Sensors based on polymer transformation

• US 5,846,744 A
• Filed: 01/16/1996
• Issued: 12/08/1998
• Est. Priority Date: 05/29/1993
• Status: Expired due to Term

• Current Assignee: Cambridge Life Sciences PLC
• Original Assignee: Cambridge Life Sciences PLC
• Inventors: Mullen, William Henry, Armstrong, Ronald D., Athey, Dale, McNeil, Calum J.
• Primary Examiner(s): SAUNDERS, DAVID A
• Application Number:
  US08/549,800
• Time in Patent Office: 1,057 Days
• Field of Search: 435/4, 435/6, 435/7.9, 435/7.92, 435/18, 435/25, 435/817, 436/150, 436/151, 436/806, 436/37, 422/82.01, 204/403
• US Class Current: 435/7.9
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/002 Electrode membranes
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: Y10S 435/817 Enzyme or microbe electrode
• CPC Class Codes: Y10S 436/806 Electrical property or magnetic property

Abstract

A sensor format is based on impedance analysis of polymer coatings of electrodes. A detectable signal is produced by the effect of a reactive or catalytic species at or very near the polymer coated electrode. The reactive or catalytic species directly or indirectly effects a reaction with the polymer layers, whereby the polymer layer becomes porous and thus causes a measurable change in electrical properties of the electrode surface.

Claims

1. In a method for determining the presence or amounts of an analyte in a sample of assay medium suspected of containing said analyte, said analyte reacting with an enzyme or catalyst to produce an amount of detectible signal which is a function of the amount of analyte in the assay medium, said detectible signal being detected at an electrode in an electrolyte, the improvement wherein:

(a) the electrode is covered with a thin layer of an electrically insulating polymer that separates the electrode from the electrolyte; and

(b) the enzyme or catalytic reaction with the said analyte directly or indirectly effects a reaction with the said electrically insulating polymer layer wherein the polymer layer becomes porous or more porous to the electrolyte, causing a measurable change in electrical properties at the electrode surface.

2. A method according to claim 1 where the electrically insulating material is a pH-sensitive polymer and where the enzyme or catalyst reaction causes a change in pH sufficient to increase the permeability of the electrode covering layer.

3. A method according to claim 2 in which the reaction is with an enzyme that reacts to cause a change in pH.

4. A method according to claim 3 in which the enzyme is urease or glucose oxidase.

5. A method according to claim 1 where the sample is aqueous, whole blood, serum, plasma, urine or saliva.

6. A method according to claim 1 in which the electrode is polarised at a potential at which a redox reaction can occur with a constituent of the electrolyte such that breakdown of the polymer layer becomes accelerated once the electrode first becomes exposed to the electrolyte.

7. A method according to claim 1 where the activity of the catalytic species results in the formation of a hydroxyl radical, which is able to react with the polymer layer resulting in an increase in the permeability to electrolyte of said layer.

8. A method according to claim 7 where the catalytic species is a hydrogen peroxide-producing oxidase and the electrolyte contains species able to promote the Fenton reaction.

9. A method according to claim 1 in which the catalytic species is a polymer-degrading enzyme which acts directly on the polymer layer to increase the permeability of the layer.

10. A method according to claim 9 in which the catalytic species is amylase or amyloglucosidase and the dielectric comprises or contains a polysaccharide.

11. A method according to claim 9 in which the catalytic species is an endonuclease and the polymer comprises or contains a nucleic acid.

12. A method according to claim 9 in which the catalytic species is a lipase and the polymer comprises or contains lipid.

13. A method according to claim 1 where the enzyme or catalyst is within the polymer layer.

14. A method according to claim 1 where the enzyme or catalyst is bound to the polymer layer.

15. A method according to claim 1 where the enzyme or catalyst is bound to another support in close proximity to the polymer layer.

16. A method according to claim 15 wherein the other support is composed of a membrane support material.

17. A method according to claim 16 wherein the membrane support material is a nitrocellulose membrane.

18. In an immunoassay method in which an enzyme-antibody or enzyme-antigen conjugate becomes bound at or very near a layer of polymer via a specific immunochemical reaction, the improvement wherein the polymer is an electrically insulating polymer, the layer of polymer covers an electrode and enzyme activity of the conjugate leads to an increased permeability of the polymer layer to electrolyte, measured by a change in capacitance or current passed by the underlying electrode.