Tuesday, 2 December 2014

Instantaneous Microbial Detection for Water

Technology focus:

New technologies based on laser-induced fluorescence (LIF) detect intrinsic fluorescence instead of growth, can operate continuously, and deliver real-time results for the microbiological monitoring of water. As applied to pharmaceutical water quality, LIF-based, instantaneous microbial detection technologies enable real-time bioburden monitoring, risk reduction, and process control.

With the technique, laser, or light, induced fluorescence is used (LIF). LIF is a spectroscopic technique capable of high sensitivity in the detection of compounds that fluoresce. Fluorescence is the luminescence that occurs with the absorption of radiation at one wavelength followed by the emission of radiation at a different wavelength. Substances that typically fluoresce may be referred to as fluorophores. Quinine is a familiar fluorophore due to its presence in tonic water.

The application of LIF to detect microorganisms has been leveraged in flow cytometry, capillary electrophoresis, solid-phase cytometry, adenosine triphosphate bioluminescence, and growth-based auto fluorescence. In a number of these techniques, microorganisms are dyed to increase the measurable fluorescence. Measuring the intrinsic fluorescence of a microorganism removes the requirement for dyes and sample preparation, but requires an instrument with significant sensitivity. As lasers of additional wavelengths at higher power levels have become commercially available, LIF has become very relevant in applications requiring detection of low levels of microbial intrinsic fluorescence.

A light source such as a laser is the excitation source in LIF. A laser of appropriate wavelength and intensity is capable of inducing intrinsic fluorescence emission from microbes due to constituent fluorophores such as tryptophan, nicotinamide adenine dinucleotides (NADH), and flavins that are present in microorganisms.7 The target excitation wavelength is based on the excitation spectra of target fluorophores such that sufficient fluorescence intensity is induced for measurement and a greater number of non-biologic materials may be excluded. Yet, non-biologic materials such as plastics, rubbers, and paper can also fluoresce pointing to the importance of software discrimination algorithms.

For further details, see Controlled Environments.

Posted by Tim Sandle