Local nano-electrode fabrication utilizing nanofluidic and nano-electrochemical control.

Miniaturized systems have attracted much attention with the recent advances in microfluidics and nanofluidics. From the capillary electrophoresis, the development of glass-based microfluidic and nanofluidic technologies has supported advances in microfluidics and nanofluidics. Most microfluidic systems, especially nanofluidic systems, are still simple, such as systems constructed with simple straight nanochannels and bulk-scale electrodes.

Room-temperature bonding of glass chips PTFE-assisted plasma modification for nanofluidic applications.

Fused-silica glass, as a desirable material with rigidity, biological inertness, and favorable light transmission for nanofluidic devices, should be assembled low-temperature bonding technology to hermetically seal channels for stable liquid manipulation in extended-nano (10-10 nm) space. Confronted with the predicament of localized functionalization of nanofluidic applications ( DNA microarray) with temperature-sensitive structures, the room-temperature direct bonding of glass chips to achieve modification of channels prior to bonding offers a considerably attractive solution to avoid component denaturation during the conventional post-bonding heating process. Therefore, we developed a nano-structure friendly and technically convenient room-temperature (RT, 25 °C) glass-glass direct bonding technology using polytetrafluoroethylene (PTFE)-assisted plasma modification without a requirement for special equipment.

Quantitative characterization of liquids flowing in geometrically controlled sub-100 nm nanofluidic channels.

With development of nanotechnologies, applications exploiting nanospaces such as single-molecule analysis and high-efficiency separation have been reported, and understanding properties of fluid flows in 10 nm to 10 nm scale spaces becomes important. Nanofluidics has provided a platform of nanochannels with defined size and geometry, and revealed various unique liquid properties including higher water viscosity with dominant surface effects in 10 nm spaces. However, experimental investigation of fluid flows in 10 nm spaces is still difficult owing to lack of fabrication procedure for 10 nm nanochannels with smooth walls and precisely controlled geometry.

Stability of enzyme immobilized on the nanofluidic channel surface.

The lifetime of an enzyme is critical to prevent system failure and optimize maintenance schedules in biological and analytical chemistry. The lifetime metrics of an enzyme can be evaluated from enzyme activity in terms of catalytic cycles per enzyme at various storage times. Trypsin, which is a gold-standard enzyme in proteomics, has been known to decrease activity due to self-digestion.

Enzyme-linked immunosorbent assay using thin-layered microfluidics with perfect capture of the target protein.

We developed a process for enzyme-linked immunosorbent assay on a glass microchip the use of a thin-layered microfluidic channel. This channel possesses a high aspect ratio (width/depth ∼200) and has an antibody layer immobilized directly on the channel surface. A depth of several microns and an excessive width and length (mm scale) of the channel provide a large-volume capacity (10 nL) and maximum capture efficiency of the analyte for a high level of detection sensitivity (10 pg mL).

Nanofluidic analytical system integrated with nanochannel open/close valves for enzyme-linked immunosorbent assay.

There have been significant advances in the field of nanofluidics, and novel technologies such as single-cell analysis have been demonstrated. Despite the evident advantages of nanofluidics, fluid control in nanochannels for complicated analyses is extremely difficult because the fluids are currently manipulated by maintaining the balance of driving pressure. To address this issue, the use of valves will be essential.

Kinetics of Enzymatic Reactions at the Solid/Liquid Interface in Nanofluidic Channels.

Nanostructures can realize highly efficient reactions due to their structural advantages. However, the mechanism of accelerating enzyme reactions in a nanospace is still unknown from a kinetic perspective because it is difficult to control a well-defined nanospace, enzyme density, and reaction time. Here, we investigated kinetic parameters of an immobilized enzyme in micro- and nanochannels using nanofabrication, partial enzyme patterning, fluidic control, and a high sensitivity detection system.

Proton diffusion and hydrolysis enzymatic reaction in 100 nm scale biomimetic nanochannels.

