| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 103 === In this research, PDMS substrates with different mechanical strength were applied for the culture of osteoblastic cells. To study the basic mechanism which would affect the attachment and proliferation of osteoblasts, the hydrophilicity of PDMS was controlled by UV light combined with ozone treatment. After the UV-ozone treatment, the PDMS surfaces with various mechanical properties presented the same hydrophilicity by applying different treatment conditions. Besides, UV-ozone treatment did not change the topography of PDMS, indicating that mechanical strengths would be the only factor which may influence cultured osteoblastic cells.
The mechanical strengths did not influence the viability and differentiation of osteoblasts on pristine PDMS. On the contrary, the cultured osteoblasts showed higher viability on PDMS which was hydrophilic. The results reveal that the cells would respond to material properties only when the cell-material interaction is high enough, which was in agreement with the results of cell attachment on hydrophilic PDMS in SEM images.
When the osteogenic medium was applied, the cell viability increased by increasing the mechanical strength of PDMS more significantly. Since the osteogenic medium can enhance the osteogenic level of cultured osteoblasts, the promotion of osteogenesis caused by stiff PDMS was more efficient if the cells were more osteogenic.
In normal culture medium, the ALP expression of cultured osteoblasts was low on all the PDMS substrates, which was not related to the mechanical strength of PDMS. On the other hand, ALP activity was significantly enhanced by increasing PDMS stiffness in osteogenic medium. This tendency was consistent with that in cell viability, meaning that the early osteogenic differentiation would be more promoted by increasing the stiffness of PDMS when osteoblasts were cultured in a mineralization-induced environment.
The viability of cultured dental pulp stem cells (DPSC) would not be influenced by the mechanical properties of PDMS, no matter in normal or osteogenic medium. From the evaluation of calcium deposition, the calcium percentage was higher on the stiffer PDMS, supporting the enhancement of late osteogenic differentiation due to the increase in substrates’ mechanical strength. Compared with the results from cultured osteoblasts, the mechanical strength of PDMS was not so efficient on the proliferation, but was still effective on late osteogenic differentiation. This was possibly because PDMS-DPSC interforce was lower than that between PDMS and osteoblasts, so it took a longer period for DPSC to respond to the biomaterials surface. Another possibility was that the osteogenic level of DPSC was lower than that of osteoblasts, leading to the limited effect of PDMS stiffness on DPSC.
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