Patent Publication Number: US-2013228475-A1

Title: Co-facial analytical test strip  with stacked unidirectional contact pads and inert carrier substrate

Description:
CROSS-REFERENCE 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 13/410,609, filed Mar. 2, 2012, which is incorporated herein by reference in its entirety and to which application we claim priority under 35 USC §120. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, in general, to medical devices and, in particular, to test meters and related methods. 
     2. Description of Related Art 
     The determination (e.g., detection and/or concentration measurement) of an analyte in a fluid sample is of particular interest in the medical field. For example, it can be desirable to determine glucose, ketone bodies, cholesterol, lipoproteins, triglycerides, acetaminophen and/or HbA1c concentrations in a sample of a bodily fluid such as urine, blood, plasma or interstitial fluid. Such determinations can be achieved using a hand-held test meter in combination with analytical test strips (e.g., electrochemical-based analytical test strips). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of the invention are set forth with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description that sets forth illustrative embodiments, in which the principles of the invention are utilized, and the accompanying drawings, in which like numerals indicate like elements, of which: 
         FIG. 1  is a simplified exploded perspective view of an analytical test strip according to an embodiment of the present invention; 
         FIG. 2  is a simplified perspective view of the analytical test strip of  FIG. 1 ; 
         FIG. 3  is a simplified perspective view of a distal portion of the analytical test strip of  FIG. 1  in contact with test meter electrical connector pins; 
         FIG. 4  is a simplified side view of the distal portion of  FIG. 3 ; 
         FIG. 5  is a top view of a patterned spacer layer of the analytical test strip of  FIG. 1 ; 
         FIG. 6  is a top view of a third electrically conductive layer of the analytical test strip of  FIG. 1 ; 
         FIG. 7  is a simplified top view of the analytical test strip of claim  1  with an integrated carrier sheet; 
         FIG. 8  is a simplified distal end view of the analytical test strip and integrated carrier sheet of  FIG. 7   
         FIG. 9  is a simplified cross-sectional view of the analytical test strip and integrated carrier sheet of  FIG. 7 ; 
         FIG. 10  is a flow diagram depicting stages in a method for determining an analyte in a bodily fluid sample according to an embodiment of the present invention; 
         FIG. 11  is a simplified exploded perspective view of an analytical test strip with inert carrier substrate according to an embodiment of the present invention; 
         FIG. 12  is a simplified perspective view of the analytical test strip with inert carrier substrate of  FIG. 11 ; 
         FIG. 13  is a simplified view of the distal portion of the analytical test strip with inert carrier substrate of  FIG. 11  inserted into a test meter and in contact with electrical connector pins of the test meter; 
         FIG. 14  is a simplified top view of the distal portion of the analytical test strip with inert carrier substrate inserted into a test meter as also depicted in  FIG. 13 ; 
         FIG. 15  is a simplified top view of another inert carrier substrate as can be employed in embodiments of the present invention; 
         FIG. 16  is a simplified top view of yet another inert carrier substrate as can be employed in embodiments of the present invention; and 
         FIG. 17  is a flow diagram depicting stages in another method for determining an analyte in a bodily fluid sample according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The following detailed description should be read with reference to the drawings, in which like elements in different drawings are identically numbered. The drawings, which are not necessarily to scale, depict exemplary embodiments for the purpose of explanation only and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. 
     As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. 
     In general, analytical test strips for use with a test meter (such as a hand-held test meter) according to embodiments of the present invention include a first insulating layer with a first insulating layer upper surface and a first electrically conductive layer disposed on the first insulating layer upper surface. The first electrically conductive layer includes a first electrode portion (such as a working electrode portion) and an electrical contact pad in electrical communication with the first electrode portion. The analytical test strips also include a patterned spacer layer disposed above the first electrically conductive layer. The patterned spacer layer includes (i) a distal portion defining a bodily fluid sample-receiving chamber therein that overlies the first electrode portion and (ii) an insulating proximal portion with an upper surface having a second electrically conductive layer disposed thereon. The second electrically conductive layer includes an interlayer contact portion and an electrical contact pad in electrical communication with the interlayer contact portion. 
