Stiffness Dependent Separation of Cells in a Microfluidic Device

PLOS ONE, Dec 2019

Abnormal cell mechanical stiffness can point to the development of various diseases including cancers and infections. We report a new microfluidic technique for continuous cell separation utilizing variation in cell stiffness. We use a microfluidic channel decorated by periodic diagonal ridges that compress the flowing cells in rapid succession. The compression in combination with secondary flows in the ridged microfluidic channel translates each cell perpendicular to the channel axis in proportion to its stiffness. We demonstrate the physical principle of the cell sorting mechanism and show that our microfluidic approach can be effectively used to separate a variety of cell types which are similar in size but of different stiffnesses, spanning a range from 210 Pa to 23 kPa. Atomic force microscopy is used to directly measure the stiffness of the separated cells and we found that the trajectories in the microchannel correlated to stiffness. We have demonstrated that the current processing throughput is 250 cells per second. This microfluidic separation technique opens new ways for conducting rapid and low-cost cell analysis and disease diagnostics through biophysical markers.

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Stiffness Dependent Separation of Cells in a Microfluidic Device

Citation: Wang G, Mao W, Byler R, Patel K, Henegar C, et al. ( Stiffness Dependent Separation of Cells in a Microfluidic Device Gonghao Wang 0 Wenbin Mao 0 Rebecca Byler 0 Krishna Patel 0 Caitlin Henegar 0 Alexander Alexeev 0 Todd Sulchek 0 Alexandre J. Kabla, University of Cambridge, United Kingdom 0 1 Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta , Georgia , United States of America, 2 Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology , Atlanta , Georgia , United States of America, 3 Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia , United States of America Abnormal cell mechanical stiffness can point to the development of various diseases including cancers and infections. We report a new microfluidic technique for continuous cell separation utilizing variation in cell stiffness. We use a microfluidic channel decorated by periodic diagonal ridges that compress the flowing cells in rapid succession. The compression in combination with secondary flows in the ridged microfluidic channel translates each cell perpendicular to the channel axis in proportion to its stiffness. We demonstrate the physical principle of the cell sorting mechanism and show that our microfluidic approach can be effectively used to separate a variety of cell types which are similar in size but of different stiffnesses, spanning a range from 210 Pa to 23 kPa. Atomic force microscopy is used to directly measure the stiffness of the separated cells and we found that the trajectories in the microchannel correlated to stiffness. We have demonstrated that the current processing throughput is 250 cells per second. This microfluidic separation technique opens new ways for conducting rapid and low-cost cell analysis and disease diagnostics through biophysical markers. - Funding: The authors thank National Science Foundation (project number CBET-0932510) and TI:GER program at Scheller College of Business at Georgia Institute of Technology for financial support of this project. The authors also thank the Presidents Undergraduate Research Award (PURA) program at Georgia Tech for providing funding to CH and the Petit Fellowship for support to RB. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Rapidly sorting and separating cells are critical for detecting diseases such as cancers and infections and can enable a great number of applications in biosciences and biotechnology. For example, diseased cells have been identified through morphological differences with healthy cells, and fluorescent molecular markers are routinely used to separate specific subpopulations of cells [1,2]. However, the morphological overlap between the diseased and healthy cells often poses a significant problem to accurate identification of cell populations. New molecular and biophysical markers which can be readily detected and used to rapidly sort cells are vital for improving separation of different cell subpopulations and accurately detecting specific disease conditions. A variety of different physical mechanisms have been used to separate cells, including magnetic fields [35], electric fields [69], optical forces [1012] and acoustic fields [1315]. However, these active separation methods require an external field which adds to the complexity and increases the cost. Alternatively, labeling of cells through specific binding of fluorescent antibodies [16] is expensive, requires highly-trained personnel, and hampers the downstream analysis of separated cells. Additionally, the separation executed by these techniques occurs only after individual readout of the labeling differentiation which limits the throughput. Consequently, a label-free method that can separate cells continuously by biophysical properties would greatly complement existing separation technologies. While a variety of techniques demonstrate separation by physical parameters such as size [17], mass [18], and adhesion [19], a straightforward method to separate cells by mechanical stiffness would benefit biomedical capabilities. A number of pathophysiological states of individual cells result in drastic changes in stiffness in comparison with healthy counterparts. Mechanical stiffness has been utilized to identify abnormal cell populations in detecting cancer [2022] and identifying infectious disease [23]. For example, several studies have shown a reduction in cell stiffness with increasing metastatic efficiency in human cancer cell lines [2325]. Recently, microfluidic methods were developed to classify and enrich cell populations utilizing mechanical stiffness [2631]. One problem with these methods is an overlap between the natural variations of different biophysical properties that can influence stiffness-based se (...truncated)


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Gonghao Wang, Wenbin Mao, Rebecca Byler, Krishna Patel, Caitlin Henegar, Alexander Alexeev, Todd Sulchek. Stiffness Dependent Separation of Cells in a Microfluidic Device, PLOS ONE, 2013, Volume 8, Issue 10, DOI: 10.1371/journal.pone.0075901