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Hepatoma cells are a promising cell source for the construction of bioartificial liver (BAL) systems owing to their high proliferative capability. However, their low liver function compared with primary hepatocytes is a major problem. In a previous study, we established a genetically modified hepatoma cell line, Hepa/8F5, in which eight liver-enriched transcription factor (LETF) genes were transduced into mouse hepatoma Hepa1-6 cells using a drug-inducible transactivator system. These cells proliferate actively under normal culture conditions, meaning that large quantities can be prepared easily. When the overexpression of the LETFs is induced by the addition of an inducer drug, cell growth stops and cell morphology changes with concomitant high expression of liver functions. However, the liver functions largely depend on the presence of the inducer drug, which must be continuously added to maintain these enhanced functions. In the present study, we attempted to modify the method of induction of LETF overexpression in Hepa/8F5 cells to remove the requirement for continual drug addition. To this end, we constructed a system in which the artificial transactivator was transcribed and amplified under the control of a heat-shock protein promoter, and introduced the system into the genome of Hepa/8F5 cells. In our modified cell line, heat-triggered LETF expression was confirmed to induce high liver function. After drug-screening of transfected cells, we established a hepatoma cell line (Hepa/HS), which exhibited high, heat-inducible liver functions. The Hepa/HS cells may represent a new cell source for hepatic studies such as the construction of BAL systems. SUPPLEMENTARY INFORMATION: The online version of this article (10.1007/s10616-021-00457-4) contains supplementary material, which is available to authorized users.

We have developed the epitaxial growth technology of Ge 1−x Sn x and related group-IV materials. The crystalline properties and energy band structure have been investigated for integrating group-IV semiconductors into Si ULSI platform.

The selective growth mechanism of GaN on a (0 0 0 1) GaN template using radio-frequency plasma-assisted molecular beam epitaxy is investigated. The effect of the mask material on selective growth is investigated using SiO 2 and Ti masks. Selective growth of GaN with excellent selectivity and a smooth surface is achieved by optimizing the growth temperature. The threshold temperatures for selective growth are 930 and 940 °C for SiO 2 and Ti masks, respectively. A high growth temperature is necessary to suppress the formation of polycrystals on the mask and to obtain selective growth. The different threshold temperatures are thought to be due to the different affinities between Ga adatoms and the two mask materials. Selective growth is also performed using wide masks. Re-evaporation of adatoms is found to be the principal process in the selective growth obtained using the SiO 2 mask, whereas adatom migration is the principal process with the Ti mask. Surface diffusion of adatoms on the Ti mask results in the formation of a denuded zone near the mask edge and protuberances on both sides of the selective growth.

We examined the numerical calculation for evaluating the energy band offset of Si1− x Sn x semiconductors and compared our calculation results with the results of previous theoretical calculation and experimental estimation. By estimating the charge neutrality level of Si1− x Sn x as a mutual basis level for comparison of the first-principles calculations for different Si1− x Sn x contents, the calculated valence band offset of Si1− x Sn x to Si was found to sensitively shift with upward bowing with increasing Sn content compared with that obtained using a conventional linear interpolation model. This is in good agreements with the experimental result.

We have carried out density functional theory (DFT) calculation for Si1− x Sn x alloy and investigated the effect of the displacement of Si and Sn atoms with strain relaxation on the lattice constant and E– k dispersion. We calculated the formation probabilities for all atomic configurations of Si1− x Sn x according to the Boltzmann distribution. The average lattice constant and E– k dispersion were weighted by the formation probability of each configuration of Si1− x Sn x . We estimated the displacement of Si and Sn atoms from the initial tetrahedral site in the Si1− x Sn x unit cell considering structural relaxation under hydrostatic pressure, and we found that the breaking of the degenerated electronic levels of the valence band edge could be caused by the breaking of the tetrahedral symmetry. We also calculated the E– k dispersion of the Si1− x Sn x alloy by the DFT+U method and found that a Sn content above 50% would be required for the indirect–direct transition.