Abstract
Although immunomagnetic separation is a useful sample pretreatment method that can be used to separate target pathogens from a raw sample, it is challenging to remove unbound free magnetic nanoparticles (MNPs) for colorimetric detection of target pathogens. Here, size-based filtration was exploited for the rapid on-site detection of pathogens separated by immunomagnetic separation in order to remove unbound free MNPs using a finger-powered microfluidic device. A membrane filter and an absorbent pad were integrated into the device and a mixture of unbound free MNPs and MNP-bound Escherichia coli (E. coli) O157:H7 was dispensed over the membrane filter by pressing and releasing the pressure chamber. A colorimetric signal was generated by MNP-bound E. coli O157:H7 while unbound free MNPs were washed out by the absorbent. Furthermore, the colorimetric signals can be amplified using a gold enhancer solution when gold-coated MNPs were used instead of MNPs. As a result, 102 CFU/mL E. coli O157:H7 could be detected by the enhanced colorimetric signal on a proposed device.
Highlights
Foodborne diseases are a national issue in undeveloped countries and in advanced countries
A membrane filter was inserted between the bottom layer and the third layer so that the sample flowing in the device can be separated through the membrane filter complex and unbound free magnetic nanoparticles (MNPs)
E. coli O157:H7 was detected by the amplified colorimetric signal using a membrane filter-integrated finger-powered microfluidic device
Summary
Foodborne diseases are a national issue in undeveloped countries and in advanced countries. Because foodborne pathogens proliferate rapidly, early-stage screening of the pathogens is important to prevent serious diseases. The traditional method based on culture-based direct plating is still the “gold standard” for the detection and identification of pathogens [2,3] This direct plating method provides information on the number of pathogens in food samples at relatively low prices with good specificity and sensitivity. Because this method visually selects presumptive positive colonies on an agar plate, morphologically similar competitive microflora are often selected and grown with target pathogens in agar media. This method requires highly skilled technicians and various cultivation processes for enrichment, isolation, and identification, which takes 3–5 days for the detection of the pathogens
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