Abstract 1697: Label-free separation and concentration of cancer cells by acoustophoresis
Authors: Magnusson Cecilia , Lenshof Andreas , Augustsson Per , Antfolk Maria , Laurell Thomas , Lilja Hans 
Published: July 2016

Introduction: Circulating tumor cells (CTCs) is a promising tool for disease monitoring and for better-targeted therapies for patients with disseminating tumors. However, isolation of CTCs is challenging due to their scarcity, variation in size, morphology, and expression profile. The lack of a universal marker impairs reliable detection and characterization of CTCs. We are using acoustophoresis, ultrasound standing wave radiation forces to enable label free separation of cancer cells from white blood cells (WBC). The cell separation is based on intrinsic cells properties such as size, density and compressibility.

Materials and Methods: The acoustic setup is a glass/silicon microchip connected to a pressure driven system. The system is temperature controlled and has a pre-alignment step for optimal separation performance. The separation system can process samples up to 10 mL, with a processing speed of 1 mL in 13 minutes without compromising the cell separation capacity. If required the separation step can be complemented with a subsequent concentration channel, which allows at least 20x concentration of the sample, by extracting the cells in a smaller liquid volume compared to the input sample. The prostate cancer cell line DU145 and the breast cancer cell line MCF7 spiked in red blood cell (RBC) lysed blood from healthy donors, are used to evaluate the model system performance for cancer cell separation.

Results and Discussion: The acoustic separation model system is flexible and can be amended to suit different requirements and conditions. The cancer cell recovery after acoustic separation of blood samples spiked with 50 DU145 cells per mL is approximately 80% with a WBC contamination level of less than 0.3%. At this performance level there is a 100x cancer cell enrichment in the collected cancer cell fraction compared to input. However, by changing parameters such as the voltage setting and sample flow rate it is possible to regulate the cancer cell recovery and WBC contamination levels after acoustophoresis. Cancer cell recovery well above 90% is possible with slightly higher WBC contamination levels. If high cancer cell purity is of importance, a 1000x cancer cell enrichment can be achieved at the cost of slightly lower cancer cell recovery. RBC lysing is required before acoustic separation, due to cell crowding in the separation channel when the cell concentration is too high. We have identified eosinophils as the major contaminant in our enriched cancer cell fraction. They constitute 85% of the contaminating WBCs. The eosinophils have similar acoustic properties as the smaller cancer cells, and can therefore not be completely isolated from the cancer cells by acoustophoresis.

This work demonstrates the flexibility with acoustophoresis that allows for integration of three previously established units: pre-alignment, sorting and concentrating, onto the same chip. It also serves as a proof of concept for in line rare cell label free sorting and isolation.

Citation Format: Cecilia Magnusson, Andreas Lenshof, Per Augustsson, Maria Antfolk, Thomas Laurell, Hans Lilja. Label-free separation and concentration of cancer cells by acoustophoresis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1697.