Research Papers

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,
Cincinnati, OH 45221
e-mail: mille4sa@mail.uc.edu

William R. Heineman

Department of Chemistry,
University of Cincinnati,
120 Crosley Tower,
P.O. Box 210172,
Cincinnati, OH 45221
e-mail: william.heineman@uc.edu

Alison A. Weiss

Department of Molecular Genetics,
Biochemistry & Microbiology,
University of Cincinnati,
2254 Medical Sciences Building,
231 Albert Sabin Way,
Cincinnati, OH 45267
e-mail: alison.weiss@uc.edu

Rupak K. Banerjee

Fellow ASME
Department of Mechanical and
Materials Engineering,
University of Cincinnati,
593 Rhodes Hall, ML 0072,
Cincinnati, OH 45221
e-mail: rupak.banerjee@uc.edu

1Corresponding author.

Manuscript received February 13, 2018; final manuscript received May 4, 2018; published online September 21, 2018. Assoc. Editor: Yaling Liu.

J. Med. Devices 12(4), 041005 (Sep 21, 2018) (6 pages) Paper No: MED-18-1032; doi: 10.1115/1.4040563 History: Received February 13, 2018; Revised May 04, 2018

Efficient detection of pathogens is essential for the development of a reliable point-of-care diagnostic device. Magnetophoretic separation, a technique used in microfluidic platforms, utilizes magnetic microbeads (mMBs) coated with specific antigens to bind and remove targeted biomolecules using an external magnetic field. In order to assure reliability and accuracy in the device, the efficient capture of these mMBs is extremely important. The aim of this study was to analyze the effect of an electroosmotic flow (EOF) switching device on the capture efficiency (CE) of mMBs in a microfluidic device and demonstrate viability of bacteria capture. This analysis was performed at microbead concentrations of 2 × 106 beads/mL and 4 × 106 beads/mL, EOF voltages of 650 V and 750 V, and under constant flow and switching flow protocols. Images were taken using an inverted fluorescent microscope and the pixel count was analyzed to determine to fluorescent intensity. A capture zone was used to distinguish which beads were captured versus uncaptured. Under the steady-state flow protocol, CE was determined to range from 31% to 42%, while the switching flow protocol exhibited a CE of 71–85%. The relative percentage increase due to the utilization of the switching protocol was determined to be around two times the CE, with p < 0.05 for all cases. Initial testing using bacteria-bead complexes was also performed in which these complexes were captured under the constant flow protocol to create a calibration curve based on fluorescent pixel count. The calibration curve was linear on a log-log plot, with R2-value of 0.96. The significant increase in CE highlights the effectiveness of flow switching for magnetophoretic separation in microfluidic devices and prove its viability in bacterial analysis.

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Grahic Jump Location
Fig. 1

Schematics (not to scale) of (a) fluorescently tagged beads, (b) mMB-fluorescent bacteria complexes, and (c) device setup used in experiments

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Fig. 2

Image of fluorescence from sample with concentration of (a) 1 × 106 beads/mL, (b) 2 × 106 beads/mL, (c) 1 × 107 beads/mL, (d) 2 × 107 beads/mL, and (e) calibration curve of fluorescence as a function of mMB concentration

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Fig. 3

Captured mMBs from (a) 2 × 106 beads/mL sample at 750 volts using constant protocol, (b) 4 × 106 beads/mL sample at 650 volts using switching protocol, and (c) 4 × 106 beads/mL sample at 750 volts using switching protocol

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Fig. 4

Comparison of relative percent difference between switching and constant flow protocols for 2 × 106 beads/mL samples for this experiment and Das et al. [20]

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Fig. 5

Capture efficiency of mMBs under switching and constant protocols at (a) 650 V and (b) 750 V

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Fig. 6

Calibration curve of bacteria-mMB complex under constant flow protocol at 650 V



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