Presentation day

Wednesday  2:10 PM

 

TITLE

Exploration of spatial distribution of drug molecules incorporated in polymer micelles with
anomalous small-angle X-ray scattering

 

Abstract

Polymer micelles are widely studied as drug vehicles in drug delivery system (DDS)
because they can incorporate hydrophobic drugs in their cores. For drug vehicles, stable retention of drug
molecules is requested to avoid side effects. Retention of drug molecules should be related to how they
distribute in the core of polymer micelles. Therefore, it is of great importance to visualize dispersion of drug
molecules in the polymer micelles. Thus, in this study, we explored the spatial distribution of Br-labeled
hydrophobic molecules in polymer micelles composed of poly(N,N-dimethylaminoethyl methacrylate)-blockpoly(
methyl methacrylate) (PDMAEMA-b-PMMA) with anomalous small-angle X-ray scattering (ASAXS)
near Br K-edge.
Fig. 1 shows comparison between SAXS and ASAXS profiles for the PDMAEMA-b-PMMA micelle
containing 9-bromofluorene (BrF). SAXS profile corresponds to form factor of hydrophobic core of the
PDMAEMA-b-PMMA micelle due to contrast matching between PDMAEMA and H2O, whereas ASAXS
profile corresponds to spatial distribution of BrF in the micelle. Radius of gyration (Rg) of spatial distribution
of BrF (1.5 nm) is much smaller than that of the hydrophobic core of the micelle (4.5 nm). This result
indicates that the micelle has BrF-rich domain in the hydrophobic core. Similar analyses were also
performed for the micelles containing bromobenzen (BrBz) and 4-bromobenzyl alcohol (BrBzOH). The
ASAXS results show that the BrBz-containing micelle also has BrBz-rich domain in the hydrophobic core,
whereas BrBzOH is homogeneously dispersed in the hydrophobic core. These results suggest that
hydrophobicity or polarity of drug molecules have significant effect on their spatial distribution in polymer
micelles.