Analysis of magnetic microbead capture with and without bacteria in a microfluidic device under different flow scenarios

[+] Author and Article Information
Samuel / A Miller

Department of Mechanical and Materials Engineering, University of Cincinnati, 598 Rhodes Hall, University of Cincinnati, Cincinnati, OH 45221

William / R Heineman

Department of Chemistry, University of Cincinnati, 120 Crosley Tower, PO Box 210172, Cincinnati, OH 45221

Alison A. Weiss

Department of Molecular Genetics, Biochemistry & Microbiology, University of Cincinnati, 2254 Medical Sciences Building, 231 Albert Sabin Way, Cincinnati, OH 45267

Rupak K. Banerjee

ASME Fellow, Department of Mechanical and Materials Engineering, University of Cincinnati, 593 Rhodes Hall, ML 0072, University of Cincinnati, Cincinnati, OH 45221

1Corresponding author.

ASME doi:10.1115/1.4040563 History: Received February 13, 2018; Revised May 04, 2018


Efficient detection of pathogens is essential to the development of a reliable point-of-care diagnostic device. Magnetophoretic separation, a technique used in microfluidic platforms, utilizes magnetic microbeads coated with specific antigens to bind and remove targeted biomolecules using an external magnetic field. For better reliability and accuracy in the device, the efficient capture of these magnetic microbeads is important. The aim was to analyze the effect of an electroosmotic flow switching on the capture efficiency of magnetic microbeads in a microfluidic device and demonstrate viability of bacteria capture. This analysis was performed at microbead concentrations of 2x106 and 4x106 beads/mL, electroosmotic flow voltages of 650 and 750 volts, and under constant and switching flow protocols. Images were taken using an inverted fluorescent microscope and the pixel count was analyzed to determine fluorescent intensity. A capture zone was used to distinguish between captured and uncaptured beads. The capture efficiency range was 31% - 42% for constant flow and 71% to 85% for switching flow. Compared to constant flow, the relative percentage increase due to the switching flow was ~2 times (p<0.05). Initial testing using bacteria-bead complexes was also performed in which these complexes were captured under the constant flow to create a calibration curve based on fluorescent pixel count. The calibration curve was linear on a log-log plot (R2 = 0.96). The significant increase in capture efficiency highlights the effectiveness of flow switching for magnetophoretic separation in microfluidic devices and prove its viability in bacterial analysis.

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