Abstract 4129: Efficient cancer cell separation using size and deformability based filtration.
Authors: Xu Yuhao , Hashmi Ali , Harb Wael A. , Hong Bin , Xu Jie 
Published: August 2014

Abstract
Break-free cancer cells in the blood stream are statistically larger (mainly &gt;15 microns) than the majority of normal cells (5-11 microns). Therefore, filters with engineered pores, for example, 8 μm circular pores, could be used to isolate rare cancer cells from billions of hematologic cells in the blood sample. Size exclusion based filtration, however, is not immune to methodological constraint. Loss of cells smaller than the size cutoff and failure of separating cancer cells from normal cells of similar sizes have been the problems. Incorporating a second separation parameter by controlling cell deformability during the enrichment process could minimize the cell loss and increase the purity of the product. Recent advances using column-wall or crescent-post microfluidic chips have demonstrated the potential of utilizing cell size and deformability based separation techniques for rare cell enrichment. In this paper, we propose an innovative filter that aims to provide similar enrichment effect at quicker time (∼minutes/mL blood) and lower manufacturing cost. The key to realize efficient filtration process is the pattern design of highly dense pores. The effect of pore size on cell separation was first studied using rectangular shaped Polydimethylsiloxane (PDMS) microchannels, which were microfabricated by the technique of soft lithography. In the experiments, intact breast cancer cells (MDA-MB-231 and MDA-MB-453) or human leukocytes were guided through the PDMS channels of different sizes. The flow rates and pressure drop were monitored. The deformation of the cells was visualized using a high-speed camera. The optimal pore size was selected to be the microchannel size that most leukocytes passed through, but not for the majority of the cancer cells, at high flow rate and low pressure-drop. As a second step, the effect of pore shape on cell separation was studied. We used the method of focused ion beam (FIB) to micromill pores into a thin polymer membrane, which have the size equal to or smaller than the optimal size obtained and a variety of shapes. FIB is an electron/ ion dual beam system, in which high-speed ion flow carries high momentum to engrave micro-sized pattern into substrate materials with high precision. The micromilled membrane was then integrated into a microfluidic flow chamber for cell separation. Pressure drop and cell deformation were recorded during the translocation of cells on the membrane. We conclude that both pore size and shape affect the size cutoff of cells to be separated. Under the pressure conditions that preserve the cell integrity and viability, cancer cells can be separated from normal cells at high flow rate, purity (&gt;70%) and recovery (&gt;80%). Our results could provide a detailed guidance for developing an efficient cell filter that can be used for rapid enrichment of rare cancer cells in blood for cancer detection and characterization.
Citation Format: Yuhao Xu, Ali Hashmi, Wael A. Harb, Bin Hong, Jie Xu. Efficient cancer cell separation using size and deformability based filtration. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4129. doi:10.1158/1538-7445.AM2013-4129