Mesenchymal stem cell (MSC) which can differentiate into many kinds of cells, even into nerve cells, are very hopeful for its application to formation of artificial neuron network and to development of advanced guide tube of nerve regeneration without any medical and ethical problems. In the neuron network formation and bio-interface between nerve system and an external electronic circuit, we need at first the adhesion control of MSC and its differentiation into nerve cells. We have achieved the arrangement adhesion of MSC on polystyrene surface by using ion implantation treatment through a pattering mask.
Spin-coated polystyrene film (500 nm) on glass were implanted with carbon negative ions through the mask with slit (aperture 50 um x 5 mm) array (70 um spacing) at 10 keV with fluence in a range from 1E13 to 1E16 ions/cm^2. After sterilization and placed on the 35-mm-polystyrene dish, MSCs deviated from rat bone marrow were seeded and cultured with a medium of DEME including serums and antibiotic in a incubator at 37 deg C with 5% CO2 flow. We observed cultured MSCs by a phase-contrast microscope, and by fluorescent microscope after DAPI staining.
In the low fluence cases below 1E14 ions/cm^2, cobblestone-shape MSCs attached on the whole surface of the sample. However, we observed aligned MSC nuclei along the pattering implantation after DAPI staining. Such round-shape cells on the unimplanted region are considered to weakly adhere rather than on the implanted region. Therefore, cells on the unimplanted region detached from the surface during the DAPI stain process. As for more fluence, we obtained clear selective MSC adhesion arranging along the mask pattern for the middle fluence cases of 3E14 and 1E15 ions/cm^2, where MSCs stretching their body along and on the implantation region and the round-shape MSCs placed on the unimplanted region. The selective adhesion was obtained by the end of cell culture of 15 days. In the dense fluence cases more than 3x10^15 ions/cm^2, we also obtained the selective MSC adhesion in a few days just after seeding. Then the stretched MSCs were observed in the unimplanted region so that the selective adhesion loosed. Details of the results and dependence on implantation energy are presented at the conference.
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