Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1994-05-18
1995-10-31
Niebling, John
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
2041531, 204415, 204403, 204409, 204412, 128642, G01N 2726
Patent
active
054626455
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a dialysis electrode or biosensor device suitable for use in medicine and the food, drink, pharmaceutical and environmental monitoring industries and other industries where it is desirable to analyse or monitor the presence of chemical substances.
Dialysis is a general sampling technique which can be used in conjunction with an appropriate analytical technique, such as electrochemical analysis, to analyse chemical substances recovered by the dialysis. Microdialysis is a technique for sampling in vivo body fluids, for example, as described in an article by Urban Ungerstedt entitled "Microdialysis--A New Bioanalytical Sampling Technique" published in Current Separations, Volume 7, No. 2 (1986) by Bioanalytical Systems, Inc. It may be used in the electrochemical analysis of chemical substances extracted from the brain and various other organs of the human or animal body. With this technique, a chemical substance diffuses into a microdialysis probe, which may be the size of a syringe needle, implanted in tissue and the concentration of the substance is determined outside the body. Particularly, the introduction of a microdialysis probe into the brain makes it possible closely to monitor the chemical events of the extracellular space, wherein chemical transmission involved in neurotransmission of information takes place.
BACKGROUND OF THE INVENTION
The problems with the dialysis technique are threefold. Firstly, the dialysate is diluted into a flowing stream. Therefore, in order to have a sufficient quantity to measure, typically, a sample must be collected over ten to twenty minutes. This leads to the second problem that the technique has poor time resolution. Thirdly, the continuous removal by dialysis disturbs the concentration of the perfusing species in the region of the probe. With a view to resolving the problem of slow response time, it has been proposed to use an on-line electrode for the analysis but even so there is a delay whilst the solution flows slowly from the probe to the electrode in the electrochemical analysing equipment.
Fast response times of less than half a second may be obtained from implanted enzyme electrodes. However, the general problem with such implanted electrodes, in which an enzymic reaction is monitored by sensing changes in electrical parameters, is that the enzyme becomes inactive. It is also not easy to supply a cofactor, such as, NADH (reduced form of nicotinamide adenine dinucleotide). Furthermore, toxicity may be a barrier to use in clinical practice.
SUMMARY OF THE INVENTION
It is an object of the present invention to alleviate the problems experienced with hitherto known dialysis and electrode techniques of sampling and to provide a analysis electrode device which produces rapid measurements of variations in the concentrations of chemical substances and, more particularly, the in vivo concentrations of chemical substances, such as, the important neurotransmitter, glutamate, occurring in the extracellular space in a human or animal brain.
The present invention consists in a dialysis electrode device comprising a hollow probe having an internal chamber and a dialysis membrane forming a wall of the chamber, a working electrode mounted in the chamber, conduit means for supplying electrolyte to the chamber and removing electrolyte therefrom, and a reference electrode arranged to be electrically coupled to the working electrode by the electrolyte.
Conventional dialysis requires the continuous flow of perfusing solution as, for example, in the case of carrying out dialysis with a probe implanted in the brain or any other organ of a human or animal body, and relatively large amounts of chemical substances may be removed. With the present invention, the dialysis electrode device may simply be primed intermittently with a flow of electrolyte solution and electrical measurements of a particular dialysate are made with the probe remaining in situ in the organ. Because measurements are made when there is no flow through
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Albery John W.
Galley Peter T.
Bell Bruce F.
Imperial College of Science Technology & Medicine
Niebling John
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