本研究利用聚二甲基矽氧烷(polydimethyl siloxane, PDMS)作為骨細胞培養基材，藉由調控寡聚物與硬化劑之間的重量比，製備出不同機械強度的膜材，以比較不同機械強度基材對細胞貼附及增生的影響。然而PDMS材料表面的高疏水性並不利於細胞貼附，所以本實驗藉由在UV照射結合臭氧改質的方式在材料表面產生大量自由基，藉由不同的操作條件，可以使不同機械強度的PDMS均達到相同的親水性，UV-臭氧改質亦未對材料表面粗糙度造成明顯改變，也就是說，機械強度為本研究中唯一影響細胞貼附及活性的變因。
在細胞的增生實驗中，於疏水的PDMS表面上，材料的機械強度未對骨母細胞的活性與分化造成影響，這代表唯有當細胞與材料間的親和力夠高，細胞表現才會受到材料表面性質的影響。在親水PDMS上以一般培養液進行培養，我們發現骨母細胞在高硬度材料上有較好的細胞增生情形，掃描式電子顯微鏡(SEM)的照片也顯示骨母細胞在高機械強度PDMS上的細胞密度及貼附情況較佳，此結果是因為細胞與材料有較好的交互作用。而當改用骨分化培養液進行骨母細胞培養時，高機械強度對骨母細胞活性的促進效果被更進一步地提高，這顯示環境越有利於骨分化情況，材料機械強度對細胞增生的促進性越明顯。
在一般培養液中培養骨母細胞後，我們發現其鹼性磷酸酶的表現量極低，且機械強度對鹼性磷酸酶分泌量的影響不大，相反的，在骨誘導培養液中，骨母細胞鹼性磷酸酶表現量隨著機械強度上升而明顯增加，此結果與細胞活性的趨勢相仿，表示細胞之骨分化程度越高，材料機械強度提高對其骨分化表現得促進效果也會越明顯。
接著我們使用牙髓幹細胞進行細胞實驗，實驗結果顯示無論使用一般或骨誘導培養液，牙髓幹細胞在不同機械強度下的材料並沒有明顯的增生情形，機械強度亦未對細胞增生造成任何差異。長時間的牙髓幹細胞培養後，可從元素分析結果發現細胞周圍的鈣沉積量隨著PDMS機械強度提高而增加，而從SEM照片中可以看出牙髓幹細胞與較硬材料之間有較好的細胞交互效應，由於鈣沉積為骨分化之中後期指標，因此我們推論材料機械強度的提升對牙髓幹細胞的後期骨分化有提升作用。與骨母細胞培養的結果相較，推測這是因為牙髓幹細胞與PDMS間的作用力遠低於骨母細胞，即骨母細胞對材料表面性質有著更高的辨認效果，故機械強度的影響對牙髓幹細胞不如骨母細胞明顯，也就是說，牙髓幹細胞需要更長的培養時間才能對材料表面特性產生反應。另一個可能性是牙髓幹細胞的骨分化程度較骨母細胞低，故材料機械性質並未對其增生與分化的影響也較為有限。

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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