GB1574414A

GB1574414A - Composite materials

Info

Publication number: GB1574414A
Application number: GB51345/75A
Authority: GB
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1975-12-15
Filing date: 1975-12-15
Publication date: 1980-09-03

Description

(54) IMPROVEMENTS IN OR RELATING TO COMPOSITE MATERIALS (71) We UNITED KINGDOM ATOMIC ENERGY AUTHORITY, London, a British Authority do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to composite materials.

According to one aspect of the present invention there is provided a composite material comprising a plurality of discrete particles of a porous rigid support material having a deformable gel retained within the pore structure of the particles of porous rigid support material.

By "deformable gel we mean a gel which itself is a non-rigid material (e.g. a xerogel). Such deformable gels include organic polymeric materials and certain inorganic materials, for example, silicic acid.

Preferably the discrete particles of porous rigid support material are discrete porous particles of inorganic material which may be prepared in accordance with our British Patent Application No. 58374/71 now British Patent 1421531 (corresponding US Patent is No. 3943072)).

The term "aerogel" has been used in the art to describe a rigid, preformed matrix containing ports and this term and the term "xerogel" are discussed in "An Introduction to Permeation Chromatography" by R. Epton and C. Holloway issued by Koch-Light Laboratories Ltd.

In one preferred embodiment of the present invention the deformable gel is an organic polymeric material chosen so as to be interactive with chemical species (e.g. macromolecules such as proteins) in solution so that the composite material is capable of sorbing chemical species from solution. The organic polymeric material can be chosen such that the interaction is predominantly chemical (for example ion exchange) or predominantly physical (for example possessing the ability to delay permeation of chemical species physically as in the case of gel filtration media and molecular sieve materials).

Examples of organic polymeric materials which can be used in accordance with the present invention are celluloses and polysaccharides to which ion exchange groupings can be, or have been, attached, and gel filtration celluloses.

In view of the foregoing statements in this specification it will be appreciated that the present invention is concerned with the provision of a rigid "skeleton" as a support for a non-rigid deformable gel. Thus deformable gels which have, or can be treated to have, useful interactive properties, but which are difficult or inconvenient to handle because of their non-rigid nature, are incorporated into a composite material of the present invention which, due to the rigidity imparted by the porous rigid support material "skeleton", can be handled and used more easily.

Thus composite material comprising discrete porous particles with a deformable gel retained therein can be loaded into, and used, conveniently in column systems.

Thus ion exchange celluloses and ion exchange polysaccharides hereinbefore mentioned have useful sorptive capacity for proteins but due to their non-rigid, deformable nature are not easily handled nor used in column separation apparatus.

We have found however that if celluloses or polysaccharides of this type are retained in accordance with the invention in discrete porous particles (for example porous particles of Celite (Registered Trade Mark) made in accordance with our British Patent (US Patent) hereinbefore mentioned) the composite material comprising cellulose, or polysaccharide, and rigid support material have been found to possess desirable properties. Thus the particles of composite material tend to settle readily in aqueous media and can be used to form columns having good flow properties. Also the particles of composite material tend to be stable and not liable to release "fines".

The particles of composite material can therefore be introduced into columns and used to function chromatographically with regard to systems containing selected chemical species (for example macromolecules such as proteins).

According to another apsect the present invention provides a method for preparing a composite material of a deformable gel retained in the pore structure of a plurality of discrete particles of a porous rigid support material which comprises introducing a precursor for the gel into the pore structure of a plurality of discrete particles of a pourous rigid support material and treating the precursor to form and retain the deformable gel in the pore structure of the particles.

It will be appreciated that the majority of the gel will be present in the internal pore structure of the particles of the porous rigid support material but also it should be noted that some gel may be formed on the surface of the particles of support material.

The gel as formed by treating the precursor may be itself interactive towards chemical species. Alternatively the gel can be formed and retained in the pore structure of the support material and subsequently further treated to make it chemically inter-active towards chemical species; i.e. the gel can be treated to make it chemically inter-active in situ in the porous rigid support material (e.g. by introducing chemical groups (such as amino or carboxylic acid) into a retained cellulose of a polysaccharide gel to form an ion exchange cellulose gel or an ion exchange polysaccharide gel composite material by known techniques.

