Dynamic tissue engineering scaffolds with stimuli-responsive macroporosity formation.

Macropores in tissue engineering scaffolds provide space for vascularization, cell-proliferation and cellular interactions, and is crucial for successful tissue regeneration. Modulating the size and density of macropores may promote desirable cellular processes at different stages of tissue development. Most current techniques for fabricating macroporous scaffolds produce fixed macroporosity and do not allow the control of porosity during cell culture. Most macropore-forming techniques also involve non-physiological conditions, such that cells can only be seeded in a post-fabrication process, which often leads to low cell seeding efficiency and uneven cell distribution. Here we report a process to create dynamic hydrogels as tissue engineering scaffolds with tunable macroporosity using stimuli-responsive porogens of gelatin, alginate and hyaluronic acid, which degrade in response to specific stimuli including temperature, chelating and enzymatic digestion, respectively. SEM imaging confirmed sequential pore formation in response to sequential stimulations: 37 °C on day 0, EDTA on day 7, and hyaluronidase on day 14. Bovine chondrocytes were encapsulated in the Alg porogen, which served as cell-delivery vehicles, and changes in cell viability, proliferation and tissue formation during sequential stimuli treatments were evaluated. Our results showed effective cell release from Alg porogen with high cell viability and markedly increased cell proliferation and spreading throughout the 3D hydrogels. Dynamic pore formation also led to significantly enhanced type II and X collagen production by chondrocytes. This platform provides a valuable tool to create stimuli-responsive scaffolds with dynamic macroporosity for a broad range of tissue engineering applications, and may also be used for fundamental studies to examine cell responses to dynamic niche properties.