Mechanical stretching induced alternation of cell attachment and detachment character of poly(N-isopropylacrylamide) gel grafted PDMS surface

Abstract

Event Abstract Back to Event Mechanical stretching induced alternation of cell attachment and detachment character of poly(N-isopropylacrylamide) gel grafted PDMS surface Yoshikatsu Akiyama1, Miki Matsuyama2, Naoya Takeda2, Masayuki Yamato1 and Teruo Okano1 1 Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University, Japan 2 Department of Life Science and Medical Bioscience, School of Advanced Science and Engineering, Waseda University, Japan Introduction: Temperature-responsive cell culture surface, poly(N-isopropylacrylamide) (PIPAAm) hydrogel grafted tissue culture polystyrene (PIPAAm-TCPS), has been utilized for cell-sheet based tissue-engineering. PIPAAm-TCPS shows temperature-dependent cell attachment and detachment character, which is one of characteristics of PIPAAm-TCPS[1]. Based on a hypothesis that thickness of graft PIPAAm hydrogel layer were altered by applying mechanical stress to PIPAAm gel grafted substrate (Fig. 1), we modified PDMS surfaces with ultra-thin PIPAAm hydrogel (PIPAAm-PDMS) and characterized stretched and unstretched PIPAAm-PDMS surfaces as a new stretchable temperature-responsive cell culture surfaces. Experimental Methods: PIPAAm-PDMS was prepared referring to a previous report[2]. IPAAm monomer dissolved in 2-propanol (monomer concentration, 40 wt%) was spread onto 4-well PDMS cell culture surfaces (each chamber size was 16 mm square), which was purchased from STREX, Inc., followed by O2 plasma and (3-aminoproyl)trimethoxysilane (APTMS) treatments. And then, the surface was subjected to EB irradiation. During EB irradiation, polymerization and grafting polymer on PDMS surface occurred simultaneously. PIPAAm-PDMS was characterized by FT-IR / ATR, XPS analysis, contact angle measurement and cell detachment / attachment assay. For the cell attachment and detachment assay, PIPAA-PDMS with about 10.0 ug/cm2 of PIPAAm graft density was used. Uniaxial mechanical-stress was applied to the PIPAAm-PDMS surfaces with a special device (purchased from STEX, Inc.). In this experiment, 20% of stretch ratio was used for the characterization of stretched PIPAAm-PDMS surface. Results: To prove a hypothesis, PDMS was selected as a model elastic substrate in this experiment. Uniaxially stretched and unstretched PIPAAm-PDMS surfaces were evaluated by a variety of surface analysis methods. By modifying PDMS with PIPAAm hydrogel, contact angle decreased from 110º (unstretched PDMS) to 78º (unstretched PIPAAm-PDMS) at 37ºC (Fig. 2). The stretched and unstrethced PIPAAm-PDMS surfaces showed temperature-dependent contact angles alternation. However, by applying 20% of uniaxial mechanical stretching stress to PIPAAm-PDMS, the contact angles increased form 78º (unstretched PIPAAm-PDMS) to 83º (stretched PIPAAm-PDMS). AFM image of PIPAAm-PDMS surface showed PIPAAm nano-particles, which uniformly covered PDMS surface. The thickness of the graft PIPAAm hydrogel layer decreased from 700 nm to 480 nm (Fig. 3). Considering that temperature-responsive cell culture surfaces with thinner PIPAAm hydrogel layer shows more hydrophobic property, that PIPAAm-PDMS surface properties were altered by the applied mechanical stretching stress. Cell attachment assay also suggested that the stretched PIPAAm-PDMS was more cells adhesive. These results possibly suggest that PIPAAm-PDMS surface properties are controllable by the degree of applied mechanical stress. Grant-in-Aid for Scientific Research (No. 23106009) in Innovative Areas "Bio Assembler" from MEXT