EP0634215A1 - Device for simultaneous determination of analytes - Google Patents

Abstract

Device for determining analytes having a sample application point, a plurality of separated sample take-off zones which are connected to the sample application point by one capillary transport section each and a plurality of test elements for individual determination of analytes, a delay zone being provided on at least one of the transport sections. <IMAGE>

Description

The invention relates to a method for determining several analytes in a multi-zone device and a device suitable therefor.

In medical diagnostics, there has been a recent development to make it easier for the treating physician or the patient himself to diagnose disease states by detecting characteristic analytes in body fluids. If complex clinical pictures are involved or if the cause of a disease has not yet been pinpointed, it is often advisable or even necessary to determine several different analytes. For example, when testing for drug abuse due to the variety of possible drugs and the often unknown history of the patient, individual tests for many drugs must be performed. A similar problem arises, for example, in the diagnosis of kidney and thyroid diseases or infectious diseases.

So-called dry tests have proven their worth for quick and easy determination of analytes. They contain a reagent or a large number of reagents in dried form on a capillary carrier which is brought into contact with the sample liquid in order to carry out the test. The reagents dissolve in the liquid and result in a signal that is characteristic of the analyte, for example a color change, which can then be used for an evaluation. With simple tests it is sometimes possible to arrange the capillary, reagent-containing supports on a single test element, which is then immersed in the liquid so that all supports are wetted by the liquid. An example of such test elements are urine test strips, the test fields for several analytes, e.g. B. leukocytes, density, pH and the like. contain.

However, such a simple procedure by immersing the test fields once is not possible, for example, for immunological determinations of analytes, such as antigens, haptens and antibodies, since these determinations are processes with a multi-stage reaction procedure. The liquid containing the analyte passes through a test section with several zones, on which the various reagents are exchanged between the liquid and the test fields. A signal characteristic of the presence of the analyte can be obtained and evaluated in a zone towards the end of the test section.

EP-A-0 467 165 describes a method and a device for determining several analytes from a pasty sample, e.g. B. proposed by chair. The device contains an eluent application field and a plurality of eluate transfer means which ensure fluid contact with test strips for ensure the desired provisions. There is an area between the eluent application field and the eluate transfer agent for the application of the pasty sample. Between the eluent application field and the sample application area lies a transport route for the pure eluent, which is designed in such a way that the eluent flow through the sample is greatly slowed down in order to achieve an effective elution of the relatively heterogeneous solid sample. First, the pure eluent is placed on this eluent application field and transported from there to the sample application area without changing the ingredients. After elution of the analyte from the sample in the sample application area, the eluate, which now contains analyte, flows through a transport zone widening in the direction of the test carrier, in which the transport routes are not separated from one another. The method described in EP-A-0 467 165 has the disadvantage that the different test strips and thus also reagents come into contact with the eluate at different times and thus different test results are obtained in some cases for the same test strips on different eluate transfer agents. This can be disadvantageous, in particular for a quantitative evaluation of analyzes. In addition, the problems increase with an increasing number of eluate transfer agents.

• einen Probenaufgabepunkt,
• mehrere getrennte Probenentnahmezonen, die durch jeweils eine Transportstrecke mit dem Probenaufgabepunkt verbunden sind,
• mehrere Testelemente zur Einzelbestimmung von Analyten,

wobei auf mindestens einer der Transportstrecken eine Verzögerungszone vorgesehen ist, sowie eine zur Ausführung des Verfahrens geeignete Vorrichtung.The object of the invention was to provide a method and a device for the determination of analytes contained in a liquid, which enables an essentially simultaneous determination of the analytes on several test elements which are uniform at different sampling points. The invention therefore relates to a method for determining analytes containing

• a sample drop point,
• several separate sampling zones, each connected to the sample drop-off point by a transport route,
• several test elements for the individual determination of analytes,

wherein a delay zone is provided on at least one of the transport routes, and a device suitable for carrying out the method.

Analytes of the method according to the invention are, in particular, constituents of body fluids, such as urine, blood, serum, saliva, sweat or plasma or liquids derived therefrom (e.g. diluted with water, buffer or alcohols) or other liquids, such as e.g. B. Solutions of powders to be tested for drug content.

Preferred body fluid is urine. Preferred analytes are dissolved chemical substances, the presence or absence or concentration of which in the respective body fluid is an indication of a disease or a body condition. Particularly preferred are analytes that are detectable immunologically, ie haptens, antigens or antibodies, but also nucleic acids and other biospecifically detectable substances. Preferred analytes in the urine are drugs such as cocaine, cannabis (hashish) or opiates (heroin), or kidney parameters such as albumin, 1M, β-NAG.

