HK1179146B - Analytic test unit and test system - Google Patents

Description

Analytical test element and test system

The invention relates to an analytical test element for use in a test device for detecting an analyte in a body fluid, in particular for carrying out a blood glucose test, having at least one test element, preferably provided in a cartridge, which has a carrier film and a reagent layer which is arranged on a carrier side of the carrier film and can be loaded with a body fluid, wherein the light-permeable carrier film can be positioned in the beam path of a photometric measuring unit for optically scanning the reagent layer. The invention also relates to a test system for processing a test unit of this type.

Analytical test elements of this type are used, for example, in portable blood glucose meters in order to enable the user to determine the blood glucose level himself in a measurement process which is as automated as possible. In this case, the reagent layer is wetted with the blood sample on the front side and the photometric measurement is carried out on the rear side through the support film. The most common approach for optical analysis is to emit light at an angle between 30 ° and 60 ° to the surface of the film and to receive light reflected perpendicular to the surface with a photodetector. The positions of illumination and detection may be exchanged instead. The purpose of these arrangements is not to allow the detection light path to be reflected directly onto the surface of the detection structure. These reflections produce a large signal height on the detector, but do not interact with the detection chemistry and therefore contain no information about the analyte that optically changes the detection chemistry. Furthermore, a small angular change between the incidence of light or the obstruction of light and the reflecting surface causes a large signal shift in the detected light, so that the modulation of the reflection cannot be distinguished due to the analyte. Furthermore, such an optical path also requires a large installation space, which is at least not available if many of the consumables integrated in this way are to be stored in a narrow space when the detection element is integrated in a sample collector which is to be used for obtaining a sample liquid by skin puncture.

The task of the invention is that: in this respect, the detection units and systems known from the prior art are further improved and an optimal detection of the optical measured values is possible with high measurement accuracy, in particular for compact hand-held instruments.

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

The invention is based on the idea of avoiding a smooth reflective interface in the detection structure by means of a topologic (topologisch) surface structure. According to the invention, it is therefore proposed that, in order to avoid reflections in the beam path of the measuring cell, the support film has a surface modified by a raised or three-dimensionally fine-structured surface structure in order to reduce reflections in the beam path of the measuring cell. In this case, "fine structuring" is to be understood in such a way that the structural elements are several orders of magnitude smaller than the modified surface itself. In this way, disturbing reflections are prevented by eliminating reflections from the optical path of the measuring cell or diverting light rays from the optical path. This can be achieved in itself by irradiation of the standard surface or of the surface normal (fl ä cheminomale), which enables a particularly space-saving direct optical coupling.

The surface structure is advantageously designed to continuously vary the refractive index of the support film in the direction of a standard surface or surface normal (Fl ä cheminomal). The surface structure can instead be formed as a micro-optical system for deflecting interfering reflections from the optical path of the measuring unit.

In a further advantageous embodiment, the surface structure is arranged on the support side and/or on a rear side of the support film facing away from the support side and pointing toward the measuring cell.

According to a particularly preferred variant, the surface structure is arranged on the support side and is designed in the form of a moth-eye structure, in particular with a periodic surface topography. The refractive index of the support film can be continuously changed towards the reagent layer by means of such a moth-eye structure, which is known per se, for example in order to eliminate reflections of the optical data carrier. I.e. there is no defined optical interface between the support film and the reagent layer and therefore no reflection.

True refractive index matching can also be achieved by such an arrangement when the refractive index of the reagent layer changes over time during the course of photometric measurement detection by wetting with body fluids.

In order to optimize the anti-reflection properties, the surface structure should have a structure height in the range between 5 and 0.2, preferably between 3 and 0.7, and most preferably between 2 and 1, times the wavelength of the measurement light of the measurement unit. This measure also makes it possible to: the transmission coefficient of the support film is increased by the surface structure compared to an unstructured flat surface.

A further particularly advantageous embodiment provides that the surface structure is formed by a prismatic contour on the rear side of the support film facing away from the support side. In this way, the measuring beam path can be influenced by light refraction in order to lead away interfering reflections.

Advantageously, the prism profile with a profile division of less than 100 μm, preferably less than 50 μm, is formed by a large number of individual prisms. By this measure, in particular a sufficient averaging of the light spots at the exit end of the light guide can be achieved, and at the same time a sufficiently defined contact surface can also be created for the optical coupling.

