Peer Review Publications

D Libster, A Aserin, and N Garti. 2006. “A novel dispersion method comprising a nucleating agent solubilized in a microemulsion, in polymeric matrix I. Dispersion method and polymer characterization.” JOURNAL OF COLLOID AND INTERFACE SCIENCE, 299, 1, Pp. 172–179. Abstract
This is the first of a two-part study focusing on a novel dispersion method which enables increasing the crystallization rate of polypropylene (PP) through the incorporation of nucleating agent HPN-68 into the molten polymer using a microemulsion as a nanovehicle. The cycle time for processing the PP is significantly reduced and thus the effectiveness of its production is increased. Our concept is based on creating an advantage in dispersion capability of the nucleator that is dissolved in a nanoreactor vehicle in comparison with its conventional introduction as a crystalline powder. The microemulsions were introduced to the target PP using a mixer. By the end of the mixing, when the water phase had evaporated, only the nucleator and the surfactant remained in the matrix. The microemulsion components that solubilized the HPN-68 were mineral oil, alcohol, surfactant, and water. DSC results showed a 24% improvement in nucleation efficiency of PP by this method. WAXS results showed that HPN-68 is a gamma-nucleator. It causes polymorphism by significantly raising the gamma-phase concentration in the PP. SEM results showed a four-fold decrease in the PP spherulite size due to the improved dispersion of HPN-68 within the matrix via microemulsion compared to conventional nucleator incorporation. (c) 2006 Elsevier Inc. All rights reserved.
Shoshana Rozner, Nissim. Garti, Shoshana Romer, and Nissim. Garti. 2006. “The activity and absorption relationship of cholesterol and phytosterols.” COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 282, Pp. 435–456. Abstract
A review. Cholesterol is an essential lipid for mammalian life, but a high cholesterol level can almost guarantee the eventual onset of vascular diseases and, in some cases, can lead to death. It has been shown that there is a direct connection between high cholesterol levels and vascular diseases. Some methods for lowering the serum cholesterol level, thereby preventing the development of these diseases, have been developed and those include drugs and food additives. Since both drugs and food additives act to inhibit the uptake of cholesterol, understanding the sterol absorption process is the key to understanding exactly how drugs and food additives reduce serum cholesterol levels. The major drawback of using anti-cholesterol drugs is related to their side effects, and therefore, natural food additives called plant sterols (phytosterols) have been developed as an attractive alternative. Phytosterols are sterols that are synthesized only in plants and that are structurally similar to cholesterol but with the inclusion of an extra hydrophobic carbon chain at the C-24 position. Phytosterols and their esters reduce cholesterol level in the blood in spite of the fact that they are poorly absorbed into the blood stream. The mechanism by which phytosterols/phytosterol esters interfere with cholesterol absorption is not completely clear, but based on the present understanding, three distinct features have been recognized: (1) physico-chem. effects (e.g. competitive solubilization and co-crystn.); (2) effects at the absorption site (e.g. hydrolysis by lipases and esterases); (3) effects on intra-cellular trafficking of sterols. Due to phytosterols' poor solubilization in oil and water, they must be taken in high doses to achieve a redn. in cholesterol level. One of the goals of the food and pharmaceutical industries, therefore, is to develop products that effectuate the same decrease in cholesterol level but in smaller sterol doses achieved by increasing sterol bioavailability. The first line of products to meet the increased bioavailability criterion was the oil-sol. esterified phytosterols combined with fatty acids, which exhibit soly. in oil 10 times higher than that of pure phytosterols. The three primary methods of phytosterol inclusion in food are suspension, pptn. and microemulsion. [on SciFinder(R)]
