Nanofiber-based colorimetric platform for point-of-care detection of E. coli

Accurate and rapid detection of bacteria in complex environmental samples using simple and portable devices is still a major challenge. This research presents a simple nanofiber-based platform for highly sensitive colori-metric/fluorometric detection of Escherichia coli (E. coli). Nanofiber membranes (NFM) were loaded with target molecules (fluorescent and chromogenic substrate) via chemical modification to prepare functional NFM (NFM-MUG and NFM-XG). The beta-glucuronidase secreted by E. coli during the metabolic process triggered the func-tionalized NFM to produce biological signals and color change. The intensity of bio-signals and color was shown to enable quantitative and qualitative detection of E. coli. The nanofiber-based platforms exhibited high stability and a wide detection range (102-107 CFU/mL). The limit of detection (LOD) of NFM-MUG and NFM-XG sensors for E. coli were 26 and 69 CFU mL-1, respectively. The sensing time required for NFM-MUG and NFM-XG was 15 mins and 30 mins respectively. The nanofiber-based platforms also exhibited high specificity and low interfer-ence from ionic compounds and pH changes. Notably, this assay was easily combined with a smartphone app as a portable device for on-site detection of E. coli, showing a great promise in the field of environmental and food safety testing.