A further development is achieved in that the prism profile is formed by a periodic triangular profile, in particular a sawtooth profile, which extends linearly in the longitudinal direction and transversely thereto.

The surface structure can be incorporated into the support film as an embossed structure, preferably hot-embossed, and formed by an embossing tool. Alternatively, the surface structure can also be produced by a casting layer that hardens in a shaped manner, in particular by means of a mold.

In order to further simplify the measuring process and the handling, it is advantageous if a collecting structure for body fluid, which is fluidically connected or can be moved with the reagent layer, in particular a capillary tube arranged on the piercing element for obtaining body fluid by skin piercing, is integrated as a structural unit.

The subject matter of the invention is also an analytical test system for detecting analytes in body fluids, in particular as a portable hand-held instrument for blood glucose testing, comprising a photometric measuring cell and at least one test element which can be positioned in the beam path of the measuring cell, the test cell having a light-transmitting support film and a reagent layer which is arranged on the support side of the support film and can be loaded with body fluid, wherein the support film has a surface which is modified by a three-dimensionally shaped surface structure and serves to reduce reflections in the beam path of the measuring cell. The detection unit according to the invention having the aforementioned features can be used particularly advantageously in such a detection system.

In order to provide a compact optical interface, it is particularly preferred that the measuring cell has a plurality of light conductors for transmitting measuring light, wherein the light conductors can be coupled, preferably in a flush manner, at the end faces to the rear side of the carrier film facing away from the reagent layer.

In this case, it has proven to be appropriate to arrange the illumination and detection light conductors in parallel in order to establish the optical interface in a minimum space (for example only within one cubic millimeter). Since, for reasons of manufacturability, such optical waveguides are intended to run parallel, there is an optical path in which all reflections from interfaces which are not located directly at the end of the optical waveguide can reach the detector. In order to avoid this, it is particularly advantageous if the light conductors are arranged parallel to one another in a common plane at least with their end sections aligned with the support film, and the surface structure is formed by a periodic prism profile which stands with its profile cross section perpendicular to the plane of the light conductor. With this arrangement, the incident light is appropriately refracted, so that direct reflection into the receiving light guide body is avoided. In this case, it is advantageous if the lateral offset of the deflected light is greater than the diameter of the light guide.

In order to increase the user comfort, it is advantageous to store a plurality of detection elements in the detection unit. In this case, the detection unit can be designed as a rotating cartridge for a single integrated sample collector (microsampler) or as a cartridge for the continuous provision of detection elements on a conveyor belt.

The invention will be explained in more detail below with the aid of some embodiments that are briefly shown in the drawing.

These figures show:

FIG. 1: a perspective view of a blood glucose analysis test system having a disposable test unit mounted therein,

FIG. 2: a partial diagram of a detection system with a light conductor carrier rod coupled to the detection element of the detection unit,

FIG. 3: in a simplified perspective view of the device according to fig. 2, in this figure the detection element has a rear-side prism structure for coupling the light conductor,

FIG. 4: the partial illustration according to fig. 3 transverse to the plane of the light guide with a symbolic light path,

FIG. 5: a side view of another embodiment of a detection unit with a moth-eye structure with reduced reflections,

FIG. 6: a perspective view of the test carrier of the test unit according to fig. 5.

The detection system 10 shown in fig. 1 comprises a device part 12 having a piercing drive 14 which moves back and forth, a photometric measuring unit 16 in a housing, not shown, as a portable hand-held instrument, and an analytic detection unit 18 which can be installed therein and has a piercing element 20 and an integrated detection element 22 for the single-use detection of a liquid sample, in particular for the determination of glucose in a blood sample. Further details of the device, for example in respect of the preparation of the detection unit from a rotating cartridge, are also known from EP 09159834.2, to which reference is explicitly made in this connection.

