Synthesis and characterization of degradable bioconjugated hydrogels with hyperbranched multifunctional cross-linkers.

Hyperbranched poly(ester amide) polymer (Hybrane S1200, M(n) 1200 gmol(-1)) was functionalized with maleic anhydride (MA) and propylene sulfide, to obtain multifunctional cross-linkers with fumaric and thiol end groups, S1200MA and S1200SH, respectively. The degree of substitution (DS) of maleic acid groups was controlled by varying the molar ratio of MA to S1200 in the reaction mixture. Hydrogels were obtained by UV cross-linking of functionalized S1200 and poly(ethylene glycol) diacrylate in aqueous solutions. Compressive modulus increased with decreasing S1200/PEG ratio and also depended on the DS of the multifunctional cross-linker (S1200). Also, heparin-based macromonomers together with functionalized hyperbranched polymers were used to construct novel functional hydrogels. The multivalent hyperbranched polymers allowed high cross-linking densities in heparin modified gels while introducing biodegradation sites. Both heparin presence and acrylate/thiol ratio had an impact on degradation profiles and morphologies. Hyperbranched cross-linked hydrogels showed no evidence of cell toxicity. Overall, the multifunctional cross-linkers afford hydrogels with promising properties that suggest that these may be suitable for tissue engineering applications.