Diagnostic method and device employing protein-coated magnetic particles

• US 4,018,886 A
• Filed: 07/01/1975
• Issued: 04/19/1977
• Est. Priority Date: 07/01/1975
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Giaever, Ivar
• Primary Examiner(s): Marantz, Sidney
• Application Number:
  US05/592,196
• Time in Patent Office: 658 Days
• Field of Search: 23/230 B, 23/253 R, 23/259, 424/12, 210/222
• US Class Current: 436/526
• CPC Class Codes: B03C 1/288 disposed at the outer circumference of a recipient
• CPC Class Codes: B03C 2201/18 Magnetic separation whereby the particles are suspended in a liquid
• CPC Class Codes: B03C 2201/26 for use in medical or biological applications
• CPC Class Codes: G01N 2035/00534 Mixing by a special element, e.g. stirrer
• CPC Class Codes: G01N 33/54326 Magnetic particles
• CPC Class Codes: G01N 35/0098 involving analyte bound to insoluble magnetic carrier, e.g. using magnetic separation magnetic particles used in immunoassays G01N33/54326; magnetic separation in general B03C
• CPC Class Codes: Y10S 436/805 Optical property
• CPC Class Codes: Y10S 530/806 Antigenic peptides or proteins
• CPC Class Codes: Y10S 530/811 Peptides or proteins is immobilized on, or in, an inorganic carrier

Abstract

Small magnetic particles are used to provide large and widely-distributed surface area for separating a select protein from a solution to enable detection thereof when present in low concentrations. The particles are coated with a protein that will interact specifically with the select protein.

Claims

1. A diagnostic method for determining the presence or absence of select protein in a liquid sample comprising the steps of:

dispersing a plurality of finely-divided magnetic particles each of which is coated with a layer directly bonded thereto of first protein molecules specific to said select protein in the sample liquid to facilitate contact between said coated particles and said sample liquid;

magnetically retrieving and separating said coated particles from said sample liquid;

washing said coated particles;

introducing said coated particles into a volume of cleaving agent solution in direct contact with a metallized surface to permit select protein, if present, to detach from the first protein-coated particles and

examining said metallized surface for the presence of protein adsorbed thereon.

2. The diagnostic method recited in claim 1 wherein the magnetic particles are selected from the group consisting of ferromagnetic and ferrimagnetic materials.

3. The diagnostic method recited in claim 1 wherein the examining step is accomplished by the use of an ellipsometer.

4. The diagnostic method recited in claim 1 wherein the magnetic particles are held by means of an electrically induced magnetic field during the washing step.

5. The diagnostic method recited in claim 1 wherein the dispersing of the magnetic particles is accomplished magnetically.

6. The diagnostic method recited in claim 1 wherein the metallized surface is substantially planar.

7. The diagnostic method recited in claim 1 wherein the metallized surface is non-planar.

8. The diagnostic method recited in claim 1 wherein the specific protein is antigen and the select protein is antibody thereto.

9. The diagnositc method recited in claim 1 wherein the select protein is antigen and the specific protein is antibody thereto.

10. The diagnositc method recited in claim 1 wherein the cleaving agent solution is a weak acid solution.

11. The diagnostic method recited in claim 10 wherein the pH of the acid solution is in the range of 1-5.

12. The diagnostic method rectied in claim 10 wherein the acid is citric acid.

13. A diagnostic device for determining the presence or absence of select protein in a liquid sample comprising in combination a plurality of finely divided magnetic particles, surface area of which is coated with antibodies directly bonded thereto, said antibodies being specific to said select protein.

14. The diagnostic device of claim 13 wherein the magnetic particles are in the size range of from about colloidal size to about 10 microns.

15. The diagnostic device of claim 13 wherein the magnetic particles are made of nickel.