PIs: Rick Koepsel
Co. Investigator: Sharon Marx and Gabriel Amitai
Title: Temperature responsive modification of microfiber tissue perfusion devices.
Description: Tissue perfusion devices based on hollow fibers have been developed for use in bioreactors and for wound healing. In both cases the perfusion devices are in direct contact with cells and tissues. The hollow fiber tubing that makes up the devices is fabricated from hydrophilic materials, which resist the direct attachment of cells and proteins in the short term but over time cells will attach to the devices. With cells and tissue attached to the device, removal of the device can disrupt the structure of the tissue that was the intended when the device was implanted. This project will extend the development of tissue perfusion devices by providing smart polymer coatings which, when activated, will facilitate the removal of the device.
Smart polymers are materials that exhibit a response to a physical stimulus. For this project we will concentrate on the temperature responsive polymer poly (N-isopropylacrylamide) (pNIPAAm). As with many temperature responsive materials, pNIPAAm in aqueous solution changes structure at a temperature called the lower critical solution temperature (LCST). In the case of pNIPAAm the LCST is about 320C, below the LCST the polymer is soluble in aqueous solution while above the LCST a change in the polymer structure causes the polymer to be come hydrophobic and form micelles in solution. When pNIPAAm is immobilized on a surface it still responds to temperature. A surface coated with pNIPAAm is hydrophobic below the LCST but becomes hydrophilic above the LCST. Cells grown on tissue culture dishes coated with pNIPAAm will attach and proliferate normally while the dishes are kept at 370C but when the temperature is lowered below the LCST the cells are sloughed off of the surface. If the cells have grown to a confluent monolayer, they will come off the surface as a cohesive sheet showing that the underlying protein layer to which the cells are attached is also sloughed from the surface. Applying a layer of pNIPAAm to the hollow fiber perfusion tubing should therefore allow a temperature change to eliminate the adhesions between the cells or tissues and the perfusion device allowing the device to be removed with considerably less trauma to the insertion site.
Term: 11/1/08 – 10/31/09