     The analytical test strips further include a second insulating layer that is disposed above the patterned spacer layer and has a second insulating layer lower surface with a third electrically conductive layer disposed thereon. The third electrically conductive layer includes a second electrode portion (such as, for example, a reference/counter electrode) and a proximal portion that overlies the interlayer contact portion. 
     In addition, the second electrode portion of the analytical test strips is disposed overlying and exposed to the sample-receiving chamber in an opposing (i.e., co-facial) relationship to the first electrode portion. Moreover, the proximal portion is operatively juxtaposed with the interlayer contact portion such that there is an electrical connection between the second electrode portion of the third electrically conductive layer and the electrical contact pad of the patterned spacer layer during use of the analytical test strip. 
     The electrical contact pad of the first electrically conductive layer and the electrical contact pad of the second electrically conductive layer are referred to as stacked unidirectional contact pads. They are “stacked” since the electrical contact pad of the second electrically conductive layer is elevated with respect to the electrical contact pad of the first electrically conductive layer. They are “unidirectional” since both are on upper surfaces and can, therefore, be accessed and contacted from the same direction. 
     Analytical test strips according to the present invention are beneficial in that, for example, their configuration and, in particular, the stacked unidirectional nature of the contact pads, is amenable to high-volume, high-yield mass production without dedicated and complex tight-alignment die cutting steps to expose the contact pads. 
       FIG. 1  is a simplified exploded perspective view of an analytical test strip  100  according to an embodiment of the present invention.  FIG. 2  is a simplified perspective view of the electrochemical-based analytical test strip of  FIG. 1 .  FIG. 3  is a simplified perspective view of a portion of the electrochemical-based analytical test strip of  FIG. 1  in contact with test meter electrical connector pins (ECP).  FIG. 4  is a simplified side view of the portion of  FIG. 3 .  FIG. 5  is a top view of a patterned spacer layer of the analytical test strip of  FIG. 1 .  FIG. 6  is a top view of a third electrically conductive layer of the analytical test strip of  FIG. 1 . 
     Referring to  FIGS. 1-6 , analytical test strip  100  for use with a test meter in the determination of an analyte (such as glucose) in a bodily fluid sample (e.g., a whole blood sample) according to an embodiment of the present invention includes a first insulating layer  102  with a first insulating layer upper surface  104  and a first electrically conductive layer  106  disposed on first insulating upper surface  104 . First electrically conductive layer  106  includes a first electrode portion  108  and a first electrical contact pad  110  in electrical communication with first electrode portion  108 . First electrode portion  108  and first electrical contact pad  110  are typically, for example, defined from contiguous first electrically conductive layer  106  by a patterned spacer layer  112 . 
     Analytical test strip  100  also includes the aforementioned patterned spacer layer  112  disposed above first electrically conductive layer  106 . Patterned spacer layer  112  has a distal portion  114  defining a bodily fluid sample-receiving chamber  116  therein that overlies first electrode portion  108 . Patterned spacer layer  112  also has an insulating proximal portion  118  with an upper surface  120  and a second electrically conductive layer  122  disposed thereon. Moreover, second electrically conductive layer  122  has an interlayer contact portion  124  and an electrical contact pad  126 . 
     Analytical test strip  100  further includes a second insulating layer  128  disposed above patterned spacer layer  112 . Second insulating layer  128  has a second insulating layer lower surface  130 . Analytical test strip  100  yet further includes a third electrically conductive layer  132  disposed on second insulating layer lower surface  130  that includes a second electrode portion  134  and a proximal portion  136  that overlies interlayer contact portion  124 . Second electrode portion  134  is disposed overlying and exposed to bodily fluid sample-receiving chamber  116  and in an opposing (i.e., co-facial) relationship to first electrode portion  108 . Analytical test strip  100  also includes a reagent layer  138  (see  FIG. 1  in particular). If desired, reagent layer  138  can have dimensions that ensure complete coverage of first electrode portion  108  despite manufacturing variation. 
