Stability Of Mixed Micelles Research Articles

PEG-Fmoc-Ibuprofen Conjugate as a Dual Functional Nanomicellar Carrier for Paclitaxel.

Ibuprofen is a kind of nonsteroidal anti-inflammatory drug (NSAIDs), and it is considered to possess some antitumor effect. In this study, a novel nanomicellar carrier based on PEG-derivatized ibuprofen, PEG2K-Fmoc-Ibuprofen (PEG2K-FIbu), was developed for delivery of anticancer agents such as paclitaxel (PTX). This conjugate readily forms stable mixed micelles with PTX with a relatively high PTX loading capacity of 67%. The release of PTX from PTX-loaded PEG2K-FIbu micelles was significantly slower than that from Taxol formulation. PTX-loaded PEG2K-FIbu micelles and Taxol showed a comparable in vitro cytotoxicity. Importantly, PTX-loaded PEG2K-FIbu micelles demonstrated a much more pronounced in vivo therapeutic efficacy compared with Taxol with respect to both inhibition of tumor growth and animal survival. Our system may represent an attractive dual-functional delivery system to achieve synergistic activity with PTX while minimizing the carrier-associated toxicity.

A prodrug micellar carrier assembled from polymers with pendant farnesyl thiosalicylic acid moieties for improved delivery of paclitaxel.

In order to achieve enhanced and synergistic delivery of paclitaxel (PTX), a hydrophobic anticancer agent, two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks, were synthesized. Both POEG-b-PFTS polymers were able to form micelles with intrinsic antitumor activity in vitro and in vivo. Employing these micelles as a carrier to load PTX, their drug loading capacity, stability, in vivo biodistribution and tumor inhibition effect were evaluated. PTX/POEG15-b-PFTS16 mixed micelles exhibited an excellent stability of 9days at 4°C with a PTX loading capacity of 8.2%, which was more effective than PTX/POEG15-b-PFTS6 mixed micelles. In vivo biodistribution data showed that DiR-loaded POEG-b-PFTS micelles were more effectively localized in the tumor than in other organs. Moreover, both PTX/POEG-b-PFTS micelles showed significantly higher antitumor activity than Taxol in a 4T1.2 murine breast tumor model, and the tumor inhibition and animal survival followed the order of PTX/POEG15-b-PFTS16>PTX/POEG15-b-PFTS6>POEG15-b-PFTS16>Taxol≈POEG15-b-PFTS6. Our data suggest that POEG-b-PFTS micelles are a promising anticancer drug carrier that warrants more studies in the future. Polymerization of drug-based monomer represents a facile and precise method to obtain well-defined polymeric prodrug amphiphiles. Currently, most reports largely focus on the synthesis methods and the biophysical properties. There is limited information about their anti-tumor activity and delivery function as prodrug carriers in vitro and in vivo. In this manuscript, we report the development of two novel prodrug copolymers, POEG15-b-PFTS6 and POEG15-b-PFTS16 composed of hydrophilic poly(oligo(ethylene glycol) methacrylate) (POEG) and hydrophobic farnesylthiosalicylate (FTS, a nontoxic Ras antagonist) blocks. Both POEG-b-PFTS polymers were able to self-assemble into nano-sized micelles with intrinsic antitumor activity in vitro and in vivo. More importantly, POEG-b-PFTS polymers were effective in forming stable mixed micelles with various anticancer agents including PTX, DOX, docetaxel, gefitinib, and imatinib. Delivery of PTX via our new carrier led to significantly improved antitumor activity, suggesting effective PTX/FTS combination therapy. We believe that our study shall be of broad interest to the readers in the fields of biomaterials and drug delivery.

Self-assembly of pH-responsive biodegradable mixed micelles based on anionic and cationic polycarbonates for doxorubicin delivery

