References 1.  Norrby, Walter E. Stamm and S. Ragnar, 2001. Urinary Tract Infections: Disease Panorama and

Challenges. The Journal of Infectious Diseases 183, S1-S4.

2.  Mohammed Zourob, Souna Elwary, Anthony Turner, 2008. Principles of bacterial detection: biosensors, recognition receptors, and microsystems. Springer; 1 edition, New York, NY,USA.

3.  Peter J. Asiello, Antje J. Baeumner 2011. Miniaturized isothermal nucleic acid amplification, a review. Lab on a Chip 11, 1420-1430.

4.  Tsugunori Notomi, Hiroto Okayama, Harumi Masubuchi,Toshihiro Yonekawa, Keiko Watanabe, Nobuyuki Amino and Tetsu Hase, 2000. Loop-mediated Isothermal Amplification of DNA. Nucleic Acids Research 28(12), e63.

5.  T Gregory Drummond, Michael G Hill, Jacqueline K Barton, 2003. Electrochemical DNA Sensors. Nature Biotechnology 21, 1192-1199.

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  Simple microfluidic chip for detection and quantification of E.coli was proposed.   The microfluidic assay detected the bacteria electrochemically using LSV method with high sensitivity and specificity.   The sensitivity of the assay was 48 CFU/ml in 35 min.   The specificity of this device was examined by using different bacteria such as Listeria and S. aureus DNA.   This device is much faster and more sensitive and consuming a much smaller amount of reagents in comparison with the other commercially available devices such as Galacto-Light Plus™ and TaqMan®. 50 µm

Escherichia coli , one of the most versatile bacteria around the world, has a number of unique features. It can exist as beneficial probiotics in the commensal of the digestive tract as well as a poisonous pathogen present in food and the environment. This bacteria is the major cause of many nosocomial diseases such as food poisoning, Meningitis , and Urinary tract infection (UTI) [1].  State of the art: The conventional method for the detection and identification of bacterial cells is culturing techniques. However, due to the time consuming (few days to several weeks) and labor-intensive protocol, it is not practical for rapid point of care (POC) diagnostics . Enzyme-linked immunosorbent assay (ELISA) is another technique that has widely been used. However, the multiple steps involved, with its semi-quantitative signal and low sensitivity detection significantly limit its reliability and accuracy. Rapidity, accuracy and sensitivity are the foremost elements for POC diagnostics devices. Recently, DNA hybridization and gene amplification techniques have widely been investigated for the rapid detection of E.coli with higher sensitivity and specificity [2]. Isothermal amplification techniques, which implement the amplification of the target nucleic acids in a constant temperature, have attracted significant interest for the rapid detection of bacteria. However, most of amplification techniques have limitations. They need either multiple enzymes for strand displacement of the DNA template or precision instruments for amplification or elaborative method, due to low specificity [3]. Loop-mediated isothermal amplification (LAMP) is an alternative isothermal amplification technique that is accurate, fast, cost-effective with high sensitivity and high specificity . It can amplify a few copies of DNA to 109 copies in less than an hour at 60-66°C [4]. LAMP amplicons can be measured optically or colorimetric using DNA-interacting dye . However, conventional florescent-based optical measurements need flurochrome labeling and expensive fluorescence analysis equipments. Colorimetric assays are less sensitive and it only provides qualitative result and analyze the existence of the DNA template in the samples. The advantages of the electrochemical detection over the optical detection techniques include not only the inherent miniaturization and portability, but also the independence from sample turbidity, extremely low-cost/ low-power requirements and compatibility with microfabrication technology [5].   Objectives: -  Integrate the merit of the LAMP, microfluidic and electrochemical detection to construct an inexpensive portable device for the rapid detection of E.coli. -  Design and fabricate a microfluidic device and integrate it with simple isothermal setup and electrochemical detection -  Test the sensitivity and specificity of the developed system -  Optimize the amplification time on the chip

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Figure 3: Shows the schematic of the electrochemical detection in the electrode chamber on microfluidic chip. (a) The redox active molecule Hoechst 33258 binds to the DNA micro groove, which causes the major reduction of electron on the surface of the electrode. (b) Linear Sweep Voltametry (LSV) as an electrochemical method demonstrating major drop in DNA detection in comparison with negative control sample. Gel electrophoresis image approves the DNA amplification.

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Figure 4: Shows the electrochemical detection of E.coli in the microfluidic chip (a) Maximum peak current in LSV for different extracted E.coli DNA concentration. The detection limit on the chip is 8.6 fg/µL. (b) Maximum peak current in LSV for different bacteria concentration. The detection limit for the bacteria detection on chip is 24 CFU/ml.

Figure 5: Shows the time optimization of DNA sample on the chip. The () illustrates the negative control and the () data represents the DNA sample. The chip detects the target DNA in 20 minutes. The DNA concentration is 35.6 ng/µL.

Figure 6: Shows the quantification of E.coli bacteria in different media. Microfluidic chip is calibrated with different samples of Bacteria spiked in (a) LB Broth (b) urine samples using 35 min. amplification time. Linear relationship exists between the logarithmic concentration and the anodic oxidation current. The R2 for the LB Broth and urine media are 0.972 and 0.964,respectively.

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Figure 7: Shows the cross reactivity test for the E.coli primes in the chip. Negative control contained of water with no E.coli DNA template. Due to existence of DNA and binding to redox molecule with its minor groove there is a small drop in the anodic oxidation peak current. The major drop is distinguishable between the E.coli DNA sample and other bacteria.

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Figure 1: Shows the schematic representation of the microfluidic chip Microfluidic chip composed of a heat block as the heat source to provide 66 °C, glass slide as the substrate and PDMS chip. The PDMS chip contained two parallel microfluidic chips for negative control and DNA detection. The microfluidic chip composed of a reaction chamber, an active valve (are not shown here) and an electrode chamber.

Figure 2: Shows the micrograph of the disposable electrode printed (DEP) chip.

Acknowledgment The authors would like to acknowledge the financial support for the project given by NSERC. The authors

wish to thank the team at the Laboratoire de Micro- et Nanofabrication (LMN) at INRS-EMT for using their facilities to fabricate the microfluidic chip and thank Dr. Mona Tolba for her useful guidance in preparation of materials.

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