GB2041941A - Microporous Bodies having Occluded Agents - Google Patents

Abstract

To form microporous bodies having occluded in their interior active agents such as enzymes, a polymer solution is mixed with the active agent dissolved or dispersed in a liquid phase compatible and miscible with the solvent used for dissolving the polymer. The final form of the microporous bodies can be imparted by extrusion, dripping or otherwise.

Description

SPECIFICATION Preparation of Microporous Bodies Wherein One or More Active Agents Are Occluded This inention relates to a process for the preparation of microporous bodies wherein one or more active agents, more particularly those agents which display a biological activity, are occluded.

It is known from Italian Patent Specification No. 836,482 that it is possible to immobilize enzymes and preparations containing them in the interior of filamentary polymeric structures. The process is carried out by preparing an emulsion of an aqueous solution of the enzyme and of a solution of the polymer dissolved in a solvent which is immiscible with water, the emulsion being subsequently extruded through a spinneret into a coagulation bath to produce a filament which occludes, in its interior, the enzymatic solution present in the emulsion. Thus, there are obtained biological catalysts which have a high activity. However, their practical use is often limited by the shape imparted thereto by the above process and by the comparative intricacy of the process.

According to the present invention, there is provided a process for the preparation of a microporous body wherein one or more active agents are occluded. which process comprises mixing an organic solution of a polymeric matrix with the active agent or agents or with a solution or a dispersion of the active agent or agents in a medium compatible therewith and miscible with the organic solvent for the polymeric matrix, and subsequently carrying out a shaping stage.

This invention relates to an improved process for the preparation of microporous bodies which occlude active agents of any nature whatsoever, especially those which display a biological activity, and which have any shape at choice, so that their practical use, i.e. their use in the commercial preparation of the reactions in which such agents are involved, is by no means restricted. Thus, there are obtained, for example, biological catalysts with a high efficiency, the exploitation of which is not restricted by practical arrangements they must undergo, by virtue of the different shapes in which they can be obtained.

In a preferred embodiment, the present invention provides a process for the preparation of microporous bodies in which are occluded one or more active agents, such as those listed hereinafter, the process comprising (a) formation of a preliminary solution of a polymeric matrix in an organic solvent; (b) whenever necessary, formation of a dispersion or solution of the active agent concerned in a medium which is both compatible therewith and miscible with the organic solvent for the polymeric matrix; (c) possible addition of the active agent, or of the product obtained by step (b), of an additive, the nature and the function of which will be better explained hereinbelow; (d) admixing the solution of the polymeric matrix with the active agent as such or with a solution of the agent, or with a dispersion according to stage (b) above, optionally containing the additive of stage (c); (e) sending the admixture from stage (d) above to a shaping treatment.

The active agents which can be occluded according to the present invention, include biological compositions such as enzymes, enzymic cells, antigens, antibodies, antisera, hormones, and coenzymes which are bound to macromolecular matrices, and the substances which have other kinds of activity or which display particular behaviours such as sequestering agents, dyestuffs having a properly selected molecular weight and, in general, all substances for which no recovery is provided but which, in the case in point, can conversely be recovered for reuse or for reactivation for reuse as the case may be. It is to be added that it is also possible to occlude once more bodies in which active agents have already occluded, either by the process of this invention or otherwise.It is also possible to ccclude other substances deriving from the physical or chemical union of active agents with appropriate substrates. Thus, for example, it is possible to give the active agent a high degree of protection. The active agent can be occluded as such, or after having been mixed with appropriate inert fillers. The process of this invention has proven to be especially efficient for the preparation of biological catalysts, particularly in view of the possibility of obtaining such catalysts in a great variety of shapes. It is thus possible to obtain fibres, fibrids, cylindrical bodies of various sizes, ellipsoids, spheroidal bodies and powders of various grit sizes, since the shape depends upon the steps used in the shaping treatment.