     In analytical test strip  100 , the proximal portion of the third electrically conductive layer is operatively juxtaposed with the interlayer contact portion of the second electrically conductive layer such that there is an electrical connection between the second electrode portion of the third electrically conductive layer and the electrical contact pad of the patterned spacer layer during use of the analytical test strip. This electrical connection provides for unidirectional stacked electrical contact pads even though the first and second electrode portions are in an opposing (i.e., co-facial) arrangement. 
     The proximal portion of the third electrically conductive layer can be operatively juxtaposed with the inter layer contact portion by, for example, attachment with an electrically conductive adhesive or by compression of a gap therebetween (in the direction of arrow A of the distal portion depicted in  FIG. 4 ) upon insertion into the test meter. Such a compression can be achieved, for example, by the application of a force in the range of 3 pounds per square-inch to 30 pounds per square inch. The operative juxtaposition can be provided by any known means including an electrically fused joint or an electrically conductive foil connection. 
     First and second electrical contact pads  110  and  126 , respectively, are each configured to operatively interface with a test meter via electrical contact with separate electrical connector pins (labeled ECP in  FIGS. 3 and 4 ) of the test meter. 
     First insulating layer  102 , insulating proximal portion  118 , and second insulating layer  128  can be formed, for example, of a plastic (e.g., PET, PETG, polyimide, polycarbonate, polystyrene), silicon, ceramic, or glass material. For example, the first and second insulating layers can be formed from a 7 mil polyester substrate. 
     In the embodiment of  FIGS. 1-6 , first electrode portion  108  and second electrode portion  134  are configured to electrochemically determine analyte concentration in a bodily fluid sample (such as glucose in a whole blood sample) using any suitable electrochemical-based technique known to one skilled in the art. 
     The first, second and third electrically conductive layers,  106 ,  122  and  132  respectively, can be formed of any suitable conductive material such as, for example, gold, palladium, carbon, silver, platinum, tin oxide, iridium, indium, or combinations thereof (e.g., indium doped tin oxide). Moreover, any suitable technique can be employed to form the first, second and third conductive layers including, for example, sputtering, evaporation, electro-less plating, screen-printing, contact printing, or gravure printing. For example, first electrically conductive layer  106  can be a sputtered palladium layer and third electrically conductive layer  132  can be a sputtered gold layer. 
     Distal portion  114  of patterned spacer layer  112  serves to bind together first insulating layer  102  (with first electrically conductive layer  106  thereon) and second insulating layer  128  (with third electrically conductive layer  132  thereon), as illustrated in  FIGS. 1 ,  2 ,  3  and  4 . Patterned spacer layer  112  can be, for example, a double-sided pressure sensitive adhesive layer, a heat activated adhesive layer, or a thermo-setting adhesive plastic layer. Patterned spacer layer  112  can have, for example, a thickness in the range of from about 50 micron to about 300 microns, preferably between about 75 microns and about 150 microns. The overall length of analytical test strip  100  can be, for example, in the range of 30 mm to 50 mm or the range of 8 mm to 12 mm and the width can be, for example, in the range of 2 mm to 5 mm. 
     Reagent layer  134  can be any suitable mixture of reagents that selectively react with an analyte such as, for example glucose, in a bodily fluid sample to form an electroactive species, which can then be quantitatively measured at an electrode of analyte test strips according to embodiments of the present invention. Therefore, reagent layer  138  can include at least a mediator and an enzyme. Examples of suitable mediators include ferricyanide, ferrocene, ferrocene derivatives, osmium bipyridyl complexes, and quinone derivatives. Examples of suitable enzymes include glucose oxidase, glucose dehydrogenase (GDH) using a pyrroloquinoline quinone (PQQ) co-factor, GDH using a nicotinamide adenine dinucleotide (NAD) co-factor, and GDH using a flavin adenine dinucleotide (FAD) co-factor. Reagent layer  134  can be formed using any suitable technique. 
