Continuous and Real-Time Detection of Drinking-Water Pathogens with a Low-Cost Fluorescent Optofluidic Sensor

Abstract

Growing access to tap water and consequent expansion of water distribution systems has created numerous challenges to maintaining water quality between the treatment node and final consumer. Despite all efforts to develop sustainable monitoring systems, there is still a lack of low cost, continuous and real time devices that demonstrate potential for large-scale implementation in wide water distribution networks. The following work presents a study of a low-cost, optofluidic sensor, based on Trypthopan Intrinsic Fluorescence. The fluorospectrometry analysis performed (before sensor development) supports the existence of a measurable fluorescence output signal originating from the tryptophan contained within pathogenic bacteria. The sensor was mounted using a rapid prototyping technique (3D printing), and the integrated optical system was achieved with low-cost optical components. The sensor performance was evaluated with spiked laboratory samples containing E. coli and Legionella, in both continuous and non-continuous flow situations. Results have shown a linear relationship between the signal measured and pathogen concentration, with limits of detection at 1.4 × 103 CFU/mL. The time delay between contamination and detection of the bacteria was practically null. Therefore, this study supports the potential application of tryptophan for monitoring drinking water against water pathogens.

Quick assessment of influenza a virus infectivity with a long-range reverse-transcription quantitative polymerase chain reaction assay

“…The rapid detection of pathogens is in high demand for the purpose of on-site inspection of specimens at hospitals and of treated water at water treatment plants [31,32]. In healthcare settings, patients with flu symptoms are usually diagnosed with an IAV diagnostic test using immunochromatography with antibodies against IAV antigens [31].…”

“…Some of the highly pathogenic avian influenza viruses, such as the H5N1 and H9N2 subtypes included in IAV, are also considered to be partially transmitted to humans through the consumption of contaminated water [37,38]. In response to this trend, methods that can be used to verify successful disinfection in real time are desirable [32]. The rapid molecular test based on long-range RT-qPCR described in the present study may represent such a solution for this issue.…”

3D microfluidic gradient generator for combination antimicrobial susceptibility testing

“…Before each day of bacteriological experiments, a fresh bacterial inoculation was created by adding a single bacterial colony harvested from the agar plate to 10 mL of LB media and incubating overnight at 37°C. The cell density of the solution was measured the next day using a UV-VIS spectrophotometer (Vernier, OR, USA) following the OD600 method 8,87 ; then, a serial dilution was performed to create an inoculation with an initial cell density of~5 × 10 5 cfu/mL following cell viability [88][89][90] and AST 38,50,52,69,91 conventions. LB media was prepared by dissolving LB powder (LB Miller Broth, Sigma-Aldrich, MO, USA) in deionized (DI) water to make a 25 g/L solution in a 1000-mL autoclave bottle (ThermoFisher Scientific), followed by autoclave sterilization at 120°C for 25 min.…”

Monitoring Approaches for Faecal Indicator Bacteria in Water: Visioning a Remote Real-Time Sensor for E. coli and Enterococci

“…In the excitation stage, fluorophores are excited by a high-energy light source, which produces the excited-state lifetime (the excited state exists for a finite time) and is followed by the fluorescence emission [69][70][71]. There are four elements involved in fluorescence detection systems: the excitation source, a fluorophore, wavelength filters to isolate emission photons from excitation photons, and a detector to register the emission photons and produce outputs [69].…”