A Spernath, A Aserin, and N Garti. 2006. “Phase transition induced by-water dilution in phospholipid U-type food-grade microemulsions studied by DSC.” Journal of Thermal Analysis and Calorimetry, 83, 2, Pp. 297–308. Abstract
In this study we used differential scanning calorimetry to clarify the role of water activity within the nano-droplets, and to explore phase transitions in novel phospholipids based fully dilutable food-grade microemulsions. The microstructure transitions were investigated along two water diln. lines (50:50 and 80:20% surfactant mixt./oil phase). From the water thermal behavior we learned that three structural regions can be identified along the water diln. lines. The thermal transition points coincide with the structural phase transition of the microemulsions as measured by other methods (elec. cond. and SD-NMR measurements). The structural transitions were detected at 20 and 45% of water along diln. line 55, where along diln. line 82 it occurs at 40 and 50% of water. The microemulsions along diln. line 82 seem to have more compact surfactant packing film, thus the film has stronger resistance to transformation upon diln., resulting in a smaller bicontinuous region than the one formed at diln. line 55. The difference in phase transition point can be used for triggering the release of future solubilizate. [on SciFinder(R)]
Aviram Spernath, Abraham Aserin, and Nissim. Garti. 2006. “Fully dilutable microemulsions embedded with phospholipids and stabilized by short-chain organic acids and polyols.” Journal of Colloid and Interface Science, 299, 2, Pp. 900–909. Abstract
Evidence on the role of phosphatidylcholine (PC) as a membrane permeability enhancer was the driving force in forming new liq. nanosized (modified microemulsions) oral delivery system contg. PC mols. We have demonstrated the feasibility of constructing phase diagrams with a large isotropic regions capable of being fully dild. with water. The microemulsions were stabilized with mixts. composed of PC and nonionic surfactant (polyoxyethylene-40 hydrogenated castor oil, HECO40) and short-chain org. acid as cosurfactant/cosolvent. When propionic acid served as the cosurfactant/cosolvent, the isotropic region was at its max. (ca. 72% of the total phase diagram area). The presence of a blend of PC and HECO40 seems to have synergistic effects, forming an isotropic region comprising 72% of the area of the phase diagram, in comparison to 20 and 50% in systems stabilized by PC and HECO40, alone, resp. The role of the PC mols. in the formation of those microemulsions is demonstrated by comparing three soy lecithins. Lecithin with a high PC content forms larger isotropic regions with more "free diln." lines. Several nonionic surfactants were investigated, yet only HECO40 seems to have a packing parameter suitable for the formation of large isotropic U-type systems. [on SciFinder(R)]
Idit Amar-Yuli and Nissim. Garti. 2005. “Transitions induced by solubilized fat into reverse hexagonal mesophases.” Colloids and Surfaces, B: Biointerfaces, 43, 2, Pp. 72–82. Abstract
Lyotropic liq. crystals of glycerol monooleate (GMO) and water binary mixts. have been extensively studied and their resemblance to human membranes has intrigued many scientists. Biol. systems as well as food mixts. are composed of lipids and fat components including triacylglycerols (TAGs, triglycerides) that can affect the nature of the assembly of the mesophase. The present study examines the effect of TAGs of different chain lengths (C2-C18) at various water/GMO compns., on phase transitions from lamellar or cubic to reverse hexagonal (L$\alpha$-HII and Q-HII). The ability of the triglycerides to promote the formation of an HII mesophase is chain length-dependent. It was found that TAG mols. with very short acyl chains (triacetin) can hydrate the head groups of the lipid and do not affect the crit. packing parameter (CPP) of the amphiphile; therefore, they do not affect the self-assembly of the GMO in water, and the mesophase remains lamellar or cubic. However, TAGs with medium chain fatty acids will solvate the tails of the lipid, and will affect the CPP of the GMO, and transform the lamellar or cubic phases into hexagonal mesophase. TAGs with long chain fatty acids are very bulky, not very miscible with the GMO, and therefore, kinetically are very slow to solvate the lipid tails of the amphiphile and are difficult to