Sulfobutylated poly(vinyl alcohol)-graft-poly(lactide-co-glycolide)s facilitate the preparation of small negatively charged biodegradable nanospheres.

The manufacturing conditions for small nanoparticles (NP) in the range of 100-500 nm are difficult to control. Novel biodegradable, brush-like branched polyesters with a negatively charged hydrophilic backbone, poly(2-sulfobutyl-vinyl alcohol)-g-poly(lactide-co-glycolide), facilitate their preparation by a modified solvent displacement procedure. Furthermore, the structure and the surface properties of the colloidal systems are investigated. NP were characterized by photon correlation spectroscopy (PCS), zeta-potential measurement (ZPM), particle charge detection (PCD), nuclear magnetic resonance spectroscopy (NMR) and transmission electron microscopy (TEM). Varying the manufacturing conditions NP with mean diameters of about 100 up to 500 nm and, depending on polymer composition, negatively charged surfaces were obtained. The NP visualized by TEM showed smooth surfaces. Furthermore, surface characterization and NMR studies suggested a core/corona structure of the particles. This study demonstrates that a simple solvent displacement technique can be used for the reproducible preparation of discrete NP with defined negatively charged surfaces and narrow size distributions. These NP may have potential for peroral or parenteral protein delivery systems.