Furthermore, the gel may be treated to couple a biologicall active substance (e.g. an enzyme) to the gel (e.g. cellulose) by known techniques. Thus, for example, an enzyme may be coupled to a cellulose gel by the carbonate link described by J.

F. Kenedy, S. A. Barber and A. Rosevear'in J. Chem. Soc., perkin Transactions I, (1973) p. 2293.

As a further alternative the gel may be chosen to have or treated to have affinity chromatography properties. The treatment can be by modifying or adding further species (e.g. ligands) to the gel. For example a composite material comprising an agarose gel retained within the pores of discrete porous celite particles can be treated to add to the gel an affinity chromatography ligand capable of retaining proteins (e.g. albumin) from human plasma (e.g. the dye Cibacron Blue 30-A ex Ciba Geigy).

Examples of discrete particles of porous rigid support materials suitable for use in forming composite materials in accordance with the present invention are disclosed in our British Patent No. 1421531 (US Patent No. 3943072) hereinbefore mentioned. Using one of the discrete porous particle materials disclosed therein we have prepared discrete particles of composite materials comprising porous rigid particles of Celite having cellulose retained therein and discrete particles comprising porous rigid particles of Celite having polysaccharides retained therein.

Celite (Registered Trade Mark) is a natural diatom-aceous earth produced by Johns-Manville Corporation.

According to one embodiment of the method of the present invention the precursor can be introduced into the pore structure of the discrete particles of porous rigid support material in solution and the solution in the support material subsequently treated with a precipitating agent to cause precipitation of a gel from the precursor solution.

An example of this embodiment of the invention is the precipitation (i.e.

deposition) of rayon gel in the pore structure by introducing an aqueous solution of the cuprammonium complex of cellulose into the pore structure and subsequently treating the solution retained in the pore structure with dilute mineral acid to cause precipitation in the pores.

Further examples of precipitation reactions which may be used in carrying out the method of the present invention are (i) the regeneration of celluloses or cellulosic ion exchangers from solutions of the corresponding xanthates (e.g. by decomposition of the xanthates of cellulose, DEAE-cellulose or CMC-cellulose by aqueous mineral acids) and (ii) decomposition of a silicate by mineral acid to give silicic acid gel.

In another embodiment of the method of the present invention a precursor can be introduced into the pore structure of the discrete particles of porous rigid support material and subsequently polymerized to form a polymer gel in the pore structure (e.g. acrylic acid derivatives may be introduced to the pore structure and subsequently polymerized to give gels of polymers and co-polymers of the derivatives).

In a further embodiment of the invention cross-linking of the precursor can be used to form a gel. The cross-linking may be carried out with a chemical crosslinking chemical agent by diffusing the agent into the pore structure in order to react with the precursor. It is very desirable to carry out the cross-linking under conditions such that significant quantities of precursor cannot diffuse out of the particles of porous rigid support material whilst the cross-linking agent is diffusing into the porous rigid support material. This can be achieved by temporarily retaining the precursor in the support material (e.g. by precipitation) and subsequently treating the precipitated precursor to cross link it. Where the precursor has been introduced to the porous material in aqueous solution precipitation can be achieved, for example, by contacting the aqueous precursor solution with a water miscible organic solvent (e.g. acetone) capable of removing water from the aqueous solution thereby to precipitate precursor in the pore structure.

For example DEAE--dextran can be precipitated from aqueous solution using acetone as the water miscible organic solvent and cross-linked by use of epichlorhydrin. Further examples of substances which can be used to produce a deformable gel in a composite material in accordance with the present invention by precipitation and cross-linking are dextran, dextran sulphate, CMC-cellulose, acrylamide, agarose and polyvinyl alcohol.

Where the precursor, precipitation mechanism and cross-linking agent are such that the cross-linking of the precursor to form the gel is slow in comparison with the rate of precipitation, the precursor and cross-linking agent can be introduced into the pore structure of the porous rigid support material together in one solution (i.e. because precipitation will be effected before cross-linking occurs).