accommodate into the lipophilic parts of the GMO. Their effect on the transitions from a lamellar or cubic phase to hexagonal is detected only after months of equilibration. In order to enhance the effect of the TAG on the phase transitions in the GMO/triglyceride/water systems, temp. and electrolytes effects were examd. In the presence of short and medium chain triglycerides, increasing temp. caused a transition from lamellar or hexagonal to L2 phase (highest CPP value). However, in the presence of long chain TAGs, increasing temp. to ca. 40 °C caused a formation of HII mesophase. In addn., it was found that in tricaprylin/GMO/water systems, the increase in temp. caused a decrease in the lattice parameter. The effect of NaCl on the HII mesophase revealed interesting results. At low concn. of tricaprylin (5 wt%), the addn. of only 0.1 wt% of NaCl was sufficient to cause the formation of well-defined HII mesophase, while further addn. of electrolyte increased the hexagonal lattice parameters. At higher TAGs concns. (10 wt%), addn. of electrolyte resulted in the formation of HII with modifications of the lattice parameter. All the examd. effects were more pronounced with increasing water content. [on SciFinder(R)]
In this second part of a paper dealing with the effect of branched alcs. on solubilization, an attempt has been made to provide explanations of exptl. data related mostly to the system Brij 97/branched alc. + dodecane = 1:1 (by wt.)/water at 27 ± 0.2 °C . Applying the Hou-Shah mechanism it was shown that for many C4-C6 branched alc. isomers having one Me branch, solubilization behavior is readily interpreted by assuming control of the crit. radius, Rc. Two parameters, both included in the definition of the branching factor, Fb (which was treated in the first part of the paper), were also used to analyze solubilization data. The first, li, is defined as the distance from the free end of the alc. mol. to the Me branch. The second, d, is virtually NA, the chain length of the alc. When li \textgreater 3, the solubilization becomes dominated by the natural radius of curvature, R0. Also, we have suggested that for Rc-control, solubilization will be enhanced in direct proportion to the distance d-li whereas for R0-control, solubilization will increase with decreasing d-li. The validity of our assumptions was demonstrated in many cases. Some examples of the more complicated case of double branching (two Me groups along the alc. chain) were also analyzed. [on SciFinder(R)]
Rivka Efrat, Abraham Aserin, Dganit Danino, Ellen J Wachtel, and Nissim. Garti. 2005. “Novel Discrete Micellar Cubic Phase From a Mixture of GMO/Ethanol/Water.” Australian Journal of Chemistry, 58, 11, Pp. 762–766. Abstract
During the reconstruction the ternary phase diagram of glycerol monooleate (GMO)/EtOH/H2O, the authors detected a novel structure not previously seen. The new phase, denoted QL (micellar cubic liq.), is located within the 4954 wt.-% H2O/4133 wt.-% GMO binary mixt. line and at 10-13 wt.-% EtOH in a small island within the phase diagram close to the cubic liq.-cryst. phase region. The QL phase is transparent (not tinted), of a low viscosity (36.6 Pa s), non-birefringent, and stable at room temp. Evidence from severe centrifugation, synchrotron small-angle x-ray scattering (SAXS) measurements, and rheol. behavior revealed that the sample is a single phase. SAXS reflections suggest that two types of domain may coexist. The symmetry of the QL phase is Pm3n. A cubic micellar structure is the dominant mesostructure of this unique sample. Cryo-TEM images show highly ordered domains with cubic symmetry, of lattice parameter 103 ± 2 \AA. A possible transformation pathway to the QL phase is a 'rupture and refusion' mechanism, as the phase seems to have discontinuous symmetry. [on SciFinder(R)]
S Ezrahi, E Tuval, A Aserin, and N Garti. 2005. “The effect of structural variation of alcohols on water solubilization in nonionic microemulsions. 1. From linear to branched amphiphiles-General considerations.” Journal of Colloid and Interface Science, 291, 1, Pp. 263–272. Abstract
