HK1163590B - Diagnostic test strip for liquid samples - Google Patents

Description

Diagnostic test strip for liquid samples

The invention relates to a diagnostic test strip for liquid samples, in particular body fluids, having a flexible transport strip which is wound or can be wound on a reel, and a plurality of test zones which are arranged on the transport strip in a longitudinally distributed manner along the strip and which comprise a detection layer (Nachweisschichcht) and a spreading web (Spreitnetz) which spans the detection layer and serves to draw the liquid sample in a planar manner.

Such a test system is especially designed for blood glucose testing in order to further improve user-friendliness compared to test strip systems on the market. In order to simplify handling of the rollable conveyor belt, a large number of test units or test zones can thus be stored compactly and can be taken up again after use by the belt conveyor. A simple assembly technique for test strips of the type described is known from EP 1593434. This enables the roller-to-roller processing to be performed at a high manufacturing speed. The fabric used as a spreading aid for improving the distribution of the liquid sample can be held only by the adhesive layer in its protruding longitudinal edge regions due to the process conditions. However, if the fabric is detached from the detection layer, it is unevenly wetted by the blood sample, and thus it is difficult to perform a correct analysis. It can also occur that the spreading web is not detached from the test field until the test field is wetted with blood. Blood then flows into the still-lying textile region, forming bubbles in the raised textile region, which can adversely affect the measurement analysis.

In this respect, the object of the invention is to further develop the products known from the prior art and to provide a durable belt structure which is also optimized with regard to mass production for reliable sample processing.

To achieve this object, combinations of features given in the independent claims are proposed. Advantageous embodiments and developments of the invention result from the dependent claims.

The first aspect of the present invention is based on the following concept: so that the stretch characteristics of the carrier band and the extensible fabric are coordinated with one another. Accordingly, it is proposed according to the invention that the fabric direction is inclined to the conveyor belt, so that all fabric yarns run obliquely to the belt longitudinal direction. This arrangement prevents only one thread system from being exposed to tensile loads. More precisely, in the case of a tensile force exerted on the carrier tape, all the fabric yarns are stressed according to their oblique position, so that a certain ratio of the transverse shrinkage to the longitudinal extension of the fabric is also produced. The different transverse shrinkage of the web and the rest of the test tape structure can thereby be reduced to a large extent, so that undesired peeling or tilting of the extension aid is avoided. The existing web material can be adapted to the properties of the carrier tape and the test field at little expense, so that the risk of the test field being unevenly wetted by the test liquid and the resulting incorrect analysis result are largely avoided.

The fabric orientation is best determined by minimizing the difference in lateral contraction of the belt and fabric for a given tensile load.

Depending on the material properties, it is advantageous if the fabric is oriented obliquely and the compensation angle, which is defined by the smallest angle between the longitudinal direction of the belt and the yarns of the fabric, is between 5 ° and 40 °, preferably between 20 ° and 25 °.

In view of the conditions of use, it is advantageous if the conveyor belt is composed of a membrane material having a poisson number of 0.3-0.5, preferably about 0.4.

It is also advantageous in terms of simplicity of manufacture that the plain weave fabric be composed of warp yarns and weft yarns, the warp yarns running closer to the longitudinal direction of the tape than the weft yarns.

According to another refinement, the textile threads, optionally provided with a hydrophobic coating, consist of monofilament thread material, in particular polyester, such as PET.

By means of the inclined position, a simple test field configuration can be realized without problems, in which the spreading web is wider than the detection layer and is bonded at its projecting side edge regions to a carrier strip with the detection layer, which is applied to the conveyor belt.

Another aspect of the invention is to utilize a peel-off prevention mechanism to prevent the carrier web from peeling off the probe layer in addition to or instead of lateral bonding to the carrier strip. In this case, it is also possible to ensure that the spacing between the spreading web and the detection layer is at most 40 micrometers, preferably less than 20 micrometers, under the conditions of use, so that the risk of uneven wetting is largely avoided, also on the basis of capillary forces.

According to an advantageous variant, the rectangular expanded mesh has material-fitting connection sections, preferably laser welded seams, as peel-off protection means at the ends thereof, each extending transversely to the longitudinal direction of the strip. In terms of manufacturing technology, test zones can advantageously be cut out of the roll product by laser cutting, whereby laser welding seams are formed.

