Fabrication and characterization of thermo-responsive nanofibrous surfaces using electron beam irradiation

We have fabricated a novel thermo-responsive nanofibrous surfaces by grafting PIPAAm by electron beam irradiation onto poly(3-hydroxybutyrate-co-3- hydroxyvalerate) (PHBV) nanofibrous mats. The electrospun PHBV nanofiber structures revealed randomly aligned fibers with average diameter of 400 nm. Increased atomic percent of nitrogen was observed on the PIPAAm-grafted PHBV mats after electron beam irradiation determined by ESCA. The amounts of PIPAAm-grafted onto PHBV films were 6.49 μg/cm² determined by ATR-FTIR. The PIPAAm-grafted surfaces exhibited decreasing contact angles by lowering the temperature from 37 to 20 °C while ungrafted PHBV surfaces had negligible contact angle change. This result indicates that PIPAAm surfaces, which are hydrophobic at the higher temperature, became markedly more hydrophiiic in response to a temperature reduction due to spontaneous hydration of the surface-grafted PIPAAm. Thermo-responsive nanofibers showed good tissue compatibility. Cultured cells were well detached and recovered from the surfaces by changing culture temperature from 37 to 20 °C.