An integrated microsystem with dielectrophoresis enrichment and impedance detection for detection of Escherichia coli.

An integrated microsystem device with matched interdigitated microelectrode chip was fabricated for enrichment and detection of Escherichia coli O157:H7. The microsystem has integrated with positive dielectrophoresis (pDEP) enrichment and in situ impedance detection, whose total volume is only 3.0 × 10-3 m3, and could provide impedance testing voltages of 0 ~ 10 V, detection frequencies of 1 KHz ~ 1 MHz, DEP excitation signals with amplitude of 0 ~ 10 Vpp and frequencies of 1KHz ~ 1 MHz, which fully meets the demands of pDEP enrichment and impedance detection for bacteria. The microfluidic chip with interdigitated microelectrodes was manufactured by microfabrication methods. The interdigital microelectrode array has sufficient contact area with a bacterial suspension to improve enrichment efficiency and detection sensitivity. Bacteria in the interdigital microelectrode area of the microfluidic chip were firstly captured and enriched by pDEP. Then, in situ impedance detection of the enriched bacteria was realized by switching test conditions. Using the self-assembly microsystem, a novel quantitative detection method was established and demonstrated to detect Escherichia coli O157:H7. Experimental results showed that the detection limits of Escherichia coli O157:H7 was 5 × 104 cfu mL-1, and testing time was only 6 min under the optimized detection voltage of 100 mV and frequency of 500 KHz. The method was successfully used to detect Escherichia coli O157:H7 in synthetic chicken synthetic samples.