Development of a smart bioreactor for mammalian adherent cell expansion for application to cell therapy

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Cell therapy, particularly stem cell therapy, shows great promise for curing many diseases and repairing defective tissues in the human body. The problem currently is the difficulty in acquiring sufficient numbers of cells directly from a patient or donor. There is an urgent need to find a way to produce large quantities of high quality cells for cell therapy. The proposed research project will develop a smart bioreactor based on thermoresponsive polymer coated beads for culturing and expanding (increasing in cell number) adherent cells (as most cells, except blood cells, need to attach onto a surface to grow). The temperature sensitive polymer, poly(N-isopropylacrylamide) (PNIPAAm), has been found to be able to support cell adhesion and growth at 37 degree C, but when the temperature drops below 32 degree C, the cells will detach from the polymer and can thus be collected easily. This has distinctive advantages over the conventional cell culture methods in which adherent cells are harvested by destroying the proteins responsible for cell adhesion through the action of an enzyme such as trypsin. However, this enzyme also damages other crucial proteins on cell surfaces, which can affect cell growth and function. Work has been done to graft PNIPAAm to flat surfaces successfully and cells were able to grow into a thin sheet which was used to repair heart tissue defects in the human body.This project will look at how to graft PNIPAAm onto the surfaces of different types of small beads for cell culture. PNIPAAm grafted beads have already been used in chromatography for separating biological compounds, but very limited research has been done on using them for culturing human cells. Culturing adherent cells on small beads is routinely done both in research laboratories and in industry to expand cells, but the enzymatic treatment is needed to harvest cells at the end of cell culture.The thermosensitive beads to be developed in this project will enable separation of cells from beads without the damaging enzymatic treatment. In the project, different types of beads will be grafted with PNIPAAm and tested to see whether: (1) they have any toxic effects on cells, (2) they support cell growth on them, (3) cells can detach from the beads when the temperature drops below 32 degree C, and (4) cells still retain their function after being cultured on the beads. Also, a purpose-designed and fabricated bioreactor, a vessel to accommodate cells and beads and supply necessary nutrients and oxygen to the cells will be developed. This so-named smart bioreactor will be used to generate high quality cells suitable for cell therapy.