TY - JOUR

T1 - Thermoresponsive poly(glycidyl ether) brushes on gold

T2 - Surface engineering parameters and their implication for cell sheet fabrication

AU - Heinen, Silke

AU - Cuéllar-Camacho, José Luis

AU - Weinhart, Marie

N1 - Funding information: The authors kindly acknowledge financial support from the German Federal Ministry of Education and Research (BMBF) via the grant FKZ: 13N13523 and from the Freie Universit?t Focus Area NanoScale. S.H. is grateful to the FCI for a Chemiefonds Scholarship. We thank Dr. Anke Hoppensack for proof reading and helpful comments during the preparation of this manuscript. The authors kindly acknowledge financial support from the German Federal Ministry of Education and Research (BMBF) via the grant FKZ: 13N13523 and from the Freie Universität Focus Area NanoScale. S.H. is grateful to the FCI for a Chemiefonds Scholarship. We thank Dr. Anke Hoppensack for proof reading and helpful comments during the preparation of this manuscript.

PY - 2017/9/1

Y1 - 2017/9/1

N2 - 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. Statement of Significance Cell sheet engineering as a scaffold-free approach towards tissue engineering resembles a milestone in regenerative medicine. The fabrication of confluent cell sheets maintains the extracellular matrix of cells which serves as the physiological cell scaffold. Thermoresponsive poly(glycidyl ether)s are highly cell-compatible and brushes thereof promote cell adhesion and growth without modification with additional cell adhesive ligands. Thus, a direct correlation of temperature-dependent serum protein adsorption and cell response with surface design parameters such as grafting density and molecular weight became accessible. Hence, surface engineering parameters of well-defined poly(glycidyl ether) monolayers for reproducible cell sheet fabrication have been identified. These design guidelines may also prove beneficial in the development of other brush-like thermoresponsive coatings for cell sheet engineering.

AB - 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. Statement of Significance Cell sheet engineering as a scaffold-free approach towards tissue engineering resembles a milestone in regenerative medicine. The fabrication of confluent cell sheets maintains the extracellular matrix of cells which serves as the physiological cell scaffold. Thermoresponsive poly(glycidyl ether)s are highly cell-compatible and brushes thereof promote cell adhesion and growth without modification with additional cell adhesive ligands. Thus, a direct correlation of temperature-dependent serum protein adsorption and cell response with surface design parameters such as grafting density and molecular weight became accessible. Hence, surface engineering parameters of well-defined poly(glycidyl ether) monolayers for reproducible cell sheet fabrication have been identified. These design guidelines may also prove beneficial in the development of other brush-like thermoresponsive coatings for cell sheet engineering.

KW - AFM

KW - Brushes

KW - Cell sheet fabrication

KW - Grafting density

KW - Molecular weight

KW - Protein adsorption

KW - Self-assembled monolayer

KW - SPR

KW - Thermoresponsive

UR - http://www.scopus.com/inward/record.url?scp=85021052293&partnerID=8YFLogxK

U2 - 10.1016/j.actbio.2017.06.029

DO - 10.1016/j.actbio.2017.06.029

M3 - Article

C2 - 28647625

AN - SCOPUS:85021052293

VL - 59

SP - 117

EP - 128

JO - Acta Biomaterialia

JF - Acta Biomaterialia

SN - 1742-7061

ER -