Terminal-Functionality Effect of Poly(<i>N</i>‑isopropylacrylamide) Brush Surfaces on Temperature-Controlled
Cell Adhesion/Detachment
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Abstract
Terminally functionalized poly(<i>N</i>-isopropylacrylamide)
(PIPAAm) brush grafted glass surfaces were prepared by a surface-initiated
reversible addition-fragmentation chain transfer radical (SI-RAFT)
polymerization. SI-RAFT mediated PIPAAm chains possessed terminal
dodecyl trithiocarbonate groups which can be substituted with various
functional groups. In this study, dodecyl groups were substituted
with hydrophilic maleimide groups for controlling the thermoresponsive
character of PIPAAm brushes. PIPAAm brushes exhibited reversible temperature-dependent
surface wettability changes around PIPAAm’s lower critical
solution temperature. Phase transition of dodecyl-terminated PIPAAm
brushes clearly shifted to lower temperature than that of maleimide-terminated
PIPAAm brushes, and this shift was attributed to promoted PIPAAm dehydration
via terminal hydrophobes. By using this feature, the specific adhesion
temperatures of bovine carotid artery endothelial cells (BAECs) on
the PIPAAm brush surfaces were successfully controlled. BAECs were
initiated to adhere on dodecyl-PIPAAm surfaces at 31 °C, while
their adhesion was significantly suppressed on maleimide-PIPAAm surfaces
under 33 °C. In contrast, terminal functionality scarcely affected
the thermoresponsive behavior of PIPAAm brushes in the polymer rehydration
process by reducing temperatures, and thus, the difference in spontaneous
cell detachment from different PIPAAm-brush surface was negligible.
Consequently, confluently cultured cells were able to be harvested
as contiguous cell sheets from individual surfaces with comparable
periods at 20 °C