Poly(5-propyl-1,3-dioxan-2-one)-b-dimethylamine modified polycarbonate (PC(MPpC-MMA)) and poly(ethylene glycol)-b-carboxylated polycarbonate (PEG-PCCOOH) diblock copolymers were prepared to construct a pH responsive, highly stable and biodegradable mixed micelle. The two copolymers self-assembled into the mixed micelle in pH 7.4 PBS driven by electrostatic and hydrophobic interactions. PC(MPpC-MMA) with hydrophobic inner core was used for carrying drug and the dimethylamine part was designed as a trigger to disassemble the mixed micelle. PEG-PCCOOH could shield the positive character of the micelle which might show disadvantage to normal tissue. In addition, the free carboxyl groups could further increase the loading efficiency of positive charged drugs. The size and zeta potential of the micelle gradually decreased with increasing the molar ratio of PEG-PCCOOH to PC(MPpC-MMA). These mixed micelles could withstand high ionic strength of plasma and were rather stable for long time storage. However, via decrease of pH value from 7.4 to 5.0, they could undergo dissociation into smaller nanoparticles which were in a diameter of 20nm and showed positive surface nature. In vitro drug delivery studies showed a faster release rate at pH 5.0 than that at pH 7.4. The MTT assays demonstrated potent cytotoxic activity against HepG2 cells. All these results indicate that the newly mixed polycarbonate micelle can show great potential in biomedical field.

Micellization behavior of binary mixtures of amino sulfonate amphoteric surfactant with different octylphenol polyoxyethylene ethers in aqueous salt solution: Both cationic and hydrophilic effects

The effect of different valent inorganic cations and the hydrophilic group of surfactant on the micellization behavior of binary surfactant mixtures constituted by an amphoteric surfactant, sodium 3-(N-dodecyl ethylenediamino)-2-hydropropyl sulfonate (C12AS), and three nonionic surfactants octylphenol polyoxyethylene ether (OP-n) with different numbers of oxyethylene glycol ethers (n), namely, OP-10, OP-7, and OP-4 was investigated in aqueous solution. These inorganic cations include Na+, K+, Mg2+, Ca2+, Ba2+, Al3+ and Fe3+. Both the tensiometry and the UV–vis spectrophotometry using pyrene as a probe were adopted to determine the critical micelle concentrations (cmc) of individual or mixed surfactants. Interaction parameters between two surfactants and other parameters were obtained based on the regular solution theory, the pseudophase separation model, Rubingh's model, etc. Thermodynamic parameters including Gibbs energy of micellization and thermodynamic stability were also calculated by both the equation proposed by Molyneux et al. and Maeda's treatment, respectively. The effect of different valent cations on both the mixed cmc of surfactant mixtures and the molar fraction of C12AS in mixed micelle (X1) can be explained theoretically by the salting-out effect, electrostatic interaction and steric effect. For three binary surfactant mixtures, the chain length of hydrophilic group of surfactant results in different micellization behaviors. On adding salts, the interaction parameters show that there exists a synergistic effect between two surfactants, and the effect increases with increasing the ratio of valence (Z) and atom radius (R) of cation, especially, for the C12AS/OP-4 mixture. With increasing the Z/R value of cation, a deviation of X1 from the ideal value shows a divergence for three binary surfactant mixtures because of different hydrophilicities of surfactant. Thermodynamic parameters indicate that the addition of cations with a large Z/R value can be contributive more effectively to the formation of stable mixed micelle than the case in the presence of cations with a small Z/R value.

Volumetric studies on binary mixtures of surfactants N,N′-bis(dimethyldodecyl)-1,2-ethanediammonium dibromide and 1-dodecyl-3-methylimidazolium bromide in aqueous solutions

The micellization of the binary mixed surfactants comprising of the Gemini surfactant N,N′-bis(dimethyldodecyl)-1,2-ethanediammonium dibromide and 1-dodecyl-3-methylimidazolium bromide has been studied by measurements of density. The apparent molar volumes were calculated for various surfactant concentrations and used to determine the critical micelle concentrations of the mixed surfactants at various compositions. An attractive effect was suggested by negative deviations of the experimental CMC values from the ideal ones. The Margules equation was applied to evaluate the micelle compositions, the activity coefficients of both components, and the excess molar Gibbs free energies of the mixed micelles. The stability of mixed micelles was shown to be enhanced as compared to those formed by single surfactants from the negative values of the excess Gibbs free energy. The comparison of the results obtained from the volumetric and ITC measurements indicated a reasonable good accordance with each other and confirmed the reliability of both methods for investigation on the properties of the mixed micelles.

