Alternate method for grafting thermoresponsive polymer for transferring in vitro cell sheet structures

Retrieval of cells for various applications involves enzymatic or mechanical methods that hamper the cell-cell and cell-extracellular matrix (ECM) binding. Poly(N-isopropylacrylamide) (PIPAAm) is a known temperature-sensitive polymer that exhibits a lower critical solution temperature (LCST) around 32 degrees C and is hydrophobic over LCST and hydrophilic below LCST. PIPAAm-grafted culture surface can be used for detaching adhered cells by lowering the temperature below LCST. In this study, polymerization and grafting of PIPPAm was done by gamma (7) ray irradiation instead of the conventional method of electron beam irradiation. The efficacy of the grafted surface was confirmed by the successful growth of different cell lines such as L-929, NRK-49F, HOS, and SIRC. The cell sheet structures with intact cell-cell and cell-ECM contact was detached by lowering incubation temperature below 20 degrees C. Live-dead staining of cells before and after transfer showed that cell sheet structures maintained viability. This approach of synthesizing thermoresponsive surface by gamma-ray irradiation method can be used to culture many other cell types and could be utilized to prepare in vitro tissue constructs for bioengineering. (c) 2007 Wiley Periodicals, Inc.