Description of Technology

The Micro PRO™ technology is based on flow cytometry, a technology that is used for counting individual, micron-sized particles (bacteria, yeast, etc.) as they pass through a beam of laser light. Many of the Micro PRO™ components are common to general flow cytometry, such as sophisticated fluidics, laser optics, electronic detectors, analog to digital converters, and a dedicated computer. The Micro PRO™ system differs from routine cytometry, however, in the specialized sample delivery system and proprietary labeling compounds.

In general, samples are prepared for analysis by labeling microbes through reaction with a stain or antibody. Once the fluorescent markers are attached, the sample is injected. The sample enters the sheath fluid flow which is traveling at a much higher velocity and serves to hydrodynamically focus the sample into a very fine stream of monodispersed cells. The particles, now in single file formation, are confined to the central region of the sheath flow creating the "sample core."

Flow Cytometry: Fluidics

A focused beam from a red diode laser impinges on the sample core, and two photomultiplier tubes collect the emitted signals for fluorescence and scatter. Various fluorescent dyes are used based on the objective of the analysis, whether it is to provide viability information or to target specific microbes for quantification and identification. Quantification is achieved through the photoelectric effect by counting the number of photons emitted at both fluorescence and scattered laser light wavelengths whose intensities meet the calibration criteria determined for a developed method.

Flow Cytometry: Optical System

The Advanced Analytical approach improves upon standard flow cytometry methods to quantify much lower concentrations within a very small controlled sample volume (0.1 mL, 0.25 mL, and 0.5 mL). The system components are optimized to enumerate microbial cells as small as 0.1 µm.

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