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Department of Chemistry, KAIST, Daejeon 305-701, Korea. *E-mail: ischoi@kaist.ac.kr Department of Marine Bio-Materials & Aquaculture, Pukyong National University, Busan 608-737, Korea Department of BioNanomaterials, Bio-Campus of Korea Polytechnic, Chung-nam 320-905, Korea Department of Science Education, Kyungnam University, Masan 631-701, Korea Department of Chemistry, Kyungpook National University, Daegu 701-702, Korea. *E-mail: jkl@knu.ac.kr Received January 28, 2013, Accepted February 24, 2013

Ali et al. performed variouschemical analyses including BAC, and found that the squidbeak consists of chitin, water, and DOPA-containing pro-teins. Although the exact role of DOPA-containing proteinshas not been elucidated, the identification of the specificprotein provided a meaningful insight to understand theextraordinary mechanical properties of squid beak. BAC hasbeen also utilized in the analysis of sandcastle worm’sunderwater adhesion.

Because the uncontrolled adhesion of cells onto synthetic surfaces causes the malfunctioning of biomedical devices, the control of cell adhesion on artificial surfaces is of importance, especially in the biomedical field. Thus, various approaches have been developed to control cell adhesion on surfaces; among them, cell-resistant polymer coatings have extensively been utilized. Poly(ethylene glycol) and zwitterionic polymers are representative examples of polymers that display cell-resistant properties, and they have successfully been introduced onto a wide range of surfaces by appropriate immobilization techniques. With the growing interest in control over cell adhesion onto surfaces, another approach to achieving this goal has recently been developed, which is based on superhydrophobic surfaces. As hydrophobic coating of nanostructured surfaces has been identified as a key method for introducing the selfcleaningand superhydrophobic-surface properties of lotus leaves, both the construction and applications of biomimetic superhydrophobic surfaces have extensively been investigated. As a result, several promising properties, including the repellence of cells, have been reported. For instance, Lei et al. fabricated superhydrophobic surfaces by using aligned carbon nanotubes and reported that platelet adhesion was considerably reduced. Stratakis et al. investigated cell adhesion on nanostructured superhydrophobic surfaces as well, and concluded that the mammalian cell adhesion could be controlled by varying the roughness and wettability of the surface. The application of superhydrophobic surface has further advanced to the selective attachment of cells. Patterning of cells on superhydrophobic surfaces was, for instance, realized by site-specific UV/plasma treatment, giving rise to the hydrophilic/superhydrophobic patterning. Line-, circle-, and square-shaped hydrophilic patterns were fabricated on the surface, with the cell adherence only onto the hydrophilic region, resulting in spatio-selective cell adhesion. Although superhydrophobic surfaces have been applied to the preparation of cell patterns, the applied methods display several drawbacks with respect to practical use. They require external instruments for modifying the superhydrophobic surfaces. In addition, the methods are transient; the hydrophilicity decreases over time, eventually reverting to the original (hydrophobic) state. Therefore, a permanent method for modifying superhydrophobic surfaces is required. Indeed, recently, a facile and robust approach to modifying superhydrophobic surfaces was developed based on polydopamine coating. During polydopamine coating, dopamine is used to modify the surface under alkaline conditions, resulting in polydopamine-coated substrates. The advantage of this method is that it can be applied to any material surfaces, including superhydrophobic surfaces. Moreover, it is known that polydopamine-coated surfaces show excellent cell-adhesive properties. We, therefore, reasoned that polydopamine-coated superhydrophobic surfaces could provide efficient platforms for controlling cell adhesion. For the preparation of a superhydrophobic surface, anodized aluminum oxide was used as a nanostructured surface onto which hydrophobic fluorosilane was deposited. After preparation, the surface was selectively coated with polydopamine to induce cell-adhesive properties. Selective polydopamine coating was performed by half-masking the surface using a polydimethylsiloxane (PDMS) slab, which was carefully removed after 18-h coating (Figure 1). Modification of the superhydrophobic surface by polydopamine was characterized by water-contact angle measurements. The significant change in the angle from 157.5 ± 3.0 to 36.3 ± 1.4 indicated that the surface was successfully modified by a layer of polydopamine (Figure 2). The surface was further analyzed by X-ray photoelectron spectroscopy (XPS). The unmodified superhydrophobic surface showed an intense CF2 peak at 291 eV, originating from the hydrophobic fluorosilane layers. After polydopamine coating, a decrease in intensity of the peak at 291 eV was observed, and the peak at 284 eV, corresponding to the C 1s of the polydopamine

