The Development of Oxygen-generating Materials and Cell Separation Techniques for Tissue Engineering

University of Minnesota Ph.D. dissertation. 2018. Major: Biomedical Engineering. Advisor: Wei Shen. 1 computer file (PDF); 167 pages.Abstract Oxygen and cells play a key role in tissue engineering. In this work, we have developed methods to address two key factors: (1) fabrication of oxygen-generating biomaterials for a sustained release of oxygen, (2) isolation of target cells with collective merits of high specificity, high yield, and minimal biochemical and biophysical perturbation. Inability to supply sufficient oxygen is one of the major reasons for cell death and tissue necrosis in the initial phase after transplantation of engineered constructs. In this work oxygen-generating microparticles and films were developed by incorporating polycaprolactone (PCL) with calcium peroxide (CaO2) to achieve a sustained oxygen delivery. Electrospraying and heat-press techniques were used for the preparation of PCL/CaO2 microparticles and films and compared with traditional techniques of homogenization and solvent-cast. Pancreatic β cells was utilized to evaluate the ability of oxygen-generating materials to support cell survival. The results show that cell viability and metabolic activity were significantly improved both in two-dimensional and three-dimensional hypoxic culture with the presence of oxygen-generating biomaterials. Heat-press technique enables fabricated PCL/CaO2 films to release oxygen for more than 3 weeks in a hypoxia incubator with 2% oxygen, and the oxygen release rate can be adjusted to a manner without compromising in vitro angiogenesis process. To compare with most of reported studies with peroxide/biodegradable polymer-based oxygen-generating biomaterials, a prolonged oxygen release with an elevated metabolic activity of cells was achieved in this work. Affinity‐based cell separation is label‐free and highly specific, but it is difficult to efficiently and gently release affinity‐captured cells due to the multivalent nature of cell‐material interactions. A label-free cell separation platform composed of a capture substrate and a cell‐releasing molecular trigger was developed in this work to address this challenge. The capture substrate is functionalized with an antibody, which captures target cells specifically, and a coiled-coil A. The cell-releasing molecular trigger B-PEG, a conjugate of a coiled-coil B and polyethylene glycol, can drive efficient and gentle release of the captured cells, because A/B heterodimerization brings B-PEG molecules to the substrate and PEG chains adopt extended conformations and break nearby multivalent cell-substrate interactions. Unlike most of current cell isolation strategies, no enzymes or excessive shear stress are involved, and the released cells have neither external molecules attached nor endogenous cell-surface molecules cleaved, which might be critical for the viability, phenotype, and function of sensitive cells