Two-hundredfold volume concentration of dilute cell and particle suspensions using chip integrated multistage acoustophoresis

Abstract

Concentrating cells is a frequently performed step in cell biological assays and medical diagnostics. The commonly used centrifuge exhibits limitations when dealing with rare cell events and small sample volumes. Here, we present an acoustophoresis microfluidic chip utilising ultrasound to concentrate particles and cells into a smaller volume. The method is label-free, continuous and independent of suspending fluid, allowing for low cost and minimal preparation of the samples. Sequential concentration regions and two-dimensional acoustic standing wave focusing of cells and particles were found critical to accomplish concentration factors beyond one hundred times. Microparticles (5 μm in diameter) used to characterize the system were concentrated up to 194.2 ± 9.6 times with a recovery of 97.1 ± 4.8%. Red blood cells and prostate cancer cells were concentrated 145.0 ± 5.0 times and 195.7 ± 36.2 times, respectively, with recoveries of 97.2 ± 3.3% and 97.9 ± 18.1%. The data demonstrate that acoustophoresis is an effective technique for continuous flow-based concentration of cells and particles, offering a much needed intermediate step between sorting and detection of rare cell samples in lab-on-a-chip systems.

A thin-reflector microfluidic resonator for continuous-flow concentration of microorganisms: a new approach to water quality analysis using acoustofluidics

“…44,45 Based on this functioning principle, concentration of a range of particles including bacterial spores, biological cells and polystyrene spherical micro-beads has been demonstrated. 15,38,[46][47][48][49][50][51] Nordin and Laurell have recently demonstrated a very significant increase in concentration of red blood cells and prostate cancer cells (up to a maximum of ~200-fold), using a two-stages half-wavelength resonator. 15 However, direct manipulation of bodies as small as bacteria by means of ARFs represents a considerable physical challenge.…”

“…15,38,[46][47][48][49][50][51] Nordin and Laurell have recently demonstrated a very significant increase in concentration of red blood cells and prostate cancer cells (up to a maximum of ~200-fold), using a two-stages half-wavelength resonator. 15 However, direct manipulation of bodies as small as bacteria by means of ARFs represents a considerable physical challenge. 43 This is mainly due (i) to the fact that the acoustic primary radiation force scales with particle's volume, 45 and (ii) to the increased particle susceptibility with respect to hydrodynamic drag forces resulting from acoustic streaming or thermal convection.…”

Focusing of sub-micrometer particles and bacteria enabled by two-dimensional acoustophoresis

“…samples including blood, [20][21][22][23] raw milk, 24 circulating tumor cells, 25,26 and yeast. 27 For bulk acoustic waves (BAW) microchannel acoustophoresis is usually carried out in the 1-10 MHz frequency range and particles are focused along a single dimension.…”

Performance Study of Acoustophoretic Microfluidic Silicon-Glass Devices by Characterization of Material- and Geometry-Dependent Frequency Spectra

“…These devices exploit standing acoustic pressure waves that, through the purely mechanical parameters, such as compressibility, density, and size, induce fluid-and particle-specific forces [1][2][3] leading to acoustophoresis [4]. This phenomenon is the basis of the development of gentle [5,6] and robust methods for concentrating [7], trapping [8], washing [9], aligning [10], and separating cells [11][12][13]. In order to be used for manipulation purposes, the acoustic pressure wave inside the microchannel must exhibit well-defined pressure nodes and intense pressure fields that effectively attract or repel particles.…”