M.Sc Thesis

M.Sc StudentRozitsky Lichen
SubjectDielectrophoretic Characterization and Manipulation
of Cells and Micro-/Nano-Particles
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisors PROF. Gilad Yossifon
PROF. Shulamit Levenberg


Dielectrophoresis (DEP) is the translational motion of neutral particles due to effects of polarization in a non-uniform electric field. It has proven to be an effective method for the characterization and manipulation of particles in general and bio-particles such as cells, viruses, DNA, etc. in particular. This research consisted of three platforms, the first of which included a quadrupole electrode design for qualitative characterization of the DEP response and cross-over frequency (COF) evaluation of 1µm and 10µm particles and of different cell types (muscle cells - C2, mouse embryonic stem cells - mESCs, human neonatal dermal fibroblasts - HNDF and human umbilical vein endothelial cells - HUVEC). The second platform consisted of an interdigitated electrode array within a micro-channel with forced flow for a quantitative characterization. Trapping percentages of particles and cells at the electrodes array at different frequencies in the range of 25kHz to 80MHz were measured. This platform was used here, for the first time, to characterize the internal electrical properties (conductivities) and the COFs of 720nm, 1µm and 4.8µm particles and different cell populations (HNDF, human ESCs, HUVEC, mESCs) by fitting the theoretical models to the DEP experimental results. In addition, it was found that Fluorescent activated cell sorter (FACS) process changes the dielectric properties of mouse ESCs and hence influence on their response to DEP. Moreover, differentiated mouse ESCs (day 3) were found to have a shift in their maximal trapping percentage to the high frequencies. This is an encouraging preliminary result that supports the hypothesis that DEP technique can distinguish between stem cells in different stages of early differentiation. The third platform used in this research consisted of inclined electrode pairs for sorting purposes. This was a proof-of-concept for the possibility to identify and separate continuously on-chip different particles\cells subpopulations using DEP.

Finally, we conclude that DEP is a robust and repeatable method for particles and cells behavior characterization. It has the potential to be used as an effective tool for biomedical applications such as monitor changes in cell viability or in the surface morphology and internal structure of cells; separate cells to high specificity for their identification and enumeration; separate cells without the need for biochemical labeling or modification; separate rare target cells from heterogeneous samples, avoiding cell loss; process samples at high cell-sorting rates. All of these attributes can be used to further advance both fundamental and applied stem cells research.