Thermoresponsive artificial extracellular matrix: N-isopropylacrylamide-graft-copolymerized gelatin

Poly(N-isopropylacrylamide)-graft-copolymerized gelatin (PNIPAM-gelatin) was prepared by iniferter-based photopolymerization of multiply derivatized dithiocarbamylated gelatin. PNIPAM-gelatins exhibited low critical solution temperature (LCST) immediately below the physiological temperature. PNIPAAm-gelatin-coated dishes induced cell adhesion at 37 degrees C but incomplete detachment at room temperature, whereas dishes coated with PNIPAM or a mixture of PNIPAAm and gelatin showed little cell adhesion. The mixture of PNIPAAm-gelatin and PNIPAAm induced cell adhesion at 37 degrees C and detachment at 20 degrees C: the degrees of cell adhesion and detachment depended on the mixed ratio of PNIPAAm-gelatin and PNIPAAm. Complete thermoresponsive adhesion and detachment were found for the mixture containing a small fraction of PNIPAAm-gelatin (approximately 5 wt% with respect to PNIPAAm; gelatin content in the mixture is 2.7 wt%). Such a mixture may serve as thermoresponsive cell matrix for fabrication of a tissue-engineered device.