Control of Cell Adhesion and Detachment on Temperature-Responsive Block Copolymer Langmuir Films
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Control of Cell Adhesion and Detachment on Temperature-Responsive Block Copolymer Langmuir Films Morito Sakuma1,2, Yoshikazu Kumashiro2, Masamichi Nakayama2, Nobuyuki Tanaka2, Umemura Kazuo1, Masayuki Yamato2 and Teruo Okano2 1 Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601 JAPAN 2 Institute of Advanced Biomedical Engineering and Science, Tokyo Women’s Medical University (TWIns), 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666 JAPAN
ABSTRACT This study used Langmuir-Schaefer (LS) method to produce thermo-responsive poly(Nisopropylacrylamide) (PIPAAm) modified surface. Block copolymer composed of polystyrene (PSt) and PIPAAm was synthesized by RAFT polymerization. PSt-block-PIPAAm (St-IP) with various chemical compositions was dropped on an air-water interface and formed Langmuir film by compression. Then, the Langmuir film changing a density was transferred on a hydrophobic modified glass substrate to produce St-IP transferred surface (St-IP LS surface). From the observation of atomic force microscope images, a nanostructure was observed on the transference of Langmuir films. Cell adhesion and detachment were also evaluated on the LS surfaces in response to temperature. Cell adhesion on LS surfaces at 37 ºC was controlled by changing the chemical compositions and densities. After reducing temperature to 20 ºC, adhering cells rapidly detached themselves with lower Am and higher composition of PIPAAm. Our method should be proved novel insights for investigating cell adhesion and detachment on thermo-responsive surfaces. INTRODUCTION Poly(N-isopropylacrylamide) (PIPAAm) exhibits temperature-dependent behaviors above/below their lower critical solution temperature (LCST) at the vicinity of 32 ºC in aqueous solutions [1-3]. This specific characteristic of PIPAAm molecule leads to the various applications on biomedical engineering. As one of the most famous applications, cell adhesion and detachment control on PIPAAm-grafted surface has been investigated intensively. Confluently cultured cells at 37 ºC on the surface are harvested as intact sheet-like cells (so called “cell sheet”) by lowering temperature below the LCST without enzymatic treatment [4,5]. For fabricating a cell sheet, temperature-responsive cell culture surfaces were prepared by various methods including grafting N-isopropylacrylamide monomer by electron beam and physical polymer coating methods such as spin coating [6-9]. This study developed a LangmuirSchaefer (LS) method, as one of the physical polymer coating methods, for fabricating PIPAAmdeposited surfaces. The PIPAAm deposited surfaces with various area per molecule (Am) and chemical compositions were characterized and cell adhesion and detachment characters on the surfaces were also discussed.
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EXPERIMENT Block copolymer of polystyrene-block-poly(N-isopropylacrylamide) (St-IP) with specific molecular weights were synthesized via reversible addition-fragmentation chain transfer radical (RAFT) polymerization. Synthesized St-IP was dissolved in chl
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