     Referring to  FIGS. 6 ,  7  and  8 , if desired, analytical test strip  100  can further include at least one integrated carrier sheet configured solely as a user handle. In the embodiment of  FIGS. 6-8 , analytical test strip  100  includes a first integrated carrier sheet  140  and a second integrated carrier sheet  142 . Moreover, a portion of the first insulating layer, first electrically conductive layer, patterned spacer layer, second insulating layer and second electrically conductive layer are disposed between first integrated carrier sheet  140  and second integrated carrier sheet  142 . First integrated carrier sheet  140  is configured such that the electrical contact pad of the first electrically conductive layer and the electrical contact pad of the patterned spacer layer are exposed. Such exposure enables electrical contact to a test meter during use. 
     The first and second integrated carrier sheets can be formed of any suitable material including, for example, paper, cardboard, or plastic materials. Since the first and second integrated carrier sheets are configured solely as a user handle in the present embodiments, they can be formed of relatively inexpensive materials. Such integrated carrier sheets are beneficial in that, for example, they improve the ease of handling of an analytical test strip that may otherwise be relatively small and difficult to handle. 
       FIG. 10  is a flow diagram depicting stages in a method  1000  for determining an analyte (such as glucose) in a bodily fluid sample (for example, a whole blood sample). Method  1000  includes introducing a bodily fluid sample into a sample-receiving chamber of an analytical test strip that has a first electrode portion of a first electrically conductive layer and a second electrode portion of a third electrically conductive layer therein (see step  1010  of  FIG. 10 ). In addition, the first electrode portion and the second electrode portion are in an opposing relationship. 
     At step  1020  of method  1000 , an electrical response of the first electrode portion and the second electrode portion is measured via an electrical contact pad of the first electrically conductive layer and via an electrical contact pad of a second electrically conductive layer of a patterned spacer layer of the analytical test strip. The patterned spacer layer is disposed between the first electrically conductive layer and the third electrically conductive layer. Furthermore, the electrical contact pad of the first electrically conductive layer and the second electrically conductive layer are configured in a unidirectional stacked relationship and the second electrode portion is in electrical communication with the electrical contact pad of the second electrically conductive layer. 
     Method  1000  also includes, at step  1030 , determining the analyte based on the measured electrical response. 
     Once apprised of the present disclosure, one skilled in the art will recognize that method  1000  can be readily modified to incorporate any of the techniques, benefits and characteristics of analytical test strips according to embodiments of the present invention and described herein. 
     In general, analytical test strips with an inert carrier substrate and for use with a test meter according to embodiments of the present invention include an analytical test strip module and an electrochemically and electrically inert carrier substrate (also referred to as an inert carrier substrate). The analytical test strip module has a first electrode portion, a second electrode portion in an opposing relationship to the first electrode portion, and first and second electrical contact pads in a stacked unidirectional configuration. The electrochemically and electrically inert carrier substrate has an upper surface and an outer edge. Moreover, the analytical test strip module is attached to the upper surface of the electrochemically and electrically inert carrier substrate such that the first and second electrical contact pads extend beyond the outer edge of the electrochemically and electrically inert carrier substrate and such that the electrochemically and electrically inert carrier substrate extends beyond the analytical test strip module. 
     As described with reference to  FIGS. 11 through 14  and depicted therein, the term “analytical test strip module” refers to a module that is attached to an inert carrier substrate to produce analytical test strips with an inert carrier substrate according to various embodiment of the present invention. Once apprised of the present disclosure, one skilled in the art will recognize that such analytical test strip modules are equivalent to that analytical test strips that are devoid of an inert carrier substrate according to inventive embodiments described elsewhere herein. This equivalency is reflected in the element label numbers of  FIGS. 11 ,  12 ,  13  and  14 . 
     The term “inert” as applied to an inert carrier substrate refers to a carrier substrate that is not electrically conductive and does not electrically or electrochemically affect, or participate in, the electrochemical and electrical functions of the analytical test strip module that is attached to the upper surface of the inert carrier substrate. Such an inert carrier substrate is also referred to herein as an “electrochemically and electrically inert carrier.” 