This article is the first part of a two-part study that exemplifies how to treat the solubilization of water in multicomponent surfactant-based systems. In particular, it aims at clarifying the role of cosurfactants in water solubilization in these systems. The judicious selection of the components in such systems to maximize water solubilization is occasionally thought to be dictated by the chain length compatibility principle, which may be expressed quant. by the BSO (Bansal, Shah, O'Connell) equation. Here we demonstrate some limitations of the equation. For example, in our best model system, C12(EO)8/dodecane + pentanol = 1:1 (by wt.)/water at 27 ± 0.2 ° C, the BSO equation predicts that no alc. is needed for max. water solubilization, contrary to our exptl. findings. We discuss how to optimize the alc./oil wt. ratio needed for stabilizing four-component microemulsions. In our model systems C12(EO)8 or C18:1(EO)10/pentanol/dodecane/water, this optimal wt. ratio is 1:1. We also highlight the difference between the effect of normal alcs. on water solubilization-which passes via a max.-and their effect on percolation processes and structured changes of proteins, which depends solely upon the alc. hydrophobicity. For the investigation of the effect of branching on phase behavior the utilization of an extended form of the geometrical branching factor F b is suggested. The meaning of this factor is elucidated by comparing it with topol. indexes. [on SciFinder(R)]
Nissim. Garti. 2005. “Nano-sized self-assembled liquids for improved solubilization.” In Abstracts of Papers, 229th ACS National Meeting, San Diego, CA, United States, March 13-17, 2005, Pp. AGFD–197. American Chemical Society. Abstract
In our recent studies we have found a unique mixt. of water, special food-grade oil, mixt. of food-grade surfactants, cosolvent (polyol) and coemulsifiers that can self-assemble to form new nanosized modified microemulsions of U-type, totally dilutable with aq. phase. The "conc." is capable of solubilizing nutraceuticals that are poorly sol. in water or oil phase at ca 15-20 folds over their soly. capacity. Nutraceuticals such as lycopene, lutein, CoQ10, phytosterols, etc. have been solubilized. We have used advanced techniques such as SAXS, SANS, SD-NMR, QELS to evaluate the microstructures in the absence and in the presence of the guest mols. The presentation will bring data on the solubilization of the nutraceuticals, their chem. protection against oxidn., and their improved bioavailability. Effects of guest mols. and microemulsions ingredients on the microstructure transitions and reactivity will be discussed. [on SciFinder(R)]
Nissim Garti and Louise. Wicker. 2005. “Pectin methylesterase modified pectin interaction with whey protein isolate and stability of double emulsions.” In Abstracts of Papers, 229th ACS National Meeting, San Diego, CA, United States, March 13-17, 2005, Pp. CELL–119. American Chemical Society. Abstract
Valencia orange pectin methylesterase (PME) isoenzymes were used to de-esterify com. pectin. Unmodified and PME modified pectin were mixed with whey protein isolate (WPI), 90% $\beta$-lactoglobulin, and the interaction was studied using fluorescence, mol. wt., and charge. Double emulsions stabilized by hybrids of WPI and modified pectins were tested for rheol. properties, droplet size and stability. The zeta potential of the hybrids at pH values below the pI of protein was neg. charged at a ratio of 4:0.5 (wt/wt) WPI/pectin. Decreasing stability of double emulsions was obsd. with WPI/pectin complex if neg. charged (pH 6), pos. charged, and highly neg. charged. Rheol. confirmed that double emulsions are most stable at pH 6.0, with highest elasticity (G'/G''= 66°). Droplets of W/O/W double emulsions made from WPI and modified pectin ranged from ca. 15 to ca. 5 $μ$m, depending on pectin. At pH 6.0, stability to coalescence was excellent after 40 days. [on SciFinder(R)]
R Lutz, A Aserin, and N Garti. 2005. “Maillard Reaction between leucine and glucose in O/W microemulsion media in comparison to aqueous solution.” Journal of Dispersion Science and Technology, 26, 5, Pp. 535–547. Abstract
