Development of biodegradable and injectable macromers based on poly(ethylene glycol) and diacid monomers

Novel biodegradable injectable poly(ethylene glycol)-(PEG) based macromers were synthesized by reacting low-molecular weight PEG (MW: 200) and dicarboxylic acids such as sebacic acid or terephthalic acid. Chemical structures of the resulting polymers were confirmed by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy characterizations. Differential scanning calorimetry (DSC) showed that these polymers were completely amorphous above room temperature. After photopolymerization, dynamic elastic shear modulus of the crosslinked polymers was up to 1.5 MPa and compressive modulus was up to 2.2 MPa depending on the polymer composition. The in vitro degradation study showed that mass losses of these polymers were gradually decreased over 23 weeks of period in simulated body fluid. By incorporating up to 30 wt % of 2-hydroxyethyl methylmethacrylate (HEMA) into the crosslinking network, the dynamic elastic modulus and compressive modulus was significantly increased up to 7.2 and 3.2 MPa, respectively. HEMA incorporation also accelerated the degradation as indicated by substantially higher mass loss of up to 27% after 20 weeks of incubation. Cytocompatability studies using osteoblasts and neural cells revealed that cell metabolic activity on these polymers with or without HEMA was close to the control tissue culture polystyrene. The PEG-based macromers developed in this study may be useful as scaffolds or cell carriers for tissue engineering applications.