     Analytical test strips with inert carrier substrates according to embodiments of the present invention are particularly beneficial in that the inert carrier substrate aids a user in manual handling of the analytical test strip and guiding insertion of the analytical test strip with inert carrier into a test meter. In addition, the analytical test strip module can be attached to the inert carrier substrate such that a bodily fluid sample is applied to a longitudinal side (i.e., side) of the analytical test strip module but an end (i.e., minor edge) of the inert carrier substrate (see  FIGS. 11 and 12  in particular). In this regard, the side-fill configuration of the analytical test strip module when considered independently of the inert carrier substrate becomes an end-fill configuration of the analytical test strip with inert carrier. Such an end-fill configuration of the analytical test strip with inert carrier can be perceived as more user-friendly by some users. 
     Analytical test strips with inert carrier substrates according to embodiments of the present invention are also beneficial in that they can be easily and inexpensively manufactured since there is no electrical connection between the analytical test strip module and the inert carrier substrate and no need for precise alignment between the analytical test strip module and the inert carrier substrate. 
       FIG. 11  is a simplified exploded perspective view of an analytical test strip with inert carrier substrate  1100  according to an embodiment of the present invention.  FIG. 12  is a simplified perspective view of the analytical test strip with inert carrier substrate of  FIG. 11 .  FIG. 13  is a simplified view of the distal portion of the analytical test strip with inert carrier substrate of  FIG. 11  inserted into a test meter (TSTM, with only the outline depicted as a dashed line) and in contact with electrical connector pins (ECP) of the test meter.  FIG. 14  is a simplified top view of the distal portion of the analytical test strip with inert carrier substrate inserted into a test meter as also depicted in  FIG. 13 . 
     Referring to  FIGS. 11-14 , analytical test strip with inert carrier substrate  1100  for use with a test meter includes an analytical test strip module  1120  with a first electrode portion  108  and a second electrode portion  134  that is in an opposing relationship to first electrode portion  108 . Analytical test strip module  1120  also includes at least a first electrical contact pad  110  and a second electrical contact pad  126 , the first and second electrical contact pads ( 110  and  126 , respectively) configured in a stacked unidirectional configuration. The remainder of the elements of analytical test strip module  1120  has been described with respect to  FIGS. 1 through 6  where like element labeling numerals indicating like elements. 
     Analytical test strip with inert carrier substrate  1100  also includes an electrochemically and electrically inert carrier substrate  1140  with an upper surface  1160  and an outer edge  1180  (see  FIG. 12  in particular). 
     Analytical test strip module  1120  is attached to upper surface  1160  of the such that first electrical contact pad  110  and the second electrical contact pad  126  extend beyond outer edge  1180  of the electrochemically and electrically inert carrier substrate  1140 . Moreover, the attachment configuration is such that the electrochemically and electrically inert carrier substrate  1140  extends beyond the analytical test strip module  1120 , thus leaving a portion of upper surface  1160  exposed (see, for example,  FIG. 12 ). 
     Referring to  FIGS. 12 ,  13  and  14  in particular, the extension of the first electrical contact pad and the second electrical contact pad is configured for the operable insertion of the first electrical contact pad and the second electrical contact pad into a test meter. Moreover, it should be noted that in the embodiment of  FIGS. 11-14 , the analytical test strip module is attached lengthwise along a minor edge of the inert carrier substrate such that the sample-receiving chamber (which is on the edge of the analytical test strip module) is on an end of the inert carrier substrate. 
     Analytical test strip module  1120  can be attached to the inert carrier substrate using any suitable technique including, for example, adhesion and lamination techniques. 
     Electrochemically and electrically inert carrier substrate  1140  can be formed of any suitable material including, for example, plastic materials (e.g., a polyethylene material including Dupont Melinex material (DuPont Corporation) with a thickness in the range of 200 μm to 500 μm). The rigidity of the material used to form the inert carrier substrate should be sufficient such that there is operationally minimal deformation of inert carrier substrate when in use. The electrochemically and electrically inert carrier substrate should not substantially buckle or bend when the analytical test strip with inert carrier is inserted into the test meter (TSTM) and contact made between the first and second electrical contact pads and ECP of the test meter (see, for example,  FIGS. 13 and 14 ). 
