Shigenori Togashi

Preparation of calcium hydroxyapatite nanoparticles using microreactor and their characteristics of protein adsorption.

The calcium hydroxyapatite Ca(10)(PO(4))(6)(OH)(2) (Hap) nanoparticles were prepared by using microreactor and employed these Hap nanoparticles to clarify the adsorption behavior of proteins. The size of Hap particles produced by the microreactor reduced in the order of a hardness of the reaction conditions for mixing Ca(OH)(2) and H(3)PO(4) aqueous solutions, such as flow rates of both solutions and temperature. Finally, the size of the smallest Hap nanoparticle became 2 × 15 nm(2), similar to that of BSA molecule (4 × 14 nm(2)). It is noteworthy that the smallest Hap nanoparticles still possesses rodlike shape, suggesting that particles are grown along c-axis even though the reactants mixed very rapidly in narrow channels of the microreactors. The X-ray diffraction patterns of the Hap nanoparticles revealed that the crystallinity of the materials produced by the microreactor is low. The FTIR measurement indicated that the Hap nanoparticles produced by microreactor were carbonate-substituted type B Hap, where the carbonate ions replace the phosphate ions in the crystal lattice. All the adsorption isotherms of acidic bovine serum albumin (BSA), neutral myoglobin (MGB), and basic lysozyme (LSZ) onto Hap nanoparticles from 1 × 10(-4) mol/dm(3) KCl solution were the Langmuirian type. The saturated amounts of adsorbed BSA (n(S)(BSA)) for the Hap nanoparticles produced by microreactor were decreased with decrease in the mean particle length, and finally it reduced to zero for the smallest Hap nanoparticles. Similar results were observed for the adsorption of LSZ; the saturated amounts of adsorbed LSZ (n(S)(LSZ)) also reduced to zero for the smallest Hap nanoparticles. However, in the case of MGB, the saturated mounts of adsorbed MGB (n(S)(MGB)) are also depressed with decreased in their particle size, but about half of MGB molecules still adsorbed onto the smallest Hap nanoparticles. This difference in the protein adsorption behavior was explained by the difference in the size and flexibility of three kinds of proteins. The reduction of n(S)(BSA) is due to the decrease in the fraction of C sites on the side face of each Hap nanoparticle; i.e., there is not enough area left on the nanoparticle surface to adsorb large BSA molecules even though the BSA molecules are soft and their conformations are alterable. The reduction of n(S)(LSZ) was explained by the reduction of P sites. Further, rigidity of the LSZ molecules was given another possibility of the depression of n(S)(LSZ) for the Hap nanoparticles. However, MGB molecules with small and soft structure were adsorbed on the Hap nanoparticle surface by changing their conformation. We could control the amounts of adsorbed proteins by changing the particle size of Hap in the nanometer range and kinds of proteins. These obtained results may be useful for developing biomimetic materials for bone grafts and successful surgical devices in the biochemical field.

Semi-automated bacterial spore detection system with micro-fluidic chips for aerosol collection, spore treatment and ICAN DNA detection.

A semi-automated bacterial spore detection system (BSDS) was developed to detect biological threat agents (e.g., Bacillus anthracis) on-site. The system comprised an aerosol sampler, micro-fluidic chip-A (for spore germination and cell lysis), micro-fluidic chip-B (for extraction and detection of genomic DNA) and an analyzer. An aerosol with bacterial spores was first collected in the collection chamber of chip-A with a velocity of 300 l/min, and the chip-A was taken off from the aerosol sampler and loaded into the analyzer. Reagents packaged in the chip-A were sequentially applied into the chamber. The genomic DNA extract from spore lyzate was manually transferred from chip-A to chip-B and loaded into the analyzer. Genomic DNA in chip-B was first trapped on a glass bead column, washed with various reagents, and eluted to the detection chamber by sequential auto-dispensing. Isothermal and chimeric primer-initiated amplification of nucleic acids (ICAN) with fluorescent measurement was adopted to amplify and detect target DNA. Bacillus subtilis was the stimulant of biological warfare agent in this experiment. Pretreatment conditions were optimized by examining bacterial target DNA recovery in the respective steps (aerosol collection, spore germination, cell lysis, and DNA extraction), by an off-chip experiment using a real-time polymerase chain reaction quantification method. Without the germination step, B. subtilis spores did not demonstrate amplification of target DNA. The detection of 10(4) spores was achieved within 2h throughout the micro-fluidic process.

