Switchable phase transition behavior of thermoresponsive substrates for cell sheet engineering

Abstract

Recently, there are significant interests in the development of biomaterials with nonlinear response to an external stimulus. Thermoresponsive polymers as a well-known class of stimuli-responsive materials represent reversible hydrophilicity/hydrophobicity characteristics around a critical temperature. This switchable behavior applies for nondestructive cellular detachment from cultivation substrates. In this study, poly (N-isopropylacrylamide) (PNIPAAm)-grafted dishes were made up to harvest retinal pigmented epithelial (RPE) and periodontal ligament cell (PDLC) sheets. Wettability assessments verified that all functionalized surfaces were inverted from hydrophilic to hydrophobic state when the temperature rises from lower critical solution temperature (LCST) at 37 °C. Other physicochemical characteristics such as chemical composition, grafting thickness, and surface topography were investigated through attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). ATR-FTIR results showed typical peaks of amide group corresponding to successful PNIPAAm polymerization. AFM microscopy results also proved creating a rough PNIPAAm layer with thickness of 29.2 nm after grafting process in the mixture of methanol and water. Cell culture experiments showed an irreversible cellular attachment/detachment from modified surfaces upon temperature changes. These results introduced thermoresponsive TCPS to noninvasively harvest RPE and PDLCs sheets especially for application in scaffold-free tissue engineering decorations. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1567–1576.