The latter treatment is preferably performed by causing the mixture of the solution of the polymeric matrix of the active agent or of its dispersion, to coagulate in a medium which is a non-solvent for the polymeric matrix. The coagulation can take place, for example, by dripping the mixture into the medium (whereby there are obtained, for example, bodies having a spherical or spheroidal shape) or by causing the mixture to flow directly into the interior of the medium (whereby fibres or the like are obtained).

An alternative shaping procedure is the dry extrusion with evaporation of the solvent of the mixture. Thus, there is obtained a continuous filament which can be severed to obtain cylindrical bodies with various cross-sectional outlines.

A further shaping procedure is to eject the mixture from a pressurized enclosure, with or without the aid of a propellent, so that fibrids or powders of various grit sizes are formed.

The polymeric matrices which can be used according to the method of this invention include cellulose polymers, esterified cellulose polymers, etherified cellulose polymers, polyamides, acrylonitrile polymers, acrylonitrile copolymers, butadiene, isoprene, acrylates methacrylates, vinyl esters, vinyl chlorides, vinylidene chloride polymers, vinylidene chloride copolymers, styrene, vinyl butyrate and methyl glutamate.

Cellulose esters have proven to be especially suitable for the purposes of the present invention.

The media in which the active agents are dissolved or dispersed, whenever it is not possible to use the active agents as such, include water; alcohols (e.g. methanol, ethanol, propanol, butanol, t-butanol, ethylene glycol and glycerol); ketones (e.g. acetone and methylethylketone); ethers (e.g. dioxan, tetrahydrofuran and ethoxyethanol); esters (e.g. ethyl and methyl acetates, propyl acetate and ethyl formate); acids (e.g. acetic acid, propionic acid and formic acid); pyridine; acetonitrile; cyclohexane; and dimethylformamide.

The solvents for the polymeric matrix can be selected from a wide range of compounds, depending upon the nature of the polymeric matrix, and include acetone, methylisobutylketone, cyclohexanone, methyl acetate, methylcellosolve, ethyl lactate, methylene chloride, propylene chioride, tetrachloroethane, nitromethane, chlorophenol, metacresol, acetic acid, formic acid, dimethylformamide, dimethylsulphoxide, alcohols (e.g. ethanol), dioxane, hydrocarbons (e.g.

benzene and toluene), ketones, esters, pyridine, chloroform, mixtures of ethanol and water, carbon tetrachloride, mixtures of ethanol and carbon tetrachloride, isopropanol and methylethylketone.

The additives mentioned above have the task of aggregating or cross-linking the active agent during admixture of the latter with the polymeric matrix. The additives which can be used include (a) polymers with different molecular weight and which are not solublein the solvent for the polymeric matrix, for example polyamines (such as polyethyleneimine, cationic polyacrylamides and anionic polyacrylamides), polyamino acids (such as polyisines), sulphonated polystyrene, poiycarboxylic acids, polyvinyl alcohols and polyvinylpyrrolidone; and (b) polyfunctional reagents such as aliphatic aldehydes, isocyanates and thioisocyanates.

The invention will now be illustrated by the following Examples. In the Examples, the cellulose acetate used was obtained from Fluka, the acetone from Carlo Erba, the polyethyleneimine and the polyethyleneimine hydrochloride for Polysciences Inc., the penicillina G from Squibb, the glutaraldehyde from Merck, the glucoseisomerase powder from Godo Shusei, and the invertase from B.D.H.

Example 1 This Example describes the preparation of spherules of beta-galactooxidase obtained by occluding Saccharomyces lactis cells.

A 10% by weight solution of cellulose acetate in acetone was prepared, and, to 375 grams of this polymeric solution, there were added, with stirring, 154 g of cellular paste (35.8 g dry weight) from 2 litres of Saccharomyces lactis fermentation broth.

The cellular dispersion thus obtained was introduced into a steel container, and was extruded through a capillary tube having a diameter of 0.4 mm, by the pressure of nitrogen.

The thin extruded filament, by being-allowed to fall for a distance of about 20 centimetres, was converted into a rosary of beads which, upon dropping into a water bath, coagulated to form spherules.

