Electrochemical membrane strip biosensor

• US 6,478,938 B1
• Filed: 06/14/2000
• Issued: 11/12/2002
• Est. Priority Date: 05/24/2000
• Status: Expired due to Term

• Current Assignee: Biodigit Laboratories Corporation
• Original Assignee: Biodigit Laboratories Corporation
• Inventors: Paek, Se-Hwan, Cho, Joung-Hwan
• Primary Examiner(s): Warden, Sr., Robert J.
• Assistant Examiner(s): Olsen, Kaj K.
• Application Number:
  US09/593,663
• Time in Patent Office: 881 Days
• Field of Search: 204/403, 204/403.01, 204/403.03, 204/403.06, 422/70, 422/82.02, 436/514, 436/518, 436/525
• US Class Current: 204/403.01
• CPC Class Codes: C12Q 1/002 Electrode membranes
• CPC Class Codes: G01N 33/5438 Electrodes

Abstract

The present invention is directed to the development of a biosensor based on the immuno-chromatographic method that can provide an assay speed and convenience required for point-of-care (the doctor'"'"'s office and emergency room) testing or home-version diagnosis. Though certain physical symptoms, such as pregnancy and ovulation, or bacterial infection may be identified by a qualitative analysis for the presence of indicating substances, most analytes for clinical investigation demand their concentrations known in specimens. Therefore, the inventors of the present invention have developed a novel biosensor by combining the immuno-chromatographic method and the electric conductivity detection technology so that on-site quantitative determination at the points of care or at home may be carried out.

Claims

1. An electrochemical membrane strip biosensor comprising

(a) a first membrane strip pad for sample application;

(b) a second membrane strip pad, partially superimposed in length with the first membrane strip pad for signal generation, said second membrane strip pad including (i) a binding protein, specifically binding to an analyte, immobilized at a defined area of the second membrane'"'"'s surface, and (ii) at least one pair of electrodes screen-printed on said second membrane'"'"'s surface such that the binding protein-immobilized area is located between the two electrodes;

(c) a third membrane strip pad, partially superimposed in length with the second membrane strip pad for absorption of an aqueous medium; and

(d) a conjugate between (i) a binding protein specifically binding to a different site on the analyte from that recognized by said immobilized binding protein of the second membrane strip, and (ii) a metal colloid having surfaces bound by a conducting polymer,

wherein said conjugate is either placed at a predetermined site on the first membrane strip pad in a dry state or is contained in a separate container and placed on said first strip membrane pad prior to use of the biosensor.

2. The electrochemical membrane strip biosensor of claim 1, wherein the first membrane strip pad is a glass fiber membrane pad, the second membrane strip pad is a nitrocellulose membrane pad, and the third membrane strip pad is a cellulose membrane pad.

3. The electrochemical membrane strip biosensor of claim 1, wherein the binding protein is an antibody, enzyme or receptor that reacts specifically with the analyte.

4. The electrochemical membrane strip biosensor of claim 1, wherein the metal colloid is a gold colloid, silver colloid or iron colloid.

5. The electrochemical membrane strip biosensor of claim 1, wherein the electrodes are screen-printed on an insulator.

6. The electrochemical membrane strip biosensor of claim 1, wherein the electrodes are screen-printed with platinum paste, gold paste, silver paste or carbon paste.

7. The electrochemical membrane strip biosensor of claim 1, wherein the electrodes are interdigitated electrodes formed on the same surface of the second membrane strip pad.

8. The electrochemical membrane strip biosensor of claim 1, wherein electric contacts to the electrodes are present on a lateral side of the second membrane strip.

9. The electrochemical membrane strip biosensor of claim 1, wherein the electrodes are positioned on opposite sides of the second membrane strip pad to form a sandwich-type electrode.

10. The electrochemical membrane strip biosensor of claim 9, wherein at least two pairs of electrodes are present to determine at least two different analytes simultaneously.

11. The electrochemical membrane strip biosensor of claim 1, wherein the conjugate is prepared by adsorbing the binding protein on surfaces of the metal colloid, subsequently binding the conducting polymer thereon, and then adsorbing a blocking protein on residual surfaces of the metal colloid.

12. The electrochemical membrane strip biosensor of claim 11, wherein the conducting polymer alone or treated with a dopant is polyaniline, polypyrrole, polythiophene or poly(p-phenylene), and the blocking protein is bovine serum albumin, casein or gelatin.

13. The electrochemical membrane strip biosensor according to claim 12, wherein the dopant is (a) an ionic salt with or without redox molecules chemically bound to said conducting polymer, or (b) a polymeric counterion non-covalently interacting with said conducting polymer.