Synthetic elastin hydrogels that are coblended with heparin display substantial swelling, increased porosity, and improved cell penetration

Abstract

Synthetic elastin hydrogels are useful tissue engineering scaffolds because they present cell binding sequences and display physical performance similar to that of human elastic tissue. Small pores and a low porosity can limit cellular penetration into elastin scaffolds. To overcome this problem, glycosaminoglycans were coblended with tropoelastin during the formation of synthetic elastin hydrogels. Heparin and dermatan sulfate increased the pore size and porosity of the hydrogels. Heparin was particularly effective as it enlarged the pore size from 6.6 ± 2.1 μm to 23.8 ± 8.5 μm, and generated structures occasionally separated by finely fenestrated thin walls, which allowed human dermal fibroblast cells to migrate as deep as ∼300 μm into the hydrogel under diffusion-limiting static culture conditions. Most cells displayed spindle-like morphology, appeared histologically normal and presented intact nuclei, as expected for a viable population. Hydrogel swelling studies showed that each of the hydrogels contracted as the temperature was raised from 4°C to 37°C; synthetic elastin-heparin was least affected by temperature with a contraction of only 22.4 ± 1.2%, which would facilitate its transition from cold storage to body temperature. All hydrogels displayed similar compression moduli of 5.5 ± 0.4 to 6.9 ± 0.6 kPa. Compressive elastic energy losses for synthetic elastin-heparin and synthetic elastin were 33.7 ± 1.3% and 31.7 ± 2.2% respectively.