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

Abstract

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 m, 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 × 10 cfu mL, 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.

Characterization Of The Electrodes Of DEP-Based Micro-Separator

“…The electric current, electrical potential, and electrical field can be evaluated by solving the Ohm's law. Fundamental equations from Ohm's law are shown from equation (3) to equation (5).…”

“…The electric force can manipulate charged particles, which is called electrophoresis, or it can manipulate uncharged particles, which is called dielectrophoresis (DEP). DEP has been used by researchers for different applications such as cell patterning [1], trapping [2,3], focusing [4], enrichment [5], separation [6] and isolation [7,8]. DEP can separate the cells based on their electrical properties (electrical conductivity and permittivity) and size.…”

Simultaneous and continuous particle separation and counting via localized DC-dielectrophoresis in a microfluidic chip

“…One popular approach is to integrate DEP with an impedance detection system. [6][7][8][9][10][11][12][13][14][15][16] The DEP force is utilized to enrich the target particles at the detection region or deplete the unwanted ones from the suspension. Due to the greatly concentrated sample, the detection sensitivity was improved.…”

“…Due to the greatly concentrated sample, the detection sensitivity was improved. Such a concept was successfully applied for the detection of bacteria, 6,7 DNA, 8,9,17 amyloid beta 10,16 and cancer cells. 15,16 There are some other types of detection means which were combined with DEP also.…”

Microfluidic-Based Nucleic Acid Amplification Systems in Microbiology

“…Splitting and merging of droplets in digital microfluidics allow for the implementation of sample preparation on the same platform [33,34]. There is interest in integrating various functions, such as sample preparation, amplification, and detection, in the same automated microfluidic device to reduce handling time and to prevent sample contamination [35,36]. Consequently, droplet-based microfluidics and particularly digital microfluidics play critical roles in designing advanced and robust nucleic acid amplification assays.…”