Comparison of turbulence models applied to backward-facing step flow by LES data base

In our previous works, we have already computed backward facing step flow by Large Eddy Simulation and obtained the satisfactory results as compared with experimental data. In this paper, the behavior of time-averaged turbulence models and the influence of the diffusion model in the turbulent energy equation were investigated by the LES data base. It was found that Rodis algebraic stress model was valid for this flow as compared with the eddy viscosity model, and the gradient-diffusion model for the turbulent diffusion term could not predict well the k distribution in the recirculating region. Hence, a new diffusion model proposed by Yoshizawa was applied, and the relation between the reattachment length and the turbulent energy distribution in the recirculating region was discussed.

Feasibility of the LES for engineering problems

Presents four examples which were researched in a large eddy simulation (LES) of turbulence for engineering applications. Explains that, in the former two cases, developments of the advanced LES are indicated in a Smagorinsky model and in the treatments of the wall and the external boundary, and, in the later cases, the LES on the boundary fitted grids are applied using the finite different method (FDM) and the finite element method (FEM), where new numerical treatments, a composite grid technique and a modified scheme, are adopted for efficient calculations. Evaluates the results, and discusses the possible application of the LES for engineering problems.

Application of Hybrid Petri Nets for a Drawing Blood Flow from Fingertip.

Our objective of this study are to make a fluid dynamical model and to conduct the flow simulation for obtaining a large amount of drawing blood from a fingertip. The processes of drawing blood are hybrid systems including both the continuity system of blood flow and the discrete systems of cuff pressing and puncture. Therefore, we made the modelling of the fingertip drwaing blood process from the analogy of fluid daynamic tank and pipe systems control using hybrid Petri nets. Using the hybrid Petri nets simulation with cuff pressing and puncture modeled as discrete and blood flow modeled as continuity, we confirmed that the simulation results were agreement with the experimental drawing blood data.

Analysis of particle in liquid using excitation-fluorescence spectral flow cytometer

We have developed a new flow cytometer that can measure the excitation-fluorescence spectra of a single particle. This system consists of a solution-transmitting unit and an optical unit. The solution-transmitting unit allows a sample containing particles to flow through the center of a flow cell by hydrodynamic focusing. The optical unit irradiates particles with dispersed white light (wavelength band: 400–650 nm) along the flow direction and measures their fluorescence spectra (wavelength band: 400–700 nm) using a spectroscopic photodetector array. The fluorescence spectrum of a particle changes with the shift of the wavelength of the excitation light. Using this system, the excitation-fluorescence spectra of a fluorescent particle were measured. Additionally, a homogenized tomato suspension and a homogenized spinach suspension were measured using the system. Measurement results show that it is possible to determine the components of vegetables by comparing measured fluorescence spectra of particles in a vegetable suspension.

Airborne virus detection by a sensing system using a disposable integrated impaction device.

