Jin Nishida

Mesoscopic patterns of molecular aggregates on solid substrates

Abstract A two-dimensional micron-sized honeycomb structure was formed when a chloroform solution of an amphiphilic polymer was cast on solid surfaces at high atmospheric humidity. This simple method is widely applicable for patterning of molecular aggregates on solid surfaces. Mesoscopic patterns are demonstrated to be formed spontaneously from a variety of amphiphilic polyion complexes, amphiphilic covalent polymers, and organic–inorganic hybrid materials. Size and structure of the patterns can be regulated by concentration, atmospheric humidity, etc.

Honeycomb-patterned thin films of amphiphilic polymers as cell culture substrates

Abstract Recently, we have found honeycomb patterns with sub-micron line width that form during the non-equilibrium process of cast film formation. The honeycomb-patterned films were fabricated using four macromolecular compounds (amphiphilic copolymers containing lactose units or carboxyl groups as side-chains and polyion complexes composed of anionic polysaccharides). The specific binding of lactose by lectin confirmed that the lactose moieties contained in the honeycomb films work as biologically active ligands. Bovine serum albumin (BSA) labeled with fluorescein was covalently attached to the honeycomb films using water-soluble carbodiimide (WSC) as an activator. Using fluorescence imaging of the modified film, we could show that the proteins are immobilized on the honeycomb patterns. Adhesion of bovine aorta endothelial cells (ECs) to the honeycomb films indicates that the honeycomb structure works as an adhesive site for the cells.

Mesoscopic patterning of cell adhesive substrates as novel biofunctional interfaces

In this report, cell adhesion to honeycomb-patterned films is described with respect to the dimensions of the honeycomb structure. The honeycomb-patterned films can be fabricated by casting a dilute solution of amphiphilic polymers on solid substrates. The honeycomb structure is not homogeneous in all dimensions. Analysis of distribution of the honeycomb hole sizes demonstrates a gradual decrease in honeycomb hole diameter along the radius of the cast area. The largest holes were located near geometric center of the cast area. The diameter of the largest honeycomb holes in the cast area could be controlled by varying the cast volume of the polymer solution. Cell cultures on the honeycomb films demonstrated that cell adhesion could be inhibited at the outer region of the cast area. The extent of the inhibition of cell adhesion was influenced by the chemical properties of the polymers constituting the honeycomb films.

Photonic and Electronic Applications of Mesoscopic Polymer Assemblies

Abstract Mesoscopic two-dimensional patterns, regular dots, stripes, and honeycomb networks are formed when dilute organic solutions of polymers are cast on solid surfaces. Dynamic patterns, so-called “dissipative structures”, formed in the non-equilibrium thermodynamic process of solvent evaporation, are fixed as the two-dimensional polymer patterns on substrates. Some photonic and electronic applications of the mesoscopic polymer patterns are described in this article.

Stabilization of Micropatterned Polymer Films as Artificial Extracellular Matrices for Tissue Engineering

Abstract Honeycomb-patterned polymer films are formed upon self-organization of water microspheres stabilized by amphiphilic polymers. The honeycomb films can work as cell culture substrates. The films composed of heparin-cationic lipid complex, however, gradually lost the honeycomb structure when immersed in culture medium. Crosslinking of the films was carried to stabilize the honeycomb pattern. A bisazido derivative was used as a crosslinker connecting the constituent polymer of the honeycomb films. Morphological study of the immersed films revealed that the crosslinked films maintained the honeycomb structure in the phosphate buffer solution.

CIRCULAR ARRANGEMENT OF AZOBENZENE CHROMOPHORES IN THE NUCLEOAMPHIPHILE MONOLAYER BY BASE-PAIRING WITH CYCLIC DNA

In order to construct chromophores arrays that precisely controlled their arrangement, monolayers of an azobenzene bearing nucleoamphiphile were prepared on various oligoDNA solutions. Monolayers of the amphiphilic adenine derivative bearing an azobenzene moiety (C12AzoC5Ade) were prepared on thymidylic acid tetramer (dT4) and octamer (dT8) solutions, and UV-vis reflection absorption spectra of the monolayers were measured to investigate aggregation structures of the azobenzene. The absorption maximum of the monolayer was blue-shifted on the dT4 solution and red-shifted on the dT8 solution. It shows that azobenzene groups in the monolayer have parallel orientation (H aggregate) on the dT4 solution. Though, azobenzene groups have head-to-tail orientation (J aggregates) on the dT8 solution. When monolayers of C12AzoC5Ade were prepared on the synthesized cyclic oligonucleotides, the absorption spectra were totally different from those of the corresponding linear oligonucleotides.