Figure 5. Distribution of glioma cells in the microchannel according to applied DEP forces. Numbers and positions of glioma cells associated with a) strong pDEP, b) pDEP, c)weak pDEP forces. Ordinary one-way ANOVA Tukey’s multiple comparison test was applied using GraphPad Prism 9. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001.
The results showed that U87 glioma cells experienced clear pDEP behavior between the frequencies of 200 kHz and 10 MHz, as shown inFigure 4. The crossover frequency for the U87 glioma cells were almost 140 kHz. However, the U87 glioma cells did not exhibited clear nDEP response based on our observations, see Supplementary Materials Video S1 . Hence, we performed dielectrophoretic characterization of U87 glioma cells using 3 Vpp, 200 kHz to 10 MHz. Figure 4a displays the number of cells those were positioned according to strength of the DEP forces generated by varying frequencies. The number of cells experienced strong pDEP behavior was 50% of the population. This subpopulation of glioma cells became distinguishable at 200 kHz. Figure 4b-4d show the number of glioma cells with pDEP behavior when 3 Vpp, and frequencies varying between 0 – 10 MHz was applied.
Figure 6 presents the viability of the U87 glioma cells. First, we confirmed viability of the cells using Student’s t-test. The difference in viability was not significant for the cells in regular growth medium and low-conductive DEP buffer (p = 0.256,Supplementary Document ). Next, we stained the cells with DAPI and PI dyes before introducing the cells into the DEP chip and obtained 3.08 % PI-positive cells in the cell population. Afterwards, we determined the number of PI-positive cells upon the DEP experiment that was performed in 10 minutes. We observed 2.06% increase in the number of PI-positive cells in the microfluidic channel.