To assist in maximising the amount of the deformable gel retained in the pore structure of the discrete particles of porous rigid support material where, in accordance with an embodiment of the method of the invention a solution of precursor is contacted with the particles of porous rigid support material to introduce precursor into the pore structure, we prefer that the volume of the solution of precursor contacted with the particles of support material (e.g. by soaking the particles of support material in the solution) is approximately equal to the volume required to fill the pore structure of the particles. It will be appreciated that to minimise the amount of deformable gel formed outside the pore structure of the particles the volume of the solution should not exceed the volume required to fill the pore structure.

Also we prefer that the volume of any reagent solutions used to treat the precursor in the pore structure to form a gel is not substantially in excess of that required to immerse the porous rigid support material.

It will be appreciated that the present invention is not limited to composite material which can be used in aqueous solution and that composite materials can be prepared which may be used in non-aqueous systems.

It will be appreciated that the deformable gel and particles of porous rigid support material should be substantially insoluble in fluid substances with which they may be contacted in use (e.g. solutions containing chemical species to be sorbed and eluting agents).

According to a further aspect the invention provides a method for sorbing chemical species from a solution comprising contacting the solution with a composite comprising a plurality of discrete particles of a porous rigid support material having a deformable gel retained within the pore structure of the particles of porous rigid support material.

The invention also provides a composite material whenever prepared by a method in accordance with the invention.

Also the invention provides a composite material obtainable by a method in accordance with the invention.

Cibacron Blue 3G-A is a group specific ligand and is known to interact specifically with the nucleotide binding side of certain enzymes (e.g. kinases and dehydrogenases).

The structure of Cibacron Blue 36-A is as follows:

The invention will now be further described, by way of example only, as follows: Example 1.

A composite material was prepared comprising an ion exchange xerogel retained within the pore structure of an aerogel porous rigid support material. An aqueous solution (15 ml) of diethylaminoethyl (DEAE) dextran (15 g/tOO ml; ex Pharmacia Fine Chemical) was contacted with, and allowed to soak into the pores of a porous rigid support material comprising porous particles of Celite prepared in accordance with out British Patent No. 1421531 (US Patent No. 3943072) (20 ml bed of 35W500 y particles). This was done by adding about 16 ml of solution until all the particles were just covered. The particles were then contacted with acetone (20 ml) whereupon DEAE--dextran was precipitated in the pores from the sdlution therein.

The particles were agitated to ensure mixing and subsequently the supernatant liquid, comprising acetone and unretained precipitated DEAE-dextran, was poured off.

The particles containing precipitated DEAE-dextran were further treated to cross-link the precursor as follows: acetone (20 ml) was contacted with the particles subsequently epichlor-hydrin (1.5 ml) (a cross-linking agent) and triethylamine (4 ml) (a base) were added and, after mixing, the cross-linking reaction was allowed to proceed for 22 hours at ambient temperature.

The particles of composite material (comprising ion exchange xerogel and porous support material) were then washed free of reagents using water and the ion - exchange properties investigated.

The particles of composite material were found to remove protein (haemoglobin) from a solution containing 5 mg protein per ml. Subsequently the particles which were perceptively brown after taking up protein, were washed to remove unbound protein, and the bound protein subsequently removed, by use of dilute alkali, for assay.

Porous particles of Celite, (as hereinbefore mentioned) not treated in accordance with the present invention, were contacted with the haemoglobin solution in a control experiment.

The assay results showed that four times as much haemoglobin was recovered from the particles of composite material as from the porous particles of Celite.

Example 2.

An essentially similar procedure to that in Example 1 was followed except that in the cross-linking dimethylformamide (4 ml) (a base) was used with the crosslinking agent epichlorhydrin. Assay results showed that three times as much haemoglobin was removed from the composite material produced in this example as from porous particles of Celite used as a control experiment.

By calcining it was determined that the composite material of Example 2 contained 39 carbohydrate by weight.

Example 3.

A composite material was prepared comprising a cellulosic xerogel retained within the pore structure of an aerogel porous rigid support material.

