1: J Control Release. 2007 Feb 12;117(2):196-203. Epub 2006 Nov 7.

Characterization of self-assembling copolymers in aqueous solutions using
Electron Paramagnetic Resonance and Fluorescence spectroscopy.

Beghein N, Rouxhet L, Dinguizli M, Brewster ME, Arien A, Preat V, Habib JL,
Gallez B.

Universite Catholique de Louvain, Unite de Chimie Pharmaceutique et
Radiopharmacie and Unite de Resonance Magnetique Biomedicale, Avenue Mounier
73.40, 1200 Brussels, Belgium.

Electron Paramagnetic Resonance and fluorescence spectroscopy have been used to
determine the micropolarity and microviscosity of self-assembling systems based
on mmePEG-p(CL-co-TMC) having different PEG chain lengths and different CL/TMC
ratios and PEG/MOG/SA (45/5/50) polymers with different PEG chain lengths. Four
reporter probes have been used: two spin probes, 16-doxyl stearic acid and
5-doxylstearic acid, and two fluorescent probes, pyrene and 1,3-bis(1-pyrenyl)
propane (P3P). We found that the micelles based on mmePEG-p(CL-co-TMC) polymers
are of a biphasic nature. The micelles are made of a hydrophilic corona with low
viscosity while the core of the micelle is more hydrophobic and more viscous.
The outer shell is made up of PEG chains, the hydrophobic part of the chains
making the core. The partial hydration of the shell seems to lead to a looser
chain network than that associated with deeper domains in the micelles. By
contrast, in micelles composed of PEG/MOG/SA, there is no clear domain
separation. This is consistent with a spatial configuration of random polymeric
chains forming a loose network. In these micelles, the microviscosity is low and
the hydrophobicity is high.

PMID: 17196699 [PubMed - in process]

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