Peer Review Publications

Paul Ben Ishai, Dima Libster, Abraham Aserin, Nissim Garti, Yuri. Feldman, Paul Ben Ishai, Dima Libster, Abraham Aserin, Nissim Garti, and Yuri. Feldman. 2009. “Molecular Interactions in Lyotropic Reverse Hexagonal Liquid Crystals: A Dielectric Spectroscopy Study.” Journal of Physical Chemistry B, 113, 38, Pp. 12639–12647. Abstract
A dielectric study of reverse hexagonal mesophases (H(II)) is presented. Conducted in the frequency range 0.01-1 MHz and temperature range 293 \textless T \textless 319 K, the study reveals complex molecular behavior in and around the interfaces of the mesoscopic structures of the gel. There exist three clearly defined dielectric relaxations related to separate moieties in the interface, as well as a temperature-activated dc conductivity. A critical temperature, T(0) = 307 K, is noted in the results and related to the dehydration of the glycerol monooleate (GMO) head groups. Effectively, this represents a break-down of the interfacial layer of water. The consequences of this act are clearly visible in the change in behavior of the fitting parameters for all processes. A physical picture emerges whereby at T(0) = 307 K, the ``loosening\''\ of the GMO heads accentuates the dangling motion of the phosphatidylcholine (PC) tails, evidenced by counterion motion along the PC head. Furthermore, it precipitates the percolation of the large TAG molecules that are intercalated in the GMO and PC tails.
Y Kim, H Lee, J Jung, J Rivner, R Lutz, R Arnold, N Garti, and L Wicker. 2009. “Valencia orange pectinmethylesterases, charge modification of pectins, and applications to food technology and drug delivery.” In Pectins Pectinases, Pp. 231–243. Wageningen Academic Publishers. Abstract
Fractionation of Valencia orange pulp prepns. resulted in PME active fractions contg. putative PMEs of 13, 27, and 36 kDa. NMR anal. indicated that pectin de-esterification by PMEs in these fractions resulted in block wise de-esterification of the substrate. Within the narrow frequency range of 0.57 to 0.76 for the dyad or 0.22-0.55 for the triad, little effect on G' value near 560 Pa is obsd. The relative contribution of total charge or distribution of charge cannot be clearly elucidated as the contribution of either depends on achieving a crit. limit of de-esterification. The position and shape of this crit. limit is influenced by the compn. of the dyads and triads of carboxylic acid groups. Applications of charge modified pectins include the ability to interact with proteins, stabilize emulsions for entrapment of addenda and for drug release. Under low pH, cationic milk proteins interact readily with pectins, esp. charge modified pectins. At pH 3.8, non fat dry milk, caseinates, $\alpha$S1,2, $\beta$- but not $ąppa$-casein pptd., esp. with modified pectin. Modified pectin apparently increased the soly. of sodium caseinate, suggesting a competition between protein-protein and protein-pectin interactions. Further, charge modified pectins reduced the surface tension and interfacial activity of dispersions and reduced the droplet size of emulsions. Finally, modified pectins showed superior entrapment and less release of indomethacin compared to com. low methoxyl pectins. [on SciFinder(R)]
Anna Kogan, Shoshana Rozner, Somil Mehta, Ponisseril Somasundaran, Abraham Aserin, Nissim Garti, and Maria Francesca. Ottaviani. 2009. “Characterization of the Nonionic Microemulsions by EPR. I. Effect of Solubilized Drug on Nanostructure.” Journal of Physical Chemistry B, 113, 3, Pp. 691–699. Abstract
The effect of the solubilized model drug, carbamazepine, on the internal structure of fully dilutable nonionic microemulsions was examd. for the first time using ESR. Systems contg. different surfactant to oil ratios, at two different pH values (4.6 and 8.5), with continuous diln. implementing structural transformations (micellar soln.-W/O-bicontinuous-O/W) were investigated. The internal order, micropolarity, and microviscosity were scrutinized utilizing pH-dependent amphiphilic probe 5-doxylstearic acid (5-DSA). In the basic environment, the probe explored the vicinity of the surfactant head region; the deeper hydrophobic region of the surfactant tails was investigated in the acidic milieu. The study demonstrated that the EPR technique enables efficient monitoring of structural changes and examn. of drug influence on structure in surfactant-poor systems. Lower order and microviscosity values were obtained in surfactant-poor systems in comparison to surfactant-rich systems. The drug functioned as a spacer of the surfactant mols. or as a cosurfactant depending on the formed microemulsion structure and the surfactant to oil ratio. The structural changes, pH variation, and presence of the drug did not alter the polarity parameter, indicating that the probe most likely does not sense a water environment in any of the examd. systems. Under the basic conditions, higher microviscosity and order values were obtained in comparison to those at low pH, suggesting a higher order packing of the surfactant chains near the surfactant heads. The structural changes initiated in the vicinity of the surfactant heads, therefore, are more apparent in the basic environment. The ability to control and monitor the intramicellar interactions within drug carrier systems may be of significant interest for understanding the kinetics of drug release. [on SciFinder(R)]
Anna Kogan, Deborah E Shalev, Uri Raviv, Abraham Aserin, and Nissim. Garti. 2009. “Formation and Characterization of Ordered Bicontinuous Microemulsions.” Journal of Physical Chemistry B, 113, 31, Pp. 10669–10678. Abstract
