The classical tissue engineering paradigm integrates a cell source, support structure, and suitable chemical and physical factors to functionally regenerate lost tissue. In recent years, considerable progress has been made in this field; however, critical problems still remain to be resolved for advancing tissue engineering into clinical application. A major barrier to creating large tissue-engineered scaffolds is sustaining proper oxygenation. Oxygen is fundamental for life, and is especially essential for maintaining cellular integrity, function and other cellular processes. In vitro, scaffold size is limited to a few hundred microns because of lack of a vascular system, thus cells rely solely on oxygen diffusion. Once scaffolds are implanted, cells rely solely on oxygen diffusion until vascular formation occurs; however, a lack of proper oxygen transport into the depths of the construct may result in decreases in cell number and contribute to eventual implant failure. Experiments with bone marrow-derived mesenchymal stem cells (MSCs) show that differentiation capacity decreases under hypoxic conditions compared to normoxic conditions. Work with neural stem/ progenitor cells (NSPCs) has shown varied results in terms of both proliferation and differentiation depending on donor age and species, oxygen level and media conditions.

 

To directly address oxygen transport deficiencies, we have created perfluorocarbon (PFC) modified chitosan (MACF) hydrogels, which we have shown are valuable to control oxygenation and to accelerate and improve dermatological wound healing responses. More recently we have formulated MACF into microgels (~20 m diameter) and demonstrated that were could include them in 3D spheroid constructs to improve oxygen transport in in vitro culture. The primary goal of this project is to integrate MACF microgels created in the Leipzig lab into established bioinks, used for 3D printing. Thus, directly conferring the ability to enhance oxygen transport to improve cell survival and functions of bioprinted constructs which include cells. Ultimately this approach would serve as a strategy for 3D printed tissue constructs to provide sufficient oxygenation to support cells while vasculature in formed after in vivo implantation.