The device according to the invention has at least 4 zones which are connected to one another by capillary action, namely 2 or more transport zones and 2 or more sampling zones. It also contains a sample drop point.

The sample application point is preferably on a capillary fleece or tissue that is chemically inert to the sample liquid. It is preferred by appropriate labeling, e.g. B. by applying visible signs such as circles, crosses, arrows or the like or by constructive separation, z. B. determined by covering the fleece surrounding the drop point.

The transport zones extend from the sample drop point to the sampling zones. A device according to the invention preferably contains as many transport zones as sampling zones, the transport zones being spatially separated from one another at least in the vicinity of the sampling zone, so that no liquid can pass from one transport path to another. The transport zones are constructed from capillary material, in particular a capillary fleece or tissue that is chemically inert to the sample liquid. In the following, a transport zone is understood to be an area on which a flat material capable of absorbing liquid extends. This material has a thickness that is less than the width and length of the surface. The sample liquid flows through the length of the transport zone. The transport zones are either spatially separated from one another or their limits are given to one another by segments of the liquid volumes moving within the transport zones towards the associated sampling zone.

A sampling zone is understood to be an area of the device which is also capillary-active and which is or can be brought with a test element in an arrangement which enables liquid contact. As soon as the sampling zone receives liquid from the transport zone, the liquid can pass onto the adjacent test element.

A capillary volume is defined by the suction volume of the transport zones and the sampling zones. This volume is smaller or at most the same size as the volume of the sample liquid applied. The volume of the liquid applied is particularly preferably as much greater than the capillary volume as it corresponds to the additional suction volume of the test elements adjacent to the sampling zone.

The distances that a certain volume of liquid travels between the sample application point and the sampling zone are referred to below as transport routes. The applied sample liquid is not changed on these transport routes, at least with regard to the analytes.

Non-woven fabrics made of synthetic fibers (e.g. polyester), to which cellulose fibers can be added if desired, are particularly suitable as the capillary-active material. Such materials are well known for the construction of test strips. The nonwovens are preferably between 0.35 and 1.5 mm thick.

• 1. (horizontale) Vergrößerung der Breite des Materials der Transportzone an mindestens einer Stelle im Vergleich zu einer anderen Transportzone,
• 2. (vertikale) Verengung der Dicke des Materials der Transportzone an mindestens einer Stelle verglichen mit einer anderen Transportzone,
• 3. Verringerung des Durchflußquerschnitts auf der Transportstrecke durch Zusammendrücken des Materials der Transportzone an mindestens einer Stelle mit einer anderen Transportzone.

It is essential for the invention that a delay zone is provided on at least one of the transport routes. The delay zone is preferably located in the transport zone. The delay zone means that the liquid flow no longer reaches the sample application point to at least one sampling zone as quickly as without the delay zone. A first way of causing the delay is to make the transport routes leading to the different sampling zones the same length. A second way is to make the areas of the transport zones the same size. To achieve transport routes of the same length, one or more transport routes may have to be extended compared to the shortest connection between the sample application point and the sampling zone or one or more hydrophobic barriers must be introduced. In principle, the following measures are suitable for realizing the same volumes:

• 1. (horizontal) enlargement of the width of the material of the transport zone in at least one place in comparison to another transport zone,
• 2. (vertical) narrowing of the thickness of the material of the transport zone in at least one place compared to another transport zone,
• 3. Reduction of the flow cross-section on the transport route by compressing the material of the transport zone at least at one point with another transport zone.

These measures can also be combined with one another.

Especially if it is not possible (e.g. if there are a large number of sampling zones) to ensure the desired delay by using volumes of the same size, it is advisable to reduce the flow cross-section on one or more transport routes or to apply hydrophobic barriers.

The shorter the shortest connection between the sample application point and the sampling zone, the greater the delay caused. Are the shortest connections between different sampling zones and the sample drop point of equal size, the delays caused on all transport routes must also be of approximately the same size.

A test element is understood to be a means for detecting the presence or the amount of an analyte, the preferred elements being constructed in the manner of the test strips. This means that they have a carrier film on which absorbent materials are attached, on which the reagents required for detection are applied. Such a test element is described, for example, in EP-A-0 374 684. If such a test element is brought into contact with the sampling zone, this is preferably done via a zone of the test element which does not yet contain any reagents. In the event that a test carrier according to EP-A-0 374 684 is to be used to determine an analyte according to the device according to the invention, the starting zone 21 described there is brought into contact with the sampling zone 3 of the device according to the invention. For the simultaneous determination of several analytes, as many test elements are brought into contact with the sampling zones as determinations are necessary.