Ordered bicontinuous microstructures formed in a fully water-dilutable, pseudoternary unique nonionic microemulsion were obtained and characterized. The conc. contained a mixt. of triacetin/D-$\alpha$-tocopherol acetate/ethanol/Tween 60. Upon diln., the conc. was transformed from a reversed micellar system to oil-in-water microemulsion droplets. The transformation occurred through an intermediate phase of ordered bicontinuous structures. The factors that governed the construction of this unique phase, and its phys. and structural properties, were characterized in detail. The techniques used included small angle X-ray scattering (SAXS), self-diffusion and quantum filtered NMR, differential scanning calorimetry, rheol. measurements, elec. cond., and dynamic light scattering. This mesophase displays microemulsion properties along with some characteristics of lyotropic liq. crystals (but is not a mixt. of the two). Similar to microemulsions, the structures were transparent and spontaneously formed and exhibited thermodn. stability. Yet, unlike microemulsions, they showed short-range order at room temp. Addnl., the microstructures exhibited non-Newtonian flow behavior, characteristic of lamellar structures. The bicontinuous ordered microemulsions were obtained upon heating (to 25 °C) from the lamellar phase existing at low temps. (5 °C). The main feature governing the bicontinuous mesophase formation was the amphiphilic nature of oil blends composed of D-$\alpha$-tocopherol acetate and triacetin. The oils functioned as cosurfactants, altering the packing parameter of the surfactant and leading to the construction of bicontinuous structures with short-range order. These unique structures might have drug or nutraceutical delivery advantages. [on SciFinder(R)]
Dima Libster, Paul Ben Ishai, Abraham Aserin, Gil Shoham, and Nissim. Garti. 2009. “Molecular interactions in reverse hexagonal mesophase in the presence of cyclosporin A.” International Journal of Pharmaceutics, 367, 1-2, Pp. 115–126. Abstract
The present work investigates the detailed mol. structure of the HII mesophase of glycerol monooleate (GMO) /tricaprylin/phosphatidylcholine/water system in the presence of hydrophobic model peptide cyclosporin A (CSA) via ATR-FTIR anal. The conformation of the peptide in the hexagonal mesophase, as well as its location and specific interactions with the components of the carrier, were studied. Incorporation of phosphatidylcholine to the ternary GMO/tricaprylin/water system caused competition for water binding between the hydroxyl groups of GMO and the phosphate groups of the phosphatidylcholine (PC) leading to dehydration of the GMO hydroxyls in favor of phospholipid hydration. Anal. of CSA solubilization effect on the HII mesophase revealed a significant increase in the strength of hydrogen bonding with surfactant hydrogen-bonded carbonyls, indicating interaction of the peptide with the C=O groups of the surfactants. The peptide probably caused partial replacement of the intramol. hydrogen bonds of the mesophase carbonyl groups with intermol. hydrogen bonds of these carbonyl groups with the peptide. Furthermore, anal. of the Amide I' peak in the FTIR spectra of the peptide demonstrated that two pairs of its internal hydrogen bonds are disrupted when it is incorporated. The partial disruption of the internal hydrogen bonds seems to cause an outward rotation of the peptide amide groups involved, resulting in more efficient intermol. hydrogen-bonding ability. Apparently, this conformational change increased the hydrophilic properties of CSA, even making it susceptible to a weak interaction with the GMO hydroxyl groups in the interfacial region. [on SciFinder(R)]
R Lutz, A Aserin, L Wicker, and N Garti. 2009. “Structure and physical properties of pectins with block-wise distribution of carboxylic acid groups.” Food Hydrocolloids, 23, 3, Pp. 786–794. Abstract
The physical and the interfacial properties of pectins de-esterified by a specific block-wise enzymatic procedure were investigated. Two major types of block-wise de-esterified pectins with different internal distribution of carboxylic acid on the pectin chains were explored. Type C and type U pectins with the same degree of methylesterification are different and a more block-wise intramolecular distribution in comparison to commercial native apple pectin. The most ordered pectin (U63 pectin, 63% methyl-esterified pectin) has the highest electrophoretic mobility (zeta-potential). It reveals more pronounced intermolecular interactions since it exhibited, at low pH, the lowest circular dichroism intensity at shorter wavelength. U63 pectin (at acidic pH, without calcium addition) has a higher viscosity and formed a stronger gel compared to the less ordered C63 pectin and/or native apple pectin. X-ray patterns show that powdered U63 pectin is more crystalline than C63 pectin, while apple pectin is mostly amorphous. The modified pectin also, most effectively, reduced the surface tension (55 mN/m) and the interfacial tension (5.6 mN/m), probably due to the preferred surface orientation of the carboxylic groups at the water/air or water/oil interfaces. It was demonstrated that the internal charge distribution within the backbone of the pectin is an effective factor in its crystalline organization and its solution properties. It is, therefore, expected that the U63 pectin will exhibit better emulsification capabilities and will form stronger complexes with proteins. (C) 2008 Elsevier Ltd. All rights reserved.
