AU592771B2 - Device composed of polymers with a membrane structure and incorporated solids particles - Google Patents

Abstract

A device comprising a water-stable, preferably sheet-like polymer, having a membrane structure and incorporated solid particles, in which these particles are preferably absorbent and in which one reactant of a chemical reaction is bound to these particles. Such a device can be used as an analytical device and in particular as a testing device.

Description

I

COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number:, Lodged: 4 4/ S Complete Specification Lodged: Accepted: Published: Priority: *Related Art: t* f Ibis dtH~i~)1~LXnd tu wrn I c i 4 Namie of Applicant: Address of Applicant: 4 Ackual Inventor: &djess for Service: BEHRINGWERKE AKTI ENGE SELLSCHAFT D-3550 Marburg 1, Federal Republic of Germany G-ERHARD SC HARF EDWD. WATERS SONS, 50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

*(,ormplete Specification for the invention entitled: it DEVICE COMPOSED OF POLYMERS WITH A MEIMRANE STRUCTURE AND INCORPORATED SOLIDS PARTICLES The following statement Is a full description of this invention, Including the best mei-iod of performing It known to *-US 1.

-la- BEHRINGWERKE AKTIENGESELLSCHAFT HOE 84/B 019 Device composed of polymers with a membrane structure and incorporated solids particles The invention relates to a device of preferably twodimensional shape, composed of a waterproof polymer with a membrane structure and incorporated solid particles and containing at least one participant in a chemical reaction.

Such a device can be used as an analytical reagent and particularly as a test device, preferably as a test strip.

The use of membrane filter-like material for the preparation of test reagents, the membrane having purely the function of a paper substitute, and in which fillers including those having adsorbing properties can be incorporated, has been described in German Offenlegungsschrift S 15 2,602,975.

German Offenlegungsschrift 1,956,214 has disclosed the suspending of cellulose, crosslinked dextrans or ion exchangers as reagent carriers in organic solutions of polymers, such as ethylcellulose or cellulose acetate, and thus the coating of plastic carriers with the suspen- N sions. The disadvantages of such a method are that the Sabsorbtive character of the reagent carriers is greatly reduced.

These are incorporated in a plastic film, the pore width of the film being only insufficiently controllable by the S production process. Moreover, the pores, for example with cellulose as the incorporated material, can be sealed when the fitls are dried.

In German Offenlegungsschrift 3,007,744, test reagents in the form of modified cellulose materials are suspended in organic polymer solutions, which have the functions of an adhesive, and are applied to plastic carriers.

"ci 2 These techniques cause great difficulties if, for example, several zones of different solids materials are to be prepared, through which a development solvent is to flow successively in the sense of a chromatographic process.

In this case, the zones must have a high absorbency and be continguous, and the reactivity of reagent carriers contained therein must be preserved.

In German Offenlegungsschrift 2,922,856, which relates to a detection of glucose, various reagent solutions are applied in parallel on, for example, a paper strip by means of pens.

In German Offenlegungsschrift 2,620,923, the problem of contiguously arranging several zones of absorbent materials is solved in such a way that the materials are successively filled into small glass columns.

The inadequacy of the existing application methods is emphasized particularly by this last process. Since, in this case, a color zone, proportional to the substance, is to be obtained by the color change of a chromogenic zone when an analytical sample flows through, the zones must have a high absorbency, and their density must be reproducible when preparing them.

If test rods are used for test reagents for the sort of Spurpose described, the applied layers must have a high 2i absorbency and, in the solid which may be porous, pores must not be sealed by the preparation process. These preconditions are not guaranteed when the indicated methods are used; this applies in particular to the absorbtive character.

i In order to regulate the absorbency of polymer films, a procedure is followed in German Offenlegungsschrift 2,910,134, in which solids particles are incorporated in polymer films during the preparation of the latter. The films are "opened" in such a way that the "film opener" 470' 7« i, 3 solids particles, such as cellulose, are incorporated, it is observed that the absorbency decreases sharply in com- Sparison with, say, the same quantity of incorporated gypsum. It must be assumed here that the pores of the cellulose are at least partially sealed and that the filmforming polymer is adhesively bonded to the surface of the cellulose.

If a cellulose, which has been modified in accordance with German Offenlegungsschrift 3,016,618 to give a polymeric enzyme substrate for peroxidase, is used as the "film opener", only a very slow reaction is detectable on immersion into a solution which contains hydrogen peroxide as well as peroxidase. In order to reach the reactivity of the normal cellulose preparations even approximately, the S' polymer content of the film-forming suspension must be Vt, lowered to such an extent that adequate mechanical strength of the Layer formed is no longer ensured.