An advantage of the device according to the invention is that the delay zones prevent the test elements from being flooded with sample liquid. In addition, the simultaneity of the contact of the test carriers with the sample liquid means that not one of the reagent carriers receives more liquid than another. Since, to carry out reliable determinations, a signal must often be read from the test element within a certain period of time after the test element has been brought into contact with the sample liquid, the simultaneous encounter of the liquid front at all sampling points according to the invention is an essential advantage of the present invention. The simultaneous arrival of the liquid also means that the test elements for different analytes do not necessarily have to be introduced into the device in an order directed at the respective sampling point, but that they can be interchanged. This is particularly important in the case of provisions in which the users themselves can provide evidence as required. Another advantage of the uniform wetting is that test elements for the determination of several analytes can be assembled into profiles as required. For example, by using appropriate test elements, the device according to the invention can either be used to create a kidney function profile, ie determination of several analytes characteristic of the kidney function, or a drug profile, e.g. B. Determination of several common drugs (drugs of abuse) can be used. The device according to the invention can therefore be sold in a form in which the test elements are already connected to the sampling zones, e.g. B. by including the test elements in the housing, or in a form that the housing with the sample application zone, the transport route and the sampling zone as a part and a number of test elements in a further container by the person who wants to carry out the analysis, can be inserted into the housing, sold.

Two preferred embodiments for the device have been found. In the first form, the sampling zones 4 are arranged essentially completely or partially radially around the sample application point 2 (FIG 1). In the particularly preferred case, the shortest connecting routes are of the same length. The transport routes can then first go through a radially symmetrical capillary-active fleece and then in parallel through as many fleeces as there are sampling zones. The latter fleeces are designed so that no liquid flow is possible between them. For example, they can take the form of webs that extend from the edge of the sample application fleece to the sampling zones. The material of the webs preferably overlaps a little with the sample application fleece, as a result of which, when the materials are compressed at the overlap point, there are locations with a smaller flow cross section, which act as delay zone 7. The overlap point is preferably about 1 to 2 mm wide. In the case shown in FIG. 1 the delay is the same on all transport routes. In the event that the sample liquid is not dosed exactly to the sample application point, the liquid will first flow to the delay zones of the other transport routes after reaching the delay zone of the shortest transport route until the capillary pressure is the same at all delay zones. Then the liquid will pass through all of the delay zones substantially simultaneously. Since the subsequent parts of the transport routes are of the same length and of the same nature, the liquid will reach the test elements at the same time. The ends of the webs located away from the point of application can themselves represent the sampling zones, or separate fleeces can be provided for this. The test elements 5 are in capillary contact with the sampling zones 4. In this embodiment, flooding of the test strips is particularly prevented.

In FIG. 2 the device is shown in section X - Y.

In a second, more manageable execution zone (FIG. 3), the sampling zones 4 lie on an imaginary straight line, so that all test elements 5 point essentially in the same direction. In this case, the delay zones differ in their delay effect if the sampling zones are at different distances from the sample application point 2. Since liquids in uniform capillary-active material would spread radially, the liquid would arrive at the sampling point 4 / I closest to the sample application point first without a delay zone and would pass to the test element. The delay must therefore be greatest on this transport route. The further the other sampling points 4 / I, 4 / II or 4 / III are from the sample application point 2, the weaker the delay must be. Here, too, the transport routes 3 / I, 3 / II or 3 / III preferably run partially through webs made of nonwoven material.

The materials that make up the transport zones and the sampling zones are located in a housing. This housing has an opening 9 in the area of the sample application point, so that the sample liquid can be applied to the material below the sample application point. The housing also has openings 6 in the area of the sampling zones, into which the test elements can be inserted, so that the fleeces or fabrics of the test elements can come into contact with the material of the sampling zone. Any sample liquid-impermeable material can be used as the material for the housing, e.g. B. one, which consists of a plastic or a paper impregnated against moisture absorption.

FIG. 4 shows how a delay in the flow of liquid from the sample application point 2 to the sampling zones 4 / I, 4 / II and 4 / III can be achieved. The simultaneous wetting of the sampling zones 4 is achieved in that route B does not represent the shortest transport route for the liquid, but is extended in relation to it, so that routes A, B and C are approximately the same length.

