High Temporal Resolution Measurements of Dopamine Uptake In-Situ

Yu, Yue 1

1. Institute of Biomaterials and Biomedical Engineering, University of Toronto

Here, we report a self-contained, automated microfluidic in vitro platform that integrates a dedicated electroanalytical dopamine detector into a cell culture chamber allowing for high resolution temporal in situ dopamine homeostasis measurements. This technique relies on digital microfluidics (DMF), a channel-free microfluidic technique where droplets are sandwiched between two horizontal parallel plates (top and bottom), and manipulated across an open surface by electrostatic forces.

DMF has proven useful for automating mammalian cell culture, and integration of analytical techniques, which we used to demonstrated a dopamine uptake assay with (1) a multi-day dopaminergic neuron culture with (2) quantitative sensor for the analysis of dopamine homeostasis. In that preliminary work, SH-SY5Y cells were cultured in close proximity (~4 mm) to the electroanalytical detector, minimizing error due to handling and excessive auto-oxidation. However, this requires the droplet containing dopamine be moved from the cell culture well to the electrochemical detector, meaning that each measurement is destructive, as the measured dopamine droplet cannot be reused. In the work presented here, we combine (1) and (2), allowing SH-SY5Y cells to be cultured directly on top of the detector. This minimizes any chance of dopamine oxidation, does not require droplet movement and allows for significantly increased time resolution.

This system was validated by temporal evaluation of dopamine uptake of differentiated SH-SY5Y cells that are co-incubated with known drugs that affect dopamine homeostasis. We propose that the integrated platform, in addition with fluorescence microscopy, will be applicable in a wide range of applications in PD and neuroscience.