Book of abstract 2008

Numerical modeling in electroporation-based biomedical applications
Nataša Pavšelj
Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
In general, cell membrane is impermeable for larger molecules; however, the application
of adequately high electric pulses to cells, either in suspension or tissue, causes the
electroporation of cell membrane, increasing its permeability and making it possible for
larger molecules, such as drug molecules or DNA, to enter the cell. Electropermeabilization
of the cell membrane, when used properly, can be used on different types of cells, does not
affect cell survival and does not disrupt cell functions. Therefore, it can be used for wide
range of applications, the most advanced being electrochemotherapy, gene electro transfer
and transdermal drug delivery.
Analytical methods used to be the only option for theoretic studying of the effects of
electromagnetic fields on cells and tissues. They are rather complicated and are only feasible
for use on problems where the geometry, material properties and boundary conditions can
be described in a defined coordinate system (like Cartesian, cylindrical, polar...). In the
last decades, however, increased computer capabilities and speed led to the development
of powerful commercial numerical methods software packages based on finite elements
method that can easily be used to model intricate biological systems. The principle of
the finite elements method is the discretization of the geometry into smaller elements
where the quantity to be determined is approximated with a function or is assumed to
be constant throughout the element. Tissue inhomogeneities and anisotropies can also
be modeled and different excitations and boundary conditions can be applied easily.
When constructed, the model consists of a system of equations that can be solved by an
appropriate numerical method.
Various parameters (current and voltage amplitude, field strength and orientation, electrode
geometries...) can thus be evaluated by means of numerical modeling. In such models,
the excitations can be changed easily, being that it only involves changing the boundary
conditions
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on the same model. Once built, a good model in agreement with experimental
results can be a powerful tool and can offer useful insight into the understanding of
biological processes modeled and helps us to plan future in vivo experiments. Also,
experimenting with such models is easier and sometimes the only possible or ethically
acceptable alternative to experimenting on real biological systems. Modeling of electric
current and electric field distribution during cell and tissue electroporation proved to
be useful for describing different aspects of the process, allowing us to design electrode
geometries and electroporation protocols as a part of treatment planning.
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