Bioinspired Engineering of Poly(ethylene glycol) Hydrogels and Natural Protein Fibers for Layered Heart Valve Constructs

Layered constructs from poly(ethylene glycol) (PEG) hydrogels and chicken eggshell membranes (ESMs) are fabricated, which can be further cross-linked by glutaraldehyde (GA) to form GA-PEG-ESM composites. Our results indicate that ESMs composed of protein fibrous networks show elastic moduli ∼3.3-5.0 MPa and elongation percentages ∼47-56%, close to human heart valve leaflets. Finite element simulations reveal obvious stress concentration on a partial number of fibers in the GA-cross-linked ESM (GA-ESM) samples, which can be alleviated by efficient stress distribution among multiple layers of ESMs embedded in PEG hydrogels. Moreover, the polymeric networks of PEG hydrogels can prevent mineral deposition and enzyme degradation of protein fibers from incorporated ESMs. The fibrous structures of ESMs retain in the GA-PEG-ESM samples after subcutaneous implantation for 4 weeks, while those from ESM and GA-ESM samples show early degradation to certain extent, suggesting the prevention of enzymatic degradation of protein fibers by the polymeric network of PEG hydrogels in vivo. Thus, these GA-PEG-ESM layered constructs show heterogenic structures and mechanical properties comparable to heart valve leaflets, as well as improved functions to prevent progressive calcification and enzymatic degeneration, which are likely used for artificial heart valves.