In 2004, Shen et al. developed a safe and efficient gene transfer system using a DNA-apatite composite layer. We have recently succeeded in improving further the gene transfer efficiency by immobilizing a cell adhesion molecule laminin, in a DNA-apatite composite layer. In this study, we showed that not only laminin but fibronectin immobilized in a DNA-apatite composite layer enhances cell adhesion and cell spreading on the layer, thereby markedly improving the gene transfer efficiency. Therefore, the immobilization of a cell adhesion molecule in a DNA-apatite composite layer is crucial for improving the gene transfer efficiency. By using fibronectin instead of laminin and optimizing the condition to prepare the fibronectin-DNA-apatite composite layer, the amount (weight) of cell adhesion molecule required was reduced to approximately one-fourth while retaining the relatively high gene transfer efficiency. It was also shown that the resulting fibronectin-DNA-apatite composite layer prepared under the optimized condition mediated the area-specific gene transfer on its surface, that is, DNA was preferentially transferred to the cells adhering to the surface of the fibronectin-DNA-apatite composite layer. The present gene transfer system with potential for area-specific transfection and advantages of safety and relatively high efficiency would be useful in tissue engineering applications, gene therapy, and production of transfection microarrays.

We have found that the dissolution rate of a copper metal film which is easy to be corroded oxidatively in CO 2 -dissolved water (CO 2 DIW) used as rinse water for wafer cleaning processes can be decreased to one-third by removal of H 2 O 2 from CO 2 DIW. DIW in semiconductor factories normally contains 10~40 µg/L H 2 O 2 , which remains also in CO 2 DIW. We have developed a palladiumloaded monolithic anion exchange resin (Pd-M) as a catalyst that is able to remove H 2 O 2 in DIW down to below 1 µg/L at an extreamly high flow rate (space velocity SV = 6000 h -1 ), with no detectable elution of impurities.

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Ultrapure water (UPW) is widely used for rinsing wafers and diluting chemicals in semiconductor manufacturing processes. The quality of UPW is severely controlled, but the generation of hydrogen peroxide (H2O2) as a impurity is inevitable due to the ultraviolet irradiation in a UPW production system (Figure 1). In our survey, it is revealed that the concentration of H2O2 in UPW reaches to 10~40 μg/L level. Considering the situation, we have developed a palladium-loaded monolithic anion exchange resin (Pd-M) as a catalyst that is able to remove H2O2 from UPW down to below 1 μg/L at an extremely high flow rate (space velocity SV = 6,000 h-1), with no detectable elution of impurities [1, 2]. Furthermore, we have found that the dissolution rate of copper which is easy to be corroded oxidatively in CO2-dissolved water (CO2 UPW) [3] can be decreased to one-third by removal of H2O2 from CO2 UPW using Pd-M catalyst [4]. In this study, we present the effects of H2O2 removal from UPW and diluted hydrofluoric acid (DHF) on the surfaces of copper, molybdenum and silicon.