Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Calorimeter
Reexamination Certificate
1999-10-22
2002-09-24
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Calorimeter
C422S051000
Reexamination Certificate
active
06455001
ABSTRACT:
The present invention concerns functional layers of high precision and their production, the use of N-acyl-N-alkyl-glycinates, N-acyl-taurates and/or N-acyl-glutamates to produce these functional layers as well as test strips and in particular diagnostic test strips which carry at least one functional layer of high precision according to the invention in their test elements.
So-called carrier-bound tests are often used for the qualitative or quantitative analytical determination of components of body fluids in particular of blood. In these the reagents are present on or in corresponding layers of a solid test carrier which is contacted with the sample. The reaction of liquid sample and reagents leads to a detectable signal especially to a change in colour which can be evaluated visually or with the aid of an instrument, usually by reflection photometry.
Test carriers are frequently in the form of test strips which are essentially composed of an oblong support layer made of plastic material and detection layers mounted thereon as test fields. However, test carriers are also known which are designed as small quadratic or rectangular plates. In the following description the term “test strips” is also intended to encompass test carriers which do not have a strip shape.
Test carriers of the above-mentioned type are for example known from the German Patent document 21 18 455. This describes diagnostic test carriers for the detection of analytes in liquids which are composed of a support layer and at least one detection layer containing the detection reagents. That surface of the detection layer that does not adjoin the support layer is provided with a cover layer. The cover layer can be composed of a fine-meshed network in the form of a fabric, knitted fabric or fleece. Plastic fabrics are stated as preferred networks in order to achieve a rapid wetting of the detection layer with sample liquid and to avoid interfering chromatographic effects. In order to detect an analyte in a liquid, such a diagnostic test carrier is dipped into a corresponding liquid, preferably urine. In this manner the detection layer comes into contact with a very large excess of liquid which cannot be taken up by the test carrier. However, depending on the duration of contact of the detection layer with the liquid to be examined different colour intensities can be observed.
As a rule the results obtained are more positive the longer the contact time is. Therefore a correct quantitative analyte determination is not possible in this manner when there is a large excess of sample.
On the other hand a sample volume that is too small for a test carrier construction is a frequent cause for false measured values in diabetes monitoring i.e. the regular control of the blood of diabetics for the content of glucose.
Test carriers which require as little volume as possible are therefore the goal of diverse current developments. However, such test carriers do not only have to yield correct measured values with very small sample volumes of about 3 &mgr;l, but they must also reliably operate with relatively large sample volumes of about 15-20 &mgr;l and must hold the sample liquid. Hygienic problems could occur if the liquid runs out of the test carrier for example if potentially infectious foreign blood is measured or if the test carrier is measured with an apparatus when there is a risk of contaminating the measuring instrument.
Test strips are known from DE-A-3042857 which have a sample distribution layer (spreading layer) on their analytical elements which has the function of uniformly distributing sample liquid applied as a spot over the entire test element. This spreading layer is composed of a cloth or a foam layer which is hydrophilized by impregnation with a wetting agent and is either pressed onto the upper gelatin layer of the analytical element which is still wet or is attached thereto by means of an additional adhesive layer.
The analytical elements of these known test strips which are referred to synonymously in the literature and in the following description as test elements, test fields, detection elements, detection fields or as detection layers have two or more layers which contain the reagents necessary to detect and quantitatively determine the analyte (in this case urea) or auxiliary substances such as radiation-absorbing substances. Such layers are referred to as functional layers in the following.
Diagnostic test carriers in the form of test strips which offer a considerable advance with regard to reproducibility of the test results even when different sample volumes are applied and with regard to hygienic handling are known from EP-A-0 821 233.
They contain a support layer with a detection layer arranged thereon having one or several functional layers which contain reagents required to determine the analyte in a liquid sample and a hydrophilic, but not capillary-active, relatively coarse-meshed overlay made of a network covering the detection layer which is larger than the detection layer and is attached to the support layer on both sides of the detection layer but in contrast rests directly on the detection layer without attachment i.e. essentially is in contact with the whole surface of this without a gap.
This network rapidly passes sample liquid applied to its surface onto the underlying detection layer and leads, with the aid of a foil layer that covers the boundary regions of the network, a sample excess which may be present into the boundary regions of the network which extend beyond the detection layer. In this manner small amounts of sample are made completely available to the detection layer but false-positive results are avoided.
Developments in the prior art apparently have the aim of achieving quantitative determinations of the analytes of interest that are as accurate as possible using test strips with smaller and smaller sample volumes. The improvement of the test strip construction also goes hand in hand with a reduction of the detection areas used for the analysis. Thus for example in a known instrument that is frequently used for the routine determination of blood sugar, the GLUCOTREND® instrument, only an area of ca. 1 mm diameter of the detection layer is evaluated.
An advantage of this trend is that small amounts of sample result in readily detectable colour signals on the small areas, but there is a risk that even slight local differences in the structure of the functional or detection layers can lead to serious measuring errors.
Conventional functional layers can contain a skeleton of a fibrous or non-fibrous porous material which incorporates the reagents required to detect the analytes and auxiliary substances and additives.
It is basically necessary to use those materials for the functional layers which are able to take up the liquid to be examined together with the components contained therein. These are so-called absorbent materials such as fleeces, fabrics, knitted fabrics, membranes or other porous plastic materials which can be used as a skeleton for the layer and of course decisively determine the structure and dimensions of the layer. The materials that come into consideration for the detection layer must of course also be able to carry reagents which are required to detect the analyte to be determined. In the simplest case all reagents required to detect the analyte are located on or in such a skeleton material.
Skeleton materials that are frequently used for the functional layer are papers, the above-mentioned textile fabrics made of natural or synthetic fibres or porous plastic materials such as membranes and in particular asymmetric porous membranes in which case the sample liquid to be examined is usually applied to the large-pored side of the membrane and the analyte is determined on the fine-pored side of the membrane. Particularly preferred porous membrane materials are polyamide, polyvinylidene difluoride, polyethersulfone or polysulfone membranes, in particular polyamide 66 membranes and hydrophilized asymmetric polysulfone membranes are used. The reagents f
Knappe Wolfgang-Reinhold
Mosoiu Dan
Knauer Richard T.
Roche Diagnostics Corporation
Roche Diagnostics GmbH
Siefke Samuel P
Warden Jill
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