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There is a growing need for natural ingredients that could be utilized for the production of food, pharmaceutical, and cosmetic emulsions. Soy protein acid hydrolysate (SPAH) is a plant-based additive used in the food industry mainly as a flavor enhancer. For the purpose of this work, however, it was mixed with a well-known natural polysaccharide, xanthan gum (XG), to produce stable 30% (w/w) sunflower oil-in-water emulsions using a rotor-stator homogenizer. In order to assess the emulsifying properties of the SPAH and its mixtures with XG, the surface tension properties of their water solutions, particle size, creaming stability, and rheological properties of the emulsions were investigated. Since the emulsions prepared using only SPAH, in various concentrations, were not stable, systems containing 5% of SPAH and 0.1, 0.2, 0.3, 0.4, or 0.5% of XG were then studied. The increase in concentration of the macromolecule led to an increase in creaming stability. The emulsions with 5% SPAH and 0.5% XG were stable for at least 14 days. The increase in XG concentration led to a decrease in d4,3, while consistency index and non-Newtonian behavior increased. The systems containing SPAH, in the absence of XG, showed shear-thinning flow behavior, which was changed to thixotropic with the addition of XG. Viscoelastic properties of emulsions containing over 0.2% of XG were confirmed by oscillatory rheological tests, demonstrating the dominance of elastic (G’) over viscous (G”) modulus.

The aim of this study was to investigate micellar and self-assembly properties of four sodium salts of naphthenic acid mixtures by determination and comparative analysis of their critical micelle concentration values at seven different temperatures ranging from 10 to 40 °C using spectrofluorophotometric measurements. It was concluded that fractions having the lowest percentage of aliphatic structures give the least flexible micelles due to sterically rigid structure of cyclic side chains, what makes them difficult to pack in the micellar core. Additionally, surface properties of aqueous solutions of investigated mixtures were studied by the determination of the maximum surface excess, Γ max and the minimum area per surfactant molecule (A min) values.

Novel delivery systems for cosmetics, drugs, and food ingredients are of great scientific and industrial interest due to their ability to incorporate and protect active substances, thus improving their selectivity, bioavailability, and efficacy. Emulgels are emerging carrier systems that represent a mixture of emulsion and gel, which are particularly significant for the delivery of hydrophobic substances. However, the proper selection of main constituents determines the stability and efficacy of emulgels. Emulgels are dual-controlled release systems, where the oil phase is utilized as a carrier for hydrophobic substances and it determines the occlusive and sensory properties of the product. The emulsifiers are used to promote emulsification during production and to ensure emulsion stability. The choice of emulsifying agents is based on their capacity to emulsify, their toxicity, and their route of administration. Generally, gelling agents are used to increase the consistency of formulation and improve sensory properties by making these systems thixotropic. The gelling agents also impact the release of active substances from the formulation and stability of the system. Therefore, the aim of this review is to gain new insights into emulgel formulations, including the components selection, methods of preparation, and characterization, which are based on recent advances in research studies.

Knowledge of nonideal behavior of surfactant mixtures of nonionic surfactants at air/aqueous solution interface is important in order to obtain surfactant mixtures with improved properties. In this work interfacial behavior of Brij S20/P407 and Triton X-100/P407 surfactant mixtures was investigated. The nonideal behavior was elucidated by extending Clint's theory and by determination of the ideal maximum surface excess concentration values. Rosen's model for mixed monolayers was used to investigate interactions between different surfactants at the interface. Synergism was noticed in Brij S20/poloxamer 407 mixtures. However, very different interfacial behavior was observed for Triton X-100/poloxamer 407 systems.