An aqueous solution of cuprammonium cellulose (16 ml) was contacted with, and allowed to soak into, the pore structure of a porous rigid support material comprising porous particles of Celite prepared in accordance with our British Patent No. 1421531 (US Patent No. 3943072 (20 ml bed of 350--500 u particles).

Cellulose was precipitated within the pores by rapidly mixing the soaked particles with dilute sulphuric acid ( 2N) thereby to give a composite material comprising cellulose gel retained within the porous particles of Celite. Unbound cellulose was removed by vigorous washing with water.

The composite was found to exhibit gel filtration properties in that it was capable of separating dextran blue from methyl red and cobalt ions from dextran blue.

By calcination it was determined that the composite material of this example contained 1.5% by weight organic material.

Example 4.

In this Example the composite material prepared in Example 2 was investigated with respect to its ability to sorb protein from solution.

A column (0.5 cm diameter by length 10 cm) was packed with the composite material. The particles settled quickly after pouring and the column was then ready for use.

The column was equilibrated with 5 mM TRIS buffer (pH8) and subsequently haemoglobin dissolved in the same buffer (lOmg I ml) was introduced to the column such that haemoglobin was sorbed by the particles of composite material.

Further TRIS buffer was passed through the column and it was noted that a red/brown colour band (of haemoglobin) was retained at the top of the column.

A 0.1 M sodium chloride solution was passed through the column and the haemoglobin band was eluted from the particles.

Example 5.

A hot aqueous solution of agarose (4% w/v) was mixed with porous particles of Celite (as disclosed in our British Patent 1421531 (US Patent 3943072); 400-700 p dia) until the porous particles were completely filled. The mixture was boiled for 5 minutes and excess liquid poured off the particles. The agarose was gelled by pouring the particles into a fluidised bed of cold water.

The agarose in the porous particles was cross-linked as follows: The particles were washed in 0.5 M caustic soda solution and then reacted with epichlorhydrin (10 ml) in 0.5 M caustic soda (50 ml) for 2+ hrs at 609. The resulting slurry was agitated at intervals to distribute the epichlorhydrin. The resulting particles were washed and stored in water. By drying and pyrolysis at 700 , it was estimated that the composite contained 8.8% by weight organic material.

Example ,6hd pores particle 6.

A hot aqueous agarose solution (50 ml) and porous particles of Celite (of the kind used in Example 5) (75 ml) were mixed together and allowed to cool thereby to form an agarose gel within the celite particles. Any agglomerations were broken down by lightly brushing through a 1200 p mesh sieve.

The agarose was then cross-linked by the following procedure: The agarose/Celite particle composite was added to an emulsion (prewarmed to 600C) formed by stirring together 50 ml 1M NaOH, 10 mls epichlorhydrin and 2.5 g "TWEEN 20" (Trade Mark of Hercules Chemical Company for a surfactant).

The composite and emulsion were kept at 600C for 2 hours and subsequently the composite was found to contain 10.1% organic material.

Example 7.

The procedure of Example 5 was followed to produce agarose precipitated in porous particles of Celite with the exception that the particles were washed with tetrahydrofuran and the cross-linking was carried in a solution of epichlorhydrin (10 ml) and triethylamine (10 ml) in tetrahydrofuran (50 ml) for 3 hrs at 200. The resulting composite contained 7.9% organic material.

Example 8.

Porous particles of Celite (of the kind used in Example 5) were soaked in a hot 4 aqueous solution of agarose and an agarose gel precipitated in the particles by dropping the mixture into cold hexane. The agarose was cross-linked as in Example 5. The composite contained 3.2% organic material.

Example 9.

A composite of agarose and particles of Celite was prepared as in Example 5 with the exception that cross-linking was achieved with a solution of epichlor hydrin (10 ml) in 0.5M caustic soda in 1:1 aqueous dimethyl sulphoxide for 2+ hrs at 60". The organic material content of the particles was 2.7%.

Example 10.

A solution of egg albumin (100 mg/ml, 15 ml) was soaked into porous particles of Celite (of the kind described in Example 5) (20 ml) and a solution of 2% tannic acid in water (50ml) was added to precipitate the albumin. Excess liquid was decanted off and the particles heated to 600 for 2+ hrs to denature the albumin thereby to render it insoluble.

