Synthesis of hyperbranched-linear poly(N-isopropylacrylamide) polymers with a poly(siloxysilane) hyperbranched macroinitiator, and their application to cell culture on glass substrates

The attachment of poly(N-isopropylacrylamide) (PNIPAM) onto glass slides by using a hyperbranched poly(siloxysilane) (HBPS) as a linker was investigated to develop a thermoresponsive glass surface for cell sheet engineering. A reversible addition-fragmentation chain transfer (RAFT) polymerization chain transfer agent (CTA) was introduced onto the termini of the HBPS via the polycondensation of an AB(2) monomer and subsequent suitable end-group modification. Living radical polymerization of NIPAM from the CTA-termini of HBPS was achieved, yielding a copolymer of HBPS and PNIPAM (HBPS-g-PNIPAM). The glass slides were PNIPAM-coated by drop casting of HBPS-g-PNIPAM in tetrahydrofuran (THF), and immobilization was confirmed by X-ray photoelectron spectroscopy, atomic force microscopy and contact angle measurements. The resulting glass slide was applied to cell culture of mouse 3T3 fibroblasts, and attachment and proliferation were successfully achieved at 37 degrees C after 2 or 4 days. Reducing the temperature to 20 degrees C for 15 min permitted the detachment of the cell sheet. The glass slide was successfully reused for cell culture, thus confirming the strong attachment of the polymer onto the surface.