Liquids in 10-100 nm spaces are expected to play an important role in biological systems. However, the liquid properties and their influence on biological activity have been obscured due to the difficulty in nanoscale measurements, either or . In this study, an analytical platform for biological systems is established.

Femtoliter-Droplet Mass Spectrometry Interface Utilizing Nanofluidics for Ultrasmall and High-Sensitivity Analysis.

In the fields of biology and medicine, comprehensive protein analysis at the single-cell level utilizing mass spectrometry (MS) with pL sample volumes and zmol to amol sensitivity is required. Our group has developed nanofluidic analytical pretreatment methods that exploit nanochannels for downsizing chemical unit operations to fL-pL volumes. In the field of analytical instruments, mass spectrometers have advanced to achieve ultrahigh sensitivity.

Characterization of pressure-driven water flows in nanofluidic channels by mass flowmetry.

With developments in analytical devices promoted by nanofluidics, estimation of the flow rate in a nanochannel has become important to calculate volumes of samples and reagents in chemical processing. However, measurement of the flow rate in nanospaces remains challenging. In the present study, a mass flowmetry system was developed, and the flow rate of water by pressure-driven flow in a fused-silica nanochannel was successfully measured in picoliters per second.

Accelerated protein digestion and separation with picoliter volume utilizing nanofluidics.

Single cell analyses can provide critical biological insight into cellular heterogeneity. In particular, the proteome, which governs cell functions, is much more difficult to analyze because it is principally impossible to amplify proteins compared to nucleic acids. The most promising approach to single cell proteomics is based on the liquid chromatography mass spectrometry (LC-MS) platform.

Single-cell-level protein analysis revealing the roles of autoantigen-reactive B lymphocytes in autoimmune disease and the murine model.

Despite antigen affinity of B cells varying from cell to cell, functional analyses of antigen-reactive B cells on individual B cells are missing due to technical difficulties. Especially in the field of autoimmune diseases, promising pathogenic B cells have not been adequately studied to date because of its rarity. In this study, functions of autoantigen-reactive B cells in autoimmune disease were analyzed at the single-cell level.

Surface Patterning of Closed Nanochannel Using VUV Light and Surface Evaluation by Streaming Current.

In nanofluidics, surface control is a critical technology because nanospaces are surface-governed spaces as a consequence of their extremely high surface-to-volume ratio. Various surface patterning methods have been developed, including patterning on an open substrate and patterning using a liquid modifier in microchannels. However, the surface patterning of a closed nanochannel is difficult.

Interleukin-31 promotes fibrosis and T helper 2 polarization in systemic sclerosis.

Systemic sclerosis (SSc) is a chronic multisystem disorder characterized by fibrosis and autoimmunity. Interleukin (IL)-31 has been implicated in fibrosis and T helper (Th) 2 immune responses, both of which are characteristics of SSc. The exact role of IL-31 in SSc pathogenesis is unclear.

Super-Resolution Defocusing Nanoparticle Image Velocimetry Utilizing Spherical Aberration for Nanochannel Flows.

Understanding fluid flows and mass transport in nanospaces is becoming important with recent advances in nanofluidic analytical devices utilizing nanopores and nanochannels. In the present study, we developed a super-resolution and fast particle tracking method utilizing defocusing images with spherical aberration and demonstrated the measurement of nanochannel flow. Since the spherical aberration generates the defocusing nanoparticle image with diffraction rings, the position of fluorescent nanoparticles was determined from the radius of the diffraction ring.

Metal-Free Fabrication of Fused Silica Extended Nanofluidic Channel to Remove Artifacts in Chemical Analysis.

In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single-molecule level due to the small size of the nanochannel. In such surroundings, contamination of the channel surface should be removed at the single-molecule level.

Stable Formation of Aqueous/Organic Parallel Two-phase Flow in Nanochannels with Partial Surface Modification.

