Increase In Hydrophobic Chain Length Research Articles

Preparation and characterization of functional compounds encapsulated microemulsion with nonionic surfactants

Influence of hydrophobic chain lengths of surfactant, co-surfactant, oil and different surfactant to co-surfactant ratios on phase behavior of Tween/alcohol/alkane/H2O was investigated with pseudo-ternary phase diagrams. The total areas of the microemulsion (ME) regions were determined. The largest ME region was formed when the ratio of surfactant: co-surfactant was 2:1 (w/w). The capacity for formation of MEs increased with an increase of hydrophobic chain length of the Tween, which was opposite to the trend for alkane (oil). N-butanol formed the largest ME region among the alcohols tested as co-surfactants. Sub-ME phases were identified by conductivity measurements. O/W MEs were observed when the water content was higher than 62-68%. The O/W sub-phase regions had significantly lower particle sizes and viscosities than either the W/O or bi-continuous sub-phases.

Binary mixture of short and long chain glycolipids and its enhanced surface activity

Biocompatible amphiphiles with high surface activity have received immense importance in the area of surfactant science with allied applications. Preparation of bio-based amphiphiles with predefined surface properties is not always economically viable. The structural variations in the glycolipid molecule like increase in hydrophobic chain length or headgroup size leads to low solubility or less surface activity issues at the air–water interface. In this work, we made an attempt to prepare a mixture of two glycolipids at various hydrophobic chain lengths. The air–water interfacial behaviors of mixed glycolipid systems were investigated by surface tension (ST) and Langmuir–Blodgett (LB) techniques. Surface parameters like critical micellar concentration (CMC), surface pressure, and area per molecule of the mixed glycolipids at air–water interface obtained from ST and LB studies were discussed. Surface-active properties, such as foaming, wetting, emulsification, and solubilization capacity were employed at different mole fraction of short chain glycolipid (χSGL) to explore synergistic and antagonistic interactions between the hydrophobic chains of glycolipids. At χSGL = 0.25, few mixed glycolipid systems exhibited significantly better surface properties than the corresponding pure glycolipids. The mixed glycolipid system provided enhanced surface activity at air–water interface. The mixing ratio at χSGL = 0.25 exhibited synergism in interfacial properties by inducing the chain length compatibility between glycolipids. The outcomes provide basis for glycolipids to select as mixed surfactants with improved interfacial efficiency.

Synthesis, surface/interfacial properties, and biological activity of amide-based Gemini cationic surfactants with hydroxyl in the spacer group

Three amide-based Gemini cationic surfactants, 1, 3-2 (alkyl amide propyl dimethyl ammonium chloride) isopropyl alcohol (abbreviated to ADQ-n, where n represents the carbon number in the raw fatty acid of 8, 12 and 16) were synthesized by a facile synthetic route. The effect of hydrophobic chain length on surface/interfacial activities, electrolytes tolerance, wettability, foaming properties were investigated. The effect of electrolytes (NaCl and CaCl2) on the interfacial tension at the oil/water interface were discussed, and the biological activity was also tested. The results showed that ADQ-n have the higher surface activities than conventional monomeric surfactant. The critical micelle concentration (cmc) decreases with the increase of hydrophobic chain length, however, the surface tension at the cmc (γcmc) shows the opposite trend. There are few differences for maximum surface excess concentration (Гmax) and minimum area per molecule (Amin). ADQ-12 has the lowest interfacial tension value (4.1 × 10−3 mN/m) than other synthesized Gemini surfactants, this is attributed to the better compatibility between hydrophobic tail of ADQ-12 and kerosene. In addition, the addition of electrolytes is favorable to decrease interfacial tension at oil/water interface. ADQ-n demonstrated readily biodegradation (>97%) in comparison with conventional alkyl chain Gemini surfactants (<37%) after seven days and could be classified as biodegradable.