It was therefore the object of the present invention to develop a form of preparation of solids with coupled reaction systems, which overccmes the disadvantages des- I cribed.

In these forms of preparation, one constituent is to ensure the strength required for practical purposes, whereas a further incorporated constituent contains or carries at least one substance which can be a participant in a chemical reaction. Within the scope of the invention, substances which are intended to provide strength to the system are meant to be membrane-forming substances, in particular waterproof plastics with a membrane filter structure. Such a form of preparation preferably has a two-dimensional shape.

I i -i 4 The invention therefore relates to a preferably two- Sdimensional device composed of solids particLes incorporated into a waterproof polymer with a membrane filter structure, and containing one or more participants in a chemical reaction, wherein at least one reactant is bonded to solids particles.

The incorporated solids particles are preferably composed of an absorbent material, such as cellulose or celluose derivatives, crosslinked dextrans, ion exchangers, poly- 1C amides, porous glasses, macroporous polymers, zeolites, kieselguhr, porous silica, kaolin or activated carbon.

The absorbency of the incorporated particles is preserved in the above process for the preparation of such a device.

These solids particles can here also be particles with a '1'5 non-absorbent core.

Methods for bonding partners in a chemical reaction to solids are known. These methods relate to purely adsorptively bonded systems such as, for example, described as early as 1916 for the adsorption of enzymes on carbon and aluminum (Weetall, Anal. Chem. 46, 602 A (1974)).

Other materials which can be used are aluminum oxide, alumiina or glass.

Methods are also known for covalently bonding chemical n reactants such as, for example, acid-base indicators, chelate formers or biologically active substances such as Senzymes, antigens or antibodies, to such solids. For example, aminopropyl derivatives of glasses which, by means of a large number of methods, can be reacted with substances which can then later function as partners in a chemical reaction, can be obtained by reaction with aminopropyl-triethoxysilane.

JI t S re ctan s sch a, fr exmple acd-bae idicaors 5 There are also solids in which a series of adsorbed microparticles are fixed on a solid core. These microparticles can be used analogously to reaction systems incorporated in membranes.

Such reagent-carrying, non-absorbent or partially absorbent solids particles can, according to the present invention, be processed to give a mechanically strong material, the absorbency and reactivity being preserved.

The products or devices described can be produced by dissolving polymers in solvent systems which contain lowboiling solvents for the polymer, higher-boiling swelling agents and precipitating agents for the polymer. The essential point here is that the precipitating agents are preferentially absorbed by the solid to be incorporated.

5 When a solid is suspended in such a polymer solvent system and the suspension is poured out onto a substrate, a coacervate forms during the evaporation of the Low-boiling polymer solvent, the coagulation starting preferentially in the vicinity of the solids particles loaded with precipitation constituents. The result is that the precipitating polymer cannot adhesively bond to the solids particles. This gives a product in which the polymer has the structure of a hollow foam, the solids particles being enveloped by the polymer.

The invention therefore relates also to a process for preparing a device as described above, which comprises mixing the solids particles with a polymer solution, which forms membrane filters, and producing waterproof membranes.

A process, using absorbent solids particles, is preferred which comprises mixing the solids particles with a polymer solution, which forms membrane filters, the solvent system being selected such that the precipitating fractions of the solvent mixture preferentially penetrate into the r 6 absorbent solids particles, and producing membranes.

j The proportion of the waterproof polymer i tie weight of the total preparation can amount to 3-50 A process is particularly preferred in which one partner in a chemicalreaction is or has been bonded to the solids particles.

This process allows the production of contiguous zones with solids materials which may differ, products then being obtained which are suitable for a chromatographylike throughput of fluids, it being possible for the flow to pass successively through the contiguous zones.

Such a product can, for example, be used for the preparat tion of a fault-free urinary sugar test. For this purpose, the various zones can have the following functinns: zone 1 contains ion exchangers which are charged with the constituents of a buffer system; zone 2 contains a polymeric enzyme substrate based on o-dianisidine coupled to cellulose, and the enzymes required for the reactions.

If a test strip prepared in this way is immersed in glucose-containing urine, interfering constituents such as r, ascorbic acid are removed in zone 1 and, at the same time, the bonded buffer substances are released and, on flowing through zone 2, this is followed by oxidation of the glucose and of the chromogen, bonded to a polymer, by peroxidase.

