Development of a Microfluidic System for Microtissue Applications - Bioreactors Based on Mass Transport

• Main Authors: Tung-Han Wu, 吳東翰
• Other Authors: Yu-Hsiang Hsu
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/64ptjk

碩士 === 國立臺灣大學 === 應用力學研究所 === 106 === Disease-on-a-chip is one of the leading research fields in personalized medicine for future health care. Among the major chronical diseases, cancer is the second leading cause of death next to cardiovascular disease. It is due to its high heterogeneity, and identification of an effective treatment sets a big challenge to cure cancer. Hence, the method to develop tumor-on-a-chip has drawn much attention in this field. By using a tumor-on-a-chip system for drug screening or genetic screening, we can design personalized medical treatment for different patients according to the screening results. In this study, two kinds of microfluidic systems to generate two different culture environments through generating different flow patterns are designed: (1) Nutrition-deprived condition, which offers a slow nutrient support through diffusive flow, (2) Convection-dominated condition, which offers a rapid nutrient support through interstitial convective flow to achieve a rapid nutrient supply. In this thesis, different initial cell numbers and nutrition supply to investigate the growth of a microtumor are studied and compared. A long microfluidic channel is designed to create a diffusion dominant microtumor chamber, and the level of nutrition deprivation is controlled by two methods. One is to control the initial loading concentration of cells, and the other is to control the perfusion rate of the nutrition supply diffuses from two side channels. Our experimental finding suggests that a lower initial cell concentration can developed into continuous microtumors across the 1 mm by 2 mm microchamber with a uniform growth rate. The growth of microtumors can be regulated by the level of nutrition deprivation. It suggests that nutrition deprivation could play an important role on the initial development of a microtumor. Applying this model system, it could potentially be optimized for the tumor growth among different kinds of tumor cells. Thus, we can provide a personalized system to develop patient specific microtumors to study the heterogeneity of tumors between patients and to identify an effective treatment. In the second study we attempt to connect microvasculature into microtumor tissue to mimic nutrition and oxygen supply of tumor. Once the tumor is formed, cancer cells can directly uptake surrounding nutritions or exclude the metabolic waste by the diffusion between the cells; however, once the tumor grows beyond the diffusion limit of 100 μm, the diffusion between the cells is insufficient, resulting in hypoxic conditions. Thus, tumors can tirger angiogenic process to create an environment for tumor growth. Otherwise, the tumor is anoxia (<2%) due to limited oxygen induction, and acidification due to reprogramming of metabolic procss, it eventually creates apoptosis and necrosis. We further design two kinds of microfluidic systems to generate two different microenvironments through different stages of tissue development. Both are nutritionally deprived and provide slow nutritional support through the diffusion transport. We successfully develop a large-scale vascular network and microtumor. It was shown that the angiogenic process is induced by the adjacent fibroblast chamber. In the second study, we successfully developed a large-scale microtumor next to developed vasculature. This platform can provide complete physiological and engineering conditions, and it is believed that vascular biomimetic cancer can be realized on this bioreactor. All microfluidic platforms are verified with finite element analysis. The microfluidic and driving pressures of different chamber height are analyzed. The flow velocity of the microfluid in the microchannel, the pressure gradient of the chamber and the velocity distribution in the chamber also are discussed. Finally, time-dependent concentration analysis is performed. The results show that we successfully developed microfluidic systems that can be applied to microtissues. These newly developed systems break through the limitations of the mm size of microtumor and blood vessels in lab-on-a-chip systems. The 3-D tissue not only improves human compatibility, and in the future, patient-specific tumor models or different cancer cell types also can be applied for personalized health before clinical applications.