Polymeric micelles have been extensively studied as nano-scale drug carriers. The studies of the micellar inner-structures that encapsulate hydrophobic drugs is important to design effective carrier. Poly(ethylene glycol)-block-poly(partially benzyl-esterified aspartic acid) is one of the most studied systems from both synthesis and biological aspects. However, little know about fundamental physical properties. We synthesized various samples with different compositions and characterized them with field flow fractionation (FFF) and synchrotron small-angle X-ray scattering (SAXS).<br/><br/>We found that the major factor to determine the micellar structures and the aggregation number is the benzylation rate of the core block: hydrophobicity of the core. By knowing the aggregation number and the core size, we can determined how the tethered PEG chains are overcrowding. We are first to quantitatively correlate the PEG-chain crowdedness and biological activity of the micelles.<br/><br/>We also used as hydrophobic compound tetrabromocathecol (TBC) as a drug-equivalent model molecule. The bromine atoms in TBC act as probes in anomalous small-angle X-ray scattering (ASAXS) allowing for its localization in the polymeric micelles. We found that the radius of the spherical region populated with bromine atoms was larger than the one of the sphere corresponding to the hydrophobic core of the micelle. This result suggests that the TBC molecules infiltrate the PEG hydrophilic domain in the vicinity of the core/shell interface.

Characterizing polymeric micelles employed for DDS by use of SAXS and FFF

250th National Meeting (2015)

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