細胞晶片之開發應用於人類自然殺手細胞對血癌細胞毒殺特性之研究

Abstract

白血病，又俗稱為血癌，是一種血液內白血球不正常甚至過度的細胞增生進而破壞人體免疫系統的嚴重疾病。自然殺手細胞是先天免疫系統中之作用細胞，由於天生具有毒殺癌細胞能力，且HLA不須完全配對亦不會產生排斥作用，因此成為極具潛力且能應用於治療白血病的免疫療法。然而，不同捐贈者的自然殺手細胞的特性各不相同，移植毒殺能力較弱的自然殺手細胞會使得復發率提高，所以如何有效分析各種自然殺手細胞之活性，成為未來細胞治療很重要的課題。 本實驗成功的開發出一種利用鞘流(sheath flow)分別捕捉自然殺手細胞(NK92)及血癌細胞(K562)的微流道晶片，並且能夠分析並檢測自然殺手細胞對於血癌細胞之毒殺能力。即時影像觀測系統、細胞培養與細胞晶片的整合，使得整個實驗可以在顯微鏡觀測下進行。被毒殺的K562細胞，則使用PhiPhiLux (OncoImmunin, Inc.)來確認。在本實驗中所指的效能細胞對目標細胞之比例(Effector to target ratio)是僅計算有接合的細胞(conjugated Effector to Target ratio)，此細胞比例的計算方法更能呈現真實參與毒殺作用過程的細胞比例。在一小時後，被比較多顆NK92細胞接合的K562細胞具有較高被毒殺的比例。比較其細胞毒殺力，可在縫隙長度100 μm與400 μm的流道間發現較大的差別。在接合的效能細胞對目標細胞之比例(conjugated E/T ratio)為1,2,3,4下，縫隙長度為100 μm的微流道所表現出的細胞毒殺力(cytotoxicity)為0.75,0.8,1,1; 縫隙長度為400 μm所表現出的細胞毒殺力(cytotoxicity)則為0.63, 0.33, 0.75, 0.67.結果顯示，而各種接合的細胞比例(conjugated E/T ratio)下，其平均的細胞毒殺力(cytotoxicity)均高於0.6。本實驗中所使用的三種流道所形成的總接合細胞比例(total conjugated E/T ratio)介於2.1和2.3之間。分別在縫隙長度為100 μm,200 μm和400 μm的流道其平均細胞毒殺力為0.85, 0.72和0.63。 對於本實驗中所使用得三種流道進行比較，亦發現比較小的流道捕捉空間形成較高的細胞密度，且表現出較好的細胞毒殺力(cytotoxicity)。 相較於傳統細胞實驗操作於培養盤中以群體細胞的表現為主，本實驗觀察少量細胞的作用行為。此實驗提供了一種僅需要少量樣本細胞數並且大幅降低培養液使用量的實驗系統。即時影像觀測系統的整合，也使得整個毒殺的過程能被更深入的了解。此微流道晶片以實驗驗證了其能夠應用於分析各種不同自然殺手細胞之活性。

Leukemia, commonly known as blood cancer, is a kind of serious diseases in which cells increase abnormally and invade adjacent tissues. High mortality rate of leukemia indicates its need of effective treatments to cure leukemia[1]. One of promising treatments is cell therapy that requires cell transplantation from healthy donors to patients. The natural killer (NK) cell therapy is chosen due mainly to its natural ability to kill tumor cells with no need of HLA match prior to transplantation. However, natural killer (NK) cells from healthy donors exhibit various levels of cytotoxicity to tumor cells. Effective investigation of the cytotoxicity of natural killer cells to tumor cells remains a great challenge. This work has developed a cell-based microfluidic device which is capable of investigating the cytotoxicity of natural killer cells against leukemic cells. The whole process of cytolytic activity was observed in real-time under the microscopic system. The lysed k562 cells (leukemic cells) were detected by PhiPhiLux (OncoImmunin, Inc.). All the E/T ratios counted in this work were in a conjugated form, which is the most specific way to count E/T ratios. It was found that the higher conjugated E/T ratio had better cytotoxicity after one hour. Morever, apparent difference in cytotoxocity of the microchannel in gap lengths of 100 μm and 400 μm was found. In a microchannel with a gap length of 100 μm, the cytotoxicity at the conjugated E/T ratio of 1,2,3,4 were 0.75, 0.8, 1, 1, respectively. In a device with a gap length of 400 μm, the cytotoxicities were 0.63, 0.33, 0.75, 0.67, respectively. The mean value of cytotoxicity over all conjugated E/T ratio was higher than 0.6. The total conjugated E/T ratios formed in three microchannels were between 2.1 and 2.3. The averaged cytotoxicities were 0.85, 0.72 and 0.63 in 100 μm, 200 μm and 400 μm channel, respectively. By comparing those three microfluidic channels, it was found that the small size channel formed the higher density of the cells and thus performed the higher cytotoxicity. Unlike the conventional cell culture experiments in dishes with large amounts of cells, this work provides a device that needs very few cells for manipulation and significantly reduces the consumption of culture medium. The microscopic system also provides an in-depth understanding of cell interaction and cytotolytic activity. This microfluidic device exhibits the capability and potential for effective investigation of natural killer cells (NK cells) against tumor cells (K562 cells).