     Analytical test strip module  1120  and electrochemically and electrically inert carrier substrate  1140  can be of any suitable dimensions. Representative, but non-limiting dimensions for the analytical test strip are a width in the range of 2.0 mm to 3.5 mm and a length of approximately 10.0 mm. Electrochemically and electrically inert carrier substrate 1140 can have, for example, a width of 8.0 mm, a length of 35. 0mm and a thickness in the range of 200 μm to 500 μm). For these representative dimensions, the first and second contact pads of analytical test strip module  1120  will extend beyond the edge of the electrochemically and electrically inert carrier substrate by 2.00 mm (since the length of the analytical test strip module is attached across the width of the inert carrier substrate) and the electrochemically and electrically inert carrier substrate will extend beyond the analytical test strip module by at least 31.5 mm to 33.0 mm. See, in particular,  FIG. 12  where both extensions are depicted. 
       FIG. 15  is a simplified top view of another electrochemically and electrically inert carrier substrate  1200  as can be employed in embodiments of the present invention. Electrochemically and electrically inert carrier substrate  1200  includes mechanical physical alignment features  1210   a  (namely a notch) and  1210   b  (namely a circular opening through the inert carrier substrate) configured to aid in the insertion of analytical test strip and electrochemically and electrically inert carrier substrate into a test meter. Such mechanical physical alignment features are configured to mate with a corresponding feature of a test meter only when the analytical test strip and electrochemically and electrically inert carrier substrate have been correctly oriented and inserted into the test meter. If desired, a surface of the electrochemically and electrically inert carrier substrate can include an informational marking such as, for example, a bar code, logo, and/or a mark designating calibration information. Providing such informational marking on the inert carrier substrate enables various optimized and flexible supply chain management strategies. For example, an inert carrier substrates with appropriate calibration code information thereon can be combined with analytical test strip modules following calibration of a batch of such analytical test strip modules. In addition, a security informational marking could be applied to the inert carrier substrates just prior to shipment. 
       FIG. 16  is a simplified top view of yet another electrochemically and electrically inert carrier substrate  1300  as can be employed in embodiments of the present invention. Electrochemically and electrically inert carrier substrate  1300  includes a sample-cavity avoidance notch  1320  aligned with the sample-receiving chamber of the associated analytical test strip module (not shown in  FIG. 16  for clarity purposes). The placement of sample-cavity avoidance notch  1320  is such that the inadvertent creation of cavities between the electrochemically and electrically inert carrier substrate and the analytical test strip module in the vicinity of bodily fluid sample application is prevented. Such cavities could, if present, present the opportunity for undesirable bodily fluid sample flow into the cavity instead of into the sample-receiving chamber. 
       FIG. 17  is a flow diagram depicting stages in a method  1400  for determining an analyte (such as glucose) in a bodily fluid sample (for example, a whole blood sample). Method  1400  includes introducing a bodily fluid sample into a sample-receiving chamber of an analytical test strip module of an analytical test strip with inert carrier substrate that has a first electrode portion of a first electrically conductive layer and a second electrode portion of a third electrically conductive layer therein (see step  1410  of  FIG. 17 ). In addition, the first electrode portion and the second electrode portion are in an opposing relationship. 
     At step  1420  of method  1400 , an electrical response of the first electrode portion and the second electrode portion is measured via a first electrical contact pad of the first electrically conductive layer and via a second electrical contact pad of a second electrically conductive layer of the analytical test strip module. Furthermore, the first electrical contact pad of the first electrically conductive layer and the second electrical contact pad of the second electrically conductive layer are configured in a unidirectional stacked relationship and the second electrode portion is in electrical communication with the second electrical contact pad of the second electrically conductive layer and the inert carrier extends beyond the analytical test strip module. 
     Method  1400  also includes, at step  1430 , determining the analyte based on the measured electrical response. 
     Once apprised of the present disclosure, one skilled in the art will recognize that method  1400  can be readily modified to incorporate any of the techniques, benefits and characteristics of analytical test strips with an inert carrier substrate according to embodiments of the present invention and described herein. 
     While preferred embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous variations, changes, and substitutions will now occur to those skilled in the art without departing from the invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that devices and methods within the scope of these claims and their equivalents be covered thereby.