Efficient emulsifying properties of glycerol-based surfactant

Two glycerol based non-ionic surfactants 1,3-bis(octylamino)propan-2-ol (BAPO-C8) and 1,3-bis(dodecylamino)propan-2-ol (BAPO-C12) were synthesized, and their surface property, critical micelle concentration (cmc), interfacial property, and emulsifying ability were studied. It was found that the surfactants exhibited low cmc and excellent ability to reduce interfacial tension. They were efficient for emulsifying hexane/water, heptane/water, octane/water and chloroform/water systems. It is worth noting that high-internal-phase emulsions (HIPE, 80% internal phase) (o/w) could be formed in the water/alkane systems. Moreover, a common water in oil emulsion (w/o) was formed in water/chloroform system stabilized by BAPO-C12. Confocal laser scanning microscopy (CLSM) results indicated that the size of droplets in the HIPEs increased with the increase of hydrophobic chain length of oil phase. The hexane/water emulsion had higher apparent viscosity (ƞ) than the emulsions with other alkanes, indicating that the emulsions had much stronger network of oil droplets. All the emulsions showed good stability with and without salts.

Micellar solubilization of poorly water-soluble drugs: effect of surfactant and solubilizate molecular structure

Objective: This study aims to clarify the role of surfactant and drug molecular structures on drug solubility in micellar surfactant solutions.Significance: (1) Rationale for surfactant selection is provided; (2) the large data set can be used for validation of the drug solubility parameters used in oral absorption models.Methods: Equilibrium solubility of two hydrophobic drugs and one model hydrophobic steroid in micellar solutions of 19 surfactants was measured by HPLC. The drug solubilization locus in the micelles was assessed by UV spectrometry.Results: Danazol is solubilized much more efficiently than fenofibrate by ionic surfactants due to ion–dipole interactions between the charged surfactant head groups and the polar steroid backbone. Drug solubilization increases linearly with the increase of hydrophobic chain length for all studied surfactant types. Addition of 1–3 ethylene oxide (EO) units in the head group of dodecyl sulfate surfactants reduces significantly the solubilization of both studied drugs and decreases linearly the solubilization locus polarity of fenofibrate. The locus of fenofibrate solubilization is in the hydrophobic core of nonionic surfactant micelles and in the palisade layer of ionic surfactant micelles.Conclusions: Highest drug solubility can be obtained by using surfactants molecules with long chain length coupled with hydrophilic head group that provides additional drug–surfactant interactions (i.e. ion–dipole) in the micelles.

Effect of surfactant molecular structure on Progesterone solubilization

Progesterone is a hydrophobic drug (LogP = 3.9) with solubility-limited oral bioavailability. One approach to improve its aqueous solubility is by solubilization in micellar surfactant solutions. We investigate systematically the effect of surfactant molecular structure on Progesterone solubility by using a set of 17 surfactants with different hydrophilic head group charge and variable hydrophobic chain length. Charged surfactants showed highest solubilization capacity, increasing Progesterone solubility from 0.01 mg/mL to above 3 mg/mL, whereas all nonionic surfactants had much smaller effect (0.5–1 mg/mL Progesterone solubility). The high solubilization of Progesterone in charged surfactant micelles was explained by ion-dipole interactions in the micelle palisade layer. The increase of hydrophobic chain length improved drug solubilization for all studied surfactants, regardless of the type and charge of the hydrophilic head. In respect to the effect of hydrophilic head group, the solubilization capacity of C-12 surfactants decreased in the order SO4− > E1SO4− > +N(CH3)3 > E3SO4− > SorbEO20 = E10 = E23. Therefore, the best candidates to improve oral Progesterone absorption through solubility enhancement are surfactants with long hydrophobic chain and charged hydrophilic head group (e.g. alkylsulfates).