Synergism in Mixed Zwitterionic Surface Activity Ionic Liquid and Anionic Surfactant Solution: Analysis of Interfacial and Micellar Behavior

Synergistic interactions between zwitterionic surface active ionic liquids (SAILs), N-alkyl-N′-carboxymethyl imidazoliumm inner salts ([N-C n , N′-CO2-Im], n = 12, 14), and a traditional twin-tail anionic surfactant (dioctyl sulphosuccinate sodium salt, AOT) in aqueous solution has been studied by surface tension and fluorescence measurements at 298.15 K. The results imply that the mixed systems have superior surface activity in comparison to individual surfactant, and they all present a non-ideal behavior with synergism. The strength of interactions between two surfactants increases with the enhancement of the hydrocarbon chain of the zwitterionic SAILs. Compared with interaction parameters in mixed monolayer, the larger value of interaction parameters in mixed micelles indicates that the mixed micelle formation is more favorable. Additionally, a series of thermodynamic parameters such as the standard Gibbs free energy of adsorption (), the standard Gibbs free energy of micellization (), and excess free energy of micellization (ΔG ex) have been calculated. The negative values of and show that both micellization and adsorption of surfactants are spontaneous, while the negative value of ΔG ex indicates the formation of stable mixed micelles for [N-C n , N′-CO2-Im]/AOT mixture, which can potentially be useful for industrial preparations and medicinal formulations.

Micellization behavior of the amphiphilic drug promethazine hydrochloride with 1-decyl-3-methylimidazolium chloride and its thermodynamic characteristics

The micellization behavior of promethazine hydrochloride (PMT) with 1-decyl-3-methylimidazolium hydrochloride, [C10mim] [Cl], at different temperatures was investigated by using electrical conductivity. The system thermodynamic properties were also studied by calculating various thermodynamic parameters (viz., the standard Gibbs energy change, ΔG°m, the standard enthalpy change, ΔH°m, the standard entropy change, ΔS°m), that favor the micellization in binary mixtures of PMT–[C10mim][Cl] compared with the pure counterparts, at two mole fractions of PMT. The synergistic interaction is examined using Regular Solution Theory for PMT–[C10mim] [Cl] binary mixtures, through the interaction parameter (β) and activity coefficient (f1 and f2) values. The synergism is also revealed in the deviations in the critical micelle concentration (cmc) from the ideal critical micelle concentration (cmc*) and micellar mole fraction (X1) from ideal micellar mole fraction (X1ideal) values. The value of excess free energy (ΔGex) for α1=0.6 at 308K favor the better condition for the formation of the most stable and compact mixed micelles.

PEG-Farnesyl Thiosalicylic Acid Telodendrimer Micelles as an Improved Formulation for Targeted Delivery of Paclitaxel

We have recently designed and developed a dual-functional drug carrier that is based on poly(ethylene glycol) (PEG)-derivatized farnesylthiosalicylate (FTS, a nontoxic Ras antagonist). PEG5K-FTS2 readily form micelles (20–30 nm) and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these micelles. PTX formulated in PEG5K-FTS2 micelles showed an antitumor activity that was more efficacious than Taxol in a syngeneic mouse model of breast cancer (4T1.2). In order to further improve our PEG-FTS micellar system, four PEG-FTS conjugates were developed that vary in the molecular weight of PEG (PEG2K vs PEG5K) and the molar ratio of PEG/FTS (1/2 vs 1/4) in the conjugates. These conjugates were characterized including CMC, drug loading capacity, stability, and their efficacy in delivery of anticancer drug PTX to tumor cells in vitro and in vivo. Our data showed that the conjugates with four FTS molecules were more effective than the conjugates with two molecules of FTS and that FTS conjugates with PEG5K were more effective than the counterparts with PEG2K in forming stable mixed micelles. PTX formulated in PEG5K-FTS4 micelles was the most effective formulation in inhibiting the tumor growth in vivo.

Interacting behavior between amino sulfonate amphoteric surfactant and octylphenol polyoxyethylene ether (7) in aqueous solution and pH effect

The micellization properties of binary mixtures of sodium n-dodecyl diamine sulfonate (C12AS) and octylphenol polyoxyethylene ether (7), OP-7, in aqueous solution at the pH of 3.5, 6.0, and 8.5 have been characterized mainly employing both the UV–vis spectroscopy method, using pyrene as a probe, and the tensiometric method. The interaction parameters between two surfactants, the activity coefficients, the molar fractions of components in mixed micelles, and thermodynamic parameters obtained using some theoretical treatments including the regular solution theory (RST), the phase separation model, the Rubingh model, Maeda's treatment, and so on, were evaluated and the effect of pH on the above parameters was also discussed. Reduction of the mixed critical micelle concentration and negative values of interaction parameter indicate synergistic effect between two surfactants for all mixed systems. The charge density and steric effect of head group of C12AS may play a vital role on the formation of mixed micelle, and the values of pH in aqueous solution can influence the ionic form of C12AS and this steric effect, thus resulting in different interacting behaviors between two surfactants. Thermodynamic data show that the process of micellization for all mixed systems is spontaneous, the stability of mixed micelle is mainly dependent on the components in bulk solution, and the more stable mixed micelle can form in neutral or weak acidic solution.