Dima Libster, Abraham Aserin, Doron Yariv, Gil Shoham, and Nissim. Garti. 2009. “Concentration- and temperature-induced effects of incorporated desmopressin on the properties of reverse hexagonal mesophase.” Journal of Physical Chemistry B, 113, 18, Pp. 6336–6346. Abstract
In this paper we report on the solubilization of desmopressin, as a model for peptide drugs, into reverse hexagonal (HII) liq. crystals. Concn.- and temp.-induced interactions of desmopressin, as well as the conformation of the peptide, were studied using small-angle X-ray scattering, ATR-FTIR spectroscopy, SD-NMR, and rheol. measurements. A considerable increase (up to 6 \AA) in the lattice parameter of the mesophases was obtained upon incorporation of the peptide. According to the ATR-FTIR anal., the chaotropic effect of peptide embedment was assigned to its interactions with hydroxyls of monoglyceride in the outer interface region. These interactions had only a minor influence on the conformation of the peptide; weakening or opening the $\gamma$-turns resulted in partial binding of the peptides free carbonyls to monoolein. Temp.-dependent SAXS measurements displayed a chaotropic destabilizing effect of desmopressin on the structure, shifting toward the lower temp. HII-L2 structural transition. Temp. increase resulted in an increase of the domain size in the presence of the peptide, in contrast to the trend obsd. in the empty mesophase. SD-NMR anal. enabled distinguishing between two factors impeding the diffusion of the peptide: the restriction of motion due to the geometrical constrain of diffusion within the water tubes, and the interactions of the guest mol. with monoglyceride. The onset of the crit. behavior at 45 °C was found to be significant, indicating considerable weakening of the monoglyceride and desmopressin interactions and the destabilizing effect of the peptide on the mesophase above this temp. Similar temp.-dependent behavior was revealed by rheol. measurements displaying the same onset of the crit. behavior. It was demonstrated by Franz diffusion cell measurements that hexagonal mesophases can potentially be used as delivery vehicles for sustained delivery of desmopressin. [on SciFinder(R)]
Rachel Lutz, Abraham Aserin, Louis Wicker, and Nissim. Garti. 2009. “Double emulsions stabilized by a charged complex of modified pectin and whey protein isolate.” Colloids and Surfaces, B: Biointerfaces, 72, 1, Pp. 121–127. Abstract
Double emulsions based on naturally occurring stabilizers for food applications were studied. Two charged biopolymers, whey protein isolate (WPI) and enzymic modified pectins, interacted in aq. soln. to form a charge-charge complex that was utilized as a hydrophilic polymeric steric stabilizer improving the double emulsion stability. The main factors that influence the interaction between protein and pectin were investigated in relation to double emulsion stability: creaming, coalescence, and water transport between aq. phases. The pH detd. the size of the complex formed. Thus at pH 6, where a sol. complex was obtained between some mol. pos. charged patches on the protein and neg. charged fractions of the hydrocolloids, the double emulsion was the most stable. With the smallest droplet size (∼15 $μ$m), the lowest creaming, highest yield, and minimized water transport were obtained. The best concn. and ratio to form the sol. complex are 4% WPI and 0.5% pectin (for 30% of the W/O inner phase). The influence of the charge distribution (degree of order of the carboxylic groups) of the pectin on the assocd. complex was also investigated, and it was found that the more "ordered" pectin (U63) formed the most stable double emulsion against water transport. [on SciFinder(R)]
Rachel Lutz, Abraham Aserin, Yariv Portnoy, Moshe Gottlieb, and Nissim. Garti. 2009. “On the confocal images and the rheology of whey protein isolated and modified pectins associated complex.” Colloids and Surfaces, B: Biointerfaces, 69, 1, Pp. 43–50. Abstract
