Fractionation of cell mixtures using acoustic and laminar flow fields

Abstract

A fractionation method applicable to different populations of cells in a suspension is reported. The sepa ration was accomplished by subjecting the suspension to a resonant ultrasonic field and a laminar flow field propa gating in orthogonal directions within a thin, rectangular chamber. Steady, laminar flow transports the cell suspen sion along the chamber, while the ultrasonic field causes the suspended cells to migrate to the mid-plane of the chamber at rates related to their size and physical proper ties. A thin flow splitter positioned near the outlet divides the effluent cell suspension into two product streams, thereby allowing cells that respond faster to the acoustic field to be separated from those cells that respond more slowly. Modeling of the trajectories of individual cells through the chamber shows that by altering the strength of the flow relative to that of the acoustic field, the desired fractionation can be controlled. Proof-of-concept experi ments were performed using hybridoma cells and Lactoba cillus rhamnosus cells. The two populations of cells could be effectively separated using this technique, resulting in hybridoma/Lactobacillus ratios in the left and right prod uct streams, normalized to the feed ratio, of 6.9 F 1.8 and 0.39 F 0.01 (vol/vol), respectively. The acoustic method is fast, efficient, and could be operated continuously with a high degree of selectivity and yield and with low power consumption.

Microscale acoustofluidics: Microfluidics driven via acoustics and ultrasonics

“…From An obvious application of this ability to segregate and focus particles in channels is flow cytometry, where current approaches that employ sheath flows or dielectrophoresis to hydrodynamically focus cells into a narrow line within the fluidic channel require ample quantities of consumables to generate sheath flow or a planar geometry for all but the latest dielectrophoretic methods (Cheng et al, 2007). A relatively early study by Kumar et al (2005) reported the acoustic separation of hybridoma and lactobacillus using ultrasound irradiation perpendicular to the main axis of flow, with modest efficiency and flow rate. Goddard and Kaduchak (2005) used ultrasound to focus 10 m particles and cells in a 190 mm long glass capillary tube with an inner diameter of 1.9 mm along a 14 mm long region exposed to acoustic radiation at 417 kHz from a pair of PZT transducers attached to either side of the tube.…”

Microfluidic bio-particle manipulation for biotechnology

“…The position of the piezoelectric material with respect to the device determines which type of configuration the resonator is in. There are three main configurations where the piezoelectric material can be placed against the chip which are transversal [61,92,107,94], layered [82,108,85,109] and surface acoustic wave (SAW) configurations [87][88][89]. In the transversal configuration, the piezoelectric material is placed on the device such that the standing wave is positioned along an axis perpendicular to the normal of the piezoelectric patch surface.…”

“…ACT methods have been implemented for bio-particle wash [95,47,96,84,125,92], trapping [125,92,[126][127][128][129][130][131][132][133][134] and separation [69,108,85,91,9,81,135,94,136,137]. Bio-particle washing relies on focusing the particles to the center of the channel, and out flowing the bio-particles collected at the center into another suspension medium.…”

“…These particles created more dominant secondary effect, and an efficient trapping of 490 nm particles were succeeded (a more detailed review of bio-particle trapping can be found elsewhere [134]). The separation of bio-particles by exploiting the difference in size and acoustic properties has been performed successfully including separation of lipid particles from erythrocytes [69], human cells from bacteria [108], human sperm from epithelial cell DNA [85], separation of plasma from the rest of the blood cells [91,9], removal of platelets from a progenitor cell product [81], separation of cells at different phases of mitosis [135], separation of viable and nonviable mammalian cells from each other [94] and detection of prostate specific antigen (PSA) in whole blood [136].…”

Acoustofluidics 23: acoustic manipulation combined with other force fields

“…Typically, particles are initially aligned to a starting position within a flow chamber using a sheath flow 14,31,32 , or an acoustic pre-alignment stage 33 , then deflected under the action of the sorting acoustic field which can be excited using bulk axial 28 , bulk lateral 29 , or surface acoustic wave excitation 16 . It can be shown 34 that in the low Reynolds number regime typically found in this work, particles reach their terminal velocity within a matter of milli-seconds.…”