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Method for electrical detection of a binding reaction

  • US 5,284,748 A
  • Filed: 04/10/1992
  • Issued: 02/08/1994
  • Est. Priority Date: 03/25/1986
  • Status: Expired due to Fees
First Claim
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1. A method of detecting a substance in a test sample, which substance is a first one of a pair of first and second substances that undergo a specific binding reaction with each other, including the steps of:

  • mixing the sample with particles under conditions effective to cause binding of the first substance, if present in the sample, to the surfaces of the particles;

    contacting the particles having the first substance bound to the surfaces thereof with a layer of the second of the pair of substances, which layer forms a path between a pair of spaced-apart electrical conductors superposed on a substantially nonelectrically conductive base, the layer of the second substance being bound to the base, such that the binding reaction between the first and second substances causes the particles to be bound to the path in aggregates;

    removing particles which are bound to the path as a result of non-specific binding and particles which are unbound to the path;

    coating exposed outer surfaces of the aggregates with an electrically conductive substance that adheres selectively to the particles forming the aggregates but which does not adhere to the remainder of the path;

    removing electrically conductive substances which remains unadhered to the aggregates;

    connecting each of the conductors to an electrical circuit which includes a source of electrical energy, the conductors and the path therein; and

    measuring a change in the electrical current flow through the circuit caused by formation of the coated aggregates on the path, the electrical change indicating the level of the substance to be detected in the test sample.

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