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Integrated Microfluidic Devices for Detection of Microorganisms

Y. Liu, E. Salm, D. Marchwiany, R. Bashir; University of Illinois, Urbana-Champaign
L. Liu, B. Panada, A. Bhunia, M. Ladisch; Purdue University

This USDA funded project through the Center for Food Safety Engineering at Purdue is focused on development of technology platforms for the detection and identification of live bacteria from food and fluid samples. We have integrated sample preparation, DEP and Antibody mediated capture, and capture and culture of bacterial cells inside microfluidic microfluidic devices. We have used dielectrophoresis (DEP) to build on-chip electrical filters and valves (Li, et al 2005) for concentrating cells and capturing them on to surface from a flow in a micro-channel. We have combined the advantages of DEP concentration and antibody (Ab) specificity to demonstrate selective capture of target cells from a mixture of cells with similar dielectric properties in a micro-fluidic biochip (Yang et al. 2006). To reduce the time for detection of culture and perform the detection electrically, we are among the first to design a microfluidic-chip in which a few bacterial cells can be concentrated from a dilute sample into volumes on the order of nanoliters and to subsequently culture these bacteria (Gomez, et al 2005).

Taking the advantage of the small volume of the biochip, we concentrated bacterial cells from a dilute sample by factors on the order of 104 to 105 into a small chamber. This novel “Impedance microbiology-on-a-chip” technique can completely eliminate the requirement for amplifying the bacterial population by enrichment in many conventional methods, thus the sensitivity and speed of the assay can be greatly improved (Figure 1). Our measurements in silicon-based microfluidic devices indicated that the metabolic activity of a minimum of just a few cells can be detected (Gomez et al., 2005). We have recently developed capabilities of running polymerase chain reactions with Listeria monocytogenes and translated this protocol to our silicon device platform to perform PCR detection. An amplification of a 508 base pair region of the performance regulatory factor A (PRFA) gene using primers which are highly specific to L. monocytogenes has been performed. We are completing these studies and publications describing these integrated devices.