Micellar solubilization of tributylphosphate in aqueous solutions of Pluronic block copolymers

Structural Behavior of Amphiphilic Triblock Copolymer P104/Water System

A detailed study of the different structural transitions of the triblock copolymer PEO₂₇-PPO₆₁-PEO₂₇ (P104) in water, in the dilute and semi-dilute regions, is addressed here as a function of temperature and P104 concentration (C_P104) by mean of complimentary methods: viscosimetry, densimetry, dynamic light scattering, turbidimetry, polarized microscopy, and rheometry. The hydration profile was calculated through density and sound velocity measurements. It was possible to identify the regions where monomers exist, spherical micelle formation, elongated cylindrical micelles formation, clouding points, and liquid crystalline behavior. We report a partial phase diagram including information for P104 concentrations from 1 × 10^-4 to 90 wt.% and temperatures from 20 to 75 °C that will be helpful for further interaction studies with hydrophobic molecules or active principles for drug delivery.

Water-pluronic-ionic liquid based microemulsions: Preparation, characterization and application as micro-reactor for enhanced catalytic activity of Cytochrome-c

Microemulsions (µEs), comprising water as polar component, pluronic (normal, L35 and reverse, 10R5) as surfactant and a hydrophobic ionic liquid (HIL) as non-polar component have been prepared and characterized. Owing to higher surface activity, pluronics have promoted the formation of µEs without the use of co-surfactant. Thus prepared µEs have been utilized as nano-reactors for the oxidation of guaiacol in the presence of Cytochrome-c (Cyt-c) at 15, 20, and 25 °C. A 3.2- and 1.3-fold increase in the rate of formation of product of enzymatic catalysis in direct µE (HIL-in-water) with reverse pluronic (10R5) is observed at 15 and 20 °C as compared to that in buffer. However, negligible enzymatic activity is observed in the direct µE formed by normal pluronic (L35). The catalytic activity of Cyt-c decreases in reverse µEs (water-in-HIL) as compared to direct µEs irrespective of the nature of pluronic used. The contrasting nature of nano-interfaces formed by pluronics in µEs and the extent of hydration of these nano-interfaces controlled by temperature exerts varying influence on the catalytic activity of Cyt-c. It is expected that the present work would result in providing a versatile platform for the creation of new IL and pluronic-based µEs for bio-catalytic applications, which have never been reported.

Tunable Polymeric Mixed Micellar Nanoassemblies of Lutrol F127/Gelucire 44/14 for Oral Delivery of Praziquantel: A Promising Nanovector against Hymenolepis nana in Experimentally-Infected Rats

Hymenolepiasis represents a parasitic infection of common prevalence in pediatrics with intimidating impacts, particularly amongst immunocompromised patients. The present work aimed to snowball the curative outcomes of the current mainstay of hymenolepiasis chemotherapy, praziquantel (PRZ), through assembly of polymeric mixed micelles (PMMs). Such innovative nano-cargo could consolidate PRZ hydrosolubility, extend its circulation time and eventually upraise its bioavailability, thus accomplishing a nanoparadigm for hymenolepiasis tackling at lower dose levels. For consummating this goal, PRZ-PMMs were tailored via thin-film hydration technique integrating a binary system of Lutrol F127 and Gelucire 44/14. Box-Behnken design was planned for optimizing the nanoformulation variables employing Design-Expert^® software. Also, in Hymenolepis nana-infected rats, the pharmacodynamics of the optimal micellar formulation versus the analogous crude PRZ suspension were scrutinized on the 1st and 3rd days after administration of a single oral dose (12.5 or 25 mg/kg). Moreover, in vitro ovicidal activity of the monitored formulations was estimated utilizing Fuchsin vital stain. Furthermore, the in vivo pharmacokinetics were assessed in rats. The optimum PRZ-PMMs disclosed conciliation between thermodynamic and kinetic stability, high entrapment efficiency (86.29%), spherical nanosized morphology (15.18 nm), and controlled-release characteristics over 24 h (78.22%). ¹H NMR studies verified PRZ assimilation within the micellar core. Additionally, the in vivo results highlighted a significant boosted efficacy of PRZ-PMMs manifested by fecal eggs output and worm burden reduction, which was clearly evident at the lesser PRZ dose, besides a reversed effect for the intestinal histological disruptions. At 50 µg/mL, PRZ-PMMs increased the percent of non-viable eggs to 100% versus 47% for crude PRZ, whilst shell destruction and loss of embryo were only clear with the applied nano-cargo. Moreover, superior bioavailability by 3.43-fold with elongated residence time was measured for PRZ-PMMs compared to PRZ suspension. Practically, our results unravel the potential of PRZ-PMMs as an oral promising tolerable lower dose nanoplatform for more competent PRZ mass chemotherapy.

