Pluronics micelles

Time-resolved in situ Small Angle Neutron Scattering (SANS) investigations have provided direct experimental evidence for the initial steps in the formation of the SBA-15 mesoporous material, prepared using the non-ionic tri-block copolymer Pluronic 123 and TEOS as silica precursor. Upon time, three steps take place during the cooperative self-assembly of the Pluronic micelles and the silica species. First, the hydrolysis of TEOS is completed, without modifications of the Pluronic spherical micelles. Then, when silica species begin to interact with the micelles, a transformation from spherical to cylindrical micelles takes place before the precipitation of the ordered SBA-15 material. Lastly, the precipitation occurs and hybrid cylindrical micelles assemble into the two-dimensional hexagonal structure of SBA-15. 

In terms of contrast, Pluronic micelles have a much more higher contrast using SANS (with D20 as a solvent) than with SAXS. It is illustrated in figure 5, where the SANS and SAXS curves in absolute units are compared for the same sample, micelles of P123 in pure D20 at 40°C and at a volume fraction of 2.6 %. The absolute intensity of the SANS curve is about 103 times greater than the SAXS ones. The maximal flux on the D22 experiment is about 10s neutrons/s. Then, in order to perform kinetics experiments with SAXS, with a temporal resolution equal or better than 30 s, the high flux of a synchrotron source (10nphotons/s or more) is needed. 

Nystatin Micelle-Water Partition Coefficients and Pluronic Micelle Core Polarities as a Function of Pluronic and Temperature... 

Kabanov, A.V., et al. 1992. Pluronic micelles as a tool for low-molecular compound vector delivery into a cell Effect of Staphylococcus aureus enterotoxin B on cell loading with micelle incorporated fluorescent dye. Biochem Int 26 1035. 

In particular, the system was able to overcome drug resistance and cross the blood-brain barrier. Preclinical studies on the DOX-loaded pluronic micelles SP1049C revealed superior tumor inhibition and extended lifespan to free drug. Phase I clinical studies showed a lower degree of DOX toxicity for SP1049C than for the free DOX, and three of 21 patients treated with SP1049C had transient partial responses. ... 

The studies in our group also indicated Pluronic block copolymers can enhance the brain penetration of selected drugs in vivo. Kabanov et al. (15,66) demonstrated increased delivery of the neuroleptic drug, haloperidol, to the brain in mice with the use of insulin or antibody conjugated Pluronic micelles. In addition, haloperidol delivery to the brain was... 

Rapoport N. Stabilization and activation of Pluronic micelles for tumor-targeted drug delivery. Colloids Surf B 1999 16 93-111. 

Page M, Alakhov VY. Elimination of P-gp-mediated multidrug resistance by solubilization in Pluronic micelles. Proceedings of the Annual Meeting of the American Association for Cancer Research (AACR), Philadelphia, PA, USA. Vol. 33, 1992. 

Pluronic formulations below their CMC with anticancer drugs have been effective in treating MDR tumors [222], whereby these positive results are linked to the functions of Pluronic (PEO/PPO/PEO) block copolymers in crossing the plasma membrane, suppressing ATP production, and to gene modulation. The formulation seems to be effective with MDR tumors but less so with sensitive tumors. This approach lacks tumor specificity, and little is known about its influence on normal cells that express Pgp. On the other hand, Pluronic micelles under ultrasound stimulation have been effective in treating MDR cells [219]. 

Pluronic poloxamers can be suitable carrier materials for this purpose due to their capacity to enhance the absorption of water-insoluble compounds by formation of micelles in aqueous environment that can host such hydrophobic compounds. Different authors have described the formation of quercetin-loaded Pluronic micelles by thin-film hydration methods and have shown that the resulting micelles enhanced the solubilization of the active compound. Ghanem et al. described the encapsulation of quercetin in Pluronic F127 via spray drying. ... 

Parmar, A., Singh, K., Bahadur, A., Marangoni, G., and Bahadnr, P. Interaction and solnbilization of some phenolic antioxidants in Pluronic micelles. Colloid and Surfaces B 86 (2011) 319-326. 

Kwon SH, Kim SY, Ha KW et al (2007) Pharmaceutical evaluation of genestein-loaded pluronic micelles for oral delivery. Arch Pharm Res 13 1138-1143... 

Pyrene molecules are hydrophobic, and thus are expected to be fully encapsulated in the PPO cores of Pluronic micelles [167], which may offer valuable information on the degree of hydration of the micellar core. Using pyrene as a fluorescent probe (excitation at A = 339 nm), the variation in the IJIy vibronic emission ratio upon gradual decrease of the solution temperature (from 60 to 10°C) in the absence or presence of coencapsulated ibuprofen (0.2 wt%), aspirin (0.5 wt%), and erythromycin (0.05 wt%) was monitored (Fig. 13.19). 

Williams DRM Bostrom M Wright M, Kurumada K-i, Robinson B Rates of incorporation of small molecules into pluronic micelles 8... 

Bae, K. H., Choi, S. H., Park, S. Y., Lee, Y, Park, T. G. (2006). Thermosensitive pluronic micelles stabilized by shell cross-linking with gold nanoparticles. Langmuir, 22, 6380-6384. 

Mortensen, K., Batsberg, W., Hvidt, S. (2008). Effects of PEO-PPO diblock impurities on the cubic structure of aqueous PEO-PPO-PEO pluronics micelles fee and bcc ordered structures in F127. Macromolecules, 41, 1720-1727. 

Block copolymer micelle studies carried out with poly(ethylene o iA )-block-poly(propylene oxide)-bZocA -poly(ethylene oxide) triblock copolymers (Pluronics) and Coumarin 343 [29, 30] as a fluorescent probe demonstrated that both the fluorescence lifetime and the emission maximum strongly depend on the probe localization in the Pluronic micelle. Water molecules in the interior of the micelles close to the core/shell interface relaxed much more slowly than those in the outer part of the shell which had almost the same mobility as bulk water. 

Analysis of the Structure, Interaction, and Viscosity of Pluronic Micelles in Aqueous Solutions by Combined Neutron and Light Scatterings... 

Water penetration profile is an interesting result. The micelle has regions of core and shell with distinctly different polymer and solvent volume fractions. The core of a Pluronic micelle is not completely dry, in agreement with theoretical prediction (IT). The polymer volume fraction in foe core is about 92 to 97 % at higher temperatures, independent of tempo-ature and concentration. This suggests that oniy... 

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