Fully Integrated and Foldable Microdevice Encapsulated with Agarose for Long-Term Storage Potential for Point-of-Care Testing of Multiplex Foodborne Pathogens

Abstract

In this study, we fabricated a fully integrated and foldable microdevice encapsulated with 2-hydroxyethyl agarose for long-term storage of reagents for the integration of isothermal amplification and subsequent colorimetric detection for the monitoring of multiplex foodborne pathogens. The microdevice comprises a reaction zone and a detection zone. Both zones were made of a thin polycarbonate film and sealed by an adhesive film to make the microdevice foldable. The 2-hydroxyethyl agarose with loop-mediated isothermal amplification (LAMP) reagents and silver nitrate were deposited in the reaction and detection chambers, respectively, for long-term maintenance of reagent activity. A thin graphene-based heater associated with a handheld battery was employed to supply a constant temperature for on-chip amplification for 30 min. To simplify the sample manipulation process, a folding motion was adopted to allow the loading of LAMP amplicons from the reaction to the detection chambers and a colorimetric strategy was used for simple visual read-out of the results on-site. Using the agarose, the reagents were successfully stored and the reagent activity was maintained for at least 45 days. Prior to performing multiplex detections, the spiked juice was thermally lysed and purified with polydopamine-coated paper. The amplifications of Salmonella spp. and Escherichia coli O157:H7 (E. coli O157:H7) were successfully demonstrated based on the stable isothermal condition attained by the heater. The microdevice can detect the low concentration of E. coli O157:H7 at 2.5 × 10 2 copies per mL. The introduced microdevice acts as a simple and user-friendly platform for the identification of foodborne pathogens, paving the way for the construction of a truly portable, read-out microdevice for use as a public healthcare monitoring device.

Paper-based microfluidics for rapid diagnostics and drug delivery

“…Recently, LAMP-based paper devices have been widely applied in food safety and foodborne pathogen detection. These pathogens including Escherichia coli (E. coli) [22,46,[79][80][81][82][83], Salmonella [22,46,81,82], Cochlodinium polykrikoides [46], Staphylococcus aureus (SA) [84], Vibrio parahaemolyticus (VP) [84], food allergens [83], Sus scrofa (porcine) [85], and Bacillus subtilis [85] have also been detected using these devices. We introduced several examples of the different foodborne pathogen detection methods mentioned above.…”

Point-of-Need Diagnostics for Foodborne Pathogen Screening

“…Origami-based devices present another promising paper-based platform that has been utilized for microbiological testing of food. 110,111 Origami is the traditional Japanese art of paper folding, which has been utilized for several centuries to construct 3D geometries using a flat piece of paper. 112 These foldable devices can be fabricated on a single sheet of paper and assembled via simple folding, which reduces production costs and complexity.…”

“…Lee and coworkers developed a foldable microdevice composed of a thin polycarbonate film that contained multiple reaction and detection zones to allow for multiplex detection. 110 To improve the PON applicability of their device, they developed a thin graphene-based heater that was powered with a low-voltage, handheld power bank. The device was able to successfully detect Salmonella and E. coli O157:H7 in spiked juice samples after a separate thermal lysis and purification step utilizing polydopamine-coated paper.…”

Current progress on COVID-19 related to biosensing technologies: New opportunity for detection and monitoring of viruses

“…Trinh et al developed a fully integrated foldable biosensor encapsulated in agarose for long-term reagent storage and multiple fluorescence detection [132] . To prevent evaporation of the sample, the sample is placed in the reaction area, sealed with an adhesive sealing film and placed on a portable heater for amplification.…”