According to a further advantageous embodiment, the expanded web is wider than the detection layer and is supported on the carrier strip in the region of its projecting side edges by adhesive strips as peel-off protection. The adhesive strip as spacer and the detection layer can have substantially the same thickness, so that the expanded mesh lies flat.

According to a further advantageous embodiment, the expanded web is fixed to the carrier strip at the periphery by an adhesive frame as a peel-off protection around the detection layer. For this purpose, the adhesive frame can advantageously be formed by laser welding and/or thermal bonding of the regions.

According to a further advantageous embodiment, the expanded web can be as wide or narrower than the detection layer transversely to the longitudinal direction of the strip and is fixed at its longitudinal edges by overlapping adhesive strips as a peel-off protection, while leaving free a central application window. It is also advantageous here if the region forming the application window is punched out of the adhesive tape.

An equally advantageous embodiment of the stripping-prevention means provides that the spreading web is formed by a grid-like fabric with a bending-resistant yarn system which can be deformed stepwise in the cross direction of the belt. For this purpose, the fabric is advantageously provided with metal weft yarns.

The peel-off prevention means may also be embodied in such a way that the carrier strip consists of a durable film material having a shear resistance of more than 0.05N/mm²The peel resistance is more than 1N/mm.

The invention also relates to a tape cassette having a diagnostic test tape according to the invention, which test tape is guided past the reversal point when a sample is applied, preferably with a tape tension greater than 1N.

The invention is explained in detail below with the aid of embodiments which are schematically illustrated in the drawings. The figures show:

FIG. 1 is a perspective cross-sectional view of a test strip having an analytical test zone;

FIG. 2 is a cross-sectional view of a test zone of the test strip according to FIG. 1;

FIG. 3 is a top view of a diagonal extensible fabric covering a test zone of the test strip according to FIG. 1;

FIG. 4 is a graph of Poisson number (Poissonnahl) versus azimuth angle of an extended fabric according to FIG. 3;

FIGS. 5-9 illustrate a portion of a test strip in which various embodiments are employed to prevent peeling of an extension fabric;

FIG. 10 shows a scheme for using rolled goods (Rollenware) to create test zones; and

fig. 11 is a perspective view of an open diagnostic tape cartridge with test tape disposed therein.

The test strip 10 shown in the drawing for carrying out a diagnostic test for blood glucose comprises a flexible, windable conveyor belt 12 and a plurality of test elements or test fields 14 stored on the conveyor belt in advance for single-use continuous use, spaced apart from one another in the longitudinal direction of the belt, which test elements or test fields as flat formations (Fl ä chengebilde) in the form of a label (etikete) having a rectangular outer periphery, comprise a carrier strip 16 which is adhesively bonded to the conveyor belt 12, a detection layer 18 which is arranged on the carrier strip, and an extension web 20 which spans the detection layer 18 on the side facing away from the carrier strip and serves to distribute in a planar manner the sample liquid (blood sample) applied to the extension web from above. The detection layer 18 acts as a dry chemical membrane, in particular enzyme-based (enzymbases), which reacts to the analyte (Analyt) (glucose) by means of a color change (farbauschlag) and is thus optically detectable through the transparent composite membrane (folienverbend) 12, 16.

As shown in fig. 1 and 2, the tape-like expanse of fabric 20 is constructed to be wider than the detection layer 18. The projecting side edges 22 of the fabric 20 are bonded to the top surface of the carrier strip 16, which is bonded to the conveyor belt 12 as a double-sided adhesive tape. On its free outer side, the lateral edges 22 of the cloth 20 are provided with a hydrophobic (hydrophobic) coating 24, so that the liquid distribution or spreading takes place in a targeted manner over the detection layer 18 in the unbonded central region 26 of the cloth 20.

The test zone 14 can be used sequentially by advancing the conveyor belt 12 at the application site. As a result of the tension applied at this point, the flexible belt mechanism expands longitudinally and contracts laterally, which may cause the central region 26 of the fabric to peel or lift above the detection layer 18. This effect occurs because the fabric in the longitudinal direction of the belt changes length due to belt tension, but does not change its width, while the carrier belt 12 decreases in width due to lateral contraction.