There were collected about 800 g of moist spherules, which, when dried in an air stream, weighed 73 g in total. One gram of these spherules was incubated at 250C with 200 ml of a 4.75% by weight solution of anhydrous lactose in a 0.1 molar phosphate buffer having a pH of 7, which solution contained 2 millimol of MgSO4.7H2O and 1 millimol of EDTA. After a two-hour reaction, 80% of the lactose had been converted into glucose and galactose, as shown by the analysis of glucose performed by the glucose test (Boehringer).

The hydrolysis of lactose with these spherules was repeated for 20 consecutive times without any noticeable loss of acclivity.

Example 2 This Example describes the preparation of spherules of penicillin-acylase obtained by occluding E. coli cells previously treated with polyethyleneimine.

E. coli cells (20 g dry weight) containing 106 units were slurried in 875 g of water and treated for 10 minutes with stirring with 25 g of a 3.3% by weight solution of polyethyleneimine. The formation of cell aggregates took place. These aggregates readily settled.

The cellulose paste was then reslurried in a small volume of water (overall weight 127 g) and vigorously stirred with 1 57 g of a 10% by weight solution of cellulose acetate in acetone. By the procedure described in Example 1, there were prepared 35 g (dry weight) of spherules. A portion of these spherules (5 g) was incubated at 370C in 400 ml of a 6% solution of penicillina G in a 0.02 molar phosphate buffer having a pH of 8. The initial activity was as great as 60,000 units (micromol an hour of hydrolysed pencillin G), and total hydrolysis was achieved within about 4 hours. The same spherules, when used repeatedly for 20 consecutive hydrolyses, retained 60% of their initial activity.

Example 3 This Example describes the preparation of spherules of peniciilin-acylase obtained by occluding E. coli cells previously treated with polyethyleneimine and glutaraldehyde.

E. coli cells (20 g dry weight) containing 106 units were slurried in 400 g of water and stirred for 10 minutes with 25 g of a 3.3% solution of polyethyleneimine and 5 g of a 25% solution of glutaraldehyde.

The cells which collected upon settling were vigorously stirred with 1 57 g of a 10% solution of cellulose acetate in acetone.

Preparation of spherules was perfored by the procedure described in the previous Examples.

There were obtained 40 g of dry spherules, 5 g of which were used for checking the activity under the conditions of Example 2. The activity was 50,000 units, and the hydrolysis was completed in just over 4 hours. In contrast to the spherules prepared without glutaraldehyde, the spherules of this Example retain their activity unaltered relative to the initial activity.

Example 4 This Example describes the preparation of spherules of glucose-isomerase obtained by occluding Arthrobacter sp. cells previously treated with polyacrylamide (Prodefloc A/1 S).

To 10 litres of a broth culture ofArthrobacter sp. cells containing glucose-isomerase enzyme, there were added, on completion of the fermentation, 500 g of a 0.3% solution of Prodefloc A/1 S. The cellular slurry was stirred for 20 minutes, whereafter the cells settled. The cellular paste (150 g dry weight) was collected and reslurried with water until an overall weight of 600 g was attained, and then admixed vigorously with 1,500 g of a 10% solution of cellulose acetate in acetone. By the procedure disclosed in the previous Example, spherules were prepared. One gram of these spherules was incubated at 600 in 100 ml of a 50% (weight/weight) solution of glucose containing 5x10-3mol of MgSO,. 7H,O, 1O-4molofCoCl2 and 0.1 mol of Na2SO3, and having a pH of 7.By polarimetric measurements, the activity was determined as 100 international units (micromol of fructose produced in one minute) with a yield (unfolded activity/occluded activity) of 56%.

These spherules, used continuously for 20 consecutive days, did not lose their activity.

Example 5 This Example describes the preparation of spherules of glucose-isomerase obtained by occluding the enzyme in solution upon treatment with polyethyleneimine and glutaraldehyde.

