Biomedical applications of dendrimer-modified polyurethanes with PEO (polyethylene oxide) attached.

Abstract

A novel approach was used to synthesize bioactive polyurethanes by applying polypropylenimine octaamine dendrimers as the chain extenders, while another approach trying to incorporate star PEO (polyethylene oxide) directly into polyurethane failed to attain appropriate polymers. A protection/deprotection strategy was used to incorporate the dendrimers into the polyurethane chains, then PEO was chemically attached after deprotection to increase the biocompatibility of the material. A generation 2.0 polypropylenimine octaamine dendrimer which has eight arms ending with amine groups, was used for the modification. The dendrimers were protected using the N-hydroxy-succinimide ester of a tert-butyloxycarbonyl (tBOC)-protected alanine or 9-Fluorenylmethyloxycarbonyl chlorocarbonate (Fmoc) in methylene chloride-triethylamine. A molar ratio of 6:1 (protecting group:dendrimer) was used to get a statistical distribution of protected dendrimers in which most of the dendrimers would have 6 arms protected. The partially protected dendrimers were used with ethylene diamine (ED) or butanediol (BDO) as a chain extender (molar ratio of dendrimer ED/DO = 1:9) to produce the dendrimer modified polyurethanes. After deprotection of the dendrimers, PEG-SPA (Polyethylene Glycol-Succinimidyl Propionate) was used to attach PEO to the polyurethane chains. (Abstract shortened by UMI.)