Physiological systems bioelectric phenomena biomechanics biomaterials biosensors biomedical signal analysis imaging medical instruments and devices biological effects of non-ionizing biotechnology tissue engineering human performance engineering physiological modelling, simulation and control clinical engineering and artificial intelligence. (Part contents).

The Biomedical Engineering Handbook

We review the current state of optical methods for sensing oxygen. These have become powerful alternatives to electrochemical detection and in the process of replacing the Clark electrode in many fields. The article (with 694 references) is divided into main sections on direct spectroscopic sensing of oxygen, on absorptiometric and luminescent probes, on polymeric matrices and supports, on additives and related materials, on spectroscopic schemes for read-out and imaging, and on sensing formats (such as waveguide sensing, sensor arrays, multiple sensors and nanosensors). We finally discuss future trends and applications and summarize the properties of the most often used indicator probes and polymers. The ESI† (with 385 references) gives a selection of specific applications of such sensors in medicine, biology, marine and geosciences, intracellular sensing, aerodynamics, industry and biotechnology, among others.

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Optical methods for sensing and imaging oxygen: materials, spectroscopies and applications

The current state of the art of optical fiber sensors is reviewed. The principles of operation are detailed and the various types of fiber sensors are outlined. Achievable performance and limitations are discussed and a description of technology used to fabricate the sensor is presented. The characteristics of acoustic, magnetic, gyro, laser diode, and other sensors are described. Trends in the development of this sensor technology and expected application areas are briefly outlined.

Optical fiber sensor technology

A detailed study of the photophysics and photochemistry of
polymer-immobilized luminescent transition-metal complex
oxygen sensors is presented. Emphasis is on understanding
the underlying origin of the nonlinear Stern-Volmer quenching response. Microheterogeneity is important in both photophysical and photochemical behavior, and the nonlinear
quenching responses in RTV 118 silicone rubber can be adequately described by a two-site model, although detailed
lifetime measurements suggest a more complex Underlying
system. Counterion studies with quenching counterions are
shown to be useful probes of the structure of the complex in
the polymer. While oxygen enhances photochemical instability, singlet oxygen is not directly implicated in sensor decomposition. In the photochemistry there is at least one reactive and one much less reactive site, although the photochemistry and quenching measurements probably sample different populations of sites. The existence of reactive sites suggests that stability can be enhanced by a preliminary photolysis to eliminate the more reactive sites.

Photophysics and photochemistry of oxygen sensors based on luminescent transition-metal complexes

The authors have developed a viable alternative to capillary zone electrophoresis (CZE) detection based on mass spectrometric interfacing. A capillary zone electrophoresis-mass spectrometry (CZE-MS) interface obviously requires a substantial departure from the conventional CZE arrangement; it is clear that the interface design and ionization method are crucial to success. The liquid flow rate in CZE (approx.1 ..mu..L/min) is highly compatible with conventional mass spectrometers even if the total column effluent was introduced directly. The direct liquid introduction interfaces developed for LC-MS suffer from orifice plugging at low flow rates and the thermal degradation of high mass-low volatility components. Thermospray ionization, though attractive, has not been shown to be effective for liquid flow rates below a few tenths of a mL/min. Therefore, the authors evaluation of the requirements for a mass spectrometer interface suggested an approach that incorporates the electrospray ionization technique developed by Dole et al. and the more recent work reported by Fenn and co-workers. In this communication, the authors report the successful development of CZE-MS instrumentation for the separation and analysis of ionic species in aqueous solutions.

On-line mass spectrometric detection for capillary zone electrophoresis

Fiber optic pH probe for physiological use.

Cette sonde est basee sur le quenching a fluorescence et consiste en 2 brins de 250 μm de fibre optique plastique se terminant par une section de polymere poreux de 3 mm de long et 0,6 de diametre

Fiber-optic probe for in vivo measurement of oxygen partial pressure.

A fiber optic probe to be implanted in human body tissue for physiologic studies involving measurement and monitoring of the partial pressure of gaseous oxygen in the blood stream, which is coursing through a particular blood vessel in the body. The use of the probe is based on the principle of dye fluorescence oxygen quenching. Structurally the probe comprises two 150-micrometer strands of plastic optical fiber ending in a section of porous polymer tubing serving as a jacket or envelope for the fibers. The tubing is packed with a suitable fluorescent light-excitable dye placed on a porous adsorptive particulate polymeric support. The tubing or jacket is usually made of a hydrophobic, gas-permeable commercial material, known as Celgard, but other suitable hydrophobic gas-permeable material could be used for such structure. The fiber optic probe of the invention is of very small size and flexible so that it can easily be threaded through small blood vessels which are located in a variety of tissues of the body.

Fiber optic POs probe

A surface pattern flow visualization technique is demonstrated based on the principle of oxygen quenching of dye fluorescence. The technique uses visible light excitation and streams of oxygen or nitrogen, which are inexpensive and nontoxic. A sensitive material can be spray coated on shapes of interest to study flow at surfaces.

Raphael V. Fitzgerald

Papers

Fiber optic pH probe for physiological use.

Fiber-optic probe for in vivo measurement of oxygen partial pressure.

Fiber optic POs probe

New technique of surface flow visualization based on oxygen quenching of fluorescence

Sonde à PO2 en fibres optiques