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

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 ∼60-kΩ impedance change. This is a clear distinction between 6.4 × 10 4 and 6.4 × 10 5 CFU/mL, covering the threshold of UTI (10 5 CFU/mL). The sensitivity of the LOC in detecting E. coli is characterized to be at least 3.4 × 10 4 CFU/mL. 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.[ 2010-0263]Index Terms-Escherichia coli (E. coli), lab-on-a-chip (LOC), point-of-care testing, urinary tract infection (UTI).

Critical overview on the application of sensors and biosensors for clinical analysis

“…With this portable biosensor, an LOD of 3.4 × 10 4 CFU mL −1 was obtained, which is lower that the threshold of urinary tract infections (10 5 CFU mL −1 ). The LOD obtained with the microfluidic biosensor proposed by Safavieh et al [138] was greater (24 CFU mL −1 ) than that obtained by Yang et al [137]. Safavieh et al [138] developed a biosensor employing loop-mediated isothermal amplification, which played a key role in quantifying the bacteria.…”

“…For example, Yang et al [137] and Safavieh et al [138] proposed two electrochemical immunosensors based on microfluidics for the detection of E. coli in urine samples ( Table 6). Detection of E. coli in human urine is used to diagnose urinary tract infections commonly related to the kidney, as it is known to cause up to 80% of such infections and is present at concentrations ≥10 5 CFU mL −1 [137]. Microfluidics reduces the consumption of costly reagents, as small volumes of liquid are manipulated in closed microscale channels.…”

“…enhances the ongoing reactions, thus leading to miniaturized biosensors with various applications [138]. The biosensor fabricated by Yang et al [137] is considered as a lab on a chip, consisting of two chambers (for concentration and sensing) connected in series and an integrated impedance detector. These two chambers help reduce the non-specific absorption of proteins such as albumin, which coexists with E. coli in urine, thereby improving the sensitivity.…”

“…In the concentration chamber, the bacteria are separated from the urine sample by the conjugation of microsized magnetic beads to E. coli antibodies. The immobilized E. coli is then transferred to the sensing chamber to measure impedance and in turn estimate the E. coli concentration [137]. With this portable biosensor, an LOD of 3.4 × 10 4 CFU mL −1 was obtained, which is lower that the threshold of urinary tract infections (10 5 CFU mL −1 ).…”

Smartphone-based, sensitive µPAD detection of urinary tract infection and gonorrhea

“…As reported, there are few LFA or mPAD methods that can efficiently detect bacteria. There are minimal amounts of methods (lines 1-4; Liao et al, 2006;Bercovici et al, 2011;Safavieh et al, 2012;Yang et al, 2011) that detect bacteria directly from a urine sample matrix using microfluidic platforms (not LFA or mPAD). Unfortunately, either pretreatment (filtration, centrifugation, and/or rinsing) was necessary or the detection limit was quite high (10 5 -10 8 CFU/mL).…”