High-throughput separation of circulating tumor cells by dielectrophoretic filtration

根据大小或密度以外的性质来分离颗粒是一项高度相关的任务，但不能普遍解决。这种分离需要一种决定性的力，这种力作用在目标粒子上比作用在混合物中所有其他粒子上要强得多；因此，要分离出性质稍有不同的粒子变得越来越困难。一个因其在液体活检中诊断价值显著的例子是从全血中分离循环肿瘤细胞（CTC）。目前研究了几种不同的分离方法，其中大多数依赖于肿瘤细胞上的特定表面标记物。然而，这限制了普遍适用性，因为这些表面标记在所有细胞上的存在是值得怀疑的。Dielectrophoresis （DEP）是一种适应性强、选择性强的电动分离技术，已经被证明可以成功地检测血液样本中的CTC。由于DEP力与电场方阵的空间非均匀性呈线性关系，因此大多数当代DEP应用都是通过微电极结构和微通道实现的。这对于产生足够强大的力以实现分离是必要的。与我们的工作组一起，我开创了介电泳过滤的概念，它能够弥合固有的DEP吞吐量差距。在这种情况下，所需的场不均匀性是在多孔介质（例如，可以是宏观的单片陶瓷泡沫）的孔隙结构中引起的。这允许从分离基质中的混合物中选择性地和电可切换地保留（捕获）目标颗粒。因此，与传统的DEP分离器相比，我们可以使用更大的通道和更高的吞吐量来操作过程。到目前为止，我们已经在模型粒子系统上测试了这个概念。在这个项目中，我想研究DEP过滤工艺选择性保留外周血单核细胞（PBMC）癌细胞的可行性。微流控模型过滤器用于寻找合适的分离参数（通量，施加电压，场频率）从t细胞中分离白血病细胞系（rmi -8226）和乳腺癌细胞系（MCF-7）。随后，靶细胞浓度将向临床相关值降低，分离过程将转向在多孔氧化铝泡沫中作为DEP过滤基质进行分离。这个项目使我们离解决一个非常相关和困难的分离问题更近了一步，但它也探索了使用DEP过滤概念对生物细胞系统进行选择性分离的可能性。

The separation of particles according to properties other than size or density is a highly relevant task but one that cannot be solved universally. Such separation requires a deterministic force that acts much stronger on the target particle than on all other particles of a mixture; consequently, it becomes increasingly difficult to separate particles that show only slightly different properties. A due to its diagnostic value in liquid biopsy significant example is the separation of circulating tumor cells (CTC) from whole blood. Several different approaches are currently investigated for this separation while most of them rely on specific surface markers on the tumor cells. This however limits the universal applicability, as the presence of these surface markers on all cells is questionable. Dielectrophoresis (DEP), a highly adaptable and selective electrokinetic separation technique, has already shown to be successful for the detection of CTC in a blood sample. Because the DEP force scales linearly with the spatial inhomogeneity of the electric field square, most contemporary DEP applications are realized using microelectrode structures and micro channels. This is necessary to generate forces that are strong enough in order to achieve separation.Together with our working group, I have pioneered the concept of dielectrophoretic filtration, which is capable of bridging the inherent DEP throughput gap. In this, the required field inhomogeneities are induced in the pore structure of a porous medium (which could be, for example, a macroscopic monolithic ceramic foam). This allows for selective and electrically switchable retention (trapping) of target particles from a mixture in the separation matrix. Consequently, compared to conventional DEP separators, we can operate the process using larger channels and higher throughputs. So far, we have tested this concept on model particle systems. In this project, I want to investigate the feasibility of the DEP filtration process for the selective retention of cancer cells from peripheral blood mononuclear cells (PBMC). Microfluidic model filters are used to find suitable separation parameters (throughput, applied voltage, field frequency) to separate a leukaemia cell line (RPMI-8226) and a breast cancer cell line (MCF-7) from T-cells. Subsequently, the target cell concentration will be decreased towards clinically relevant values and the separation process will be transferred towards separation in porous alumina foams as DEP filtration matrix. This project brings us a step closer towards solving a very relevant and difficult separation problem but it also explores the possibilities for selective separation of biological cell systems using the DEP filtration concept.