TBP induced double cloud point in aqueous EO13PO30EO13 solutions: investigating the evolution of associated micellar characteristics as a function of temperature

TBP solubilized Pluronic L64 solutions exhibit inter-micellar attraction driven micellar cluster formation upon cooling, which is unique in non-ionic micellar systems.

Solubilisation of Oils of Different Polarity in Aqueous Solutions of Pluronic Triblock Copolymers

The micellisation behaviour of Pluronic F108 was studied as a function of the addition of various more or less polar additives, such as hexanol, geraniol, toluene, methyl heptanoate, polyproylene oxide (PPO), and nitropropane. It is observed that the critical micellisation temperature (CMT) is substantially reduced upon the solubilisation of most of the additives (but not for methyl heptanoate and PPO) and at the same time the concomitant enthalpy of micellisation becomes larger. Both changes in CMT and enthalpy of micellisation are linear with respect to the concentration of additive. The pronouncedness of this effect is related to the polarity of the additive (as characterised for instance by its water solubility) and for instance similar effects are achieved for much smaller amounts of geraniol compared to hexanol. The structural evolution of the Pluronic solutions upon addition of the additives was also followed by SANS experiments and show that relatively small amounts of added solubilisate can have a very pronounced effect on the extent of the micellisation and size of the aggregates formed, i.e., effectively lowering the CMT by rendering the amphiphilic system more hydrophobic and especially the medium chain alcohols show pronounced synergism.

Small-angle neutron scattering study of solubilization of tributyl phosphate in aqueous solutions of L64 Pluronic triblock copolymers

We have studied the solubilization behavior of tributylphosphate (TBP) in aqueous solutions of L64-Pluronics, using light and small angle neutron scattering (SANS). Varying the temperature and the oil content, the system presents a nontrivial phase behavior. In particular, at 308 K, a first solubilization followed by an emulsification failure and a resolubilization is found. We have measured the microstructure by SANS and characterized the microemulsion droplet core size, corona thickness, polydispersity, and interactions. It is shown that at low oil content, the system is made of small swollen micelles. After the phase separation, the resolubilization is carried by larger oil droplets decorated by copolymer. From specific surface measurements at large angles, a surprising change in surfactant conformation is found to accompany this morphological evolution which is also supported by previous results obtained from ¹H NMR experiments. In independent measurements, our structural modeling is confirmed using contrast-variation SANS.

Swelling of ionic and nonionic surfactant micelles by high pressure gases

The influence of different solvent environments on the size, shape, and characteristics of surfactant micelles of Pluronic F127 and CTAB was investigated by small-angle neutron scattering (SANS). SANS experiments were undertaken on dilute micellar surfactant solutions of F127 and CTAB that between them were exposed to liquid and supercritical carbon dioxide, liquid propane, ethane, and heptane under various pressures and temperatures. Swelling of the surfactant micelles could be directly related to the solubility of the solvents within the micelles, especially within their cores. Carbon dioxide produced the largest swelling of the Pluronic F127 micelles, compared to propane and ethane, which mirrors the solubility of the gases in the PPO core of the micelles. Conversely, the extent of swelling of the cores of CTAB micelles was greater with propane compared to carbon dioxide, which again relates to the solubility of the solvents in the alkane core of the CTAB micelles.