November 10th CTE Seminar Presentations

Student Presentation 1

Title: Quantitative Characterization of Electroporation Induced Cellular Permeability In Vitro

Presenting author: Daniel Sweeney, Biomedical Engineering

Research group: Bioelectromechanical Systems Laboratory

Electroporation is a phenomenon in which pulsed electric fields (PEFs) generate defects in the
cell membrane that enhance small molecule transport through electrodiffusive mechanisms.
Tissue-scale electroporation technologies exploit this mechanism to deliver small molecule
drugs and plasmids into tissues using PEFs that often comprise hundreds to thousands of
individual pulses. However, the mechanisms by which transmembrane transport is enhanced is
not yet well understood. Towards this end, we use fluorescent tracer molecules to examine the
permeability of cell membranes in vitro following PEF application. We show that tissue-level
observations of short, bipolar electrical pulses resulting in more homogenous, predictable
lesions than longer monopolar PEFs extend to the multi- and single-cell levels. We have also
developed a methodology to quantitatively estimate the diffusive permeability of cell
membranes in vitro in the minutes following PEF application. We show that a single electrical pulse can generate a
>104-fold enhancement in a cell membrane’s diffusive permeability for a small molecule solute over a naïve
membrane. Currently, the processes resulting in this permeability increase are being examined through a simplified
model using this quantitative permeability data. Such a model could be integrated into tissue-scale computational
models of ablation to provide estimates of the degree of permeabilization generated in clinically relevant tissue
volumes. Accounting for cell-level phenomenon in tissue-level PEF treatments will help narrow the gap clinical PEF
applications and cell-level disruption that dictates their clinical efficacy.

Student Presentation 2

Title: 3D micro-tissue models to analyze the effects of ultra-low dose LPS on vascular sprouting
dynamics in the brain tumor microenvironment

Presenting author: Megan Cox, Biomedical  Engineering

Research group: Laboratory of Integrative Tumor Ecology

Cellular growth, which is regulated by a complex interplay of nutrient signaling and growth factor signaling pathways, remains poorly understood in higher eukaryotes. Specifically, growth in unicellular eukaryotes, in contrast to multicellular eukaryotes, depends only on nutrient availability and not on growth factor signaling. However, the complexity of the interactions in the regulatory network for cellular growth precludes an intuitive understanding of nutrient signaling mediated regulation of cell growth. Here, we propose an ODE-based dynamical model of the regulatory mechanism governing cell growth in the budding yeast Saccharomyces cerevisiae. The model captures the metabolic signaling network composed of components from the TORC1, Snf1, and the Ras-cAMP-PKA pathways, and captures the interactions that impinge on the ribosome biogenesis regulon, which governs the mass growth rate. This model can simulate variations in cellular growth rates as a function of varying macronutrient inputs, namely carbon and nitrogen sources.