To avoid this peeling effect, which is detrimental to the uniform distribution of blood, the fabric 20 is inclined to the conveyor belt 12, as shown in fig. 3. The fabric 20 has fabric yarns 28, 30 crossing at right angles, all of which run obliquely to the belt longitudinal direction or belt edge 32.

The plain weave (Leinwandbindung) fabric 20 is preferably made up of warp yarns (Kettf ä den) 28 and weft yarns (Schussf ä den) 30 in the form of PET monofilaments (monofilame). To process a rolled product, it is desirable to have the long warp yarns 28 extend closer to the tape longitudinal direction than the short weft yarns.

The orientation of the fabric 20 can be described by the compensation angle α, which is defined by the minimum angle between the belt edge 30 and the fabric yarn (i.e., warp yarn 28 in FIG. 3).

Fig. 4 shows the poisson number mu as a function of the compensation angle alpha of the fabric 20. In general, the poisson number represents the ratio of the variation of the lateral dimension d to the physical length extension Δ L of the length L, see the following relation:

the fabric 20 is oriented in a manner such that the difference in lateral contraction of the conveyor belt 12 and the fabric 20 is minimized under a predetermined tensile load. Accordingly, if the poisson's number of the conveyor belt 12 is given to be about 0.4, the compensation angle should be between 20 ° and 25 °.

In the embodiment of fig. 5-9, identical or similar parts are provided with the same reference numerals as previously described. Here, the anti-peeling mechanism 32 is used instead of the inclined position to prevent the span wire 20 from lifting or peeling off from the detection layer 18. In various embodiments, such peel prevention mechanisms 32 are provided with a carrier strip 16 in addition to or in addition to the lateral bonding of the side edges 22 of the expanded web 20. The design of the spreading net 20 is not limited to a textile fabric, but can also comprise other flat structures as liquid distribution means, for example a membrane with fine holes. In any case, the anti-peeling means 32 is designed such that the distance between the central region 26 of the expanded mesh 20 and the detection layer 18 is at most 40 μm, preferably less than 20 μm, under the application conditions of the test strip.

According to the embodiment shown in fig. 5, the ends of the rectangular expanded mesh 20 facing the longitudinal direction of the strip are each secured by a transversely running laser weld 34. This fixation may be performed by melting of the web material as the test area 14 is laser cut, as described in more detail below.

If the ramp 36 seen in fig. 2 can be avoided in the cross-section of the expanded mesh 20, the durability of the test strip 10 is further improved. This can be achieved according to fig. 6 by the fact that the spreading web 20 is wider than the detection layer 18 and is supported laterally on the carrier strip 16 in the region of its projecting lateral edges 22 by adhesive strips 36 serving as peel-off protection 32. In this case, the adhesive tape strips 36 should have substantially the same thickness as the probe layer 18 so that the span wire 20 lies flat.

According to the exemplary embodiment shown in fig. 7, the expanded mesh 20 also projects at the end face beyond the detection layer 18 and is fixed on its underside by a circumferential adhesive frame 38 (ringsum) as the detachment protection means 32 to the carrier strip 16. This can be done by laser welding or a combination of adhesive film and laser welding. It is also possible to use a production variant in which an adhesive film with thermal adhesive bonds is used as an intermediate carrier during the production of the tape, in order to transfer the adhesive bonds with a precise fit to the short and long sides of the adhesive frame 38.

According to the embodiment shown in fig. 8, the expanded web 20 has at most the same width as the detection layer 18 so that the web does not bulge in the relaxed state. All components are then secured by lateral adhesive strips 40 which act as peel-off protection 32. The adhesive strip 40 thus overlaps the longitudinal edges of the layer structure 16, 18, 20, wherein a central application window 42 for applying the liquid sample remains free. The area forming the application window 42 may also be punched out of the adhesive tape member 40 that extends transversely therethrough.

According to the embodiment shown in fig. 9, the expanded web 20 is provided with a bending-resistant yarn system 44 extending in the belt cross direction as the peeling prevention mechanism 32. The transverse threads are designed in such a way that they can be pressed to the edge of the detection layer 18 largely without air gaps. The best way to achieve this may be to use a fabric 20 with metal weft yarns.

