Combined dielectrophoretic and impedance system for on‐chip controlled bacteria concentration: Application to Escherichia coli

Abstract

Abbreviations: Impedance analysis (IA), escherichia coli (E. coli), digital lock-in (DLIA), analog-to-digital converter (ADC), finite element method (FEM). 2 AbstractThe present paper reports a bacteria autonomous controlled concentrator prototype with a userfriendly interface for bench-top applications. It is based on a micro-fluidic lab-on-a-chip and its associated custom instrumentation, which consists in a dielectrophoretic actuator, to preconcentrate the sample, and an impedance analyser, to measure concentrated bacteria levels.The system is composed by a single micro-fluidic chamber with interdigitated electrodes and custom electronics instrumentation. The prototype is supported by a real-time platform connected to a remote computer which automatically controls the system and displays impedance data which is used to monitor bacteria accumulation status on-chip. The system automates the whole concentrating operation. Performance has been studied for controlled volumes of Escherichia Coli (E. coli) samples injected into the micro-fluidic chip at constant flow rate of 10 µl/min. A media conductivity correcting protocol has been developed, as so as the preliminary results shown the distortion of impedance analyser measurement produced by bacterial media conductivity variations through time. With the correcting protocol, the measured impedance values were related to the quantity of bacteria concentrated with a correlation of 0.988 and a coefficient of variation of 3.1%. Feasibility of E. coli on-chip automated concentration, using the miniaturized system, has been demonstrated and impedance monitoring protocol adjusted and optimized, to handle electrical properties changes of the bacteria media over time.3

Combined Dielectrophoresis and Impedance Systems for Bacteria Analysis in Microfluidic On-Chip Platforms

“…This can be evidenced in the growing number of published articles and citations reflected in Web of Science (WOS). This emergent trend is also evident for bacteria detection and concentration ( Figure 1 ) since several research groups reported the simultaneous measure of the concentrated bacteria in a single piece of equipment [ 14 , 30 , 35 , 36 , 37 , 38 ].…”

“…DEP uses a nontoxic electrical stimulation to induce a frequency-dependent dipole in cells [ 45 ]. The dielectrophoretic force is defined by Equation (1) [ 36 , 46 , 47 ]: where F concerns to the dipole approximation to the DEP force, refers to the permittivity of the medium surrounding the sphere, ω is the radian frequency of the applied field, R corresponds to the radius of the particle, r is the spatial coordinate, and E refers to the complex applied electric field. CM is the Clausius-Mossotti (CM) factor that is given by: where and are the complex permittivities of the medium and the particle, respectively, and are each given by = ε + σ /( jω ), where σ is the conductivity of the medium or particle, ε is the permittivity of the medium or particle, , and j is .…”

“…The combination of DEP and IA has demonstrated to be effective for the detection of DNA [ 101 , 102 ], RNA [ 100 ], yeasts [ 59 , 103 ], virus [ 104 ], cell trapping, detection and lysis [ 105 , 106 ], cancerous cells [ 107 , 108 , 109 , 110 ], and for bacteria [ 35 , 36 , 38 , 76 , 90 , 111 , 112 , 113 , 114 , 115 , 116 , 117 , 118 ]. Some of the devices used in bacteria concentration and detection are summarized in Table 1 .…”

Dielectrophoresis for Biomedical Sciences Applications: A Review

“…The inhibition of the antibiotic was measured by the positive DEP frequency response and the length of the bacteria. In addition, the interdigitated DEP electrodes combine with the impedance analyzer were used to measure the bacteria concentration [143]. As the trapped bacteria concentration increases, the impedance decreases.…”

A microchip electrophoretic assay for DNA methyltransferase activity based on methylation‐sensitive endonuclease DpnⅡ

“…Microchip electrophoresis (ME) is a rapid analysis technique with low sample consumption as well as automated analysis process and has been widely applied for DNA analysis [21][22][23], bacterial detection [24][25][26][27], and protein analysis [28][29][30]. Ronen et al reported a fluorescent microfluidic platform for the analysis of HpaⅡ MTase activity based on methylation-sensitive endonuclease HpaⅡ [31].…”