The Maillard reaction is controlled by temp., pH, nature of reactants (sugars and amino acids), and water activity. The authors carried out reactions between glucose and leucine in U-type nonionic microemulsions to obtain regioselectivity and control reaction rates. Reactants were oriented at the interface and water activity was adjusted using blends of surfactant and propylene glycol (PG). U-type microemulsions, previously studied by the authors, served as microreactors for the Maillard reaction. The reactions in the microemulsion media were slower than those carried out in aq. soln. and formed unique arom. compds. Reaction rates increased when using systems richer in water, as the water activity was enhanced. The surfactant plays a key role in detg. water activity and reagent reactivity in all the microemulsions. The presence of PG slows the reaction, mainly when it resides at the interface, facilitating the formation of a bicontinuous structure. Phase transitions within the U-type microemulsions were detd. by viscosity and SD-NMR, and were correlated to the interfacial presence of the reactants and their reactivity. [on SciFinder(R)]
Anan Yaghmur, Abraham Aserin, Atallah Abbas, and Nissim. Garti. 2005. “Reactivity of furfural-cysteine model reaction in food-grade five-component nonionic O/W microemulsions.” Colloids and Surfaces, A: Physicochemical and Engineering Aspects, 253, 1-3, Pp. 223–234. Abstract
In our present study, a model Maillard furfural/cysteine reaction was chosen for exploring and understanding the different aspects that control the reactivity in five-component fully dilutable U-type food-grade oil/water (O/W) microemulsions of R(+)-limonene/ethanol/water/propylene glycol/Tween 60. It was found that these self-assembled nanosized structured systems are capable of enhancing the rate of Maillard reactions in which the selectivity and the reactivity are controlled by the compn. of the interface and its curvature. The sulfur-contg. flavor formation is very efficient if carried out in those O/W microemulsions (modified oil-swollen nanoreactors) and the reaction yields high amts. of key aroma compds. The proposed Tween 60-based O/W systems show strong preference for the formation of 2-(2-furanyl)-thiazolidine (the main product). The O/W reaction medium enhances furfural-cysteine reaction rate (microemulsion catalysis) in comparison to the water-based reaction. It was found that the initial reaction rate (V0) is affected by the solubilized aq. phase content. The furfural-cysteine reaction is affected also by the process conditions (temp., pH, time of reaction). These results suggest that O/W microemulsions are a promising choice for generation of flavors and food products. [on SciFinder(R)]
Gil Zomber, Shaul Reuveny, Nissim Garti, Avigdor Shafferman, and Eytan. Elhanany. 2005. “Effects of Spontaneous Deamidation on the Cytotoxic Activity of the Bacillus anthracis Protective Antigen.” Journal of Biological Chemistry, 280, 48, Pp. 39897–39906. Abstract
Protective antigen (PA) is a central virulence factor of Bacillus anthracis and a key component in anthrax vaccines. PA binds to target cell receptors, is cleaved by the furin protease, self-aggregates to heptamers, and finally internalizes as a complex with either lethal or edema factors. Under mild room temp. storage conditions, PA cytotoxicity decreased (t1/2 ≈ 7 days) concomitant with the generation of new acidic isoforms, probably through deamidation of Asn residues. Ranking all 68 Asn residues in PA based on their predicted deamidation rates revealed five residues with half-lives of \textless60 days, and these residues were further analyzed: Asn10 in the 20-kDa region, Asn162 at P6 vicinal to the furin cleavage site, Asn306 in the pro-pore translocation loop, and both Asn713 and Asn719 in the receptor-binding domain. We found that PA underwent spontaneous deamidation at Asn162 upon storage concomitant with decreased susceptibility to furin. A panel of model synthetic furin substrates was used to demonstrate that Asn162 deamidation led to a 20-fold decrease in the bimol. rate const. (kcat/Km) of proteolysis due to the new neg. charged residue at P6 in the furin recognition sequence. Furthermore, reduced PA cytotoxicity correlated with a decrease in PA cell binding and also with deamidation of Asn713 and Asn719. On the other hand, neither deamidation of Asn10 or Asn306 nor impairment of heptamerization could be obsd. upon prolonged PA storage. We suggest that PA inactivation during storage is assocd. with susceptible deamidation sites, which are intimately involved in both mechanisms of PA cleavage by furin and PA-receptor binding. [on SciFinder(R)]