Material assembly and gelation kinetics of PEG-heparin hydrogels using multiple particle tracking microrheology

Recently, heparin functionalized polymer scaffolds have been developed for tissue engineering applications. Such materials are designed to mimic the structural and mechanical properties of the extra-cellular matrix, while providing controlled sequestration and release of soluble factors, such as growth factors. We investigate the material properties of these chemically crosslinked, synthetic hydrogel systems. The experimental system is composed of the crosslinker, linear dithiolated poly(ethylene glycol), and the network backbone, maleimide functionalized heparin. Multiple particle tracking is performed on material with I Am poly(styrene) probes embedded into it. Experiments capture the material response over short and long times. The short time data is taken to study the gelation kinetics of the material, while equilibrium measurements provide information about the final hydrogel properties. The hydrogel composition and the functionality of the heparin are systematically varied to establish regions of gelation. With this information, we are able to create a quantitative library of material assembly conditions as a function of crosslinker to backbone ratio, backbone functionality and total polymer concentration for applications in tissue engineering.