Laboratory for Chemistry and Physics of Interfaces, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Koehler-Allee 103, 79110, Freiburg, Germany.
Sci Rep. 2019 Feb 4;9(1):1246. doi: 10.1038/s41598-018-37541-3.
Circulating tumor cells (CTCs) play a key role during the metastatic process of human cancers and their reliable detection and characterization could enable new and effective ways of cancer diagnosis, monitoring and treatment. However, due to their ultralow concentration in patient blood, the CTCs must first be enriched before such analysis can be performed. Classical microfiltration is an important and widely used method for the mechanical enrichment of CTCs. This method exploits that CTCs are generally larger than the accompanying blood cells, however, does not differentiate the cells in other ways. In an affinity filtration, selectivity is added by functionalizing the membrane with specific antibodies against a CTC-characteristic surface protein such as the epithelial cell adhesion molecule (EpCAM). A common shortcoming of both filtration approaches is that there is still a poor understanding of the enrichment process and the systems developed so far are frequently operated under non-optimized conditions. To address this, systematic filtration experiments are performed in this work using the EpCAM cell line MCF-7 as CTC-model and standard track-etched membranes modified with or without antibodies against EpCAM. The influences of the key filtration parameters time and applied pressure are studied and it is found that in all cases the extent of cell recovery is limited by a lysis process which occurs on the membrane surface. Counterintuitively, it is found that filtration at rather high pressures is advantageous to ensure high recovery rates. To describe the pressure-induced lysis process a biophysical model is developed. This model allows the determination of optimum filtration conditions to achieve both high cancer cell recovery and large blood sample throughput. It is demonstrated that this way practically 100% of spiked cancer cells can be recovered from milliliters of undiluted whole blood within seconds.
循环肿瘤细胞（CTCs）在人类癌症的转移过程中起着关键作用，它们的可靠检测和特征描述可以为癌症的诊断、监测和治疗提供新的有效方法。然而，由于它们在患者血液中的浓度极低，因此在进行此类分析之前，必须首先对 CTC 进行富集。经典的微孔滤过法是一种重要且广泛应用的 CTC 机械富集方法。该方法利用 CTC 通常比伴随的血细胞大的特点，但不能以其他方式对细胞进行区分。在亲和过滤中，通过用针对 CTC 特征表面蛋白（如上皮细胞黏附分子（EpCAM）的特异性抗体对膜进行功能化，增加了选择性。这两种过滤方法的一个共同缺点是，对富集过程的理解仍然很差，到目前为止开发的系统经常在非优化的条件下运行。为了解决这个问题，本工作使用 EpCAM 细胞系 MCF-7 作为 CTC 模型，用或不用针对 EpCAM 的抗体对标准的刻蚀膜进行了系统的过滤实验。研究了关键过滤参数时间和施加压力的影响，发现无论在何种情况下，细胞回收率都受到膜表面发生的溶胞过程的限制。反直觉的是，发现以相当高的压力进行过滤有利于确保高回收率。为了描述压力诱导的溶胞过程，开发了一种生物物理模型。该模型允许确定最佳过滤条件，以实现高癌细胞回收率和大的血液样本通量。结果表明，这种方法可以在几秒钟内从几毫升未经稀释的全血中回收几乎 100%的掺入癌细胞。