Investigation of fundamental properties of colloidal systems of cationic surfactants is important for practical and theoretical reasons. In this work, the nonideal behavior in cetyltrimethylammonium bromide and Triton X-100 mixtures was studied, during the mixed micelle formation. In order to study the aggregation behavior, excess Gibbs energy (GE), excess enthalpy (HE) and excess entropy (SE) were determined. The thermodynamic parameters were monitored as a function of the molar ratio, at different temperatures (283.15–328.15 K). GE, HE and SE were obtained based on the critical micelle concentration values of investigated mixtures. The results of the study indicate existence of synergism in the surfactant mixtures. The increase of the stability of the mixed micelles (GE

The development and optimization of systems consist of polymers and surfactants are strongly related to the presence of interactions between them. Therefore, the interpolymer complexes between biopolymer xanthan gum and synthetic polymer Carbopol 940 were investigated before and after the addition of surfactant. The mechanism of interactions in ternary system consisted of xanthan gum, Carbopol 940 and anionic surfactant (sodium dodecylsulfate) as well as nonionic surfactant (Tween 80) was studied by the combination of different techniques such as viscometry, conductometry, tensiometry, spectrophotometry and fluorimetry. Xanthan gum and Carbopol 940 formed complexes through hydrogen bonding and hydrophobic interactions. Therefore, the calculated specific viscosities of polymer blends were much lower than experimentally determined values. Namely, both polymers participated in the association process with sodium dodecylsulfate or Tween 80. In case of anionic surfactant hydrophobic interactions between sodium dodecylsulfate and xanthan gum-Carbopol 940 complexes exist together with electrostatic repulsive forces between the same charged groups. Tween 80 interacts with xanthan gum-Carbopol 940 complexes through hydrogen bonds and hydrophobic interactions. The formed xanthan gum-Carbopol 940 complexes with sodium dodecylsulfate or Tween80 could find their application by optimizing the interactions in the system of xanthan gum and Carbopol 940 using the appropriate concentration of surfactant.

Knowledge about mechanisms responsible for induction of tumor cell apoptosis is important for the development of anticancer drugs. Mounting evidence suggests that the inhibition of anti-apoptotic proteins of Bcl-2 family is important part of antitumor activity of natural chalcones. In order to gain insights into their binding affinity and binding mechanism, the MM-GBSA binding energies were determined for 63 natural chalcones to Bcl-2, Bcl-xL and Mcl-1, by employing multiple crystal structures of each anti-apoptotic protein. It was noticed that the chalcones have high affinity to the BH3-binding groove. The driving forces behind the binding and the anchor points on the proteins were determined for the top-ranked chalcones, whereas the 300-ns Molecular Dynamics (MD) simulations provided more insights into the binding in the most stable complexes. The importance of ring A, ring B and the side chains of the chalcones for the interactions with the hydrophobic cavities of anti-apoptotic proteins was noticed. Although the natural compounds showed mainly favorable pharmacokinetic properties, some limitations in binding to the proteins, compared to the synthetic ligands, were noticed. This pointed out towards possible future directions of chemical modifications of the most potent natural compounds. It is envisioned that the results of this study could be useful for the selection of lead antitumor natural compounds as well as for the design of new synthetic BH3-mimetics.

In the present study, binary mixed micelles of poloxamer 407 and a homologous series of polysorbate surfactants (polysorbate 20, polysorbate 60, polysorbate 80, polysorbate 85) were investigated. Rubingh’s model was applied to determine the physicochemical parameters of the poloxamer/polysorbate binary systems. The obtained negative values of the interaction parameter and excess Gibbs energy showed the existence of synergism. By comparing the values of the investigated parameters, and the values of micropolarity measurements, it was noticed that the inclusion of polysorbate surfactants with longer and more saturated hydrophobic chains leads to improved packing in the micellar interior and stronger interactions.

Binary surfactant mixtures of Tween 85/Triton X100 and Tween 85/Triton X165 have been investigated in water solution over the temperature range from 273.15 K to 323.15 K. At the temperatures of 273.15 K and 283.15 K between different building units of binary mixed micelles, synergistic interactions exist whose size is not affected by difference in length of the polyoxyethylene chains. At higher temperatures, the longer polyoxyethylene chain of Triton X165 shows a more stabilizing effect in mixed micelle with Tween 85 than in mixed micelles of Tween 85/Triton X100. For the investigated binary mixed micelles, regular solution theory approximation about zero value of excess entropy of binary mixed micelle formation cannot be accepted.

