Novel poly(N-isopropylacrylamide)-poly[(R)-3-hydroxybutyrate]-poly(N-isopropylacrylamide) triblock copolymer surface as a culture substrate for human mesenchymal stem cells

A thermoresponsive surface was fabricated by coating a substrate with a thermoresponsive amphiphilic triblock copolymer, poly(N-isopropylacrylamide)-poly[(R)-3-hydroxybutyrate]-poly(N-isopropylacrylamide) (PNIPAAm-PHB-PNIPAAm), and used for the attachment and nonenzymatic temperature-induced detachment of human mesenchymal stem cells. The copolymer self-assembled into micelles in water and formed stable attachments to the substrate by hydrophobic interactions between the micelle core and the substrate surface. The stability of the polymer attachment was confirmed by ATR-FTIR analysis of the polymer-coated substrates before and after soaking in water. Illustration of the copolymer coating on the cell culture substrate was accomplished by applying Farago's implicit-solvent model for studying the self-assembly of large molecules. The copolymer coating enhanced the proliferation of human mesenchymal stem cells compared with either PNIPAAm homopolymer-coated or noncoated surface. The copolymer-coated substrate showed a change in the surface hydrophilicity when the temperature was changed. After a period of culture, the cells could be detached by cooling at 4 °C for 20 min without trypsin treatment.