Understanding the interaction of concanavalin a with mannosyl glycoliposomes: A surface plasmon resonance and fluorescence study

The specificity of carbohydrate-protein interaction is a key factor in many biological processes and it is the foundation of technologies using glycoliposomes in drug delivery. The incorporation of glycolipids in vesicles is expected to increase their specificity toward particular targets such as lectins; however, the degree of exposure of the carbohydrate moiety at the liposome surface is a crucial parameter to be considered in the interaction. Herein we report the synthesis of mannose derivatives with one or two hydrophobic chains of different length, designed with the purpose of modifying the degree of exposure of the mannose when they were incorporated into liposomes.The interaction of glycovesicles with Con A was studied using: (i) agglutination assays; measured by dynamic laser light scattering (DLS); (ii) time resolved fluorescence methods and (iii) surface plasmon resonance (SPR) kinetic measurements. DLS data showed that an increase in hydrophobic chain length promotes a decrease of liposomes hydrodynamic radius. A longer hydrocarbon chain favors a deeper insertion into the bilayer and mannose moiety results less exposed at the surface to interact with lectin. Fluorescence experiments showed changes in the structure of glycovesicles due to the interaction with the protein. From SPR measurements the kinetic and equilibrium constants associated to the interaction of ConA with the different glycolipid synthetized were determined.The combination of SPR and fluorescence techniques allowed to study the interaction of Con A with mannosyl glycovesicles at three levels: at the surface, at the interface and deeper into the bilayer.

Wettability of amphiphilic poly(amido amine) (PAMAM) dendrimers on quartz: Effect of electrostatic and hydrophobic interaction

ABSTRACTWettability of amphiphilic poly(amido amine) (PAMAM) dendrimer on quartz surfaces was studied as a function of structure differences. The dependence of contact angle on concentration presented various tendencies with the increase of hydrophobic chain length, in which, maximum value of θ–log C curve occurred only for QPAMC16 with more hydrophobicity. However, slightly changes were observed in the tendency of contact angle versus concentration specifically for QPAMC12, with large contact angle value emerged instead, indicating a large hydrophobic group density on quartz surface differing from that of traditional surfactants. In addition, the amphiphilic dendrimer with long hydrophobic chain has obvious ability to alter the wettability of oil-wet surfaces.Quantitative and qualitative descriptions of the adsorption were investigated to explore the wettability nature. Significant morphological differences in QPAMCm were observed after adsorption on quartz, which transformed from spherical micelles into hemimicelles for QPAMC8 induced by the affinity of molecules onto the surface, however, regularly spherical aggregates tended to form for QPAMC12 and QPAMC16, and the size and thickness have dependence of bulk concentration. The results indicated that the affinity of head group and the self-association driven by the chain length for amphiphilic dendrimers revealed synergistic effect both in adsorption and wetting properties.

Lipophilic counterion effect on aggregation and adsorption behavior of quaternary ammonium surfactants

ABSTRACTThe obvious different aggregation and adsorption behavior of six newly quaternary ammonium surfactants with different lipophilic counterions has been discoverd by measurements of equilibrium and dynamic surface tension, fluorescence and conductivity. Interestingly, the critical micelle concentration (CMC) and its surface tension γCMC decrease with the increasing counterion chain length. However, three methods have confirmed that an exception of CMC increases slightly from C16NC1 to C16NC2. According to experimental results, a balanced mechanism between hydrophobicity and electrostatic of counterion is proposed. Besides, the dynamic surface tension results show the diffusion coefficient increases with the increasing counterion length both at a short time (Dt → 0) and long time (Dt → ∞), which indicates a faster adsorption process. Unlike the inorganic counterion, the diffusion coefficient decreases with the increase of hydrophobic chain length. This is attributed to the strong electrostatic interactions between counterions and cationic headgroups.

Hydrophobic behavior, ROS production, and heme degradation of hemoglobin upon interaction with n-alkyl sulfates

