Development of Microfluidic Glucose Sensors BME 273: Kristen Jevsevar, Jason McGill, Sean Mercado, Rebecca Tarrant Advisors: Jennifer Merritt, Dr. John Wikswo, Dr. David Cliffel Department of Biomedical Engineering, Vanderbilt University, Nashville TN USA. 1.5”. 3/8” Diameter. 1/4” Diameter.
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BME 273: Kristen Jevsevar, Jason McGill, Sean Mercado, Rebecca Tarrant
Advisors: Jennifer Merritt, Dr. John Wikswo, Dr. David Cliffel
Department of Biomedical Engineering, Vanderbilt University, Nashville TN USA
Figure 2. (left) A schematic of the Pine Instruments screen-printed electrode showing the working, reference, and counter electrodes. The microfluidic channel (red) is placed over these electrodes.
DESIGN PERFORMANCE & RESULTS
Figure 3. (right) An enzyme film of glucose oxidase and nafion is spotted onto the electrode. A chemical reaction takes place on the electrode wherein glucose reacts with glucose oxidase to form hydrogen peroxide (H2O2). H2O2 is oxidized, releasing an electron. This generates a current, allowing the measurement of glucose concentrations.
Figure 6. Initial calibration experiments were done to determine if there was a linear response of the enzyme coating to glucose concentration. During these electrode precalibrations, when the electrode is placed in a beaker containing various concentrations of glucose, there is a linear relationship between glucose concentration and current.
Figure 4. A schematic of the electrode housing shown from above (left) and from the side (above). A CNC milling machine is used to make an acrylic negative. A PDMS mold is created using the negative. Acrylic plates with drilled holes are placed on either side of the electrode and PDMS mold. Nuts and bolts allow the plates to be tightened, sealing the system. Holes drilled through the upper plate allow tubing to connect to input and output tubing ports.
Figure 7. In this experiment, the microfluidic device switches between continuous flow calibration fluids and stop/flow cell media from the multianalyte microphysiometer (MAMP) bioreactor. The continuous flow data is a smooth curve (circled in red) and the stop/flow data appears as repeating peaks (circled in green).
Figure 8. To determine if the microfluidic glucose sensor would work downstream of a cell culture, it was attached to the end of a MAMP. Initial experiments showed that it did measure glucose concentration downstream of cells without a loss of signal or disruption due to cellular byproducts. While running experiments downstream of the MAMP, glucose concentration was also being measured by a known device to act as a comparison. The peaks, indicating glucose consumption durinig the stop period of the stop/flow cycle, are the same for the MAMP data (blue) and our microfluidic data (red).
A valve is used to alternate flow between bioreactor media and calibration solutions.
A bioreactor cultures a small amount of cells. An internal pump perfuses the cells with media, which is then sent to the electrode.
A LabView pump driver is used to control the Harvard Apparatus Pico Pump. The Harvard Apparatus pumps calibration solutions to the electrode.
Figure 1. Commercially produced Pine Instruments electrode.
Figure 5. This experimental diagram depicts the setup used to obtain glucose concentration measurements.
Glucose concentrations are measured using a CH Instruments electrochemical workstation. A potentiostat controls the electrical potential between the working and reference electrode, maintaining a constant voltage. The sensor detects current from the enzyme reaction.
Data is collected using CH Instruments computer software that plots current versus time.