應用磁鉗於小鼠結腸癌細胞(CT26)生物力學性質之研究

Abstract

了解生物力學特性有助於了解細胞運動和細胞本身的性質，使我們對於細胞有更進一步的認識。機械應力證明影響細胞的外型和影響細胞骨架的組織，細胞骨架控制細胞眾多行為，包括細胞生長、細胞分化和細胞死亡等等都與之有關聯。因此探討細胞外型和細胞骨架的架構是非常重要的課題。因此，本文的目的利用實驗室自製磁鉗，產生外加磁場藉由具有良好生物相容性的奈米級超順磁磁顆粒（Fe3O4），施加非侵入式外力於細胞內部，觀察細胞行為。實驗方法是將活體細胞與超順磁磁顆粒一起隔夜培養，利用其本身的吞噬效應將磁顆粒引入細胞內。利用磁鉗施加外力於細胞內，並利用CCD記錄並分析影像，藉由影像分析軟體分析磁顆粒位移相對於時間的函數。並且分別帶入兩種模型分析，等效黏彈體模型及指數律模型。 結果顯示，細胞的潛變行為符合指數律模型，並且求得的指數呈現常態分佈；當施加交變磁場於細胞內之磁顆粒，一段時間之後，可以發現彈性系數隨著時間有上升的趨勢，呈現細胞應變硬化的特性。本實驗呈現磁鉗是一套極具潛力研究細胞力學之系統，並且量測細胞力學性質，可用於日後探討細胞於不同生長環境下之力學特性。

Bio-mechanic is a subject of interest for understanding the living cell properties. Mechanical stresses on the cells affect the morphology and cytoskeleton structure of cells, and further contribute for cell migration, growth, differentiation and apoptosis. The goal of this thesis is to explore the mechanical behavior of cells utilizing a home-constructed magnetic tweezers, which with advantages of exerting a non-invasive force on living cells. The experimental approach is that, at first, the living cell of mouse colon carcinoma, CT26, were incubated in media with superparamagnetic nano-particles of Fe3O4. Waiting for overnight, then, the nano-particles were uptake by cells. Further, the magnetic tweezers were utilized to exert magnetic force to the cell, and the motions were recorded by a CCD camera. As observed, the cell creeped and relaxed in subject to the repeated forces. The mechanical properties of cell varied systematically with magnitude of external applied forces. Derive from motion pictures, we were able to obtain the displacement of particles in function of time. Further, two models, viscoelastic solid model and power law model, have been applied to analyze the displacement. The results have depicted that cell creep function over three time decades in different magnitude of forces conformed to a weak power law. It is noticed that cells have shown a stiffening behavior when subjected to cyclic forces. The significance of the fitting parameters obtained from analyzed experimental with theoretic models will be discussed in this thesis. The results have demonstrated that magnetic tweezers is a potential techniques for studying bio-mechanics of living cells.