The oxygen-containing free radical species form upon interaction of amphiphilic substances such as sodium dodecyl sulfate and hemoglobin. Under these conditions, hemoglobin is converted to methemoglobin and simultaneously results in heme degradation. Since heme is located in a hydrophobic moiety of hemoglobin, we hypothesized that other hydrophobic substances or amphiphilic xenobiotics can dispose hemoglobin to oxidative stress. Here this hypothesis was tested by investigating heme degradation of hemoglobin during interaction with n-alkyl sulfates. This was accomplished using UV–Vis and fluorescence spectroscopy, chemometric analysis, and chemiluminescence methods. We determined whether a relationship exists between the alkyl tail length (surfactant hydrophobicity) of n-alkyl sulfate homologues, reactive oxygen species (ROS) production, and heme degradation pattern of hemoglobin. We also proposed a mechanism for these types of interactions and induction of heme degradation. Our results indicated that hemoglobin structural–functional changes including globin denaturation are the key factors in starting the heme degradation process, and heme degradation product patterns were dependent on each alkyl sulfate. However, the number of fluorescent components (heme degradation products) was independent of the alkyl sulfate type. The reason for this phenomenon was the mechanism of reaction in which the amount of hydrogen peroxide was changed with each homologue, but the mechanism of degradation remained the same. Thus, an increase in hydrophobic chain length of the surfactants correlated with the enhanced ROS production and heme degradation of hemoglobin.

Equilibrium and dynamic surface tension properties of Gemini quaternary ammonium salt surfactants with hydroxyl

Abstract Five quaternary ammonium salt Gemini surfactants 2-hydroxyl-propanediyl-α,ω-bis (alkyldodecyl ammonium chloride) (n-3(OH)-n, where n represents hydrocarbon chain lengths of 10, 12, 14, 16, and 18) were synthesized and characterized by 1H NMR. Surface activity, adsorption and aggregation behaviors of these cationic Gemini surfactants were investigated by methods of measuring equilibrium surface tension, dynamic surface tension and transmission electron microscope (TEM). The critical micelle concentration (CMC) decreased with an increase in hydrophobic chain length, while the surface tension at the CMC (γCMC) showed little change. With TEM measurements, formations of vesicles in n-3(OH)-n (n = 16, 18) solutions occurred and vesicles dimensions depended on their n values. Moreover, data obtained were analyzed in accordance with Word-Tordai equation, and the diffusion coefficients for ionic liquid molecular adsorption in the initial stage and final stage under different concentration were figured out respectively. The results indicated that the adsorption process was controlled by a diffusion step at low surfactant concentration while by a mixed kinetic-diffusion adsorption mechanism at high surfactant concentration.

Mixed Micellar and Interfacial Interactions of a Triblock Polymer (EO37PO56EO37) with a Series of Monomeric and Dimeric Surfactants

AbstractThe mixed micellar and interfacial properties of mixtures of triblock polymer (TBP) with a series of monomeric (dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, and cetyltrimethylammonium bromide, and dimeric (dimethylene bis[alkyldimethylammonium bromide], m‐2‐m, where m = 10, 12, and 14) cationic surfactants were investigated using surface tension and viscosity measurements in aqueous solutions at different temperatures. Various physicochemical properties such as critical micelle concentration, mixed micellar mole fraction, interaction parameter, interfacial, and thermodynamic parameters were evaluated. All the binary mixtures exhibit synergistic interactions which increase with temperature and pass through a minimum with the increase in hydrophobic chain length of the cationic surfactants. The contribution of TBP in mixed micelle formation also increases with the hydrophobic chain length of the surfactants. The interfacial and thermodynamic parameters reveal that the adsorption of the surfactant mixtures at the air–solution interface is more favorable than that of micelle formation and the unfavorable enthalpy changes are overwhelmed by favorable entropy changes. Further, the mixtures of TBP with smaller chain length surfactants show a sharp rise in relative viscosity at higher mole fractions of these surfactants.

Effect of alkyl chain length on the surface dilational rheological and foam properties of N-acyltaurate amphiphiles

The dynamic dilational properties of sodium 2-(2-(alkylaryloxy)-alkylamido)ethanesulfonates (12+nB-Ts) at the air–water interfaces were investigated by drop shape analysis, and their foam properties were also measured. The influences of time and bulk concentration on surface dilational properties were expounded. The results show that the molecular interaction controls the nature of adsorption film during lower concentration range, and the film behaves elastic in nature. During higher concentration range, the diffusion exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase in hydrophobic chain length enhances the molecular interaction at low concentration and speeds up the diffusion exchange process at high concentration, which results in the different variations of modulus at different concentration regions. For 12+nB-Ts, too short a chain probably produces bad film elasticity, whereas too great a length produces too fast liquid drainage. Therefore the optimal length in the branched chain leads to the best foam stability.

