Metabolic viability of Escherichia coli trapped by dielectrophoresis in microfluidics

Authors

  • Sandra S. Donato,

    1. INESC Microsistemas e Nanotecnologias and IN-Institute of Nanoscience and Nanotechnology, Lisbon, Portugal
    2. IBB – Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal
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  • Virginia Chu,

    1. INESC Microsistemas e Nanotecnologias and IN-Institute of Nanoscience and Nanotechnology, Lisbon, Portugal
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  • Duarte M. F. Prazeres,

    1. IBB – Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal
    2. Department of Bioengineering, Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal
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  • Joao P. Conde

    Corresponding author
    1. Department of Bioengineering, Instituto Superior Técnico, Technical University of Lisbon, Lisbon, Portugal
    • INESC Microsistemas e Nanotecnologias and IN-Institute of Nanoscience and Nanotechnology, Lisbon, Portugal
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  • Colour Online: See the article online to view Figs. 1–5 in colour.

Correspondence: Professor Joao P. Conde, INESC Microsistemas e Nanotecnologias and IN-Institute of Nanoscience and Nanotechnology, Technical University of Lisbon, Rua Alves Redol, 9, Lisbon 1000-029, Portugal

E-mail: joao.conde@ist.utl.pt

Fax: +351-21-3145843

Abstract

The spatial and temporal control of biological species is essential in complex microfluidic biosystems. In addition, if the biological species is a cell, microfluidic handling must ensure that the cell's metabolic viability is maintained. The use of DEP for cell manipulation in microfluidics has many advantages because it is remote and fast, and the voltages required for cell trapping scale well with miniaturization. In this paper, the conditions for bacterial cell (Escherichia coli) trapping using a quadrupole electrode configuration in a PDMS microfluidic channel were developed both for stagnant and for in-flow fluidic situations. The effect of the electrical conductivity of the fluid, the applied electric field and frequency, and the fluid-flow velocity were studied. A dynamic exchange between captured and free-flowing cells during DEP trapping was demonstrated. The metabolic activity of trapped cells was confirmed by using E. coli cells genetically engineered to express green fluorescent protein under the control of an inducible promoter. Noninduced cells trapped by negative DEP and positive DEP were able to express green fluorescent protein minutes after the inducer was inserted in the microchannel system immediately after DEP trapping. Longer times of trapping prior to exposure to the inducer indicated first a degradation of the cell metabolic activity and finally cell death.

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