Abstract
Early stage detection of lymphoma cells is invaluable for providing reliable prognosis to patients. However, the purity of lymphoma cells in extracted samples from human patients' marrow is typically low. To address this issue, we report here our work on using optically-induced dielectrophoresis (ODEP) force to rapidly purify Raji cells' (a type of Burkitt's lymphoma cell) sample from red blood cells (RBCs) with a label-free process. This method utilizes dynamically moving virtual electrodes to induce negative ODEP force of varying magnitudes on the Raji cells and RBCs in an optically-induced electrokinetics (OEK) chip. Polarization models for the two types of cells that reflect their discriminate electrical properties were established. Then, the cells' differential velocities caused by a specific ODEP force field were obtained by a finite element simulation model, thereby established the theoretical basis that the two types of cells could be separated using an ODEP force field. To ensure that the ODEP force dominated the separation process, a comparison of the ODEP force with other significant electrokinetics forces was conducted using numerical results. Furthermore, the performance of the ODEP-based approach for separating Raji cells from RBCs was experimentally investigated. The results showed that these two types of cells, with different concentration ratios, could be separated rapidly using externally-applied electrical field at a driven frequency of 50 kHz at 20 Vpp. In addition, we have found that in order to facilitate ODEP-based cell separation, Raji cells' adhesion to the OEK chip's substrate should be minimized. This paper also presents our experimental results of finding the appropriate bovine serum albumin concentration in an isotonic solution to reduce cell adhesion, while maintaining suitable medium conductivity for electrokinetics-based cell separation. In short, we have demonstrated that OEK technology could be a promising tool for efficient and effective purification of Raji cells from RBCs.
Highlights
B-cell lymphomas are a species of lymphomas derived from the carcinogenesis of B lymphocytes in the human lymphatic system
Investigation of Raji cellular adhesion phenomenon inside an optically-induced electrokinetics (OEK) chip In a typical experimental procedure to investigate the cell-tosubstrate adhesion phenomenon, Raji cells suspended in an isotonic solution consisting of 8.5% (w/v) sucrose and 0.3% (w/v) glucose were introduced into the OEK chip
The adhesion force between amorphous silicon (a-Si):H surface and mammalian cells were in the order of nanonewtons, while the optically-induced dielectrophoresis (ODEP) force was in the order ranging from tens to hundreds of piconewtons
Summary
B-cell lymphomas are a species of lymphomas derived from the carcinogenesis of B lymphocytes in the human lymphatic system. The density gradient centrifugation method [3,4] is a label-free method commonly used to remove the RBCs or plasma for isolating the cancerous cells in peripheral blood, using the density variation mechanism of cells with the assistance of commercial available liquid kits (e.g., using Ficoll as given in [5]) This technique, simultaneously contaminates all of the isolated RBCs. This technique, simultaneously contaminates all of the isolated RBCs Another label-free technique is using microfluidic systems, i.e., based on purely hydrodynamic forces. Dielectrophoresis (DEP) force, generated by the interaction between an applied non-uniform electric field and the dielectric objects in the field, can be used to induce motions of different directions on the objects, reflecting the differential inherent properties (e.g., dielectric properties and sizes) of the objects This technique is a label-free manner and has been applied to separate cancerous cells [11,12,13]. Integrated micro pumps/valves are needed to enhance the separation performance, which complicates the fabrication process of the experimental system
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