Bile acid anions are biosurfactants which form small micelles. To enhance the hydrophobic volume of the micelle, bile salts are used as mixed micelles with non-ionic surfactants. Micellar-bound bile acids (sodium-hyodeoxycholate, HD and sodium-cholate, C in binary mixed micelles with non-ionic surfactant Triton X-100) at concentration of 10 cmc have higher pKa values than bile acids from the aqueous solution. Different pKa values of micellar and non-micellar bile acids (ΔpKa) are due to the excess Gibbs energy G HA E which is a function of interaction coefficient and mole fraction of Triton X-100 in the binary surfactant mixture. In the mixed micelles ΔpKa values show synergistic interactions between different building units, similarly as interaction coefficient.

The study examines binary mixed micelles of sodium-hyodeoxycholate (HD) and polysorbates: Tween 20 (T-20), Tween 60 (T-60) from α = 0.1 to α = 0.5 molar fraction of polysorbates in the mixture of surfactants at 298.15 K. At every value of α there are synergistic reactions between different building units of mixed micelle. In the mixed micelle HD–T-20 the thermodynamic stability of the real mixed micelle compared to the ideal binary mixed micelle is greater than in the mixed micelle HD–T-60. The pKa values of the micellarly bound bile acids are higher than the pKa values of non-micellar bile acids (ΔpKa). At constant ionic strength this means that the change in Gibbs energy of protolysis of the micellar bile acid has excess Gibbs energy determined by the energy of stability of bile acid in micellar phase. The ΔpKa value of the micellar bile acid from the mixed micelle of bile salts and homologous polysorbates, similar to the interaction coefficient (βij) from regular solution theory, characterizes the thermodynamic stability of the mixed micelle and also enables its fast evaluation.

It is important to find binary surfactant systems having synergistic interactions (negative value of the interaction parameter) since it means that a binary surfactant mixture composition exists in these systems, having lower critical micelle concentration value than more hydrophobic mixture component. In this work, influence of hydrophobic segment length of homologues Tweens in mixed micelles with Triton X-100 on the interaction parameter value ( β i j ) and on the excess Gibbs energy ( G E ) was studied. Also, influence of temperature on the stability of investigated mixed micelles has been investigated (298.15–328.15 K). The critical micelle concentration values of pure surfactants and their binary mixtures were determined spectrofluorimetrically using pyrene as a probe molecule. It was found for every investigated temperature that increase in length of saturated aliphatic side chain of a polysorbate increases the stability of investigated mixed micelles ( β i j 0 and G E 0 ) compared to the ideal mixed micelles. Presence of the C9 double bond in oleic acid residue of Tween 80 reduces synergistic effect of this polysorbate compared to Tween 60 which contains hydrophobic segment with the same number of C atoms but without olefin bond. The excess free enthalpy below the 298.15 K is determined with entropic contribution, but above 298.15 K with enthalpic contribution.

In this work mixed micelles of Na salts of bile acids and Tween 80 are studied. In the experiment, number and orientation of OH and oxo groups in the steroid skeleton of bile acid anion varies. In every investigated mixture, mole fraction of Tween 80 (α) varies from 0.05 to 0.5 of the total surfactant concentration. Critical micelle concentrations of binary surfactant mixtures are determined by tensiometric and conductometric methods (modified Philips method of data processing). By employing regular solution theory for every studied binary surfactant mixture, values of interaction coefficient (β1,2) are determined. Based on the obtained β1,2 values, investigated bile acid anions form two groups. Group I consists of bile acids having only OH groups attached to the steroid skeleton. Characteristics of mixed micelles of this group are negative values of β1,2 for α to 0.1 (synergistic effect between different types of the micelle building units), and positive values of β1,2 for α over 0.1 (antagonistic effect). This change of sign of β1,2 as a function of α can be explained by phase transformation in mixed micelle as a pseudophase, and due to rigid geometry of cis-oleic residue of Tween 80. Group II is formed of bile acid anions having one or more oxo groups in the steroid skeleton. Mixed micelles of Tween 80 and group II of bile acid anions are characterized by positive β1,2 values in the whole investigated range of α. Based on the intensity measurements at different temperatures of first (I1) and third (I3) vibrational bands of pyrene (probe molecule) emission spectrum as a function of total surfactant concentration, it can be concluded that mixed micelles having Tween 80 are less rigid than mixed micelles having Tween 40. This also indicates that in hydrophobic domain of mixed micelles, cis-oleic residues are more difficult to pack together compared to the palmitic residues of Tween 40.