Role of 1-methyl-3-octylimidazolium chloride in the micellization behavior of amphiphilic drug amitriptyline hydrochloride

The mixed micellization behaviour of amitriptyline hydrochloride (AMT) with ionic liquid (IL) 1-methyl-3-octylimidazolium hydrochloride, [C8mim][Cl], have been investigated using electrical conductivity, at different temperatures. The non-ideal behaviour (i.e., synergistic interaction) of AMT–[C8mim][Cl] binary mixtures, explained by the deviations in critical micelle concentration (cmc) from ideal critical micelle concentration (cmc*) and micellar mole fraction (Xm) from ideal micellar mole fraction (Xideal) values. The values of interaction parameter (β) and activity coefficients (f1 and f2), also confirm the synergistic interaction. The excess free energy (ΔGex) for the AMT–[C8mim][Cl] binary mixtures explains, stability of mixed micelles in comparison to micelles of pure, AMT and [C8mim][Cl]. The calculated thermodynamic parameters (viz., the standard Gibbs energy change, ΔGm∘, the standard enthalpy change, ΔHm∘, the standard entropy change, ΔSm∘), suggest the dehydration of hydrophobic part of the drug at higher temperatures (>313K), not only in case of AMT but also in the presence of [C8mim][Cl].

On the Applicability of the Regular Solution Theory to Multicomponent Systems

AbstractThe critical micelle concentration (CMC) of aqueous mixtures of decyl‐ (C10TAB), dodecyl‐ (C12TAB), and tetradecyl trimethyl ammonium (C14TAB) bromides has been studied in the complete triangular diagram. The results have been analyzed on the basis of the multicomponent regular solution theory for mixed micelles (MRST). It has been found that the mixtures of both, two or three components, contrary to the MRST theory assumptions, have a nonideal behavior. Both the experimental CMC, (CMCijk)exp, and that computed with the MRST, (CMCijk)calc), were lower than the ideal one, (CMCijk)id, indicating an attractive interaction. Moreover, in the majority of the triangular diagram (CMCijk)exp differs significantly from (CMCijk)calc. This suggests that the assumption in the MRST that the interaction among the three different homologue molecules in the mixed micelle computed using the binary regular solution theory interaction parameters obtained from binary mixtures may be an oversimplification. This has been reinforced by analysis of the intramicellar activity coefficients of components, indicating differences in the surrounding of the component molecules when they are in bi‐ or tricomponent micelles. The excess free energy of micellization in three‐component systems indicates that the more stable mixed micelles are those having an excess of the shorter components (C10TAB–C12TAB) and <50 % of the longer one (C14TAB). Furthermore, the common statement that mixtures of homologue surfactants are ideal is not supported by this work.

Mechanism of Solubilization of Phospholipid Liposomes, Revisited

Solubilization of membranes by detergents, commonly described by phase diagrams, is an essential tool in membrane biochemistry and biophysics.In spite of its importance in assuring that the states of aggregation in lipid-detergent mixtures are at equilibrium, the mechanism(s) of solubilization proposed thus far are based on ambiguous analyses of indirect, not necessarily relevant evidence. Our recent analysis of the available data, particularly kinetic studies yielded better understanding of the mechanism.Specifically, at sub-solubilizing detergent concentrations, partitioning of detergent into the bilayers of small vesicles induces size growth via a disproportionation mechanism, at higher detergent concentration, in the range of co-existence of detergent-saturated vesicles and lipid-saturated mixed micelles (between the onset and completion of solubilization) electron micrographs show thread-like micelles and vesicles with pores of increasing size, in agreement with the leakage of entrapped solutes of increasing sizes. In several electro micrographs, thread-like micelles have been observed attached to perforated bilayers. These probably transient microstructures indicate that the micellization of detergent super-saturated vesicles occurs via a series of three stages: (i) bending of detergent-rich monolayers into curved thread-like cover of the perimeter of the holes, (ii) formation of thread-like micelles attached to the vesicles due to the line tension of the holes and (iii) detachment of the (most stable) mixed micelles from the vesicles. All the available data (spectroscopic, microscopic and calorimetric) are consistent with this mechanistic model.

