Thermoresponsive Poly(glycidyl ether) Brushes on Gold: Surface Engineering Parameters and their Implication for Cell Sheet Fabrication
Silke Heinen, José Luis Cuéllar-Camacho, Marie Weinhart – 2017
Thermoresponsive polymer coatings, optimized for cell adhesion and thermally-triggered cell detachment, allow the fabrication of confluent cell sheets with intact extracellular matrix. However, rational design guidelines for such coatings are rare, since temperature-triggered cell adhesion and detachment from thermoresponsive surfaces are mechanistically not well understood. Herein, we investigated the impact of molecular weight (2, 9, 24 kDa), grafting density (0.04 – 1.4 chains nm-2), morphology, and roughness of well-characterized thermoresponsive poly(glycidyl ether) brushes on the cell response at 37 and 20 °C. NIH 3T3 mouse fibroblasts served as a model cell line for adhesion, proliferation, and cell sheet detachment. The cell response was correlated with serum protein adsorption from cell culture medium containing 10% fetal bovine serum. Intact cell sheets could be harvested from all the studied poly(glycidyl ether) coated surfaces, irrespective of the molecular weight, provided that the morphology of the coating was homogenous and the surface was fully shielded by the hydrated brush. The degree of chain overlap was estimated by the ratio of twice the polymer’s Flory radius in a theta solvent to its interchain distance, which should be located in the strongly overlapping brush regime (2 Rf/l > 1.4). In contrast, dense PNIPAM (2.5 kDa) control monolayers did not induce protein adsorption from cell culture medium at 37 °C and, as a result, did not allow a significant cell adhesion. These structural design parameters of functional poly(glycidyl ether) coatings on gold will contribute to future engineering of these thermoresponsive coatings on more common, cell culture relevant substrates.