Micropatterned thermoresponsive polymer brush surfaces for fabricating cell sheets with well-controlled orientational structures.

Newly developed fabrication technique of thermoresponsive surface using RAFT-mediated block copolymerization and photolithography achieved stripe-like micropatterning of poly(N-isopropylacrylamide) (PIPAAm) brush domains and poly(N-isopropylacrylamide)-b-poly(N-acryloylmorpholine) domains. Normal human dermal fibroblasts were aligned on the physicochemically patterned surfaces simply by one-pot cell seeding. Fluorescence images showed the well-controlled orientation of actin fibers and fibronectin in the confluent cell layers with associated extracellular matrix (ECM) on the surfaces. Furthermore, the aligned cells were harvested as a tissue-like cellular monolayer, called "cell sheet" only by reducing temperature below PIPAAm's lower critical solution temperature (LCST) to 20 °C. The cell sheet harvested from the micropatterned surface possessed a different shrinking rate between vertical and parallel sides of the cell alignment (approximately 3:1 of aspect ratio). This indicates that the cell sheet maintains the alignment of cells and related ECM proteins, promising to show the mechanical and biological aspects of cell sheets harvested from the functionalized thermoresponsive surfaces.