Appeal No. 2001-2410 Page 3
Application No. 08/914,700
Claim 19 stands rejected under 35 U.S.C. § 103 as obvious in view of
Hossom, Leuvering, Olsen, and Akers.
We reverse.
Background
The specification discloses a method for detecting analytes using
“non-captive substrate liquid phase immunoassay techniques.” See page 2. The
specification states that
[o]bservations of colloidal gold or silver concentrations have been
used in immunoassays in conjunction with solid phase diffusion
assays. For example, European Patent No. 207,152 discloses a
solid phase diffusion assay utilizing a porous sheet having ligands
or receptors prebound to the sheet prior to the application of an
analyte and a colloidal gold or silver labeled ligand or receptor.
Id. This method, however, has the drawback that the “ligand or antiligand coated
porous films must be specifically tailored for a particular analyte and . . . may be
ineffective if the affinity of the substrate bound antiligand for the labeled analyte
is low.” Id.
The specification also discusses a sandwich immunoassay method that
involves “premixing a biological specimen with: (1) a colloidal gold labeled ligand
or antiligand and (2) solid phase captive particles coated with a ligand or
antiligand and applying the subsequent mixture onto the surface of a porous
film.” Id. This method also has a drawback, in that the solid phase captive
particles (e.g., latex particles) “may distort the visual detection measurements
because uncoupled captive particles may block the pores of the substrate and
prevent rapid passage of uncoupled colloidal gold.” Id., pages 2-3.
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