Collect. Czech. Chem. Commun. 2004, 69, 1643-1656

Degradation Behavior of Poly(ethylene glycol) Diblock and Multiblock Polymers with Hydrolytically Degradable Ester Linkages

Alena Braunov√°*, Michal Pechar and Karel Ulbrich

Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, 162 06 Prague 6, Czech Republic


Diblock and multiblock polymers of poly(ethylene glycol) containing degradable ester bonds between the blocks were synthesized and characterized. Monofunctional poly(ethylene glycol) (PEG 2000) was modified by aliphatic dicarboxylic acids (malonic, succinic, glutaric, maleic) to obtain monocarboxylic polymers PEG-COOH containing ester bonds. Diblock polymers (4000) were prepared by polycondensation of a diamine (ethane-1,2-diamine, L-lysine) and the semitelechelic PEG-COOH. The relationship between the structure of the linkage connecting two PEG blocks and the rate of its hydrolytic degradation was studied at pH 5.5, 7.4 and 8.0. The rate of hydrolysis of all polymers was significant already under mild alkaline conditions (pH 7.4 and 8.0) and increased with increasing pH. The ester bonds of polymers with saturated dicarboxylic acid moieties were stable at pH 5.5. However, the presence of double bond in the acid moiety substantially decreased the stability of the polymer not only in alkaline but also in acid medium. The results of this model study can be utilized in the design of biodegradable high-molecular-weight drug carriers and polymers for preparation of "stealth" systems intended for therapeutic application.

Keywords: PEG; Block copolymers; Degradable bonds; pH sensitivity; Hydrolyses; Protein modification; Drug release; Polymer drugs; Tumour therapy; Drug carriers; Biocompatible polymers.

References: 21 live references.