Fabrication of thermo-responsive cell-culture membranes with Poly(N-isopropylacrylamide) by electron-beam graft polymerization

Cell-sheet engineering aims to generate tissues and organs through lamination and transplantation of acquired cell sheets. The technique has become used in the field of regenerative medicine, and the development of cell-culture plates equipped with a switching function for cell adhesion/cell-sheet detachment has been in progress. Our research group has produced thermo-responsive cell-culture membranes by grafting poly(N-isopropylacrylamide) (PNIPAAm) onto an ethylene-tetrafluoroethylene copolymer (ETFE). Grafting is achieved via electron beam (EB) pre-irradiation grafting methods. The high biocompatibility of ETFE is well known, and high yields of trapped radicals can be obtained through the use of ionizing radiation. Increased thermo-responsivity of the cell-culture membranes can be achieved by increasing the amount of grafted PNIPAAm. In the present study, we fabricated grafted membranes with different grafting yields (GY), and evaluated the thermo-responsivity and cell-adhesion/cell-sheet-detachment abilities. First, C2C12 cells were cultured at 37°C for 2 days on the grafted samples, then the cell sheet was detached by reducing the temperature to 20°C after cell proliferation. In the fabricated samples with the GY of 14.9% ± 1.0%, cells reached confluence in 2 days, and the resulting cell sheet was detached within 15 min without any damage.