The conditions necessary to form an assocd. complex between whey protein isolate (WPI) and enzymically modified pectin in water, at pH values above the isoelec. point of the protein, have been documented. The existence of the complex is not easily verified and its characterization in soln. is even more complicated, since the structure is an intermediate entity between the non-interacting, incompatible aq. sol. mixt. of the biopolymers, and a strongly interacting coacervated pptg. complex. Evidence for the formation of this assocd. complex is provided from confocal laser scanning microscope images and rheol. behavior of the aq. mixts. The assocd. complex is characterized by small fluorescent "patches" interpreted as small aggregates. The viscosity of this soln. is greater than that of its individual biopolymer constituents, indicating a synergy of attractive interactions that occurs in the soln. While individually, the pectin and the WPI solns. at the studied range of concns. exhibit moderately non-Newtonian behavior, at sp. wt. ratios, mixts. of the two behave either as highly entangled polymeric structures or as weak gels. The values of the storage modulus G' are equal to or greater than those of the loss modulus G''. We conclude that the assocd. complexes are formed at pH 6, and at 4 wt% WPI with a pectin concn. ranging from 0.1 to 0.75 wt%. The influence of the charge distribution (degree of order of the carboxylic groups) of pectin on the assocd. complex was also investigated, and it was found that the more "ordered" pectin (U63) favors the formation of the assocd. sol. complex. [on SciFinder(R)]
Dima Libster, Abraham Aserin, Doron Yariv, Gil Shoham, and Nissim. Garti. 2009. “Soft matter dispersions with ordered inner structures, stabilized by ethoxylated phytosterols.” Colloids and Surfaces, B: Biointerfaces, 74, 1, Pp. 202–215. Abstract
This paper describes the formation and characterization of liq. cryst. dispersions based on the hexagonal phase of GMO/tricaprylin/water. As a stabilizer of the soft particles dispersed in the aq. phase, a non-ionic, non-polymeric surfactant-ethoxylated phytosterol with 30 oxyethylene units (PhEO) was utilized. In contrast to Pluronic copolymers, normally utilized in the stabilization of liq. cryst. dispersions with ordered inner structure, use of such non-polymeric surfactant is not a common practice in this field. The authors revealed how properties of these particles, such as internal structure, size, and stability, can be rationally modified by the concn. of the stabilizing agent and processing conditions. The phys. stability of the hexosomes was further examd. by the LUMiFuge technique. Structural effect of PhEO solubilization on the properties of the bulk HII mesophase system showed that phase behavior was greatly influenced following phase transitions: HII → HII + cubic → cubic + L$\alpha$ → L$\alpha$. The decrease of hydrogen bonding of the hydroxyl and carbonyl groups of monoolein with water and simultaneous hydration of EO groups of PhEO appeared to be important for the obsd. behavior. The use of PhEO as a dispersant resulted in a soft matter multi-phase water dispersion with bimodal distribution of the particle population. Effective stabilization of hexosomes was obtained in an extremely narrow concn. range of PhEO (0.1-0.2%), coexisting with small vesicles and disordered particles. At higher PhEO content, particles had disordered inner structure, and unilamellar and multilamellar vesicles, at the expense of hexosomes in consequence of incorporation of the dispersant into the hexosome structure. PhEO was found to induce lamellar phase formation, introducing disorder into the hexagonal LLC and reducing their domain size. Finally, hexosomes were evaluated as delivery vehicles for the therapeutic peptide desmopressin. Sustained release of this drug was obsd. during the first 10 h; however, permeation drastically increased in the 10-24 h range. [on SciFinder(R)]
Rachel Lutz, Abraham Aserin, Louise Wicker, and Nissim. Garti. 2009. “Release of electrolytes from W/O/W double emulsions stabilized by a soluble complex of modified pectin and whey protein isolate.” Colloids and Surfaces, B: Biointerfaces, 74, 1, Pp. 178–185. Abstract
W/O/W double emulsions (DEs) stabilized by charged sol. complexes of whey protein isolate (WPI) and modified pectins were investigated in relation to their stability and the release of two types of electrolytes, NaCl and sodium ascorbate. WPI alone cannot properly stabilize the DEs. The droplet size is relatively large (100 $μ$m) and increases with time. However, addn. of modified pectin to form a sol. complex with WPI significantly improved the stability. DEs prepd. with two types of oils (medium chain triglycerides (MCT) and R(+)-limonene) were studied by measuring droplet size, creaming, viscosity, and electrolyte release. Irresp. of their very different oil phase nature, both emulsions were stable against coalescence, but R(+)-limonene formed smaller droplets (25 $μ$m) than MCT (35 $μ$m). The electrolyte release rate was significantly higher from the R(+)-limonene that formed DEs with much lower viscosity. R(+)-limonene-DE released 75% of the NaCl after 28 days, while MCT-DE released only 50%. NaCl was released more slowly than sodium ascorbate. Apparently, the release mechanism from R(+)-limonene-DE was found to be "thinning the outer interface and release of the entire inner droplets" while it seems that the release from MCT-DE was slower and "diffusion controlled". DEs stabilized by WPI/C63 released 12% of the sodium ascorbate after 1 day in milk and remained stable for at least 8 days. However, DEs stabilized with only WPI released about 50% of the sodium ascorbate after 1 day, and phase sepd. after 8 days. [on SciFinder(R)]
Shoshana Rozner, Anna Kogan, Somil Mehta, Ponisseril Somasundaran, Abraham Aserin, Nissim Garti, and Maria Francesca. Ottaviani. 2009. “Characterization of Nonionic Microemulsions by EPR. Part II. The Effect of Competitive Solubilization of Cholesterol and Phytosterols on the Nanostructure.” Journal of Physical Chemistry B, 113, 3, Pp. 700–707. Abstract
One of the theories for the redn. of cholesterol (CH) in the blood stream by the consumption of phytosterols (PS) states that these two types of sterols compete for solubilization within the dietary mixed micelles (DMM). In this study, a fully dilutable nonionic microemulsion system was used as a model to explain a possible competitive solubilization mechanism of CH and PS mols. using an EPR technique that reveals relevant intra-micellar properties. The effect of the solubilized sterols on the structural changes occurring in the vicinity of the surfactant head groups or closer to the oil phase was examd. by controlling the pH of the environment, which influences the probe locus between the surfactant mols. The results indicate that the structure transformations in the surfactant layer closer to the vicinity of the head groups region are more pronounced than the structural changes occurring in the region between the surfactant tails closer to the oil phase, except for the oil-in-water (O/W) micelles region. The study also shows that when each of the sterols is solubilized alone, they occupy different solubilization sites within the microemulsion nanostructures, in comparison to their solubilization together. This behavior is most pronounced in 3:1 (wt. ratio) CH/PS systems. The main conclusion is that co-solubilization of these sterols leads to competitive solubilization between the surfactant tails closer to the oil phase locus, where the CH mols. are pushed toward the interface by the PS mols. This conclusion might better explain the competitive solubilization of the two sterols in the human digestive tract. [on SciFinder(R)]
E Acosta. 2008. “Regulatory aspects of nutrient delivery systems.” In Delivery Controlled Release Bioact. Foods Nutraceuticals, Pp. 429–449. Woodhead Publishing Ltd. Abstract
A review discusses the selection of food grade ingredients and their acceptable daily intake. Addnl., the procedures and documentation necessary to register new food additives are introduced in view of the issue that additives typically used in controlled released applications are not approved for food products, and therefore need to undergo this registration process. It addresses the regulatory issues regarding the stability of the product, esp. in terms of biol., chem. and phys. stability. It also discusses the regulatory aspects concerning the effectiveness of the formulation. [on SciFinder(R)]
E Acosta. 2008. “Testing the effectiveness of nutrient delivery systems.” In Delivery Controlled Release Bioact. Foods Nutraceuticals, Pp. 53–106. Woodhead Publishing Ltd. Abstract
A review discusses the key variable s that det. the effectiveness of the delivery system at different stages of this journey, and the appropriate test methods to evaluate their ability to protect and release the active ingredient. It tackles the different vehicles and encapsulation methodologies currently in use in food products, and pertinent test methods used to validate the prodn. process, and the stability of the product. It then presents the test methods employed to evaluate the in vivo bioavailability of micronutrients and nutraceuticals. Finally, it introduces the issues surrounding the validation of in vitro release test methods, and in particular the aspects surrounding the evaluation of controlled-release formulas. [on SciFinder(R)]