Postdoctoral Research, 2010-2013

For my postdoctoral research in the Allbritton Lab at the University of North Carolina, I characterized a microfluidic device for single-cell enzyme assays and applied this device to measurements of peptidases and kinases in single cells.

Single-Cell Enzyme Assays. Individual cells, even when they seem the same, can behave vary differently. In fact, this cell-to-cell variation is important in many biological processes, including embryonic development, immunity, and drug resistance. Variation in enzyme activity is an important source of cellular heterogeneity [1], but single-cell enzyme measurements are challenging because cells are small, complex, and dynamic. In the Allbritton lab, I used microfluidic device to steer cells toward a laser pulse for lysis, then separated the cell contents by electrophoresis, and detected a fluorescent-labeled reporter peptide to measure enzyme activity. We applied this technology to single-cell measurements of peptidase activity in leukemia cells treated with a peptidase-inhibiting drug, Tosedostat [2], [3].

Chip design for single-cell enzyme assays.

COMSOL Simulations. One of my first projects in the Allbritton lab was to refine a COMSOL model built by former postdoc Dr. Hsuan-Hong Lai and use the model to characterize sample transport on our microfluidic device. Modeling is a powerful tool for microfluidic device design because different geometries and parameters can be tested much more quickly in simulations than in the lab. The COMSOL Multiphysics program uses finite element analysis to solve a system of differential equations that describe the physics of a system. For our model, I modeled the electric fields, pressure-driven flow, diffusion, and electrokinetic forces in the device. The results of these simulations were validated with experiments performed under the same conditions. The results agreed well and suggested that the device design works best for analytes with a high electrophoretic mobility[4].

Experiments (A-D) and simulations (E-G) of sample transport on the device.

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