As can be seen from fig. 2, the puncturing element 20 is provided with capillary grooves 24 which guide blood, which is obtained, for example, from a finger of a test person (Probanden) during skin puncturing, on the front side to the suction-capable spreading layer 26 of the integrated detection element 22. This test element has a support film 28 and, on its support side 30, a dry chemical reagent layer 32 which is enclosed below the spreading layer 26 and which, when wetted with a body fluid, reacts irreversibly to the analyte by changing color. This can be detected on the reverse side through the transparent support film 28. For this purpose, the measuring unit 16 has an optical adapter 34, which is inserted as a plunger into the lancing drive 14 and comprises three parallel light conductors 36, which can be brought into collision contact with a rear side 38 of the support membrane 28 at their free end faces. In this case, the light conductors 36 are aligned in the direction of the surface normal. The outer light conductor is connected to a light emitter, while the inner light conductor guides the measurement light scattered at the reagent layer 32 back to a light receiver of the measurement cell 16, as is shown in fig. 2 by the arrow as a light path 40.

In order to reduce disturbing reflections in the optical path 40 as far as possible, the support film 28 is provided on its rear side 38 and/or on its front side 30 with surface structures 42 which are formed three-dimensionally on a fine scale and which lead to a continuous refractive index profile or form an optical system for deflecting light.

Fig. 2 to 4 show such an optically effective surface structure 42 in the form of a rear prism contour or prism guide (prism profile) 44 on the carrier film 28. This prism profile 44 extends linearly parallel to one side of the rectangular support film 28 and has a periodic sawtooth profile 46 transversely thereto. The dimensions of this contour are selected such that the inhomogeneities of the light guide 36 across its cross-section are also averaged out and a reliable support (autoflage) is ensured. When the diameter of the light guide body is 125 μm, it is suitable for the prism profile 44 to have a profile graduation (profileilung) of 25 to 30 μm. This makes it possible to obtain a sufficient averaging over the cross-section of the light guide, while the profile structure is still sufficiently large to enable manufacture.

The manufacture of the prism structure can be accomplished, for example, by machining techniques. It is also conceivable to form a casting layer on the carrier film 28, which is cured by shaping with the aid of a suitably shaped tool.

The case of deflecting light rays by means of the prism profile 44 is shown in fig. 4. The light conductors 36 standing perpendicular to the support film 28 on the contour surface are arranged parallel to one another on a plane which is perpendicular to the illustrated contour cross-sectional surface. Since the sawtooth profile 46 is inclined, the central light beam 48 emerging from the light conductor 36 deviates laterally by refraction from the plane of the light conductor 36 (partial light beam 50). This portion of light is typically reflected at the interface to reagent layer 32 without interaction with the detection chemistry. This reflected light beam 52 comes out at an angle to the vertical and therefore no longer reaches the optical path of the measuring unit. The deflection angle of prism profile 44 should be selected according to the acceptance angle of light conductor 36 and the distance of its end side to the reflective interface.

Only this part of the incident light 50 reaches the measuring cell 16 partly through the receiving optical conductor: this light reaches the reagent layer 32 and is scattered back from there as a diffuse beam of light (Lichtkeule) 54. The measuring light thus interacts with the detection chemical and contains information about the analyte.

Fig. 5 and 6 show an exemplary embodiment of a reflection-reducing surface structure 42, which supports the reagent layer 32 on the support side of the component formed by the support film 28. Such a detection element 22 can also be integrated into the puncturing element 20 described above. It is also conceivable to install in a cassette as the detection unit 18, which comprises a large number of detection units 22 on a transparent transport tape 56 that can be wound.

In this case, the surface structure 42 has a periodic surface structure 58 in the manner of a so-called "moth-eye structure" (mottenaugustur), as described, for example, in EP-a 0288140, formed by projections (and complementary recesses), which are not illustrated to scale. The provision of such a surface structure avoids a defined interface and leads to a continuous change of the refractive index towards the reagent layer 32, thus leading to an effective elimination of reflections. As in fig. 5, for the sake of simplicity, only the marginal beam 50 of the light cone emerging from the light conductor 36 is shown, virtually no reflection occurs at the moth-eye structure 58, which increases the transmission of the support film 28 (transmissiongrad) and, above all, only the return scatter 54 emerging from the reagent layer 32 enters the light-receiving conductor as measurement light.

For example, when narrow-band excitation is carried out with a measurement wavelength of 365 nm, the elevations or depressions of the moth-eye structure 58 have a structure height or structure depth in the range of between 5 and 0.2 times, preferably between 3 and 0.7 times, and preferably between 2 and 1 times, the measurement wavelength. The structural period of the side faces should also be in the order of the wavelength of the measuring light. Such a nano-scaled finely structured surface can be formed, for example, by hot embossing by an embossing die onto the carrier film 28, wherein the die surface can be produced by etching if necessary.