Nanostructure formation in aqueous solution of amphiphilic copolymers of 2-( N, N-dimethylaminoethyl)methacrylate and alkylacrylate: Characterization, antimicrobial activity, DNA binding, and cytotoxicity studies

Three amphiphilic random copolymers poly(2-(dimethylaminoethyl)methacrylate-co-alkylacrylate) (where, alkyl = hexyl, octyl, dodecyl) with 16 mol% hydrophobic substitution were synthesized. Surface tension, viscosity, fluorescence probe, dynamic light scattering (DLS), as well as transmission electron microscopic (TEM) techniques were utilized to investigate self-assembly formation by the hydrophobically modified polymers (HMPs) in pH 5. Formation of hydrophobic domains through inter-polymer chain interaction of the copolymer in dilute solution was confirmed by fluorescence probe studies. Average hydrodynamic diameter of the copolymer aggregates at different polymer concentration was measured by DLS studies. The copolymer with shorter hydrophobic chain exhibits larger hydrodynamic diameter in dilute solution, which decreased with either increase of concentration or increase of hydrophobic chain length. TEM images of the dilute solutions of the copolymers with shorter as well as with longer hydrophobic chain exhibit spherical aggregates of different sizes. The antimicrobial activity of the copolymers was evaluated by measuring the minimum inhibitory concentration value against one Gram-positive bacterium Bacillus subtilis and one Gram-negative bacterium Escherichia coli. The copolymer with the octyl group as pendent hydrophobic chain was found to be more effective in killing these microorganisms. The interaction of the cationic copolymers with calf-thymus DNA was studied by fluorescence quenching method. The polymer-DNA binding was found to be purely electrostatic in nature. The hydrophobes on the polymer backbone were found to have a significant influence on the binding process. Biocompatibility studies of the copolymers in terms of cytotoxicity measurements were finally performed at different concentrations of the HMPs to evaluate their potential application in biomedical fields.

Interfacial dilational rheological property and lamella stability of branched alkyl benzene sulfonates solutions

The dynamic dilational properties of branched alkyl benzene sulfonates at the air–water and decane–water interfaces were investigated by drop shape analysis, and their lamella stability was measured. The influences of time, dilational frequency, and bulk concentration on surface dilational elasticity and dilational viscosity were expounded. The results show that the molecular interaction controls the nature of adsorption film during lower concentration range and the film behaves elastic in nature. During higher concentration range, the diffusion-exchange process controls the dynamic dilational properties and the surface film shows remarkable viscoelasticity. An increase in hydrophobic chain length enhances the molecular interaction, which results in the increase of dilational parameters and lamella stability. The data correlation suggests that the ability to form a stable lamella is linked to the intrinsic surface dilational elasticity.

Effects of Surfactants and Lipids on the Preparation of Solid Lipid Nanoparticles Using Double Emulsion Method

In this article, double emulsion method was used to prepare solid lipid nanoparticles (SLN). Different kinds of SLN were synthesized by changing the species and contents of lipids and surfactants in microemulsion. The effects of the hydrophobic chain length of surfactant inside and surfactant outside, the type of lipid and the ratio of Span/Tween on SLN were systematically investigated. Dynamic light scattering (DLS) and zeta potential were applied to study the change trend of particle size and surface charge of SLN. The DLS results show that the size of SLN increases as the hydrophobic chain length of lipid enhances, and decreases with the increase of hydrophobic chain length of Tween or that of Span or the ratio of Span/Tween. And the absolute value of zeta potential as well as the stability of SLN dispersion decreases as the hydrophobic chain length of Span or lipid increases, and increases when the hydrophobic chain length of Tween or the ratio of Span/Tween increases.

