of PC into the W/O interface; (4) diclofenac affects the phys. properties of the microemulsion increasing the viscosity of the W/O microemulsion system and completely changing the cond. profile of the system upon water diln.; (5) cryo-TEM images indicate that above 70% water the droplets are spherical; (6) diclofenac permeability through Caco-2 monolayer cells increases when PC is embedded into the interface. [on SciFinder(R)]
Nissim Garti, Marganit Avrahami, and Abraham. Aserin. 2006. “Improved solubilization of celecoxib in U-type nonionic microemulsions and their structural transitions with progressive aqueous dilution.” Journal of Colloid and Interface Science, 299, 1, Pp. 352–365. Abstract
Celecoxib (clxb) is an important drug for treatment of rheumatoid arthritis and osteoarthritis by specifically inhibiting the enzyme cyclooxygenase-2 (COX-2). Clxb is a type 2 drug characterized by low H2O soly. (\textless5 $μ$g/mL) and fast transmembrane transport. The present formulations require high dosage since the transmembrane transport fluctuates and is very difficult to control. Dissolving the drug within an oil phase was not practical since its dissoln. was very small and its dispersion in H2O was impossible. In recent studies, the authors learned to construct U-type phase diagrams and to formulate reverse microemulsions (oil-based concs.) that are progressively and fully dilutable with aq. phase. The authors solubilized clxb in nanostructures of reverse micelles of U-type nonionic microemulsions that consisted of R(+)-limonene, alc., propylene glycol (PG), and hydrophilic surfactant (Tween 60). The solubilization capacity of the drug in these systems is many times higher than in either the oil or the aq. phase. The clxb solubilized microemulsions are fully dild. with aq. phase without phase sepn. The solubilization capacity decreases as the H2O content increases. Elec. cond., viscosity, and self-diffusion (SD) coeffs. of the microemulsion components were measured along a suitable H2O diln. line. The 3 major microemulsion regions were detected and the transitions between the W/O to bicontinuous phase and from this phase to the O/W droplets were identified (at 30 and 70% aq. phase, resp.). From the SD coeffs., the drug is initially solubilized at the interface of the W/O droplets and there are no significant structural changes. The transition to a bicontinuous phase occurs at the same H2O content as in the empty (i.e., without drug) system. From the viscosity profiles, the drug affects the structure of the bicontinuous phase as reflected in the H2O content at which the oil-continuous network is destroyed and full inversion occurs (50 vs. 55% in the drug-loaded system). Upon further diln. the drug remains solubilized at the interface and is oriented with its hydrophilic part facing the H2O, and is strongly affects the inversion to O/W droplets. From Small Angle x-ray Scattering (SAXS) measurements the drug effects the structure of microemulsion droplets and forms ill-defined structures, probably less spherical. Yet, the overall droplet sizes at the high dilns. did not change very much. [on SciFinder(R)]
Anna Kogan and Nissim. Garti. 2006. “Microemulsions as transdermal drug delivery vehicles.” Advances in Colloid and Interface Science, 123-126, Pp. 369–385. Abstract
A review. Microemulsions are clear, stable, isotropic mixts. of oil, water, and surfactant, frequently in combination with a cosurfactant. Microemulsions were intensively studied during the last decades by many scientists and technologists because of their great potential in many food and pharmaceutical applications. The use of microemulsions is advantageous not only due to the facile and low cost prepn., but also because of the improved bioavailability. The increased absorption of drugs in topical applications is attributed to enhancement of penetration through the skin by the carrier. Satd. and unsatd. fatty acids serving as an oil phase are frequently used as penetration enhancers. The most popular enhancer is oleic acid. Other permeation enhancers commonly used in transdermal formulations are iso-Pr myristate, iso-Pr palmitate, triacetin, isostearylic isostearate, R(+)-limonene, and medium chain triglycerides. The most popular among the enhancing permeability surfactants are phospholipids that were shown to enhance drug permeation in a different mode. L-$\alpha$-phosphatidylcholine from egg yolk, L-$\alpha$-phosphatidylcholine 60%, from soybean and dioleylphosphatidyl ethanolamine which are in a fluid state may diffuse into the stratum corneum and enhance dermal and transdermal drug penetration, while distearoylphosphatidyl choline which is in a gel-state has no such capability. Other very commonly used surfactants are Tween 20, Tween 80, Span 20, Azone, Plurol Isostearique, and Plurol Oleique. As cosurfactants commonly serve short-chain alkanols such as ethanol and propylene glycol. Long-chain alcs., esp. 1-butanol, are known for their enhancing activity as well. Decanol was found to be an optimum enhancer among other satd. fatty alcs. that were examd. (from octanol to myristyl alc.). Many enhancers are concn.-dependent; therefore, optimal concn. for effective promotion should be detd. The delivery rate is dependent on the type of the drug, the structure and ingredients of the carrier, and on the character of the membrane in use. Each formulation should be examd. very carefully, because every membrane alters the mechanism of penetration and can turn an enhancer to a retarder. Various potential mechanisms to enhance drug penetration through the skin include directly affecting the skin and modifying the formulation so the partition, diffusion, or soly. is altered. The combination of several enhancement techniques such as the use of iontophoresis with fatty acids leads to synergetic drug penetration and to decrease in skin toxicity. Selected studies of various microemulsions contg. certain drugs including retinoic acid, 5-fluorouracil, triptolide, ascorbic acid, diclofenac, lidocaine, and prilocaine hydrochloride in transdermal formulations are presented in this review. In conclusion, microemulsions were found as an effective vehicle of the solubilization of certain drugs and as protecting medium for the entrapped of drugs from degrdn., hydrolysis, and oxidn. It can also provide prolonged release of the drug and prevent irritation despite the toxicity of the drug. Yet, in spite of all the advantages the present formulations lack several key important characteristics such as cosmetic-permitted surfactants, free diln. in water capabilities, stability in the digestive tracts and sufficient solubilization capacity. [on SciFinder(R)]