Such products with sufficient stability in use cannot be produced by means of the known techniques.

The process according to the invention gives products in which solids particles are enclosed in waterproof polymers of the type of hollow foam, the absorbency of any absorbent particles being preserved and it being possible for a partner in a chemical reaction to be bonded to these i i 7 i particles.

At polymer contents of between 3 and 50,-f, preferably 6 and 35 of the total applied material after drying, the products have a very good mechanical strength.

Moreover, when the solids/polymer suspensions are poured out onto plastics carriers, welding of the polymer forming membrane filters to the substrate can be effected.

By pouring out several parallel, continuous zones, test reagents can be obtained which are suitable for solving the problems in the above-described systems operating in a manner similar to chromatography.

The process described above can also be used to produce devices consisting of more than one layer of a membrane with incorporated solid particles. In particular, if transparent carrier materials are used, further layers with filtering, light-reflecting or ion-exchanging properties may be placed on top of the chromogenic zone which is on the carrier.

It was surprising that solids which carry reactants can be incorporated into membranes in such a way that the S 20 absorbency and reactivity are preserved.

SThis is not at all self-evident, for example in the case of the incorporation of cellulose derivatives into polymer solutions which form membrane filters. Systems based on certain cellulose derivatives as the polymers forming memt 25 brane filters give hardly absorbent products, in many cases with cellulose as the filler, in usual solvent systems comprising acetone/alcohols/water. If the polymer content is lowered in order to preserve the absorbency, the products show insufficient mechanical, strength.

In order to ensure adequate absorption of the precipitating constituents by the solid, the choice of a struc- 1; 8turaly sufficiently different polymer, forming membrane filters, is essential, in addition to a sufficient differentiation in the affinity of the solvent constituents to the solid. Hydrophobic polymers, for example especially PVC or polystyrene, are suitable in the case of cellulose.

Apart from the general addition of surfactants, hydrophobic polymers such as PVC can here be substantially modified with respect to their wetting behavior by an addition of surface-active substances which are miscible with the polymer. In the case of PVC, this can be effected, for example, by adding low-molecular polyoxyethylene or trialkylmethylammonium halides.

Quite generally, the absorbency and wear resistance can be controlled by mutually independent measures. The pore width and a well formed membrane filter structure, on the one hand, and the absorbency of the solids particles, on the other hand, are essential for the absorbency. The absorbency of the product can be further improved by an addition of a detergent Jhe detergent can be used in a quantity from 0 to 25-f of the product.

The wear resistance naturally depends on the proportion of incorporated solids in the total mass. However, the 1 quality of the membrane filter structure, the rubber elasticity and the flexibility of the polymer and also the I 25 applied thickness and sedimentation of the'aolids, which may possibly take place during the evaporation step, also S.c play a role.

Well formed membrane filter structures can also be used, without incorporated solids, for pure transport functions in combination with devices according to the invention.

In particular, when several contiguous zones are applied, one zone can be used for defining the suction volume of a S- 9 sample to be analyzed. In this case, incorporated hydrophiLic solids might possibly have the disadvantage that their suction capacity depends on the degree of drying, that is to say on the atmospheric humidity and the ambient temperature.

Naturally, membrane filter zones can be processed with any desired other -,ontiguous zones, for example of paper, fibers or fabrics, to give systems, the application of which can be of importance within the scope of chromatography-like processes.

The invention is described below by reference to some nonrestrictive examples.

Example 1 I t '"0.25 g of diethylamino-cellulose was suspended in 0.025 ml of water, 0.1 ml of ethyl acetate and 1 ml of tetrahydrofuran. 0.3 g of a 10% by weight PVC solution in tetrahydrofuran was then added. After homogenization, the suspension was poured onto a glass plate and spread out to a thickness of 300 micrometers. After the drying, this gave a highly absorbing membrane with integrated cellu- S lose material.

Example 2 SAnalogously to Example 1, a suspension was prepared and, t Likewise in 300 p thickness, applied to a 0.5 mm thick PVC s e5 sheet. After drying, the material proved to be highly absorbent and to be welded to the carrier. The welded-on membrane is wear-resistant in the dry state and in the moist state. To examine the structure, the membranes welded to PVC were investigated by electron microscopy.

The images, in particular the element distribution images with respect to the element chlorine by means of an energydispersive X-ray spectrometer, confirm the presumed PVC membrane structure.