In microfluidics, various chemical processes can be integrated utilizing parallel multiphase flows. Our group has extended this research to nanofluidics, and recently performed the extraction of lipids using parallel two-phase flow in nanochannels. Although this was achieved in surface-modified nanochannels, a stable condition of parallel two-phase flow remains unknown due to difficulties in device fabrication, for a suitable method of bonding surface-modified substrates is lacking.

B Cell Depletion Inhibits Fibrosis via Suppression of Profibrotic Macrophage Differentiation in a Mouse Model of Systemic Sclerosis.

Objective: We undertook this study to investigate the effect of B cell depletion on fibrosis in systemic sclerosis (SSc) and its mechanism of action.

Methods: Mice with bleomycin-induced SSc (BLM-SSc) were treated with anti-CD20 antibody, and skin and lung fibrosis were histopathologically evaluated. T cells and macrophages were cocultured with B cells, and the effect of B cells on their differentiation was assessed by flow cytometry.

Isotope Effect in the Liquid Properties of Water Confined in 100 nm Nanofluidic Channels.

Liquids confined in 10-100 nm spaces show different liquid properties from those in the bulk. Proton transfer plays an essential role in liquid properties. The Grotthuss mechanism, in which charge transfer occurs among neighboring water molecules, is considered to be dominant in bulk water.

Fabrication of Infrared-Compatible Nanofluidic Devices for Plasmon-Enhanced Infrared Absorption Spectroscopy.

Nanofluidic devices have offered us fascinating analytical platforms for chemical and bioanalysis by exploiting unique properties of liquids and molecules confined in nanospaces. The increasing interests in nanofluidic analytical devices have triggered the development of new robust and sensitive detection techniques, especially label-free ones. IR absorption spectroscopy is one of the most powerful biochemical analysis methods for identification and quantitative measurement of chemical species in the label-free and non-invasive fashion.

Advanced Top-Down Fabrication for a Fused Silica Nanofluidic Device.

Nanofluidics have recently attracted significant attention with regard to the development of new functionalities and applications, and producing new functional devices utilizing nanofluidics will require the fabrication of nanochannels. Fused silica nanofluidic devices fabricated by top-down methods are a promising approach to realizing this goal. Our group previously demonstrated the analysis of a living single cell using such a device, incorporating nanochannels having different sizes (10-10 nm) and with branched and confluent structures and surface patterning.

Picoliter enzyme reactor on a nanofluidic device exceeding the bulk reaction rate.

Single-cell analyses have recently become important to understand cell heterogeneity, the mechanism of cell function, and diseases. In contrast to single-cell analyses that target nucleic acids, single-cell protein analyses still pose challenges. We have proposed a general concept of integration and extended this concept to the 10-1000 nm scale with femtoliter-picoliter volumes which are smaller than the volume of a single cell exploring ultimate analytical performances (e.

Lipid Bilayer-Modified Nanofluidic Channels of Sizes with Hundreds of Nanometers for Characterization of Confined Water and Molecular/Ion Transport.

Water inside and between cells with dimensions on the order of 10-10 nm such as synaptic clefts and mitochondria is thought to be important to biological functions, such as signal transmissions and energy production. However, the characterization of water in such spaces has been difficult owing to the small size and complexity of cellular environments. To this end, we proposed and fabricated a biomimetic nanospace exploiting nanofluidic channels with defined dimensions of hundreds of nanometers and controlled environments.

Ultrasensitive detection of nonlabelled bovine serum albumin using photothermal optical phase shift detection with UV excitation.

Ultrasensitive detection of nonlabelled bovine serum albumin is performed in micro/nanofluidic chips using a photothermal optical phase shift (POPS) detection system. Currently, micro- and nanofluidics allow the analysis of various single cells, and their targets of interest are shifting from nucleic acids to proteins. Previously, our group developed photothermal detection techniques for the sensitive detection of nonfluorescent molecules.