Abstract
We report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without (immuno) labeling. Two IM-C units were placed upstream and downstream of the DEP-D unit for enumeration, respectively, before and after the cells were treated in DEP-D unit, where the difference in cell count gave the total number of trapped cells based on their DEP characteristics. Conductivity of the running buffer was matched the conductivity of cytoplasm of wild type K562 and CCRF-CEM cells. Results showed that DEP responses of drug resistant and wild type K562 cells were statistically discriminative (at p = 0.05 level) at 200 mS/m buffer conductivity and at 8.6 MHz working frequency of DEP-D unit. For CCRF-CEM cells, conductivity and frequency values were 160 mS/m and 6.2 MHz, respectively. Our approach enabled discrimination of resistant cells in a group by setting up a threshold provided by the conductivity of running buffer. Subsequent selection of drug resistant cells can be applied to investigate variations in gene expressions and occurrence of mutations related to drug resistance.
Highlights
We report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without labeling
DEP-based Multidrug resistance (MDR) studies, which are summarized in Table 1, have been started in 2003 by Labeed et al They reported that the cytoplasmic conductivity of doxorubicin resistant K562 cells was 2.2 times higher than that of wild type K562 cells, as analyzed by DEP collection s pectra[17]
The hypothesis, built based on the significant difference between the average cytoplasmic conductivity of K562/imaR and K562/wt cells, was that K562/imaR cells should be trapped on electrodes, while wild type cells should flow to the outlet
Summary
We report the development of a lab-on-a-chip system, that facilitates coupled dielectrophoretic detection (DEP-D) and impedimetric counting (IM-C), for investigating drug resistance in K562 and CCRF-CEM leukemia cells without (immuno) labeling. Khamenehfar et al identified leukemia cells in clinical blood samples by using dielectrophoresis (DEP), i.e. electrical cell detection technique[13] They achieved to keep leukemia cells in the predetermined position in microchannel and to apply chemotherapeutic drugs and MDR inhibitors on trapped cells. Electrical approaches as label-free, rapid, and real-time alternative techniques for the diagnosis of MDR have gained popularity in the last two decades since MDR changes the electrophysiological properties of cancer cells Such methods are electrical cell-substrate impedance s ensing[15,16] and dielectrophoresis (DEP)[17,18,19,20]. In 2008, Duncan et al applied ion channel blockers to drug resistant and wild type K562 cells to understand reasons behind differences in cytoplasmic conductivity As a result, they interpreted that P-gp can have a chloride channel modulation function in cells[22]. All of these studies showed the usability of DEP methods for MDR detection
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