Tuning reversible cell adhesion to methacrylate-based thermoresponsive polymers: Effects of composition on substrate hydrophobicity and cellular responses.

Abstract

Thermoresponsive polymer (TRP) cell culture substrates are widely utilized for nonenzymatic, temperature-triggered release of adherent cells. Increasingly, multicomponent TRPs are being developed to facilitate refined control of cell adhesion and detachment, which requires an understanding of the relationships between composition-dependent substrate physicochemical properties and cellular responses. Here, we utilize a homologous series of poly(MEO₂ MA_x -co-OEGMA_y ) brushes with variable copolymer ratio (x/y) to explore the effects of substrate hydrophobicity on L-929 fibroblast adhesion, morphology, and temperature-triggered cell detachment. Substrate hydrophobicity is reported in terms of the equilibrium spreading coefficient (S), and variations in copolymer ratio reveal differential hydrophobicity that is correlated to serum protein adsorption and initial cell attachment at 37°C. Furthermore, quantitative metrics of cell morphology show that cell spreading is enhanced on more hydrophobic surfaces with increased (x/y) ratio, which is further supported by gene expression analysis of biomarkers of cell spreading (e.g., RhoA, Dusp2). Temperature-dependent cell detachment is limited for pure poly(MEO₂ MA); however, rapid cell rounding and detachment (<20 min) are evident for all poly(MEO₂ MA_x -co-OEGMA_y ) substrates. These results suggest that increased MEO₂ MA content in poly(MEO₂ MA_x -co-OEGMA_y ) substrates elicits enhanced protein adsorption, cell adhesion, and cell spreading; however, integration of small amounts of the more hydrophilic OEGMA unit facilitates both cell attachment/spreading and detachment. This study demonstrates an important role for the composition-dependent control of surface hydrophobicity in the design of multicomponent TRPs for desired biological outcomes. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2416-2428, 2017.