To better understand protein/material and cell/material interactions at the submolecular level, well-defined polymer brushes consisting of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) on silicon wafers were prepared by atom transfer radical polymerization (ATRP). Silicon wafers were treated with 3-(2-bromoisobutyryl)propyl dimethylchlorosilane (BDCS) to form a monolayer that acts as initiators for ATRP. Silicon-supported BDCS monolayers were soaked in a methanol/water mixture solution containing Cu(I)Br, bipyridine, and a sacrificial initiator. After MPC was added to the solution, ATRP was carried out for 18 h. The molecular weight and thickness of the PMPC brush layer on the silicon surface increased with an increase in the polymerization time. The dense polymer brushes were obtained by the "grafting from" system. By selective decomposition of the BDCS monolayer by UV light-irradiation, the PMPC brush region and the sizes were well controlled, resulting in fabricating micropatterns of the PMPC brushes. When the thickness of the PMPC brush layer was greater than 5.5 +/- 1.0 nm (3 h polymerization), serum protein adsorption and fibroblast adhesion were effectively reduced, i.e., proteins and cells could recognize such thin polymer brushes on the surface. In addition, the density of the adherent cells on the patterned PMPC brush surface could be controlled by changing the size of the pattern.

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Silicon wafers (100 orientation, P/B doped) were purchased from Yamanaka Semiconductor Co., Ltd., Tokyo, Japan. 2-methacryloyloxyethy phosphorylcholine (MPC) was synthesized by previously reported methods. Glycidyl methacrylate (GMA) and ethyl-2-bromoisobutyrate were purchased from Tokyo Chemical Industry Co., Ltd., Tokyo, Japan, and Sigma-Aldrich, Japan, respectively, and purified by distillation before use. 3-(2-Bromoisobutyryl)propyl dimethylchlorosilane (BDCS) was synthesized as previously described. Purified water (reverse osmosis) was further purified on a Millipore Milli-Q system that involves reverse osmosis, ion exchange, and filtration steps (18.2 M ). Goat anti-mouse IgG F(ab') 2 fragment and goat anti-mouse IgG fluorescein isothiocyanate (FITC) conjugate F(ab') 2 fragment were purchased from Sigma-Aldrich, Japan. Other chemicals were used as received without further purification. Preparation of nanofilaments on Si wafer and initiator immobilizationSilicon wafers were cut into 1.2 cm x 1.2 cm pieces, cleaned before use by ultrasound in toluene for 5 min, and rinsed with toluene, absolute acetone, and absolute ethanol.After being dried in an argon gas stream, the wafers were washed by O 2 plasma for 30 min and placed in a clean oven at 120°C for 2 h. Silanization was immediately performed after treatment of the wafers.The BDCS monolayer on the silicon wafer was prepared by the method previously reported. Briefly, cleaned silicon wafers were held in a custom-designed holder and placed in a dry flask to which 30 mL of dry toluene, triethylamine (21 µL, 0.15 mmol),