Process for the production of analytical devices

Details Process for the production of analytical devices Process for the production of analytical devices

1999-04-01

2001-03-27

Gray, Linda L. (Department: 1734)

Adhesive bonding and miscellaneous chemical manufacture

Methods

Surface bonding and/or assembly therefor

C156S257000, C156S254000, C156S268000, C156S269000, C156S270000, C422S051000, C422S051000, C422S067000

Reexamination Certificate

active

06207000

ABSTRACT:

FIELD OF THE INVENTION
The invention concerns a process for the production of analytical devices with a capillary-active zone, preferably of analytical test elements for examining liquid samples. In particular the invention concerns a process for the production of analytical devices from tape material. In addition the invention concerns analytical devices which have been produced by the process according to the invention.
BACKGROUND AND SUMMARY OF THE INVENTION
So-called carrier-bound tests (test carriers, test elements) are often used for the qualitative or quantitative analytical determination of components of liquid samples e.g. body fluids such as blood, serum or urine. In these tests the reagents are embedded in corresponding layers of a solid carrier which is contacted with the liquid sample. If a target analyte is present, the reaction of the liquid sample and reagents leads to a detectable signal, which is usually a colour transition, which can be evaluated visually or with the aid of an instrument e.g. by reflection photometry.
Test elements or test carriers are often in the form of test strips which are essentially composed of an elongate support layer made of plastic material and detection layers as test zones that are attached thereto. However, test carriers are also known which are designed as quadratic wafers.
Test elements for clinical diagnostics that are evaluated visually or by reflection photometry are frequently constructed such that the sample application zone and the detection zone are arranged above one another in a vertical axis so that for example the sample is applied from above onto a sample application zone and a change of colour is observed from below. This mode of construction is problematic. When the test strip loaded with sample has to be inserted into an instrument for example a reflection photometer, for measurement, potentially infectious sample material can come into contact with parts of the instrument and may contaminate them. Furthermore volumetric dosing can only be achieved with difficulty especially in cases in which the test strips are used by untrained persons for example in the self-control of blood sugar by diabetics. Moreover conventional test elements often require relatively large sample volumes due to their construction in order to enable reliable measurements. The more sample volume is required, the more painful the sample collection may be for the patient whose blood is to be examined. The goal is therefore to provide test strips which require as little sample material as possible.
The use of analytical test elements with capillary-active zones is one method of reliably dosing small amounts, typically a few microlitres, of sample volume and transporting it within the test element. Such test elements are described in the prior art.
EP-B 0 138 152 concerns a disposable cuvette which is suitable for almost simultaneously taking up sample liquid into a sample chamber with the aid of a capillary gap and measuring it. Reagents can be provided inside the void space of the capillary. The void space is at least partially bordered by a semi-permeable membrane. The reagents can for example be accommodated in the void space by coating the walls or by embedding the reagents in a semi-permeable membrane.
EP-A-0 287 883 describes a test element which utilizes a capillary interstitial space between a detection layer and an inert carrier for the volumetric dosing. In order to fill the capillary space, the test element is dipped into the sample to be examined which requires large sample volumes and is why this type of volumetric dosing is preferably used for examining sample material that is present in excess such as urine.
An analytical test element with a capillary-active zone is also known from EP-A 0 12 314. In order to manufacture this test element it is proposed that an intermediate layer which contains a cut-out corresponding to the capillary-active zone is placed between two plastic layers. According to EP-A 0 212 314 the cut-out should already be present in the intermediate layer before assembly. Especially when using flexible intermediate layers such as for example double-sided adhesive tapes, it is difficult to assemble the analytical element since an exact, reproducible positioning of the intermediate layer which already contains a cut-out is difficult and complicated to accomplish.
The object of the invention is to eliminate the disadvantages of the prior art. In particular the object of the present invention is to provide a process with which analytical devices can be produced cheaply, reproducibly and exactly.
The subject of the invention is a process for the production of analytical devices with a capillary-active zone in which
(a) a carrier layer is prepared;
(b) a spacer layer is laminated onto the carrier layer;
(c) a contour which determines the shape of the capillary-active zone is punched, cut or stamped through the spacer layer laminated onto the carrier layer;
(d) those parts of the spacer layer are removed from the carrier layer which are not required for shaping the capillary-active zone; and
(e) a cover layer is placed on the spacer layer so that a capillary-active zone is formed as well as analytical devices produced accordingly.
Analytical devices in the sense of the invention are understood as devices which can automatically take up sample liquids with the aid of their capillary-active zone, i.e. by capillary forces, and can make them available for a simultaneous or later analysis. The capillary-active zone can be present as a capillary gap or can be generated by using capillary-active porous materials such as e.g. fleeces, papers or membranes.
Analytical devices can preferably be analytical test elements in which suitable detection reactions which allow the determination of the presence or amount of an analyte in the sample proceed already during or after the uptake of sample liquid. However, analytical devices in the inventive sense can also be cuvettes or pipettes which only utilize the sample pick-up by the capillary zone and in which the sample is either released again for the analysis or in which the analysis occurs without subsequent reactions. The analytical devices can of course also be used to store and keep sample liquids.
The presence of a capillary-active zone in the analytical devices produced according to the invention enables an automatic uptake of a defined sample volume if the capillary-active zone is manufactured accurately and reproducibly enough. The capillary-active zone can have any desired shape provided capillarity is ensured in at least one dimension. The capillary-active zone can for example have a triangular, rectangular or semi-circular ground plan and the corners of the outlined areas are preferably rounded as a precaution against the risk of remnants of adhesive in the capillary-active zone. Capillary-active zones are preferred according to the invention with an essentially cuboid geometry i.e. with an essentially rectangular ground plan.
Many materials that are conventionally used to manufacture analytical devices can be employed as the carrier layer to produce an analytical device according to the invention such as test elements e.g. metal or plastic foils, coated papers or cardboards and, although less preferred, glass. If the analytical device is used to examine nonpolar liquids, an adequate capillarity of the capillary zone of the analytical device produced according to the invention is already achieved by using nonpolar carrier layers e.g. plastic foils. In order to achieve an adequate capillarity when examining aqueous samples such as e.g. water samples or biological liquids such as blood, serum, urine, saliva or sweat, it is advantageous if the carrier material that is used has a hydrophilic surface on at least the side facing the capillary-active zone.
In this connection hydrophilic surfaces are water-attracting surfaces. Aqueous samples, also including blood, spread well on such surfaces. Such surfaces are characterized among others in that a water drop placed on it forms

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