Example 11.

A solution of acrylamide (3.1 g), + bis acrylamide (0.04 g) in 58 ml of water were degassed and mixed with 0.09ml of TEMED (Registered Trade Mark) (NNN'N'-tetramethyl 1:2 diaminoethane). An aqueous solution of ammonium persulphate (3 ml, 15 mg/ml) was added to initiate polymerisation and the solution soaked into porous particles of Celite (of the kind used in Example 5) (100 ml) in a flask which was purged with nitrogen. The nitrogen blanket was maintained for 20 min when the particles were washed, brushed through a sieve and stored in water.

The inorganic content was 10.7%.

Example 12.

A hot aqueous solution of poly vinyl alcohol (10%) was soaked into porous particles of Celite (of the kind used in Example 5) and the poly vinyl alcohol in the particles precipitated with cold acetone. The particles were washed in 0.5M caustic soda in acetone/water (3:2), then added to 40 ml of this solvent containing 5 ml of epichlorhydrin and kept at room temperature for 2+ hrs. The organic content of the composite was 7.0%.

Example 13.

A mixture qf 50 ml of hot 10% aqueous poly vinyl alcohol and porous particles of Celite (of the kind used in Example 5) (75 ml) were added to cold acetone to precipitate poly vinyl alcohol in the particles. The particles were then reacted with epichlorhydrin (5 ml) and 0.5M caustic soda in 1:1 aqueous acetone (25 ml) at room temperature for 4+ hrs. The organic content was 9.8%.

Example 14.

A solution of cellulose acetate in acetone (5 ml), 8.0% was soaked into 10 ml porous particles of Celite (of the kind used in Example 5) and the cellulose acetate precipitated by adding water (15 ml). The cellulose acetate (ester) was saponified with 10 ml of 1M caustic soda for 6 hours. The organic content off the composite was 6.3%.

Example 15.

5 ml of particles of an agarose/Celite particle composite prepared in accordance with Example 5 were covered with a 12.5% solution of titanium chloride in hydrochloric acid and dried overnight in an oven at 450. The particles were washed and soaked in a solution of amyloglucosidase (A.B.M. LE90) overnight at 4"C to give a light brown particulate product being a composite of Celite, agarose and amyloglucosidase. When asseyed for enzyme activity using thinned starch as the substrate the enzyme bearing composite was found to be 50% more active than a sample of TiCI4 activated celite treated with amyloglucosidase overnight at 40C.

Example 16.

An example of an alubumin/Celite particle composite described in Example 10 was soaked in a 5% solution of glutaraldehyde for 2+ hrs, washed, covered by a solution of amyloglucosidase (A.B.M. LE90) and left overnight at 4"C. The activity of the resulting enzyme bearing composite was similar to that of the enzyme bearing composite in Example 15.

Example 17.

The proportion of the pore volume of the composite materials of Examples 5 and 11 accessible to molecules of different sizes (gel permeation properties) was determined by mixing equal volumes of the particles of composite material and solutions of marker compounds of known M.Wt (1 mg/ml in 1% salt). The particles were shaken with the solutions, centrifuged and the dilution of the marker estimated by measuring the OD of the supernatant solution at 280 nm.

The results are presented in the following table.

i)ilution factor Markers in order of increasing M.Wt Agarose/celite Acrylamide/celite Myoglobin 1.9 2.1 Ovalbumin 1.7 1.7 y-globulin 1.6 1.3 Blue Dextran 1.5 1.5 Note: The smaller the dilusion factor the less of the pore volume is available to that molecule.

Example 18.

An agarose/Celite particle composite as prepared in accordance with Example 5 (8.8% organic content) was treated to introduce affinlty chromatography properties thereto by the covalent coupling an affinity chromatography dye to the agarose.

Thus, 5 mls of the composite were washed in water, the water was decanted and 5 ml of water added. The composite was heated to 600C and a solution of Cibacron Blue 3G-A in water (4% w/v, 1 ml) was added and the particles and solution mixed. After 15 minutes sodium chloride (0.5 g) was added, the mixture was heated to 900C and a solution of sodium carbonate (10% w/v, 1 ml) added.

