Biodegradable nanospheres self-assembled from complementary hydrophilic dextran macromers

Supramolecular self-assemblies are predominately driven by noncovalent molecular forces, and electrostatic interactions are the major force for charged molecules. In this paper, we demonstrate the self-assembly of hollow nanospheres from oppositely charged dextran-based hydrophilic macromers. Charged dextran derivatives were obtained by incorporating 2-bromoethylamine (Dex-BH) and chloroacetic acid (Dex-CA) into dextran. In a pH 5.0 buffer solution, Dex-BH and Dex-CA became protonated and deprotonated, respectively, and self-assembled into well-defined nanospheres. Dynamic light scattering (DLS) detected that these nanospheres have a uniform size distribution with a mean diameter of approximately 160 nm, but their size and distribution are largely dependent on molecular weight and pH value. Scanning electron microscopy (SEM) analysis revealed that these nanospheres could form a hollow architecture, which might be attributed to the hydrophilic characteristics of dextran macromers. An in vitro albumin release study indicates that the release rate reflects the nanosphere architecture, and further demonstrates their potential as drug delivery vehicles. (C) 2011 Elsevier Ltd. All rights reserved.