Appeal No. 1996-3973
Application No. 08/048,657
“reactive unit” comprising a spreading agent and an analyte-reactive reagent and (iii) an indicator
layer comprising an indicator reagent impregnated into a porous substrate. For example, when
determining glucose with a two-layered reactive unit test strip, a drop of liquid sample, e.g.,
blood, is applied to a top layer comprising the spreading agent through the aperture. This
“spreading” layer allows the applied drop to spread out and penetrate through into a second layer
comprising the reactive reagent. The penetrating sample dissolves the reactive reagent and
glucose in the sample reacts therewith to form a reaction product which then penetrates through
into a bottom indicator layer where it dissolves and reacts with an indicator reagent to produce a
detectable product, e.g., a dye, which is indicative of the glucose in the sample.
A preferred reactive reagent comprises a mixture of glucose oxidase, peroxidase and
MBTH (3-methyl-2-benzothizolinone hydrazone hydrochloride) (specification, page 12, lines 20-
34). A preferred indicator reagent comprises DMAB (3-dimethylaminobenzoic acid)
(specification, sentence bridging pages 11-12). Preferred spreading agents include
polyoxyethylene ether and diatomaceous earth (specification, page 13, lines 20-22 and page 14,
lines 16-26). Preferably, the porous substrate is a nylon membrane (specification, page 11, lines
26-28).
According to the specification, the claimed test strip has two innovations over the prior
art: (1) the indicator reagent and the reactive reagent are placed into two separate layers so that
they cannot interact chemically during storage prior to use and (2) a spreading layer is provided
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