Nanometric grafting of poly (N-isopropylacrylamide) onto polystyrene film by different doses of gamma radiation

Poly N-isopropylacrylamide was successfully grafted onto a polystyrene cell culture dish by gamma ray. In this study, the effect of a radiation dose (radiation absorbed dosages of ۱۰, ۲۰, ۳۰, ۴۰ KGy) under appropriate temperature and grafting conditions was investigated. The FTIR analysis showed the existence of the graft PNIPAAm on the substrate. The optimal value of the dose for grafting was ۴۰ KGy at ۵۰°C. The SEM and AFM images clearly showed that increasing the absorbed dose of radiation would increase the amount of grafting. Surface topography and graft thickness in AFM images of the radiated samples showed that the PNIPAAm at the absorbed dose of radiation was properly grafted. The thickness of these grafts was about ۵۰–۱۰۰ nm. The drop water contact angles of the best grafted sample at ۳۷°C and ۱۰°C were ۵۵.۳ ± ۱.۲o and ۶۱.۲ ± ۰.۹o respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. DSC analysis also revealed the LCST of the grafted sample to be ۳۲°C. Thermo-responsive polymers were grafted to dishes covalently which allowed fibroblast cells to attach and proliferate at ۳۷°C; the cells also detached spontaneously without using enzymes when the temperature dropped below ۳۲°C. This characteristic proves that this type of grafted material has potential as a biomaterial for cell sheet engineering.

Keywords:

Nanometric grafting , PNIPAAm , polystyrene film , gamma ray , cell engineering