There are remarkably few papers in the literature on this topic [conductivity used to monitor enzyme catalysis, at least that I have been able to find that are relevant to the present work). However it is hardly a recent topic, since Henri used the method to measure gelatin hydrolysis by trypsin in 1903! Conductimetry has been widely applied in micro-biosensors, but I have excluded these (with an exception at the end) as they are  'High-Tech'. A recent literature search [07/04/2019] did not reveal any papers after the ones listed here , the latest being 2015. If you know of other publications that are relevant plase let me know. so I can include them.

 

For an excellent  general text on enzyme assays I would like to refer you to the book of this title edited by Robert Eisenthal & Mike Danson

(see Google for online version) 

 

This book contains a chapter written by my PhD supervisor Keith Brocklehurst

 

I also authored a book 'Molecular Enzymology' with Robert who was a very clever & original guy who devised, by lateral thinking, the Direct Linear Plot for kinetic analysis

 

 Enzyme catalysed reactions measured by conductivity changes

see highlighted paper below

 

Urease: (this paper is in French)

Hanss, M. & Rey, A. (1971) Biochem et Biophysics Acta, 227, 630-638

 

Cholinesterase: (this paper is in French)

Hanss, M. & Rey, A. (1971) Biochem et Biophysics Acta, 227, 618-629

 

 

 

A wide range of enzymes: (online & very useful, see link below)

Lawrence, A.J. & Moores, G.R. (1972) Eur. J. Biochem. 24, 538-5 

 

Trypsin & Chymotrypsin

Hill, G.R. & Tomalin, G. (1982) Anal. Biochem. 120, 165-172

 

Microchip assay for alkaline phosphatase:

Faure, M., Sotta, B. & Gamby, J (2014) Biosensors & Bioelectronics, 58, 61-67

Kechadi,M., Sotta, B. & Gamby, J. (2015) Talanta 132, 785-789

 

These last two references demonstrate the 21st century micro-technology approach to the topic, where reaction volumes are in the low nanolitres and there is no direct electrical contact with the reagents. Expensive lasers & other kit is needed is needed to fabricate the chips but they can then be manufactured on a large scale to give an inexpensive device such as the modern (diabetes) glucose analyser (e.g. £15, but limited to glucose analysis). 

 

It is important to appreciate that the many papers tht cover glucose sensing use amperometric rather than conductometric measurements. Amperometric detection involvesd a chemical redox reaction at one of the electrodes, unlike conduction methods that do not.The amperometric method has a potential advantage in that it is more specific in that it detects a redox species that has been generated by a chemical or enzyme reaction. Glucose sensors generally use glucose oxidase, which generate hydrogen peroxide from glucose and this is detected by the redox electrodes. Much effort is currently (ha ha!) being applied to the development of non-enzymic methods, which could be simpler and more robust.

 

An interesting, more recent paper, which uses amperometric detection, is:

 

Electrochemical detection of uric acid using graphite screen-printed electrodes modified with Prussian blue/poly(4-aminosalicylic acid)/Uricase

By: da Cruz, Filipe Soares; Paula, Fernanda de Souza; Franco, Diego Leoni; et al.

JOURNAL OF ELECTROANALYTICAL CHEMISTRY   Volume: 806   Pages: 172-179   Published: DEC 1 2017

 

I have not, as yet,  been able to devise a method using conductivity for the assay of uric acid, which is important for the diagnosis of gout.

 

COMMERCIAL SYSTEMS

 

For a comparison with a modern hand-held bedside clinical analysis system see Abbott i-STAT. An assay set takes just 2 min. This is used in some Emergency Departments for rapid diagnosis/ treatment but has not generally been adopted because of the cost, which is £10-£20 per assay set (about 6-8 tests of different parameters for each chip). The capital cost of the equipment is ca. £7000 - £10000. It typically requires about 100 microlitres of blood per test set (1 chip).

 

Radiometer & Siemens (amongst others) manufacture high throughput systems for central laboratories, that perform the testing for the whole hospital and often region.

 

 

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