Thermoresponsive and Active Functional Fiber Mats for Cultured Cell Recovery.

Thermoresponsive and active functional fiber mats were prepared from random copolymer of poly(pentafluorophenyl acrylate-co-N-isopropylacrylamide) (P(PFPA-co-NIPAM))， which was synthesized by a controlled radical polymerization process based on reversible addition-fragmentation chain transfer (RAFT). As reactive sites， pentafluorophenyl ester (PFP) groups were incorporated in the copolymer to allow for a multiple post-polymerization modification. UV-cross-linkable moieties were first introduced by partially reacting PFP groups in the copolymer with ortho-nitrobenzyl (ONB)-protected diamine. Electrospinning the resulting ONB-containing P(PFPA-co-NIPAM)， followed by UV-induced cross-linking， yielded stable cross-linked thermoresponsive PNIPAM-based fiber mats. The remaining PFP active groups on the surface of copolymer fiber mats allowed for further conjugation with an H-Gly-Arg-Gly-Asp-Ser-OH (GRGDS) peptide， a well-known cell adhesive peptide sequence that was selected as a model in order to promote cell growth. At 37 °C， fibroblast cells were found to attach， spread， and proliferate well on the GRGDS-immobilized cross-linked (CL) fiber mat， as opposed to those on the GRGDS-immobilized un-cross-linked (UCL) fiber mat. By decreasing the temperature down to 20 °C， i.e. below the lower critical solution temperature (LCST) of thermoresponsive PNIPAM， cultured cells could easily be released from both GRGDS-immobilized CL and UCL fiber mats， whereas no cells were detached from tissue culture polystyrene (TCPS). These results suggest that the thermosensitive and active functional fiber mat obtained in this research represent an attractive and versatile platform for cultured cell recovery， which is beneficial for tissue engineering applications.