10 i Example 3 According to German Auslegeschrift 3,016,618, Example 1, a polymeric chromogen, based on cellulose as the carrier and tetramethylbenzidine as the chromogen, was prepared as an enzyme substrate for the peroxidase/hydrogen peroxide system.

0.25 g of this polymeric chromogen was suspended with 0.05 g of water, 0.1 ml of absolute alcohol, 0.9 ml of tetrahydrofuran and 0.1 ml of a 10% by volume solution of polyethylene glycol 400 in tetrahydrofuran, and 0.25 g of a 7% by weight solution of PVC in tetrahydrofuran was then added, and the suspension was homogenized after 5 minutes.

The suspension was then applied in a thickness of 300 p to a PVC carrier by means of a knife blade. After drying, this gave a highly absorbent membrane welded to the carrier. On immersion into a solution of pH 5, which contained 0.1% by volume of hydrogen peroxide and a little peroxidase, the polymeric chromogen integrated in the membrane was oxidized, a green color being formed.

Example 4 DIazotized p-aminobenzyl-cellulose was prepared according to German Offenlegungsschrift 1,956,214, Example 19.

Sodium acetate was added in small portions, with vigorous S stirring, at OOC to the solution containing hydrochloric *25 acid, until the pH value was about 4.5. The same volume of a 5% by volume solution of N,N-dimethylaniline in N,Ndimethylformamide, which was cooled beforehand to OOC, was then added and the mixture was stirred for 30 minutes in an ice bath. After filtration with suction, the cellulose product was then extensively washed with water.

The material proved to be a polymeric, non-bleeding acid/ base indicator which changes from yellow to red on addition of acid.

r 11 By means of 250 thick steel stencil showing a St.

Andrew's cross, the dried material was applied in accordance with Example 1 to a yellow-pigmented adhesive PVC label. After drying, acid-containing water produced a red warning cross.

Example For using the polymeric acid/base indicator from Example 4 for the determination of pH values, a white-pigmented PVC carrier was coated, by means of a coating apparatus, with seven parallel, 3 mm wide strips at a mutual spacing of 4 mm. The intermediate zones were coated with PVC colors of 3 mm width, the PVC colors being adapted in graduated steps of 0.2 pH to the change colors of the indicator in S the region from 4.6 to 3.4.

After drying, the carrier was cut into strips, perpendicular to the color zones.

This non-bleeding indicator test strip has advantages over the existing products in pH allocation. Due to the closely adjoining color zones of similar color structure and surface structure, the subjectively achievable accuracy of allocation is improved over existing test strips.

Example 6 0.15 g of a cellulose preparation, on which Congo Red had been absorbed by substantive dyeing, was suspended in a mixtture of 0.3 g of 10% by weight PVC in tetrahydrofuran, 0.6 ml Sof tetrahydrofuran and 0.2 ml of alcohol and applied in a thickness of 400 p to a carrier of rigid PVC.

After the evaporation of the solvents, this gave a highly absorbent and largely wear-resistant coating which can be used as an acid/base indicator which is substantially secure against bleeding.

Claims (4)

1. A device comprising: a membrane-filter like structure, made of 3 to of a waterproof polymer having 50 to 97 of solids particles loosely incorporated into said polymer one or more participants in a chemical Sreaction 4 wherein at least one reactant is bonded to solids particles. 1 2. The device as claimed in claim 1, wherein the incorporated solids particles are absorbent. S3. The device as claimed in claim 1, in a two-dimensional form.

4. The device as claimed in claim 1, wherein the proportion of the waterproof polymer is 6 to 35 The device as claimed in claim 1, wherein the proportion of solids particles is 65 to 94

6. The device as claimed in claim 1, containing 0 to e 25 of a detergent. t t

7. A process for preparing a device as claimed in claim 1, which comprises mixing the solids r particles with the polymer solution, which forms membrane filters, and producing membranes. \O o 0 1 1 i 13 I i I A process for preparing a device as claimed in claim 1, the solids particles being absorbent, which comprises mixing the solids particles with a polymer solution, which forms membrane filters, the solvent system being selected such that the precipitating fractions of the solvent mixture preferentially penetrate into the absorbent particles, and producing membranes. DATED this 24th day of October 1989. BEHRINGWERKE AKTIENGESELLSCHAFT t r WATERMARK PATENT TRADEMARK ATTORNEYS, Queen Street MELBOURNE. VIC. 3000 AUSTRALIA DBM:LPS:jl(8.27) I i:((f t "C1(I B L i I tfQfr'r E C