FIG. 5 shows how a form of the capillary-active material that is suitable for the simultaneous wetting of the sampling points 4 / I, 4 / II and 4 / III can be determined. The areas F1, F2 and F3, through which sample liquid flows on the way to the individual sampling points, and which lie between the sample application point and the sampling zone, should be essentially of the same size.

In FIG. 6 the material is shown on a transport path in which a delay in the flow of liquid is achieved by vertical constriction, in this case by constant light compression of the nonwoven material. The pressure can be generated by opposite or offset webs in the bottom and / or cover part of the device. The height of these webs can be used for a different transport delay on different transport routes.

FIG. 7 shows a cross section of a transport route in which the materials involved overlap at the sample application point and the sampling zone. With a constant distance from the lid and bottom part of the device, a pressing overlap is achieved, which in turn causes a delay. The effect can be enhanced by additional inert materials.

In the event of a delay due to hydrophobic barriers, at least two possibilities are possible in principle. Impregnation of an absorbent material to be traversed by the liquid with a temporarily or permanently hydrophobicizing substance (e.g. needle impregnation 5 mm wide with 3% Mowiol / polyvinyl alcohol solution) slows down the liquid flow. In a second possibility, a material with higher hydrophobicity (e.g. a paper or a membrane) can be installed in the transport route. Such hydrophobic barriers can be integrated anywhere in the test strip between the sample application zone and the first reagent zone.

In a method according to the invention for determining a plurality of analytes contained in a sample liquid, the sample liquid is applied at a single sample application point. This can be done, for example, by pipetting or dripping on the liquid. About as much or a little more liquid is preferably added than the entire device has a capillary-active volume. Due to capillary transport, the liquid travels along the transport routes to several sampling zones. By delaying the liquid transport on the transport routes that are closest to the sample application point, a simultaneous wetting of the test elements is achieved.

The following examples are intended to illustrate the invention:

example

A piece of paper with the contours 10 of FIG. 3 is cut out of a paper TI 532 (from Binzer). This piece of paper is inserted into a housing half 8 which is injection molded from polystyrene and which contains cutouts for the contour of the paper and the test strip 5. The test strips 5 (for example Mikral® test strips from Boehringer Mannheim GmbH) are then inserted in such a way that the starting fleece or the first fleece on which the reagents are located are in direct contact with the sampling zones 4. A second housing half, which contains no cutouts for the paper or the test strips, but which has a recess in the vicinity of the sample application point 2, through which sample liquid can be applied to the sample application point, is then glued on. The entire device has a length of approximately 15 cm, a width of 7 cm and a thickness of 0.5 cm.

To perform a test for multiple analytes in a sample, approx. 10 ml urine is pipetted onto the sample application point. After a predetermined time, which depends on the reagents of the inserted test strips, the color developed at this point in time is compared with a comparison scale and a value for the presence or amount of the analyte is taken therefrom.

If only 2-3 ml of sample liquid are available, the dimensions of the capillary-active material should be approximately halved.

The same regulation can also be used for the production and use of the device shown in FIGS. 1 and 2.

Reference list

1

device according to the invention

2nd

Sample drop point

3rd

Transport route

4th

Sampling zone

5

Test element

6

Recess for the test element

7

Delay zone

4 / I, 4 / II, 4 / III

Sampling zones

8th

casing

9

Housing opening

10th

Contour of the capillary active fleece

F1, F2, F3

Areas of the capillary active material between 2 and 4

Claims (10)

Method for determining several analytes contained in a sample liquid using a multi-zone device - by applying the liquid to a single sample application point; - capillary transport of the liquid to several sampling zones over several transport routes, at least one of the transport routes containing a delay zone; and - Application of the liquid at the sampling zones on test elements which contain reagents for the determination of the analytes. A method according to claim 1, characterized in that the liquid is transported on the test elements without stopping until the reagents are reached. A method according to claim 1, characterized in that the liquid reaches the reagents on different test elements at substantially the same time. Containing device for the determination of analytes - a sample drop point, several separate sampling zones, each of which is connected to the sample application point by a capillary transport route, - several test elements for the individual determination of analytes, characterized in that a delay zone is provided on at least one of the transport routes. Device according to claim 4, characterized in that the transport routes are of equal length. Apparatus according to claim 5, characterized in that the transport routes are arranged radially. Apparatus according to claim 4, characterized in that the transport routes are of unequal length. Apparatus according to claim 4, characterized in that the cross section of the transport route in the region of the delay zone is reduced compared to the transport route without a delay zone. Device according to Claim 4, characterized in that the delay zone contains a material which delays liquid transport. Use of delay zones for the simultaneous wetting of test elements with a sample liquid.

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