Yuma Suzuki

Influence of structural dimensions of micro-pillar array in reaction field on sensitivity of enzyme-linked immunosorbent assay (ELISA)

ABSTRACT For high sensitivity and rapid reaction of enzyme-linked immunosorbent assay (ELISA), the film-stack reaction field with micro-pillars array was designed and developed. The film-stack reaction field was fabricated by a nanoimprint process and an automatic punch-press process. The films with different gaps between micro-pillars (5, 10 and 50 μm) were prepared. These reaction fields were evaluated by IgA ELISA using 96-well microtitre plates and the computational simulation analysis of the fluid flow and the particle trajectory. Compared with ELISA using only the microtitre plate, higher detection sensitivity and shorter incubation time were achieved using the film-stack reaction field due to the increased surface area and the circulating flow through the space between films in a well by the rotation of the film-stack reaction field. Furthermore, in the ELISA results obtained using the film-stack reaction fields, the fluorescence intensities in 10-μm and 50-μm pillar gaps were the minimum and maximum values, respectively. This trend was due to the flow rate between micro-pillars, and the number and the diffusion distance of supplied biomolecules to the inertial space in the film-stack reaction field. In simulation results, the trend of the number of adsorbed biomolecule particles with different gaps between micro-pillars was in agreement with the trend in the ELISA results. Hence, these simulation analyses were validated in the quantitative evaluation of this reaction field and could be applied in the design of this reaction field as an effective design tool.

The Optimization of Vertically Aligned Carbon Nanotubes’ Synthesis According to the Selected Parameters

Vertically aligned carbon nanotubes (VACNTs or CNTs) were synthetized by thermal chemical vapor deposition method on the Si/SiO2 substrates, using Al/Fe as catalyst. In the present study, the influence of the annealing duration and synthesis time on the length, grow rate and quality of the VACNTs according to 9 different regimes was investigated. The outcomes of the study was observed using scanning electron microscope, atomic force microscopy and Raman spectroscopy analysis was utilized in order to evaluate the quality of the obtained nanotubes. Results have shown that the length of the VACNTs increases with the rise of annealing time, however only to a certain degree, after which the deterioration of the nanotubes occurs and the reduction of their length is noticeable.

Rapid ELISA Using a Film-Stack Reaction Field with Micropillar Arrays

A film-stack reaction field with a micropillar array using a motor stirrer was developed for the high sensitivity and rapid enzyme-linked immunosorbent assay (ELISA) reaction. The effects of the incubation time of a protein (30 s, 5 min, and 10 min) on the fluorescence intensity in ELISAs were investigated using a reaction field with different micropillar array dimensions (5-µm, 10-µm and 50-µm gaps between the micropillars). The difference in fluorescence intensity between the well with the reaction field of 50-µm gap for the incubation time of 30 s and the well without the reaction field with for incubation time of 10 min was 6%. The trend of the fluorescence intensity in the gap between the micro pillars in the film-stack reaction field was different between the short incubation time and the long incubation time. The theoretical analysis of the physical parameters related with the biomolecule transport indicated that the reaction efficiency defined in this study was the dominant factor determining the fluorescence intensity for the short incubation time, whereas the volumetric rate of the circulating flow through the space between films and the specific surface area were the dominant factors for the long incubation time.

Computational simulation of biomolecules transport with multi-physics near microchannel surface for development of biomolecules-detection devices

BACKGROUND The quantitative evaluation of the biomolecules transport with multi-physics in nano/micro scale is demanded in order to optimize the design of microfluidics device for the biomolecules detection with high detection sensitivity and rapid diagnosis. OBJECTIVE This paper aimed to investigate the effectivity of the computational simulation using the numerical model of the biomolecules transport with multi-physics near a microchannel surface on the development of biomolecules-detection devices. METHODS The biomolecules transport with fluid drag force, electric double layer (EDL) force, and van der Waals force was modeled by Newtonian Equation of motion. The model validity was verified in the influence of ion strength and flow velocity on biomolecules distribution near the surface compared with experimental results of previous studies. The influence of acting forces on its distribution near the surface was investigated by the simulation. RESULTS The trend of its distribution to ion strength and flow velocity was agreement with the experimental result by the combination of all acting forces. Furthermore, EDL force dominantly influenced its distribution near its surface compared with fluid drag force except for the case of high velocity and low ion strength. CONCLUSIONS The knowledges from the simulation might be useful for the design of biomolecules-detection devices and the simulation can be expected to be applied on its development as the design tool for high detection sensitivity and rapid diagnosis in the future.