Surface and Solution Properties of Amphiphilic Drug‐Nonionic Surfactant Systems

AbstractA surface tension study was performed on mixed amphiphilic drug‐nonionic surfactant systems. The drugs used were adiphenine hydrochloride and nortriptyline hydrochloride whereas surfactants were ethoxylated sorbitan esters and polyethylene oxide–polypropylene oxide–polyethylene oxide triblocks. The critical micelle concentration (CMC) and CMCid (CMC at ideal mixing condition) values suggest nonideal and attractive interactions among the components. The micellar mole fraction values calculated using Rubingh's model indicate predominance of the nonionic surfactant in micelle formation. The mole fraction of surfactant in mixed monolayer values are greater than values, indicating a greater contribution of surfactant in monolayer formation. Thermodynamic parameters, viz. Gibbs energy of micellization , Gibbs energy of adsorption , and excess free energy of mixed micelles and monolayers were also evaluated. All these values suggest stable mixed micelle and mixed monolayer formation.

Micellization and Phase Behavior of Binary Mixtures of Anionic and Nonionic Surfactants in Aqueous Media

The micellization and phase behavior of the binary mixed systems comprising the anionic surfactants sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/sodium alkyl phenol ether sulfate (APES) and nonionic polyoxyethylene alkyl ether surfactants (C10E8/C10E10/C13E10) have been investigated by surface tension, fluorescence spectroscopy, and cloud point measurements. Various micellar characteristics, surface active properties, thermodynamic parameters, aggregation numbers, and Stern–Volmer constants have been evaluated for these systems. Lower cmc values, negative interaction and thermodynamic parameters, higher aggregation numbers, and improved surface active properties for the proposed mixed systems indicate the existence of strong synergistic interactions and the formation of thermodynamically stable mixed micelles. Observed elevation in the cloud point (CP) shift suggests the formation of charged micelles that increases the intermicellar repulsions and poses a hindrance to the coacervation of micelles. It sub...

Thermosensitive, biocompatible and antifouling nanogels prepared via aqueous raft dispersion polymerization for targeted drug delivery

Poly(5-propyl-1,3-dioxan-2-one)-b-dimethylamine modified polycarbonate (PC(MPpC-MMA)) and poly(ethylene glycol)-b-carboxylated polycarbonate (PEG-PCCOOH) diblock copolymers were prepared to construct a pH responsive, highly stable and biodegradable mixed micelle. The two copolymers self-assembled into the mixed micelle in pH 7.4 PBS driven by electrostatic and hydrophobic interactions. PC(MPpC-MMA) with hydrophobic inner core was used for carrying drug and the dimethylamine part was designed as a trigger to disassemble the mixed micelle. PEG-PCCOOH could shield the positive character of the micelle which might show disadvantage to normal tissue. In addition, the free carboxyl groups could further increase the loading efficiency of positive charged drugs. The size and zeta potential of the micelle gradually decreased with increasing the molar ratio of PEG-PCCOOH to PC(MPpC-MMA). These mixed micelles could withstand high ionic strength of plasma and were rather stable for long time storage. However, via decrease of pH value from 7.4 to 5.0, they could undergo dissociation into smaller nanoparticles which were in a diameter of 20 nm and showed positive surface nature. In vitro drug delivery studies showed a faster release rate at pH 5.0 than that at pH 7.4. The MTT assays demonstrated potent cytotoxic activity against HepG2 cells. All these results indicate that the newly mixed polycarbonate micelle can show great potential in biomedical field.

Construction of mixed micelle with cross-linked core and dual responsive shells

A core cross-linked (CCL) mixed micelle with dual responsive shells was constructed from two amphiphilic block copolymers poly(methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate)-b- poly(N-isopropylacrylamide) (P(MMA-co-MPMA)-b-PNIPAAm) and P(MMA-co-MPMA)-b-poly(2-(diethylamino)ethyl methacrylate) (P(MMA-co-MPMA)-b-PDEA) via a two-step process: cooperative aggregation of the two block copolymers into core-shell mixed micelles in acidic aqueous solution at room temperature followed by cross-linking of the hydrophobic core via an acid-catalyzed sol–gel process. The reversibly structural transformation of the core-shell mixed micelles into core-shell-corona (CSC) mixed micelles took place when subjected to elevated temperature or pH value, that is, high temperature resulted in the fabrication of CSC mixed micelle with shrunk PNIPAAm chains as the inner shell and stretched PDEA chains as the outer corona, and alkaline pH led to the formation of CSC mixed micelle with collapsed PDEA chains as the inner shell and extended PNIPAAm chains as the outer corona. Due to the existence of thermo- and pH- dually responsive shells, the structurally stable CCL mixed micelle may find practical applications in biomedical fields such as drug delivery and intelligent release.