After I hour at 900C the blue particles were washed and investigated with respect to their capacity to remove albumin from solution.

Thus, the particles were mixed with a solution of human plasma ( I mg protein/ml) in 3% sodium chloride solution. After 20 minutes the particles were washed, the protein desorbed with an equal volume of 400 mM potassium thio cyanate in 1% sodium chloride solution and the soluble protein estimated by its adsorption at 280 nm. The W280 value was 0.388. (W28Oo is Optical Density at 280 nm in a 10 mum cell).

Example 19.

10 ml of a solution containing hydroxethyl methacrylate (1.1 ml) and bis acryl amide (0.015 g) in 0.1M tris buffer (pH 7.5) were dry mixed with porous particles of Celite (15 ml) (of the kind used in Example 5). The mixture was deaerated and purged with nitrogen before being irradiated with 1 Megarad of y-radiation. The particles were washed and found to contain 12.4% organic material.

A sample of the composite particles was treated with Cibacron Blue 3G-A as in Example 18.

The capacity of the particles to remove albumin from solution was tested as in Example 18 and the W21800 of the thiocyanate extract was - 0.181.

Example 20.

A sample of the composite prepared in Example 13 was treated with Cibacron Blue 30-A as in Example 18 to give deep blue composite particles.

The albumin removal capacity of these particles was tested as in Example 18 and the W,208 of the thiocyanate extract was 0.100.

Examples 21 to 24.

These Examples relate to the production of ampholytic ion exchange composites.

Four solutions were used; polyethylene imine (BDH 10%) (Example 21) and three solutions containing polyethylene imine (BDH 10%) mixed in various ratios with monosodium glutamate (20UXo). (Examples 22-24).

.5 ml samples of the four solutions wer dry mixed with 8 ml samples of porous particles of Celite (of the kind used in Example 5) and a 1:1 mixture of acetone/50% glutaraldehyde (10 ml) was added. This localised the solution in the particles. The reaction proceded for 8 hrs at 200 before the particles were washed and their ion exchange capacity determined by back titration with N hydrochloric acid. This capacity ranged from 3.5 mequivalents/ml of the mixture containing no glutamate to 2.5 meq/ml of one containing 3 parts glutamate to 1 part imine. The maximum buffering capacity for the ampholyte composites was as shown in the following table:

Composite pH Ex. 21 - imine alone 5.5 Ex. 22 - 3 parts imine : 1 part glutamate 5.0 Ex. 23 - 1 part imine : 1 part ,, 4.7 Ex. 24 - 1 ,, ,, 3 parts ,, 2.7 Examples 25 to 29.

Solutions of polyethylene imine (1 part) and monosodium

Example 30.

An agarose compound was treated to impart ion exchange properties thereto.

Agarose/Celite particle composite (prepared as in Example 5) (75 ml) was washed in I M sodium hydroxide and subsequently mixed with a solution of chloro.ethylamine hydrochloride (5 g) in I M sodium hydroxide to form a slurry. The slurry was heated to 900 for 2 hrs and then washed free of reagent.

The ability of the ion exchange composite material thus produced to bind heamoglobin was tested as in Example 1. The composite material bound twice as much haemoglobin as a control sample of Celite.

WHAT WE CLAIM IS: 1. A composite material comprising a plurality of discrete particles of a porous rigid support material having a deformable gel (as hereinbefore defined) retained within the pore structure of the particles of porous rigid support material.

2. A composite material as claimed in Claim 1, wherein the deformable gel is capable of sorbing chemical species from solution, or has ion exchange properties, or gel permeation properties or molecular sieve properties.

3. A composite material as claimed in Claim I or Claim 2, wherein the discrete porous particles are those prepared in accordance with our British Patent No.

1,421,531.

4. A composite material as claimed in any one of Claims 1 to 3, wherein the deformable gel is an organic polymeric material.

5. A composite material as claimed in Claim 4, wherein the organic polymeric material has ion exchange properties.

6. A composite material as claimed in Claim 4, wherein the organic polymeric material has gel filtration or molecular sieve properties.

