posted on 2016-11-22, 00:00authored byVo Thu
An Nguyen, Marie-Claire De Pauw-Gillet, Olivier Sandre, Mario Gauthier
Water-dispersible
polyion complex (PIC) micelles were prepared
by the self-assembly of an arborescent polystyrene-graft-poly(2-vinylpyridine) copolymer (denoted G0PS-g-P2VP or G1) serving as core and a poly(acrylic acid)-block-poly(2-hydroxyethyl acrylate) (PAA-b-PHEA) double-hydrophilic
block copolymer (DHBC) forming a shell. Varying the density of hydrophilic
polymer chains in the stabilizing layer provided control over the
size and structure of the entities obtained, from large flocculated
species to stable isolated PIC micelles with diameters ranging from
42 to 67 nm. The hydrodynamic radius (determined from dynamic light
scattering measurements), and the weight-average molar mass (M̅w) and radius of gyration of the scatterers
(extracted from static multiangle light scattering data) evidenced
the formation of either isolated or aggregated PIC micelles depending
on the self-assembly conditions used (pH, concentration and mixing
molar ratio f). Changes in the morphology of the
arborescent copolymer after complexation were observed by atomic force
microscopy (AFM) imaging. In particular, by varying the force applied
with the AFM tip on the samples, the core–shell structure of
the PIC micelles was clearly evidenced. The PIC micelles displayed
no significant cytotoxicity toward mouse fibroblast L929 cells, a
standard cell line recommended for toxicity assays, due to the good
biocompatibility of the hydrophilic PAA-b-PHEA shell.
In spite of a negative residual zeta potential due to an excess of
negative charges, fluorescently labeled PIC* micelles were successfully
internalized by L929 cells, as confirmed by laser scanning confocal
microscopy (LSCM) and transmission electron microscopy (TEM).