Controlled Chain Length and Graft Density of Thermoresponsive Polymer Brushes for Optimizing Cell Sheet Harvest

Novel thermoresponsive polymer brush surfaces for harvesting cell sheet were fabricated by the surface-initiated RAFT polymerization of N-isopropylacrylamide (IPAAm) on azoinitiator-immobilized glass substrates in the presence of dithiobenzoate compound as a chain transfer agent (CTA). The chain length of the grafted PIPAAm on the surface was controlled by changing CTA concentration. Additionally, PIPAAm graft density on the surface was successfully regulated by grafting from azoinitiator-immobilized surfaces with various densities. By adjusting both the chain length and the density of grafted PIPAAm, a series of thermoresponsive polymer brush surfaces were prepared to regulate cell adhesion/detachment behavior by solely temperature change across the PIPAAm's lower critical solution temperature of 32 degrees C. PIPAAm brush surfaces were successfully optimized to recover the cell sheets of bovine carotid artery endothelial cells. Additionally, the immunostaining study revealed that the cell sheets can be recovered with their intact extracellular matrix (ECM) from PIPAAm surfaces, indicating that the cell sheets can be effectively transplanted to damaged tissues and organs.