Poly(organo phosphazene) nanoparticles surface modified with poly(ethylene oxide)

✍ Scribed by J. Vandorpe; E. Schacht; S. Stolnik; M. C. Garnett; M. C. Davies; L. Illum; S. S. Davis

• Book ID: 102651995
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 738 KB
• Volume: 52
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/(sici)1097-0290(19961005)52:1<89::aid-bit8>3.0.co;2-v

✦ Synopsis

The use of biodegradable derivatives of poly(organo phosphazenes) for the preparation of nanoparticles and their surface modification with the novel poly(ethy1ene oxide) derivative of poly(organ0 phosphazene) has been assessed using a range of in vitro characterization methods. The nanoparticles were produced by the precipitation solvent evaporation method from the derivative cosubstituted with phenylalanine and glycine ethyl ester side groups. A reduction in particle size to less than 200 nm was achieved by an increase in pH of the preparation medium. The formation (and colloidal stability) of these nanoparticles seems t o be controlled by two opposite effects: attractive hydrophobic interactions between phenylalanine ester groups and electrostatic repulsions arising from the carboxyl groups formed due t o (partial) hydrolysis of the ester bond(s) at the high pH of the preparation medium. The poly[(glycine ethyl esterlphosphazenel derivative containing 5000-Da poly(ethy1ene oxide) as 5% of the side groups was used for the surface modification of nanoparticles. Adsorbed onto the particles, the polymer produced a thick coating layer of approximately 35 nm. The coated nanoparticles exhibited reduced surface negative potential and improved colloidal stability toward electrolyte-induced flocculation, relative to the uncoated system. However, the steric stabilization provided was less effective than that of a Poloxamine 908 coating. This difference in effectiveness of the steric stabilization might indicate that, although both the stabilizing polymers possess a 5000-Da poly(ethy1ene oxide) moiety, there is a difference in the arrangements of these poly(ethy1ene oxide) chains at the particle surface.