Differences in dynamic behavior of single diatom cells caused by changing wavelengths.

We investigate a motion of diatom cells stimulated by a halogen lamp irradiation. Diatom cells are single-celled organisms which have chloroplast. Chloroplast contains photosynthetic pigment which absorbs blue light (wave length of the light is 400 nm-450 nm) and red one (650 nm-700 nm).

Preparation of Thermoresponsive Nanostructured Surfaces for Tissue Engineering.

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir-Schaefer method. Amphiphilic block copolymers composed of polystyrene and PIPAAm (St-IPAAms) were synthesized by reversible addition-fragmentation chain transfer (RAFT) radical polymerization. A chloroform solution of St-IPAAm molecules was gently dropped into a Langmuir-trough apparatus, and both barriers of the apparatus were moved horizontally to compress the film to regulate its density.

Use of a microchamber for analysis of thermal variation of the gliding phenomenon of single Navicula pavillardii cells.

In this study, we used a microchamber to observe and analyze the gliding phenomenon of Navicula pavillardii diatom cells at different temperatures. The temperature of the culture medium was varied from 17.0 to 30.

Thermoresponsive nanostructured surfaces generated by the Langmuir-Schaefer method are suitable for cell sheet fabrication.

Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-immobilized surfaces for controlling cell adhesion and detachment were fabricated by the Langmuir-Schaefer method. Block copolymers composed of polystyrene and PIPAAm (St-IPAAms) having various chain lengths and compositions were synthesized by reversible addition-fragmentation chain transfer radical polymerization. The St-IPAAm Langmuir film at an air-water interface was horizontally transferred onto a hydrophobically modified glass substrate while regulating its density.

Stripe-patterned thermo-responsive cell culture dish for cell separation without cell labeling.

A stripe-patterned thermo-responsive surface is prepared to enable cell separation without labeling. The thermo-responsive surface containing a 3 μm striped pattern exhibits various cell adhesion and detachment properties. A mixture of three cell types is separated on the patterned surface based on their distinct cell-adhesion properties, and the composition of the cells is analyzed by flow cytometry.

Control of cell adhesion and detachment on Langmuir-Schaefer surface composed of dodecyl-terminated thermo-responsive polymers.

This study used Langmuir-Schaefer (LS) method to produce thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) modified surface. Dodecyl terminated-PIPAAm (PIPAAm-C12) was synthesized by reversible addition-fragmentation chain transfer radical polymerization. PIPAAm-C12 was dropped on an air-water interface and formed Langmuir film by compressing.

Rate control of cell sheet recovery by incorporating hydrophilic pattern in thermoresponsive cell culture dish.

Thready stripe-polyacrylamide (PAAm) pattern was fabricated on a thermoresponsive poly(N-isopropylacrylamide) (PIPAAm) surface, and their surface properties were characterized. A PIPAAm surface spin-coated with positive photoresist was irradiated through a 5 µm/5 µm or a 10 µm/10-µm black and white striped photomask, resulting in the radical polymerization of AAm on the photoirradiated area. After staining with Alexa488 bovine serum albumin, the stripe-patterned surface was clearly observed and the patterned surface was also observed by a phase contrast image of an atomic force microscope.

A molded hyaluronic acid gel as a micro-template for blood capillaries.

Fabrication of blood capillaries in tissue-engineered tissue is necessary for creating thick three-dimensional (3D) tissue with a high cellular density. For inducing blood capillaries in the tissue in vitro, a molded hyaluronic acid (HA) capillary-shaped gel was made as a template for blood capillaries by photolithography and power free pumping techniques. The fabricated HA capillary-shaped gel was sandwiched between two cell sheets consisting of neonatal normal human dermal fibroblasts (NHDFs), human umbilical vein endothelial cells (HUVECs), or co-cultured NHDFs and HUVECs, and eventually covered with the cells.

Modulation of cell adhesion and detachment on thermo-responsive polymeric surfaces through the observation of surface dynamics.

Various thermo-responsive polymeric surfaces were evaluated in terms of cell adhesion/detachment and surface analysis. Three kinds of thermo-responsive poly(N-isopropylacrylamide) (PIPAAm) surfaces were prepared by an electron beam irradiation (PIPAAm-EB), a reversible addition fragmentation polymerization (PIPAAm-RAFT), and a redox polymerization (PIPAAm-Redox). Although cell adhesion and detachment on surfaces of PIPAAm-EB and PIPAAm-RAFT were able to be modulated by altering their surface characters with changing the amounts of polymers, the adhesion and detachment were hardly controlled on PIPAAm-Redox surfaces, even though the amounts of polymers on the surface were able to be modulated.

Semi-circular microgrooves to observe active movements of individual Navicula pavillardii cells.

