The use of perfluorocarbons in encapsulated cell systems: their effect on cell viability and function and their use in noninvasively monitoring the cellular microenvironment
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Implantation of tissue engineered pancreatic constructs can provide for a physiologic regulation of blood glucose levels. A major concern in designing such constructs is ensuring sufficient oxygenation of the cells, as oxygen is usually the limiting nutrient affecting cell viability and function. Furthermore, in vivo factors influencing construct oxygenation often lead to implant failure, and are detected primarily on end physiologic effects. The ability of perfluorocarbons (PFCs) to dissolve large amounts of oxygen and their high fluorine content makes these compounds a potentially valuable oxygen delivery tool and good 19F Nuclear Magnetic Resonance (NMR) markers for dissolved oxygen concentration (DO). Experimental studies and simulations showed that although the addition of 10 vol% PFC increased construct oxygenation, this improvement was minimal and had limited benefits on the growth and function of encapsulated bTC-tet cells under normoxic and hypoxic conditions. A dual PFC method that utilizes 19F NMR spectroscopy was developed to noninvasively monitor DO within a tissue construct and in its surroundings. In vitro studies using an NMR-compatible bioreactor demonstrated the feasibility of this method to monitor the DO within alginate beads containing metabolically active bTC-tet cells, relative to the DO in the culture medium, under perfusion and static conditions. In vivo, the method was capable of acquiring real-time DO measurements in murine models. Measured DO can be correlated with the physiological state of the implant examined post-explantation and was compatible with the therapeutic function of the implant.