E-mail: haeshin@kaist.ac.krReceived November 1, 2012, Accepted December 10, 2012Key Words : Biomimetics, Surface modification, HOPG, Characterizations, BiocompatibilityCarbon substrates, including highly ordered pyrolyticgraphite (HOPG), carbon nanotubes, and graphene, havegained a great deal of attention because of their usefulfeatures that stem from their favorable mechanical, elec-trical, and thermal properties.

Department of Marine Bio-Materials & Aquaculture, Pukyong National University, Busan 608-737, Korea *E-mail: smk12@pknu.ac.kr Department of Chemistry, KAIST, Daejeon 305-701, Korea. *E-mail: ischoi@kaist.ac.kr Graduate School of Nanoscience & Technology, KAIST, Daejeon 305-701, Korea Department of Chemistry, Ewha Womans University, Seoul 120-750, Korea Received June 4, 2013, Accepted July 25, 2013

Biosilicification in diatoms and sponges potentially promises physiological, mild reaction conditions for controlling silica structures at the nanometer scale. Since Sumper et al. had isolated catalytic peptides (i.e., silaffins) from diatoms, a number of polymers bearing tertiary amine or ammonium groups have been used as a counterpart of silaffins to biomimetically synthesize silica structures. This biomimetic silicification has several advantages over conventional chemical methods. For instance, biomimetic silicification provides relatively uniform films over large areas under physiological reaction conditions without special equipment. Moreover, this method can be simply incorporated into conventional processes. As a result, recent years have witnessed a growing interest in the applications of biomimetic silicification, such as surface coating and patterning, sensors, (bio)catalysis, nanohybrids, and biotechnology. Especially, micropattern generation through biomimetic silicification has been of interest due to its potential applications in microelectronics. For example, Stone et al. generated sub-micrometer sized silica patterns by holographic two-photon-induced photopolymerization. In addition, Choi et al. reported the controlled pattern generation of silica on a solid substrate through atom-transfer radical polymerization and silicification. However, previous examples were performed on the limited kinds of materials due to the lack of versatility, and thus a versatile method of silica pattern generation has been required for wider applications. Very recently, a material-independent silica coating method was investigated by a combination of mussel-inspired polydopamine coating and subsequent diatom-inspired silicification. This method enabled us to achieve the silica coating of many diverse materials. Furthermore, it was successfully applied to the preparation of thermally stable silica/ polyethylene separators utilized in Li-ion batteries. The musseland diatom-inspired silica coating method has another advantage to use. It can be easily combined with a micromolding in capillaries (MIMIC) technique, which is a soft lithographic technique. In MIMIC technique, microchannels of poly(dimethylsiloxane) (PDMS) are filled with a solution, and the solution is then incubated for interfacial reaction onto surfaces. In the same manner, as the alkaline solution of dopamine is injected into the microchannels, polydopamine films are selectively deposited on the surface. Herein, we demonstrate a procedure for generating silica patterns by the above-mentioned method. Figure 1 shows the schematic description of the procedure. Briefly, MIMIC

Tego Science, Daerung Technotown 3. #101, 488 Ga san-dong, Gumcheon-gu, Seoul 153-803, KoreaReceived April 6, 2004Key Words : Stimuli-responsive surfaces, Bioadhesion, Surf ace-initiated polymerization, Thermoresponsive-ness, Poly(N-isopropylacrylamide)Stimuli-responsive surfaces, which switch their physical,chemical and biological properties in response to externalstimuli, have a great potential in many technologicallyimportant areas such as nanoelectromechanical systems,bioanalysis, and biomimetics.