We performed a trajectory analysis of movements of Navicula pavillardii diatom cells that were confined to semi-circular microgrooves with several different curvature radii. Using the semi-circular micropattern, we succeeded in observing change of velocity of the same cell before and after the stimulation by N,N-dimethyl-p-toluidine (DMT). Because the looped grooves had longer contour length than straight grooves, it was effective to achieve the long term observation of the stimulated active cells.

Thermoresponsive poly(N-isopropylacrylamide)-based block copolymer coating for optimizing cell sheet fabrication.

Thermoresponsive surfaces are prepared via a spin-coating method with a block copolymer consisting of poly(N-isopropylacrylamide) (PIPAAm) and poly(butyl methacrylate) (PBMA) on polystyrene surfaces. The PBMA block suppresses the removal of deposited PIPAAm-based polymers from the surface. The polymer coating affects the temperature-dependent cellular behavior of the surfaces with respect to protein adsorption.

Temperature-modulated adsorption of poly(N-isopropylacrylamide)-grafted ferritin on solid substrate.

Ferritin grafted with temperature-responsive poly(N-isopropylacrylamide) (PIPAAm-ferritin) was synthesized by a coupling reaction using PIPAAm and ferritin for obtaining stimuli-responsive biomaterials. The hydrodynamic diameter of PIPAAm-ferritins in aqueous solution increased at 37 °C at a higher protein concentration (>0.2mg/mL) because of the intermolecular aggregation through the hydrophobic interaction of PIPAAm chains.

Two-dimensional trajectory analysis of the diatom Navicula sp. using a micro chamber.

We describe a trajectory analysis of diatom cell locomotion by combining a micro chamber and two-dimensional position coordinate analysis. By shutting cells in a micro chamber, continuous microscopic observation of Navicula sp. cells was possible.

Characterization of ultra-thin temperature-responsive polymer layer and its polymer thickness dependency on cell attachment/detachment properties.

Ultra thin poly(N-isopropylacrylamide) (PIPAAm) modified glass coverslips (PIAPAm-CS) using electron beam irradiation exhibited a clear relationship between the polymer thickness and thermal cell adhesion/detachment behavior. The polymer thickness dependency and the characteristic of ultra thin PIPAAm layer, has been illustrated in terms of the molecular motion of the modified PIPAAm chains. PIPAAm-CSs surfaces with various area-polymer densities and thicknesses were characterized by AFM and protein adsorption assay.

Cell attachment-detachment control on temperature-responsive thin surfaces for novel tissue engineering.

Temperature-responsive intelligent surfaces, prepared by the modification of an interface mainly with poly(N-isopropylacrylamide) and its derivatives, have been investigated. Such surfaces exhibit temperature-responsive hydrophilic/hydrophobic alterations with external temperature changes, which, in turn, result in thermally modulated attachment and detachment with cells. The advantage of this system is that cells cultured on such temperature-responsive surfaces can be recovered as single cells and/or confluent cell sheets, while keeping the deposited extracellular matrix intact, simply by lowering the temperature without conventional enzymatic treatment.

Fabrication of transferable micropatterned-co-cultured cell sheets with microcontact printing.

The purpose of the present study is to develop a novel method for the fabrication of transferable micropatterned cell sheets for tissue engineering. To achieve this development, microcontact printing of fibronectin on commercially available temperature-responsive dishes was employed. Primary rat hepatocytes were seeded on the dish surfaces printed with fibronectin.

Growth of giant two-dimensional crystal of protein molecules from a three-phase contact line.

A novel method to fabricate a two-dimensional (2D) crystal of protein molecules has been developed. The method enables us to control both the position of nucleation and the direction of the crystal growth. The crystal obtained using a protein molecule, ferritin, was found to be composed of a number of densely packed single crystal domains with an unprecedentedly large size of approximately 100 microm(2).

Dynamic interfacial properties of poly(ethylene glycol)-modified ferritin at the solid/liquid interface.

Poly(ethylene glycol)-modified ferritins (PEG-ferritins) with various molecular weights were synthesized by the grafting method, and their dynamic interfacial properties at the solid/liquid interface were investigated. The number of PEG grafted to ferritins was controlled by the amount of 1,1'-carbonyldiimidazole-modified PEG adding to the reaction solution. The adsorption kinetics and energy dissipation of PEG-ferritins onto bare Si substrate and amino-modified Si substrate were investigated with a quartz crystal microbalance (QCM) in 10 mM bis-Tris/HCl buffer (pH 5.

Mechanism underlying specificity of proteins targeting inorganic materials.

Adhesion force analysis using atomic force microscopy clearly revealed for the first time the mechanism underlying the specific binding between a titanium surface and ferritin possessing the sequence of Ti-binding peptide in its N-terminal domain. Our results proved that the specific binding is due to double electrostatic bonds between charged residue and surface groups of the substrate. Furthermore, it is also demonstrated that the accretion of surfactant reduces nonspecific interactions, dramatically enhancing the selectivity and specificity of Ti-binding peptide.