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Separating and Detecting Escherichia Coli in a Microfluidic Channel for Urinary Tract Infection Applications

by Yongmo Yang, Sangpyeong Kim, Junseok Chae
Journal of Microelectromechanical Systems ()

Abstract

We report a lab-on-a-chip (LOC) that can separate and detect Escherichia coli (E. coli) in simulated urine samples for urinary tract infection (UTI) applications. The LOC consists of two (concentration and sensing) chambers connected in series and an integrated impedance detector. The two-chamber approach is designed to reduce the nonspecific absorption of a protein, e.g., albumin, that potentially coexists with E. coli in urine. We directly separate E. coli K-12 from cocktail urine in a concentration chamber containing microsized magnetic beads conjugated with anti-E. coli antibody. The immobilized E. coli is transferred to a sensing chamber for the impedance measurement. The measurement at the concentration chamber suffers from nonspecific absorption of albumin on the gold electrode, which may lead to false-positive response. By contrast, the measured impedance at the sensing chamber shows a <formula formulatype="inline"><tex Notation="TeX">$\sim\!\! 60\hbox{-k}\Omega$</tex> </formula> impedance change. This is a clear distinction between <formula formulatype="inline"><tex Notation="TeX">$6.4 \times 10^{4}$</tex></formula> and <formula formulatype="inline"><tex Notation="TeX">$6.4\times 10^{5} \ \hbox{CFU/mL}$</tex></formula>, covering the threshold of UTI <formula formulatype="inline"><tex Notation="TeX">$(10^{5} \ \hbox{CFU/mL})$</tex></formula>. The sensitivity of the LOC in detecting E. coli is characterized to be at least <formula formulatype="inline"><tex Notation="TeX">$3.4 \times 10^{4} \ \hbox{CFU/mL}$</tex></formula>. We also characterized the LOC for different age groups and white blood cell spiked samples. These preliminary data show promising potential for application in portable LOC devices for UTI detection. <formula formulatype="inline"><tex Notation="TeX">$\hfill$ </tex></formula>[2010-0263]

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