Synthetic hydrogels of Poly(ethylene glycol) diacrylate (PEG-DA) have shown great promise as tissue engineering scaffolds. PEG-DA hydrogels are ideal for directing cell function due to their biocompatibility, their capability to readily control mechanical properties as well as to selectively incorporate cell signaling molecules with key functionalities of the natural extracellular matrix (ECM). However, the effect of the polymerization conditions, not only on the material properties of the scaffold, but also on the level of incorporation of biologically functional molecules into the hydrogel has yet to be elucidated. Thus, the development of computational models of PEG hydrogel formation that quantitatively predict the spatio-temporal distribution of physical properties and incorporated biological signals will provide significant insight in identifying the polymerization conditions required to optimize cell-biomaterial interactions. The clinical use of implantable synthetic materials to promote tissue viability and regeneration relies on the scaffolds'capacity to support the tissue demands for oxygen and on their ability to induce and promote angiogenesis which is essential for long term viability. The coordinated interactions between endothelial cells (ECs) and the ECM-like molecules that stimulate angiogenesis are dependent upon the architecture of the biopolymer microstructure, and the spatial arrangement of the biologically active components integrated in the scaffold. Studies have also shown that angiogenesis can be guided by physical and chemotactic gradients of proteins. This proposal aims to couple novel computational models of PEG-DA hydrogel formation with experimental techniques to engineer scaffolds with gradients of physical properties as well as gradients of multiple immobilized ECM-like molecules. This will be accomplished using the technique of interfacial photopolymerization (IP) as a scaffolding approach. Thus this proposal aims to test the hypothesis that IP can be used to produce PEG-DA scaffolds with controlled gradients of crosslink density as well as gradient compositions of functional biomolecules for stimulating angiogenesis in vitro. To test this hypothesis we propose to develop computational models of PEG hydrogel formation based on the kinetics of free-radical polymerization that predict the spatio-temporal incorporation of functional biomolecules in the scaffold. These models will be verified with experimental data will be subsequently used as a guide to fine tune the biophysical properties of these materials based on multiple inputs in order to facilitate desired cell behavior. ECs will be cultured on these scaffolds and adhesion, proliferation, migration and angiogenesis will be examined as a function of gradient as well as homogeneous crosslinking and biological signal availability. The predictive capability of these models to produce scaffolds with desired properties will incorporate a rigorous engineering approach to the highly-interdisciplinary field of tissue engineering. These studies will prove invaluable insight in developing biomaterials that stimulate therapeutic angiogenesis for numerous pathologic situations in which it plays a critical role.
The proposed experimental and computational hydrogel studies will provide invaluable insight in developing biomaterials that stimulate therapeutic angiogenesis for pathologic situations in which it plays a critical role.