Salts of bile acids are steroid amphiphilic compounds which form micelles consisting of 2–12 monomer units. In nature, the formation of mixed micelles with phospholipids (gall bladder) increases the capacity of bile salts to solubilize cholesterol. Oxo derivatives of bile salts are of special research interest because of their lower membrane toxicity compared to the corresponding OH analogues. In view of the fact that the micelles of anions of oxo derivatives have lower hydrophobicities, it was interesting to study mixed micelles of bile salts and the hydrophobic nonionic cosurfactant Tween 40. With this aim, the critical micelle concentrations were determined by conductometric and tensiometric methods. It was found that the absolute value of the interaction parameter (measure of the synergism between different constitutive units, i.e., the measure of the departure from an ideal micelle) increases with the increase in the number of equatorial OH or oxo groups in the steroid skeleton of the bile acid anion...

Knowledge of physicochemical parameters of mixed micelles is important in order to develop drug delivery systems with required characteristics. Investigated bile salts and Tweens are relatively nontoxic surfactants, extensively studied as biocompatible colloidal drug carriers. The micellization behavior of binary anionic–nonionic surfactant mixtures built of sodium cholate or sodium deoxycholate and one of two Tweens (Tween 20 or Tween 60) was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint’s, Rubingh’s, and Motomura’s theories for mixed binary systems. The determined physicochemical properties, particularly the negative values of the interaction parameter, indicate synergism between the individual surfactants in the mixed micelles. It was noticed that Tween with a longer hydrophobic tail shows stronger interactions with selected bile salts. However, it was found that the more hydrophilic bile salt (sodium cholate) generates the strong...

The present study is concerned with the determination of the critical micelle concentration (cmc) of mixed micelles of sodium dodecyl sulfate with one of five nonionic surfactants (Triton X-100, Tween 20, Tween 60, Tween 80 or Tween 85) from conductance measurements. Based on the calculated values of the ? parameters we have noticed that SDS-nonionic surfactants mostly showed strong synergistic effect. It was found that nonionic surfactants with mainly longer and more hydrophobic tail show stronger interactions with hydrophobic part of SDS, thus expressing stronger synergism. In SDS-Tween 80 binary system the strongest synergistic effect was noticed. SDS-Tween 85 micellar system showed antagonistic effect, most probably because the presence of the double bond in its three hydrophobic tails (three C18 tails) makes it sterically rigid.

Background In order to develop colloidal drug carriers with desired properties, it is important to determine physico-chemical characteristics of these systems. Bile salt mixed micelles are extensively studied as novel drug delivery systems. The objective of the present investigation is to develop and characterize mixed micelles of nonionic (Triton X-100) or anionic (sodium lauryl ether sulfate) surfactant having oxyethylene groups in the polar head and following bile salts: cholate, deoxycholate and 7-oxodeoxycholate. Results The micellization behaviour of binary anionic-nonionic and anionic-anionic surfactant mixtures was investigated by conductivity and surface tension measurements. The results of the study have been analyzed using Clint's, Rubingh's, and Motomura's theories for mixed binary systems. The negative values of the interaction parameter indicate synergism between micelle building units. It was noticed that Triton X-100 and sodium lauryl ether sulfate generate the weakest synergistic interactions with sodium deoxycholate, while 7-oxodeoxycholate creates the strongest attractive interaction with investigated co-surfactants. Conclusion It was concluded that increased synergistic interactions can be attributed to the larger number of hydrophilic groups at α side of the bile salts. Additionally, 7-oxo group of 7-oxodeoxycholate enhance attractive interactions with selected co-surfactants more than 7-hydroxyl group of sodium cholate.