An enzyme solution was prepared by dissolving 2 g of glucose-isomerase powder in 8 g of water.

To this solution, there were added, with stirring, 4 g of a 3.3% solution of polyethyleneimine and 4 g of a 2;5% solution of glutaraldehyde. This enzymic preparation was admixed with 100 g of a 10% solution of cellulose acetate in acetone at room temperature. By the procedure described in the previous Examples, spherules were prepared. The weight of the spherules, upon drying in air, was 12 g. A portion of these spherules (2 g) was incubated at 600C with 100 ml of a 50% (weight/weight) solution of glucose containing 5x 10-3 mol of MgSO4. 7H2O, 1 0- mol of CoCI2 and 0.1 mol of Na2SO3 and having a pH of 7, for determining the activity. This activity was 500 international units, and the yield was 30%--409/0.

Example 6 This Example describes the preparation of cylindrical bodies of cellulose acetate occluding polyethyleneimine as a sequestering agent.

1 5 g of cellulose acetate were dissolved in 85 g of acetone (pure reagent). To the polymeric solution, there were added, slowly and with stirring, 1 5 g of a 33% (weight/weight) aqueous solution of polyethyleneimine hydrochloride and 5 g of a 1% solution of glutaraldehyde. The mixture was transferred to a steel cylinder having connected thereto, at the top, nitrogen bottle, and, at the bottom, a spinneret immersed in a water bath. By nitrogen pressure, the mixture was extruded from the spinneret. The mixture coagulated so that a continuous filament was obtained. This filament was severed by a cutting device in samples 1-2 cm long. One gram of these cylindrical bodies was contacted for 4 hours with a cupric solution having a content of 1 8.3 ppm, obtained by dissolving CuSO4. 5H2O in distilled water.By the use of an atomicabsorption spectrophotometer (Varian-Techtron 1200), .he copper content of the solution treated with the cylinders was measured. This content was 1.1 ppm. Upon washing of the cylinders with 50 ml of normal HCI, the copper content was 1 7 ppm.

The cylinders were contacted again for 4 hours with the copper solution. The copper content of the solution was measured once more, and was found to be 1.2 ppm. This sequence of operation was repeated 10 times, and it was found that the cylinders do not lose their copper sequestering ability.

Example 7 This Example describes the preparation of fibrids of invertase obtained by occluding the enzyme in a solution to which polyvinylpyrrolidone has been added.

A solution of 50 g of invertase, after the addition thereto of 10 g of polyvinylpyrrolidone (K30), was vigorously stirred with 333 g of a 15% solution of cellulose acetate in acetone. The solution was introduced into an autoclave and was then extruded by nitrogen pressure (50 atmospheres) through a 500 micron nozzle to form a dry powder of the hybrid type, the particle size of which is in the range of 1 60-1 600 microns. The activity of the invertase enzyme occluded in the fibrids was measured on a solution of 20% sucrose in a 0.1 molar phosphate buffer having a pH of 4 and a temperature of 250C. The activity, in terms of milligrams of inverted sucrose per minute and per gram of fibrid, iies in the range of 8-50, depending upon the fibrid size.

Example 8 This Example describes the preparation of fibres of hydroxyprimidine hydrolase and Ncarbamoyl-Daminoacid hydrolase obtained by occluding Agrobacterium radiobacter cells to which polyethyleneimine has been added.

Agrobacterium radiobacter cells (4 g dry weight were slurried in 100 g of water and treated, with stirring, with 2 g of a 3% solution of polyethyleneimine. After 10 minutes, stirring was discontinued and the cells which had settled were collected and slurried in 25 g of water. The slurry was vigorously stirred with 20 g of a 20% solution of cellulose acetate in acetone. The resulting preparation was introduced into a steel cylinder having connected thereto, at its top, a nitrogen bottle and, at the bottom, a monofilament spinneret having a diameter of 1 mm. By means of a metering pump, the preparation was extruded through the spinneret in the form of a continuous filament which was allowed to dry in air by evaporation of the acetone during a drop of 4 metres. The entire thread (8 g dry weight) was incubated at 400C under a nitrogen blanket in a 0.1 molar phosphate buffer having a pH of 8 and containing 4 g of DL-phenylhydantoin, for determining the activity of the two enzymes. After 20 hours of reaction, the conversion of the hydantoin to D(-)phenylglycine was complete, as shown by an analysis made by the use of an aminoacid analyser. The same thread, when used 10 times for successive hydrolyses, iost 30% of its initial activity.