Claims (20)

1. Analytical test element for use in a test device for detecting an analyte in a body fluid, having at least one test element (22) which has a carrier film (28) and a reagent layer (32) which is arranged on a carrier side (30) of the carrier film (28) and can be loaded with a body fluid, wherein the light-permeable carrier film (28) can be positioned in the beam path of a photometric measuring cell (16) for optical scanning of the reagent layer (32), characterized in that the carrier film (28) has a surface which is modified by a raised surface structure (42) in order to reduce reflections in the beam path of the measuring cell (16).

2. The analytical test element according to claim 1, characterized in that the surface structure (42) continuously changes the refractive index of the support film (28) in the direction of the surface normal or the surface structure (42) forms an optical system for deflecting interfering reflections of the light path from the measuring cell (16).

3. The analytical detection unit according to claim 1 or 2, characterized in that the surface structure (42) is arranged on the support side (30) and/or on a rear side of the support membrane (28) facing away from the support side (30) and pointing towards the measurement unit (16).

4. The analytical test element according to claim 1 or 2, wherein the surface structure (42) is arranged on the support side (30) and forms a surface topography (58) in the form of a moth-eye structure.

5. The analytical detection unit according to claim 1 or 2, characterized in that the surface structure (42; 58) has a structural height in a range between 5 times and 0.2 times the wavelength of the measuring light of the measuring unit (16).

6. The analytical detection unit according to claim 1 or 2, characterized in that the transmission of the support film (28) is increased by the surface structure (42) compared to an unstructured flat surface.

7. The analytical detection unit according to claim 1 or 2, characterized in that the surface structure (42) is formed by a prism contour (44) on a rear side (38) of the support film (28) facing away from the support side (30).

8. The analytical test element according to claim 7, wherein the prism profile (44) is formed by a plurality of individual prisms (46), the prism profile having a profile pitch of less than 100 μm.

9. The analytical test element according to claim 7, characterized in that the prism profile (44) is formed by a triangular profile which extends linearly along the longitudinal direction and is periodic transversely thereto.

10. The analytical test element according to claim 1 or 2, wherein the surface structure (42) is incorporated into the carrier film (28) as a preferably hot-embossed structure formed by an embossing tool.

11. The analytical test element according to claim 1 or 2, characterized in that the surface structure (42) is formed by a cast layer.

12. The analytical test element according to claim 1 or 2, characterised in that the analytical test element is provided with a collecting structure (24) for body fluid which is in fluid connection with the reagent layer (32) or can be moved.

13. The analytical test element according to claim 1 or 2, wherein the test device is used for blood glucose testing.

14. The analytical test element according to claim 7, wherein the prism profile (44) is formed by a sawtooth profile.

15. The analytical test element according to claim 11, wherein the cast layer is mold-hardened.

16. The analytical test element according to claim 12, wherein the collection structure (24) is a capillary tube arranged on the puncturing element (20) for obtaining body fluid by skin puncturing.

17. Detection system for detecting an analyte in a body fluid, comprising a photometric measurement cell (16) and at least one detection element (22) which can be positioned in the beam path of the measurement cell (16) and which has a light-permeable support film (28) and a reagent layer (32) which is arranged on a support side (30) of the support film (28) and can be loaded with a body fluid, characterized in that the support film (28) has a surface which is modified by a three-dimensionally shaped surface structure (42) and serves to reduce reflections in the beam path of the measurement cell (16).

18. The analytical detection system according to claim 17, wherein the measuring unit (16) has a plurality of light conductors (36) for transmitting measuring light; and the light guide (36) is preferably coupled in an impact manner at the end face to a rear side of the carrier film (28) facing away from the reagent layer (32).

19. The analytical detection system according to claim 18, wherein the light conductors (36) are arranged parallel to one another in a common plane at least with their end sections pointing towards the support membrane (28); and the surface structure (42) is formed by a periodic prism contour (44) which is perpendicular to the plane of the light guide (36) with its contour cross section.

20. The analytical testing system of any one of claims 17 to 19, wherein the analytical testing system is configured as a portable, hand-held instrument for blood glucose testing.