A Novel Thermoresponsive Graft Copolymer Containing Phosphorylated HEMA for Generating Detachable Cell Layers

A novel polymeric formulation based on N-isopropylacrylamide (NIPAAm), methylmethacrylate (MMA), and phosphorylated hydroxylethyl methacrylate (Phosp-HEMA) was synthesized and characterized. NIPAAm was copolymerized with a known quantity of MMA to form a poly(NIPAAm-MMA) copolymer and was subsequently grafted with Phosp-HEMA by gamma irradiation to a total dose of 0.5 kGy. The thermoresponsive graft copolymer was characterized by differential scanning calorimetry, Fourier transform infrared spectroscopy, contact angle measurements, and energy dispersive X-ray analysis. The cytotoxicity of the graft copolymer analyzed using L-929 fibroblast cells showed noncytotoxic response. The cell adhesion on the graft copolymer was studied using rabbit corneal cells (SIRC) and human osteoblasts (HOS). The adhered cells were found to spread leading to the formation of cell layers. The cell layers with intact cell-cell and cell-extra cellular matrix contact were detached by lowering temperature below the lower critical solution temperature (29 degrees C) of the graft copolymer. The viability and morphology of the cells in detached cell sheets were assessed by live dead staining and environmental scanning electron microscopy, respectively. This interesting feature of cell adhesion to form cell layers and cell sheet retrieval is implicit to be due to the properties of phosphate moieties on thermoresponsive copolymer. To the authors knowledge there is no previous report on phosphate moiety containing thermo responsive polymeric formulations which can modulate cell adhesion and cell sheet retrieval. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 52-62, 2010