Photopolymerizable scaffolds of native extracellular matrix components for tissue engineering applications

In recent years, significant success has been made in the field of regenerative medicine. Tissue engineering scaffolds have been developed to repair and replace different types of tissues. The overall goal of the current work was to develop scaffolds of native extracellular matrix components for soft tissue regeneration, more specifically, neural tissue engineering. To date, much research has been focused on developing a nerve guidance scaffold for its ability to fill and heal the gap between the damaged nerve ends. Such scaffolds are marked by several intrinsic properties including: (1) a biodegradable scaffold or conduit, consisting of native ECM components, with controlled internal microarchitecture; (2) support cells (such as Schwann cells) embedded in a soft support matrix; and (3) sustained release of bioactive factors. In the current dissertation, we have developed such scaffolds of native biomaterials including hyaluronic acid (HA) and collagen. HA is a nonsulphated, unbranched, high-molecular weight glycosaminoglycan which is ubiquitously secreted by cells in vivo and is a major component of extracellular matrix (ECM). High concentrations of HA are found in cartilage tissue, skin, vitreous humor, synovial fluid of joints and umbilical cord. HA is nonimmunogenic, enzymatically degradable, non-cell adhesive which makes HA an attractive material for biomedical research. Here we developed new photopolymerizable HA based materials for soft tissue repair application. First, we developed interpenetrating polymer networks (IPN) of HA and collagen with controlled structural and mechanical properties. The IPN hydrogels were enzymatically degradable, porous, viscoelastic and cytocompatible. These properties were dependent on the presence of crosslinked networks of collagen and GMHA and can be controlled by fine tuning the polymer ratio. We further developed these hydrogel constructs as three dimensional cellular constructs by encapsulating Schwann cells in IPN hydrogels. The hydrogel constructs supported cell viability, spreading, proliferation, and growth factor release from the encapsulated cells. Finally, we fabricated scaffolds of photopolymerizable HA with controlled microarchitecture and developed designer scaffolds for neural repair using layer-by-layer fabrication technique. Lastly, we developed HA hydrogels with unique anisotropic swelling behavior. We developed a dual-crosslinking technique in which a super-swelling chemically crosslinked hydrogel is patterned with low-swelling photocrosslinked regions. When this dual-crosslinked hydrogel is swelled it contorts into a new shape because of differential swelling among photopatterned regions.