Microfluidic separation of viruses from blood cells based on intrinsic transport processes

Abstract

Clinical analysis of acute viral infection in blood requires the separation of viral particles from blood cells, since the cytoplasmic enzyme inhibits the subsequent viral detection. To facilitate this procedure in settings without access to a centrifuge, we present a microfluidic device to continuously purify bionanoparticles from cells based on their different intrinsic movements on the microscale. In this device, a biological sample is layered on top of a physiological buffer, and both fluids are transported horizontally at the same flow rate in a straight channel under laminar flow. While the micron sized particles such as cells sediment to the bottom layer with a predictable terminal velocity, the nanoparticles move vertically by diffusion. As their vertical travel distances have a different dependence on time, the micro-and nanoparticles can preferentially reside in the bottom and top layers respectively after certain residence time, yielding purified viruses. We first performed numerical analysis to predicate the particle separation and then tested the theory using suspensions of synthetic particles and biological samples. The experimental results using dilute synthetic particles closely matched the numerical analysis of a two layer flow system containing different sized particles. Similar purification was achieved using diluted blood spiked with human immunodeficiency virus. However, viral purification in whole blood is compromised due to extensive bioparticle collisions. With the parallelization and automation potential offered by microfluidics, this device has the potential to function as an upstream sample preparation module to continuously provide cell depleted bio-nanoparticles for downstream analysis.

The effect of red blood cell aggregation on velocity and cell-depleted layer characteristics of blood in a bifurcating microchannel

“…Microfluidic technologies are increasingly being utilized as an alternative tool due to their many advantages, such as small sample size, disposability, flexibility, etc. For example, such devices have been used for separating viruses, 39 stem cells, 40 cancer cells, 41 and plasma [42][43][44][45] from blood samples. Many of these devices use the two-phase nature of microvascular blood flow and bifurcating geometries to enhance separation, but the influence, and possible benefit of RBC aggregation has generally been overlooked, despite evidence that it enhances phase separation 26 and increases leukocyte margination.…”

Gravity-induced swirl of nanoparticles in microfluidics

“…In the past few years, multistream flow containing nanoparticles has attracted interest for nanoparticle separation, concentration (Yamada et al 2004; Huh et al 2007; Zhao and Cheng 2011; Abecassis et al 2008), assembly (Lin et al 2003; Bresme and Oettel 2007), enhancement of heat transfer and fluid flow (Zhao et al 2011; Yang et al 2012) as well as thermal insulation (Zhao et al 2012). In these applications, adjacent streams from separate inlets are usually assumed to remain parallel, while mass transport across streams happens exclusively through diffusion.…”

Preface to Special Topic: Microsystems for manipulation and analysis of living cells

“…The efforts of bioMEMS Cheng and co-workers from Lehigh University describe a simple and elegant approach for separating viral nanoparticles from blood cells. 6 In this approach, blood carrying viral nanoparticles is layered on top of a buffer stream inside a microfluidic channel. Because the flow is laminar, diffusion is the main driving force in the transport of nanoparticles through the fluid stream.…”

“…1,2 This special topics section provides a sample of the types of microsystems being developed for cell analysis and manipulation. The research directions covered in this thematic section include sorting of mammalian cells, 3,4 pairing of mammalian cells, 5 sorting of viral particles, 6 concentration of bacteria, 7 cultivation of cells in microfluidic devices, 8,9 on-chip monitoring of cell function, 10 and on-chip flow cytometry.…”