There are many respiratory infections such as influenza that cause epidemics. These respiratory infection epidemics can be effectively prevented by determining the presence or absence of infections in patients using frequent tests. We think that self-diagnosis may be possible using a system that can collect and detect biological aerosol particles in the patients breath because breath sampling is easy work requiring no examiner. In this paper, we report a sensing system for biological aerosol particles (SSBAP) with a disposable device. Using the system and the device, someone with no medical knowledge or skills can safely, easily, and rapidly detect infectious biological aerosol particles. The disposable device, which is the core of the SSBAP, can be an impactor for biological aerosol particles, a flow-cell for reagents, and an optical window for the fluorescent detection of collected particles. Furthermore, to detect the fluorescence of very small collected particles, this disposable device is covered with a light-blocking film that lets only fluorescence of particles pass through a fluorescence detector of the SSBAP. The SSBAP using the device can automatically detect biological aerosol particles by the following process: collecting biological aerosol particles from a patients breath in a sampling bag by the impaction method, labeling the collected biological aerosol particles with fluorescent dyes by the antigen-antibody reaction, removing free fluorescent dyes, and detecting the fluorescence of the biological aerosol particles. The collection efficiency of the device for microspheres aerosolized in the sampling bag was more than 97%, and the SSBAP with the device could detect more than 8.3  ×  10(3) particles l(-1) of aerosolized influenza virus particles within 10 min.

Optimization of Chemical Reaction Processes in Microreactors Using Reaction Rate Analyses

We applied microreactors to the three following reactions: a consecutive bromination reaction, the two-step Sandmeyer reaction, and an acetylation reaction including solvent effects. We obtained the reaction rate constants from few experimental data or quantum chemical calculations and optimized the reaction conditions such as the reaction times and temperature. We then experimentally validated them by microreactors. A consecutive bromination reaction, where the objective reaction was followed by the side reaction, was one of the processes. The reaction temperature played an important role in the effects of a microreactor. The yield of the objective product was improved by about 40% using a microreactor. The two-step Sandmeyer reaction was also applied, where the 1st-step reaction was followed by the 2nd-step reaction to produce the objective product. The 1st-step reaction had the diffusion-controlled process, while the 2nd-step reaction had the reaction-controlled one. The yield of the objective product was improved when microreactors were used and the reaction time for the 2nd-step reaction was set appropriately. Moreover, an acetylation reaction including solvent effects on reaction rates was considered and the solvent effects could be predicted from quantum chemical calculations. The calculation suggested that acetic acid with the larger electron-accepting property gave more stability to the species formed in the transition state. The reaction time was shortened using a microreactor, when the reaction process was changed from reaction-controlled to diffusion-controlled by changing the solvent used.Copyright

Prediction of Chemical Reaction Yield in a Microreactor and Development of a Pilot Plant Using the Numbering-Up of Microreactors

The chemical reaction yield was predicted by using Monte Carlo simulation. The targeted chemical reaction of a performance evaluation using the microreactor is the consecutive reaction. The main product P1 is formed in the first stage with the reaction rate constant k1. Moreover, the byproduct P2 is formed in the second stage with the reaction rate constant k2. It was found that the yield of main product P1 was improved by using a microreactor when the ratio of the reaction rate constants became k1/k2 >1. To evaluate the Monte Carlo simulation result, the yields of the main products obtained in three consecutive reactions. It was found that the yield of the main product in cased of k1/k2 >1 increased when the microreactor was uesd. Next, a pilot plant involving the numbering-up of 20 microreactors was developed. The 20 microreactor units were stacked in four sets, each containing five microreactor units arranged. The maximum flow rate when 20 microreactors were used was 1 × 104 mm3 /s, which corresponds to 72 t/year. Evaluation of the chemical performance of the pilot plant was conducted using a nitration reaction. The pilot plant was found to capable of increasing the production scale without decreasing the yield of the products.Copyright

Microreactor System Using the Concept of Numbering-Up

Microreactor system using 20 numbering-up microreactors was developed. The 20 microreactor units were stacked five deep and in four rows like a computer blade server. The maximum flow rate using the 20 microreactors was 72 tons/year. Moreover, a nitration reaction of phenol with nitric acid was done as a real evaluation using a chemical reaction. It was found that the microreactor system using the 20 numbering-up microreactors was able to increase the production scale without decreasing the yield of the products.