Another option for improving durability is to select a suitable membrane material for the carrier strip 16. The material should have (to DIN EN 1943) a value of 40N/625mm²Within the range of a shear resistance, the peel resistance (Sch ä lffetigkeit) should be about (to DIN EN 1939) 25N/25mm². Such membrane materials are available under the product trademark, for example, Duplocol VP 20242.

In order to achieve high production speeds and flexibility when producing the test strips 10, a roll-draw-roll method is specified. Fig. 10 shows a prestage for multi-pass fabrication of test region 14. Here, the double-sided adhesive tape is fed through the manufacturing line between two rollers 46, 48. A plurality of parallel detector films 18' are applied from a reel 50 to the adhesive tape. The mechanism is laid with the extensible fabric 20' drawn from the other reel 52. The secondary layer structure is then secured in place by a heat transfer film 54. The laser 56 then produces transversely running laser cuts which separate the parallel test fields 14 from one another at the end. The laser 56, by appropriately selecting the parameters, not only can intercept the test field 14, but also can bond the edge regions to one another for forming the weld 34 (fig. 5). The entire process is monitored by the camera system 58, so that rejects (Ausschuss) are largely avoided. The test zones 14 thus prepared can be transferred and bonded brandingly over the application edge (Spendekante) to the carrier tape 12, and the multi-pass test strip 10 is then cut longitudinally.

The test strip 10 is loaded into the handheld device as a consumable in the form of a cartridge 60 shown in fig. 11 so that the patient can always perform a number of glucose tests (e.g., 50 tests) himself on site. The tape cassette 60 has for this purpose an unwinding reel 62 for unwinding unused test tape and an winding reel 64 for winding used test tape, wherein the test tape 10 is drawn off via an application tip 66 in order to provide the test field 14 there in succession for drawing off a sample. Further details of the detection of measured values are known, for example, from EP-A1878379, to which reference is made in particular.

While transporting the tape, the test tape is guided past the application tip 66 under a tape tension of about 4N. To further avoid undesirable peeling of the delay network 20, the radius of the commutation edge 68 is appropriately adjusted. Increasing the radius greatly reduces the stress on the multi-component structure 12, 14, thereby reducing the warpage. However, an excessively large radius may cause the tip 66 to widen, which may disadvantageously enlarge the sample application surface or the required sample volume. In any case, a planar tensioning between the two deflecting edges 68 is to be ensured.

Claims (6)

1. A cassette comprising a test tape for the diagnosis of liquid samples, which test tape comprises a flexible carrier tape (12) which is wound or can be wound on reels (62, 64) and a plurality of test zones (14) which are arranged distributed over the carrier tape (12) in the longitudinal direction of the tape and which comprise a carrier strip (16) applied to the carrier tape (12), a detection layer (18) lying on the carrier strip and an expanded mesh (20) spanning the detection layer (18) for the planar uptake of the liquid sample, wherein the expanded mesh (20) is wider than the detection layer (18), characterized in that the expanded mesh (20) is supported on the carrier strip (16) in its region which projects beyond the side edges (22) of the detection layer (18) by means of an adhesive strip (36) as an anti-peeling means (32) and is prevented from peeling off from the detection layer (18), wherein the adhesive strip (36) and the detection layer (18) have substantially the same thickness, so that the expanded mesh (20) is supported steplessly, the expanded mesh (20) being wider than the detection layer (18) in a direction transverse to the test strip.

2. The cartridge according to claim 1, characterized in that the anti-peeling means (32) is designed such that the spacing between the spreading screen (20) and the detection layer (18) is at most 40 μm in the use condition.

3. The cartridge according to claim 2, wherein the anti-peeling mechanism (32) is designed such that the spacing between the extendable network (20) and the detection layer (18) is less than 20 microns under use conditions.

4. The cartridge according to claim 1, characterised in that the expansion web (20) is fixed circumferentially on the carrier strip (16) by an adhesive frame (38) as a peel-off prevention means (32) surrounding the detection layer (18).

5. The cartridge as in any of claims 1-4, wherein the carrier strip (16) is formed from a durable film material having a shear resistance of greater than 0.05N/mm²The peel resistance is more than 1N/mm.

6. The cartridge of any one of claims 1-4, wherein the liquid sample is a bodily fluid.