Chemistry: analytical and immunological testing – Involving an insoluble carrier for immobilizing immunochemicals
Patent
1997-07-23
1999-07-13
Chin, Christopher L.
Chemistry: analytical and immunological testing
Involving an insoluble carrier for immobilizing immunochemicals
204400, 204403, 204414, 204424, 422 55, 422 57, 422 681, 422 8205, 422 83, 422 88, 4352871, 4352872, 4352875, 4352887, 435807, 435808, 436149, 436164, 436524, 436527, 436525, 436805, 436806, 436807, G01N 33543
Patent
active
059226161
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a sensor for detecting chemical compounds in particular in the gaseous or vapour phase. The invention also relates to novel media for biochemical reactions and a method for monitoring an analyte by determining a biocatalytic reaction of a substrate with a bioreceptor or biomimic, the concentration of the analyte being relatable to that of the substrate.
Many gas sensors are known. They often suffer from lack of specificity and one method for overcoming such lack of specificity is to incorporate a catalyst or biological catalyst, even whole bacteria, which usually have high specificity.
In DE-A-4032599 a non-biological gas sensor is described. A three dimensional polyurethane matrix containing an electrolyte and a catalyst is positioned at a test electrode. The current generated between the test electrode and a second, counter electrode is dependent upon the partial pressure of the test components. However, this reference does not relate to bioelectrochemical reactions and therefore the specific requirements for maintaining a bioreceptor or biomimic in an active state.
Generally reactions monitored using biological catalysts are carried out in bulk aqueous solution. This is largely because in order to maintain the activity of a bioreceptor and sometimes a biomimic, a hydration shell is needed around the bioreceptor or biomimic. This is essential to retain the three dimensional structure of the bioreceptor or biomimic which in turn is essential for its activity. In these types of sensor, generally an analyte for detection must be dissolved in solution in the bulk aqueous liquid prior to detection.
However, gas sensors based on bulk aqueous liquids have inherent short-comings: limited shelf life due to solvent evaporation and, a particular problem when detection is electrochemically, electrode corrosion.
In solution biocatalytic activity may even result in damaged seals and eventually cause leakage of the bulk liquid.
In European J. Appl. Microbiol. Biotechnol (1981) 12:102-106, Okada et al describe a biological methane gas sensor in which bacteria are immobilised in acetylcellulose filters with agar gel and their respiration is monitored using an oxygen electrode. However, such detectors detect only the respiration activity of the bacteria and not the reaction of an enzyme with its substrate. It would be desirable to detect the reaction itself as this would confer increased sensitivity on an apparatus.
It is also known to use detection of an analyte using enzymes in a bulk liquid medium which is not an aqueous liquid. For example, reactions in organic or micro-aqueous solvents are monitored by the method of apparatus as described in WO89/04364. In this publication, enzymes are retained at a support on an electrode by either covalent bonding or by hydrophilic attraction to a membrane comprising polymeric material and the electrode is immersed in the bulk solvent medium. This method does not detect a gaseous or vapour phase analyte.
It is also known to use as the support material, for the enzyme, a solid/gel phase comprising for example an inorganic salt, as is described in European patent application No. 93306738.1. Organic or inorganic solid supports for enzymes are also described in WO88/01299. This disclosure relates to a sensor which monitors a colour change to indicate the presence of a reaction due to the presence of a substrate for the enzyme. The enzyme support disclosed does not therefore need to be conducting and micro crystalline cellulose is the only example given.
L. H. Goodson and W. B. Jacobs, in Enzyme Engineering Ballstock 2, Plenum Press, New York, 974, page 393 edited by E. K. Pye and L. B. Wingard Jr. describe immobilised enzymes for detecting the presence of an enzyme inhibitor by electrochemical means. The enzymes are immobilised trapped in starch gel on the surface of open pore polyurethane foam. It is reported that the open pore structure of the polyurethane foam is used because it enables both air and liquid to pass through simultaneously to enable the substr
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J. Wang et al., "Organic-Phase Enzyme Electrode For the Determination of Trace Water in Nonaqueous Media", Anal Chem., vol. 54, pp. 845-847 (1993).
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T. Okada et al., "Microbial Sensor System Which Uses Methylomonas sp. For the Determination of Methane", European J. Appl. Microbiol Biotechnol, vol. 12, pp. 102-106, (1981).
L. Goodson et al., "Application of Immobilized Enzymes to Detection and Monitoring", Midwest Research Institute, pp. 393-400.
Dennison Manus Joseph
Hall Jennifer Maeve
Turner Anthony Peter Francis
Chin Christopher L.
Cranfield University
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