Label-free cell separation and sorting in microfluidic systems

Abstract

Cell separation and sorting are essential steps in cell biology research and in many diagnostic and therapeutic methods. Recently, there has been interest in methods which avoid the use of biochemical labels; numerous intrinsic biomarkers have been explored to identify cells including size, electrical polarizability, and hydrodynamic properties. This review highlights microfluidic techniques used for label-free discrimination and fractionation of cell populations. Microfluidic systems have been adopted to precisely handle single cells and interface with other tools for biochemical analysis. We analyzed many of these techniques, detailing their mode of separation, while concentrating on recent developments and evaluating their prospects for application. Furthermore, this was done from a perspective where inertial effects are considered important and general performance metrics were proposed which would ease comparison of reported technologies. Lastly, we assess the current state of these technologies and suggest directions which may make them more accessible.FigureA wide range of microfluidic technologies have been developed to separate and sort cells by taking advantage of differences in their intrinsic biophysical properties

Recent advances in microfluidic techniques for single-cell biophysical characterization

“…84,85 Early work on cell electrical measurements dates back to the 1910s, [86][87][88] the foundation for interpreting the electrical properties of cells, where the cell is modeled as a spherical cytoplasm surrounded by a thin dielectric membrane. 89,90 Generally, the electrical properties of a plasma membrane are affected by the membrane morphology, lipid bilayer composition and thickness, and embedded proteins.…”

Continuous-flow ferrohydrodynamic sorting of particles and cells in microfluidic devices

“…Simply increasing the flow rate can further increase sorting throughput. Current microfluidic sorting schemes use flow rates ranging between ~10 μl/min and ~1 ml/min (Gossett et al 2010). With such flow rates and 10 7 -10 8 cells/ml concentration, maximum sorting throughput of our device in theory can go up to 10 9 cells per hour.…”

“…Compared to high-specificity and label-based cell sorting techniques such as 0fluorescence-activated cell sorter (FACS) (Bonner et al 1972) and magnetic-activated cell sorter (MACS) (Miltenyi et al 1990), microfluidic sortings are mostly label-free, relying on cells' intrinsic properties such as size, shape, density, deformability, electric and magnetic properties for manipulation specificity (Pamme 2007;Tsutsui and Ho 2009;Gossett et al 2010;Lenshof and Laurell 2010). When applicable, microfluidic sortings are favored over label-based ones, because they are inexpensive and require minimal user training for operation (Gossett et al 2010). Among them, those based on channel design including pinched flow fractionation (Yamada et al 2004) and deterministic lateral displacement (Huang et al 2004;Davis et al 2006) combine laminar flows with mechanical structures to direct particles of different sizes into separate streamlines.…”

A Comparative Study of Image Processing Methods for the Assessment of the Red Blood Cells Deformability in a Microfluidic Device

“…Due to its complexity, many analytical techniques require the previous separation and sorting of blood cells, which consumes time and resources [1,2]. Microfluidic devices have arisen to overcome some limitations of the existing techniques and make it possible the use of small samples and less biochemical labels that may change cells properties [3].…”