Claims (13)

Claims

1. A process for the preparation of a microporous body wherein one or more active agents are occluded, which process comprises mixing an organic solution of a polymeric matrix with the active agent or agents or with a solution or a dispersion of the active agent or agents in a medium compatible therewith and miscible with the organic solvent for the polymeric matrix, and subsequently carrying out a shaping stage.

2. A process according to Claim 1, comprising (a) forming a solution of polymeric matrix in an organic solvent; (b) if desired, forming a dispersion or solution of the active agent or agents in a medium compatible therewith and miscible with the organic solvent for the polymeric matrix; (c) if desired, addition to the active agent or agents or to the dispersion or solution obtained by step (b), an additive selected from (i) at least one polymer of different molecular weight not soluble in the solvent for the polymeric matrix and (ii) at least one polyfunctional reagent selected from aliphatic aldehydes, isocyanates and thioisocyanates; (d) mixing the solution obtained by step (a) with the active agent or agents as such, or with the dispersion or solution obtained by step (b) with or without the additive added in step (c); (e) subjecting the mixture obtained by step (d) to a shaping treatment.

3. A process according to Claim 1 or 2, wherein the shaping is performed by coagulating the mixture in a medium which is a non-solvent for the polymeric matrix.

4. A process according to Claim 3, wherein the coagulation is effected by dripping the mixture into the medium.

5. A process according to Claim 3, wherein the coagulation is effected by causing the mixture to flow directly into the medium.

6. A process according to Claim 1 or 2, wherein the shaping is performed by extrusion, in dry condition, of the mixture.

7. A process according to Claim 1 or 2, wherein the shaping is performed by ejecting the mixture from a pressurised enclosure.

8. A process according to any of Claims 1 to 7, wherein the active agent(s) is (are) selected from enzymes, enzymic cells, antigens, antibodies, antisera, hormones, coenzymes bound to macromolecular matrices, sequestering agents and dyestuffs.

9. A process according to any of Claims 1 to 8, wherein the polymeric matrix is selected from cellulose polymers, esterified and etherified alkyl or cellulose polymers, polyamides, polymers, or copolymers of acrylonitrile, butadiene, isoprene, acrylates, methacrylates, vinyl esters, vinyl chloride, vinylidene chloride, styrene, vinyl butyrate and y-methyl glutamate.

10. A process according to any of Claims 1 to 9, wherein the solvent for the polymeric matrix is selected from acetone, methylisobutylketone, cyclohexanone, methyl acetate, methylcel losolve acetate, methyl Celiosolve (registered Trade Mark), ethyl lactate, methylene chloride, propylene chloride, tetrachloroethane, nitromethane, chlorophenol, m-cresol, acetic acid, formic acid, dimethylformamide, dimethylsulphoxide, alcohols, dioxan, hydrocarbons, ketones, esters, pyridine, chloroform, mixtures of ethanol and water, ethanol and CCl4, isopropanol and methylethylketone.

11. A process according to Claim 2 or according to any of claims 3 to 10 when directly or indirectly appendant to claim 2, wherein the medium used in step (b) is selected from alcohols, ketones, ethers, esters, acids, pyridine, acetonitrile, cyclohexane and dimethylformamide.

12. A process for the preparation of a microporous body wherein one or more active agents are occluded, substantially as described in any of the foregoing Examples.

13. A microporous body wherein one or more active agents are occluded, when prepared by a process according to any of claims 1 to 12.