Continuous Real-time Detection of Microbial Contamination in Water using Intrinsic Fluorescence

Abstract

The use of intrinsic fluorescence to study cellular metabolic components has been explored since the 1950s [8][9][10]. Remote, realtime detection and quantification of live cells, dead cells, and spores in fluids (air, water) and on surfaces and sub-surfaces (like those of food, surgical theaters, soils, rock, ice) at low concentrations has been demonstrated [11][12][13]. Some microbes have demonstrated specific fluorescence signatures that depend on their environment or growth conditions [14], e.g., Escherichia coli, Enterococcus faecalis and Staphylococcus aureus in otitis media and contamination source tracking of several Pseudomonas spp. in dairy products [15]. Our approach makes use of the following metabolic intrinsic fluorescence signatures to detect the presence of microbes that are present under physiological conditions: reduced pyridine nucleotides (RPNs), flavins, cytochromes, calcium dipicolinic acid (DPA) and others [11][12][13][15][16][17]. Metabolic signals, which are indicators of live cells, fluoresce in the bluegreen region with 340-360 nm excitations. The fluorescence emitted is directly proportional to the concentration of metabolites and thus to the average number of live cells [11]. Flavins and protoporphyrin IX, which also fluoresce in the red region upon 565-595 nm excitations, are found in both live and dead cells. Cytochromes fluoresce in the near IR upon 610-640 nm excitations. Excitations in the deep UV (e.g., 250-300

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

“…The light source used was two commercial Deep UV Light Emitting Diodes (LEDs), with a 6° view angle, so light dispersion would be minimized until it reached the sample. Both light sources were displaced at 90 °C ( Figure 2 b) from the detector to optimize the signal to noise ratio [ 22 ]. An optic bandpass filter with a 340 nm central wavelength and 20 nm bandwidth, was used to block light that comes from scattering the water molecules, as well as other external interferences.…”

Compact Color Biofinder (CoCoBi): Fast, Standoff, Sensitive Detection of Biomolecules and Polyaromatic Hydrocarbons for the Detection of Life

“…Fluorescence spectroscopy has been used to detect a wide range of organic and biogenic materials such as microbes, amino acids, nucleic acids, chlorophyll, bacteria, algae and phytoplankton, fungi, proteins, dissolved organic matter in water, PAHs, lipids, biominerals, fossils, etc. 9–36 Similarly, minerals containing transition metals and rare-earth ions also give strong luminescence signals, which overlap with the fluorescence signals from organic materials in the wavelength domain. This interference from mineral luminescence has been an issue for detecting biological materials among rocks when using traditional instrumentation.…”