7. A composite material as claimed in any one of Claims 4 to 6, wherein the organic polymeric material is a polysaccharide.

8. A composite material as claimed in Claim 7, wherein the polysaccharide is a cellulose.

9. A composite material as claimed in any one of Claims 1 to 8, in the form of discrete particles comprising discrete porous rigid particles of a natural diatomaceous earth having a polysaccharide retained therein.

10. A composite material as claimed in any one of Claims 1 to 9 wherein a biologically active substance is coupled to the deformable gel.

I 1. A method for preparing a composite material of a deformable gel (as hereinbefore defined) retained in the pore structure of a plurality of discrete particles of a porous rigid support material which comprises introducing a precursor for the gel into the pore structure of a plurality of discrete particles of a porous rigid support material and treating the precursor to form and retain the deformable gel in the pore structure of the particles.

12. A method as claimed in Claim 11 wherein the precursor is introduced into the pore structure of the particles of porous rigid support material in solution and the solution in the support material is subsequently treated with a precipitating agent to cause precipitation of a gel from the precursor solution.

13. A method as claimed in Claim 11 or 12 wherein the deformable gel is an organic polymeric material.

14. A method as claimed in any one of Claims 11 to 13 wherein the gel is interactive towards chemical species.

15. A method as claimed in any one of claims 11 to 13 wherein the gel is treatedto make it chemically inter-active in situ in the porous rigid support material.

16. A method as claimed in Claim 12 wherein an aqueous solution of a cuprammonium complex of cellulose is introduced into the pore structure of the particles and subsequently the solution retained in the pore structure is treated with dilute mineral acid to precipitate rayon gel in the pore structure.

17. A method as claimed in Claim 12 wherein a cellulose or a cellulosic ion exchanger is precipitated in the pore structure of the particles by regeneration of the cellulose or cellulosic ion exchanger from a solution of the corresponding xanthate.

18. A method as claimed in Claim 12 wherein a silicic acid gel is precipitated in the pore structure by of the particles decomposing a silicate by mineral acid.

19. A method as claimed in Claim 11 wherein the precursor is introduced into the pore structure of the particles of the porous rigid support material and is subsequently polymerised to form a polymer gel in the pore structure of the particles.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 30. An agarose compound was treated to impart ion exchange properties thereto. Agarose/Celite particle composite (prepared as in Example 5) (75 ml) was washed in I M sodium hydroxide and subsequently mixed with a solution of chloro.ethylamine hydrochloride (5 g) in I M sodium hydroxide to form a slurry. The slurry was heated to 900 for 2 hrs and then washed free of reagent. The ability of the ion exchange composite material thus produced to bind heamoglobin was tested as in Example 1. The composite material bound twice as much haemoglobin as a control sample of Celite. WHAT WE CLAIM IS:

1. A composite material comprising a plurality of discrete particles of a porous rigid support material having a deformable gel (as hereinbefore defined) retained within the pore structure of the particles of porous rigid support material.

1,421,531.

20. A method as claimed in Claim 11 wherein the precursor is introduced into

the pore structure of the porous rigid support and is cross-linked to form a gel.

21. A method as claimed in Claim 20 wherein the precursor is temporarily retained in the pore structure by precipitation prior to cross-linking.

22. A method as claimed in Claim 20 wherein the precursor is introduced into the pore structure of the particles of the porous rigid support material in aqueous olution and the aqueous solution in the pore structure is contacted with a water miscible organic solvent capable of removing water from the aqueous solution thereby to precipitate precursor in the pore structure of the particles.

23. A method as claimed in Claim 11 wherein the precursor is dextran, DEAEdextran, dextran sulphate, CMC%cellulose, acrylamide, agarose or poly vinyl alcohol.

24. A composite material whenever prepared by a method as claimed in any one of claims 14 to 23.

25. A composite material substantially as hereinbefore described with reference to any one of Examples 1 to 17 and 30.

26. A method for preparing a composite material substantially as hereinbefore described with reference to any one of Examples 1 to 16.