An Acoustic Microfluidic Device for Hematopoietic Stem Cell Enrichment from Whole Blood
Recorded On: 02/06/2018
Emerging cell therapies require efficient methods for purification of target cells prior to subsequent processing. In the case of stem cell-based therapies large numbers of hematopoietic stem cells (HSCs) must be collected and purified from patient peripheral blood; a challenging task because even after mobilization, the concentration of HSCs in the collected product is typically less than 1% of all cells. Existing processing techniques, such as density gradient centrifugation and subsequent magnetic separation, achieve some of the requirements, however, they often provide low yield, are costly, time-consuming, and labor intensive. Acoustic separation has emerged as a versatile technology for flow-through liquid handling and particle manipulation. The technique relies upon differences in the size, density, and compressibility of various blood components in order to achieve rapid label-free discrimination between target and off-target cells.
Here, we present a system that continuously separates HSCs from both healthy and diseased whole blood using acoustically-mediated separation in a plastic microfluidic device. We and others have previously demonstrated acoustic separation of bacteria, beads, and liposomes from blood cells, but this is the first report showing enrichment of HSCs directly from patient samples. In addition, because our microchannel is constructed entirely of polystyrene, it is suitable for scale-up to clinically relevant processing rates, with the potential for flow rates approaching 100 ml/hr. Our device consists of a microchannel mounted on a piezoelectric actuator and a temperature-controlled stage. The actuator excites an acoustic standing wave within the fluid cavity, transverse to the flow direction. This standing wave exerts a force on blood cells which drives them toward the centerline of the flow. Larger and denser cells experience a larger force compared to smaller and less dense cells, and are more strongly focused. At the downstream end of the channel, a trifurcating outlet allows for the separation of strongly focused cells (e.g., red blood cells and neutrophils) from those that are weakly focused (e.g., HSCs and lymphocytes). In this work the system is tuned to enable the separation and collection of HSCs.
We achieve enrichment of the HSC population (CD34+ as % total white blood cells) from 9% to 22%, a factor of 2.4x, starting from unpurified whole patient blood. This enrichment was achieved in a single pass through the device with HSC recovery of 40% and reduction of the red blood cell concentration by 62%. These figures can be improved by multiple passes through the system and by device optimization. Our results demonstrate that we are able to efficiently and specifically purify HSCs from whole blood in a continuous flow-through device. In addition, our device is fabricated from low-cost components and is straightforward to operate, giving it the potential for future use in sample purification for cell therapy.
Charles Lissandrello is a Senior Member of the Technical Staff in the Nano Structured Materials group at Draper. He received his Ph.D. in Mechanical Engineering at Boston University in 2015, where he conducted research with Kamil Ekinci on the transition from hydrodynamic to kinetic gas behavior in fluid systems far from equilibrium. At Draper, he has worked with a team of collaborators to develop novel microfluidic devices for biological sample processing.