(601d) Assessment of Thermoresponsive Film Stability for Mammalian Cell Release

Stimuli responsive surfaces are of great interest in the bioengineering community. One example is poly(N-isopropyl acrylamide), which when tethered to a surface, can be used to induce a spontaneous release of a sheet of mammalian cells in response to a slight temperature change. Above its lower critical solution temperature (LCST), the polymer is relatively hydrophobic, and mammalian cells grown on pNIPAM-grafted surfaces act in a similar fashion as those grown on typical tissue culture polystyrene (TCPS): they proliferate into a confluent sheet. Below the LCST (i.e., room temperature) the polymer physically changes, becoming more hydrophilic and swelling. Furthermore, when the temperature of the cell culture is dropped below the LCST of the polymer, the cells will detach and can be harvested for tissue engineering applications. In this work, we assessed the long-term stability of these pNIPAM films, which were deposited using via spin coating and plasma polymerization. Characterization of the surface chemistry of the pNIPAM substrates was done using X-ray photoelectron spectroscopy (XPS), interferometry, and contact angle measurements. From these results, we concluded that storage temperature affects the efficacy of pNIPAM films, including cell release and thermoresponse.