Effect of Surfactants on Association Characteristics of Di- and Triblock Copolymers of Oxyethylene and Oxybutylene in Aqueous Solutions: Dilute Solution Phase Diagrams, SANS, and Viscosity Measurements at Different Temperatures

The interactions in poly(oxyethylene) (E) – poly(oxybutylene) (B) of EB or EBE type block copolymers-sodium dodoecyl sulfate (SDS) or dodecyltrimethylammonium bromide (DTAB) and/or t-octylphenoxy polyethoxyethanol, (TX-100) have been monitored as a function of surfactant concentration and temperature. The addition of ionic surfactants to copolymer micellar solutions in general induced not only shape transition from spherical to prolate ellipsoids at 30∘C in the copolymer micelles but also destabilize them and even suppress the micelle formation at high surfactant loading. DTAB destabilizes the copolymer micelles more than SDS. TX-100, being nonionic, however, forms stable mixed micelles. The block copolymer-surfactant complexes are hydrophilic in nature and are characterized by high turbid and cloud points. Triblock copolymer micelles got easily destabilized than the diblock copolymer ones, indicating the importance of the interaction between the hydrophilic E chains and surfactants. The effects of destabilization of the copolymer micelles are more dominating than the micellar growth at elevated temperatures, which is otherwise predominant in case of copolymer micelles alone.

Synergistic Interactions in Mixed Micelles of Cationic 14-<em>s</em>-14 Gemini with Conventional Surfactants: Spacer and Counterion Effects

The mixed micelle formation of binary cationic 14-s-14 gemini with conventional single chain surfactants was studied by conductivity measurements. The critical micelle concentration (cmc) and the degree of counterion binding values (g) of the binary systems were determined. The results were analyzed by applying regular solution theory (RST) to calculate micellar compositions (X), activity coefficients (f1, f2), and the interaction parameters (β). The synergistic interactions of all the investigated cationic gemini+conventional surfactant combinations were found to be dependent upon the length of hydrophobic spacer of the gemini surfactant. The excess Gibbs free energy of mixing was evaluated, and it indicated relatively more stable mixed micelles for the binary combinations.

Interaction and Stability of Mixed Micelle and Monolayer of Nonionic and Cationic Surfactant Mixtures

Interaction and stability of binary mixtures of cationic surfactants hexadecyltrimethylammonium bromide (HTAB) or hexadecylpyridinium bromide (HPyBr) with nonionic surfactant decanoyl-N-methyl-glucamide (Mega-10) have been studied at different mole fraction of cationic surfactants by using interfacial tension measurements and fluorescence probe techniques. From interfacial tension measurements, the critical micellar concentration and various interfacial thermodynamic parameters have been evaluated. The experimental cmc's were analyzed with the pseudophase separation model, the regular solution theory, and the Maeda's approach. These approaches allowed us to determine the interaction parameter and composition in the mixed state. By using the static quenching method, the mean micellar aggregation numbers of pure and mixed micelles of HTAB + Mega-10 were obtained. It has been observed that the aggregation number of mixed micelles deviates negatively from the ideal behavior. The micropolarity of the micelle was monitored with pyrene fluorescence intensity ratio and found to be increase with the increase of ionic content. The polarization of fluorescence probe Rhodamine B was monitored at different mole fraction of cationic surfactants.

Mixed micelles made of Pluronic and PEG-PE for solubilization of poorly soluble anticancer drug paclitaxel

Stable mixed micelles have been prepared based on Pluronic 105 and poly(ethylene glycol)-phosphatidyl ethanolamine conjugate (PEG-PE) and loaded with the poorly soluble anticancer drug, paclitaxel (PCT). To increase the drug loading, Pluronic L61 was also added to the composition. Drug concentration was achieved of up to 450 μg/mL of the micelle suspension, while the solubility of the free drug is about 1 μg/mL. The PCT-loaded mixed micelles were stable upon storage and firmly retained the incorporated drug. PCT-loaded mixed micelles demonstrated high cytotoxicity against MCF-7 cancer cells in vitro.