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  • Title: A microfluidic device for label-free detection of Escherichia coli in drinking water using positive dielectrophoretic focusing, capturing, and impedance measurement.
    Author: Kim M, Jung T, Kim Y, Lee C, Woo K, Seol JH, Yang S.
    Journal: Biosens Bioelectron; 2015 Dec 15; 74():1011-5. PubMed ID: 26264268.
    Abstract:
    While sensors that allow for high-throughput enumeration of microorganisms within drinking water are useful for water quality monitoring, it is particularly challenging to accurately quantify microorganisms that are present in low numbers (<100 CFU/mL) in a high-throughput manner. Negative dielectrophoresis (nDEP) is typically utilized in DEP-based cell focusing methods; however, due to its low conductivity, drinking water cannot be analyzed by this approach. Here, we report a positive DEP (pDEP)-based Escherichia coli detection system that is integrated with a focusing and sensing electrode. By incorporating a passivation layer, we avoided issues with adhesion of E. coli to the electrode, and achieved efficient cell focusing under high flow rate conditions (1500 μL/h). The resulting focused E. coli cells were then trapped on the sensor electrode, resulting in changes in impedance. The proposed system was evaluated using four different E. coli populations (150-1500 CFU/mL). We successfully enumerated populations as low as 300 CFU/mL within 1 min, and the signal variation was 1.13±0.37%. The device introduced in this study provides the basis for the development of portable, highly sensitive microorganism sensors that enable rapid detection of bacteria in drinking water.
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