Effect of Surfactant Mixing on Partitioning of Model Hydrophobic Drug, Naproxen, between Aqueous and Micellar Phases

Mixed surfactants may improve the performance of surfactant-enhanced solubilization of drugs and thus can serve as the tool for increased bioavalaibility, controlled drug release, and targeted delivery. Solubilization of Naproxen by micellar solutions at 25 degrees C using single and mixed surfactant systems was measured and compared. Solubilization capacity determined with spectrophotometry and tensiometry has been quantified in terms of molar solubilization ratio, micelle-water partition coefficient, and locus of solubilization. Cationic surfactants exhibited higher solubilization capacity than nonionics and anionics, the efficiency increasing with chain length. Mixing effect of surfactants on mixed micelle formation and solubilization efficiency has been discussed in light of regular solution approximation (RSA). Equimolar cationic-nonionic surfactant combinations showed better solubilization capacity than pure cationics or nonionics, which, in general, increased with increase in hydrophobic chain length. Equimolar cationic-nonionic-nonionic ternary surfactant systems exhibited intermediate solubilization efficiency between their single and binary counterparts. Use of RSA has been extended, with fair success, to predict the partition coefficient of ternary surfactant systems using data from binary mixtures. The theoretical micelle-water partition coefficients calculated from the geometric mean equation compared well with experimental values. Locus of solubilization of NAP in different micellar solutions was probed by UV-visible spectroscopy.

Preparation and surface activity of modified soy protein

AbstractA series of novel surfactants have been prepared by the reaction of hydrolyzed soy protein with alkyl succinic anhydride. These novel surfactants exhibit excellent surface active properties including surface tension, foaming, emulsifying, wetting power, and buffer ability. The hydrophobic modified protein exhibit more surface activity than original protein because of the enhanced hydrophobicity in structure. The increase in hydrophobic chain length leads to an increase in the surface activity. The surface tension reduction is correlated to the hydrophobicity of the modified molecule, which was determined by a fluorescent probe. In application on cotton bleaching procedures, these surfactants increase the whiteness of fabrics. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3498–3503, 2006

Preparation and surface activity of gelatin derivative surfactants

Surface active gelatin derivative surfactants were formed by covalent attachment of hydrophobic groups to gelatin hydrolyzate molecules. The surface activity was evaluated by surface tension, wetting ability, emulsifying power and foaming properties. It was found that, the modified gelatins are more surface active than the gelatin hydrolyzate. The increase in hydrophobic chain length and the number of attached alkyl chains per gelatin hydrolyzate molecule leads to an increase in the surface activity. The modified gelatins also have high foaming ability and a high emulsifying ability, while the maximal surface activity is obtained by the C 12 modified gelatin. The emulsification properties of the gelatin derivative surfactants were also compared to that of sodium dodecyl sulfate (SDS) and polyoxyethylene nonyl phenyl ether (NP-9), both emulsifying ability were equivalent to the C 12 modified gelatin.

Emulsification and Foaming Properties of Hydrophobically Modified Gelatin

Surface active gelatins were formed by covalent attachment of hydrophobic groups to gelatin molecules by reactingN-hydroxysuccinimide esters of various fatty acids (C4–C16) with the lysine groups. The surface activity was evaluated by emulsification and foaming properties, and by adsorption at the oil–water interface. It was found that, in general, the modified gelatins are more surface active than the native gelatin. The increase in hydrophobic chain length and the number of attached alkyl chains per gelatin molecule leads to a decrease in the emulsion droplet's size and to more stable emulsions. Adsorption isotherms, at the o/w interface, show much higher surface concentration, at saturation, of the modified gelatin than the native gelatin. The modified gelatins also have high foaming ability and a high foam stability, while the maximal foam activity is obtained by the C8modified gelatin. The foaming properties of the surface-active gelatins were also compared to that of sodium dodecyl sulfate (SDS) and it was found that below the CMC of SDS, both foam activity and stability were higher for the modified gelatins. On the other hand, above the CMC the foam activity of SDS was higher, but the foam stability was lower than for C8–C16-modified gelatins.