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The development of transparency-based electrochemical and paper-based colorimetric analytic detection platforms is presented as complementary methods for food and waterborne bacteria detection from a single assay. Escherichia coli and Enterococcus species, both indicators of fecal contamination, were detected using substrates specific to enzymes produced by each species. β-galactosidase (β-gal) and β-glucuronidase (β-glucur) are both produced by E. coli, while β-glucosidase (β-gluco) is produced by Enterococcus spp. Substrates used produced either p-nitrophenol (PNP), o-nitrophenol (ONP), or p-aminophenol (PAP) as products. Electrochemical detection using stencil-printed carbon electrodes (SPCEs) was found to provide optimal performance on inexpensive and disposable transparency film platforms. Using SPCEs, detection limits for electrochemically active substrates, PNP, ONP, and PAP were determined to be 1.1, 2.8, and 0.5 μM, respectively. A colorimetric paper-based well plate system was developed from a simple cardboard box and smart phone for the detection of PNP and ONP. Colorimetric detection limits were determined to be 81 μM and 119 μM for ONP and PNP respectively. While colorimetric detection methods gave higher detection limits than electrochemical detection, both methods provided similar times to positive bacteria detection. Low concentrations (10 1 CFU/mL) of pathogenic and nonpathogenic E. coli isolates and (10 0 CFU/mL) E. faecalis and E. faecium strains were detected within 4 and 8 h of pre-enrichment. Alfalfa sprout and lagoon water samples served as model food and water samples, and while water samples did not test positive, sprout samples did test positive within 4 h of pre-enrichment. Positive detection of inoculated (2.3 × 10 2 and 3.1 × 10 1 CFU/mL or g of E. coli and E. faecium, respectively) sprout and water samples tested positive within 4 and 12 h of pre-enrichment, respectively.

Self-pumping porous microfluidic devices have attracted significant interest because of their low cost and broad applicability in point-of-care and low resource settings. One limitation of many of the devices is sensitivity and selectivity for detection. Electrochemistry can provide a sensitive, selective detection method while still using low cost, portable instrumentation as typified by handheld glucometers. Here, the development of electrochemical paper-based analytical devices (ePADs) is reviewed. Given the importance of electrode geometry and composition, fabrication methods are reviewed first. This is followed by a review of example applications demonstrated for ePADs. Finally, major accomplishments and future directions are summarized., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)