Biodegradable Thermogelling Poly[(R)-3-hydroxybutyrate]-Based Block Copolymers: Micellization, Gelation, and Cytotoxicity and Cell Culture Studies

A series of biodegradable multiblock poly(ester urethane)s having poly [(R)-3-hydroxybutyrate] (PHB), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments was prepared. The critical micellization concentration (CMCs) of these water-soluble poly(ester urethane)s were determined at different temperatures in order to calculate the thermodynamic parameters for the process of micelle formation. The process for micelle formation was found to be entropy-driven. The thermogelling behavior of the aqueous polymer solution was studied by H-1 and C-13 NMR spectroscopy at different temperatures, We obtained valuable molecular level information regarding the state of the copolymer in solution based on the variation of the peak widths. Cytotoxicity studies performed on the extracts of the copolymer gel indicate good cell compatibility. Cells attach on the surface of the gel much better than on the commercially available PEG-PPG-PEG triblock copolymer. These studies indicate a potential for the copolymer gel to be used for tissue engineering applications.