Differentiation of live and heat-killed E-coli by microwave impedance spectroscopy

SENSORS AND ACTUATORS B-CHEMICAL

卷:255

Article

Li, Hang¹  Multari, Caroline¹  Palego, Cristiano²  Ma, Xiao³  Du, Xiaotian³  Ning, Yaqing³  Buceta, Javier⁴  Hwang, James C. M.³  Cheng, Xuanhong¹ 

[1] Lehigh Univ, Mat Sci & Engn, Bioengn Dept, Bethlehem, PA 18015 USA

[2] Bangor Univ, Sch Elect Engn, Bangor, Gwynedd, Wales

[3] Lehigh Univ, Elect & Comp Engn, Bethlehem, PA 18015 USA

[4] Lehigh Univ, Chem & Biomol Engn, Bioengn Dept, Bethlehem, PA 18015 USA

关键词: Impedance sensing;    Bacterial detection;    Cell viability;    Biosensor;    Microfluidic device;    Lab on a chip;   

DOI  :  10.1016/j.snb.2017.08.179

来源: Elsevier

【 摘 要 】

The detection of bacteria cells and their viability in food, water and clinical samples is critical to bioscience research and biomedical practice. In this work, we present a microfluidic device encapsulating a coplanar waveguide for differentiation of live and heat-killed Escherichia coli cells suspended in culture media using microwave signals over the frequency range of 0.5-20 GHz. From small populations of similar to 15 E. coli cells, both the transmitted (vertical bar S-21 vertical bar) and reflected (vertical bar S-11 vertical bar) microwave signals show a difference between live and dead populations, with the difference especially significant for vertical bar S-21 vertical bar below 10 GHz. Analysis based on an equivalent circuit suggests that the difference is due to a reduction of the cytoplasm conductance and permittivity upon cell death. The electrical measurement is confirmed by off-chip biochemical analysis: the conductivity of cell lysate from heat-killed E. coli is 8.22% lower than that from viable cells. Furthermore, protein diffusivity increases in the cytoplasm of dead cells, suggesting the loss of cytoplasmic compactness. These changes are results of intact cell membrane of live cells acting as a semipermeable barrier, within which ion concentration and macromolecule species are tightly regulated. On the other hand, the cell membrane of dead cells is compromised, allowing ions and molecules to leak out of the cytoplasm. The loss of cytoplasmic content as well as membrane integrity is measurable by microwave impedance sensors. Since our approach allows detection of bacterial viability in the native growth environment, it is a promising strategy for rapid point-of-care diagnostics of microorganisms as well as sensing biological agents in bioterrorism and food safety threats. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

Free