Munehiro Yamaguchi

Cell Patterning Using a Template of Microstructured Organosilane Layer Fabricated by Vacuum Ultraviolet Light Lithography

Micropatterning techniques have become increasingly important in cellular biology. Cell patterning is achieved by various methods. Photolithography is one of the most popular methods, and several light sources (e.g., excimer lasers and mercury lamps) are used for that purpose. Vacuum ultraviolet (VUV) light that can be produced by an excimer lamp is advantageous for fabricating material patterns, since it can decompose organic materials directly and efficiently without photoresist or photosensitive materials. Despite the advantages, applications of VUV light to pattern biological materials are few. We have investigated cell patterning by using a template of a microstructured organosilane layer fabricated by VUV lithography. We first made a template of a microstructured organosilane layer by VUV lithography. Cell adhesive materials (poly(d-lysine) and polyethyleneimine) were chemically immobilized on the organosilane template, producing a cell adhesive material pattern. Primary rat cardiac and neuronal cells were successfully patterned by culturing them on the pattern substrate. Long-term culturing was attained for up to two weeks for cardiac cells and two months for cortex cells. We have discussed the reproducibility of cell patterning and made suggestions to improve it.

Neuronal cell patterning on a multi-electrode array for a network analysis platform.

We studied neuronal cell patterning on a commercial multi-electrode array (MEA). We investigated the surface chemical modification of MEA in order to immobilize Poly-D-lysine (PDL) and then to pattern PDL with a photolithographic method using vacuum ultraviolet light (VUV). We have clarified that the PDL layer was not fully decomposed but was partially fragmented by short-time irradiation with VUV, resulting in a change in the cell adhesiveness of the PDL. We succeeded in patterning primary rat cortex cells without manipulating the cells on MEA more than two months. This cell-adhesiveness change induced by VUV can be applied to any immobilized PDL on other kinds of MEA and culturing substrate. We conducted electrophysiological measurements and found that the patterned neuronal cells were sufficiently matured and developed neural networks, demonstrating that our patterning method is useful for a neuronal network analysis platform.

Effect of polymer addition and temperature on the structure of silicon-based polymer films deposited by excimer laser ablation of hexaphenyldisilane

Abstract The effects of the cooling target, heating substrate, and the addition of polysilanes were studied to control the film structure and properties of silicon-based polymer films synthesized by laser ablation deposition of hexaphenyldisilane (HPDS). The cooling target reduced the thermal effect, and the resultant film structure differed from that without cooling. The film structure was changed by the heating substrate and exhibited significant microhardness, while the thermal stability was not improved. The addition of polysilanes, in particular poly(dimethylsilane) (PDMS), was very effective in developing the Si–C network structure in the resultant films.

“Soft” and “hard” laser treatments of noble metals nanoparticles. How do they work in particle size and shape control?

From particle heating-melting-evaporation model, proposed in [1], and further developed in our previous works [2,3], two critical regimes of irradiation of nanocolloid, “hard” and “soft” irradiation, can be determined. The first one corresponds to the conditions when particle into a colloid will be evaporated completely by one laser pulse. The second one corresponds to the conditions when particle into a colloid will be melted completely but not evaporated yet. In other words, if “hard” irradiation corresponds to full evaporation regime, the “soft” one corresponds to the threshold of particle evaporation. Both critical regimes depend on particular noble metal, particle size, shape and laser wavelength. Both ones can be calculated with classical thermodynamics approach. For example, “soft” laser fluence is depicted in Fig. 1 as the function of particle diameter for spherical silver and gold nanoparticles irradiated by fundamental wavelength, 2nd and 3rd harmonics of Nd:YAG laser.