Ex Parte KRANTZ et al - Page 4

                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                           
                        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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