Storage of materials

Abstract

A material or mixture of materials which is not itself storage stable is rendered storage stable by incorporation into a water-soluble or swellable glassy or rubbery composition which can then be stored at ambient temperature. Recovery is by adding aqueous solution to the composition.

Description

where I is the initial LDH activity (units/ml) in the solution used to prepare the glass.

The preparation was assayed periodically for LDH activity, as described in Example 1. No loss of activity could be detected after 1 month storage at 25° C.

The glass temperature of the preparation was determined by differential scanning calorimetry as 32° C.

EXAMPLE 3

To 1 g Ficoll 400 were added 100 μl of a solution of EcoR I restriction endonuclease in 50% aqueous glycerol and a glass was prepared as described in Example 1. The final preparation was stored for 10 days in the laboratory with temperatures fluctuating between 20 and 30° C.

A quantity of the preparation equivalent to 2 units of enzyme, based on the assumption that the enzyme was still fully active, was dissolved in the following buffer: 100 mM Tris-HCl pH 7.5. 10 mM MgCl₂. 50 mM NaCl. 0.1 mg/ml bovine serum albumin. An assay for enzyme activity was carried out by the following procedure (which is taken from LKB Laboratory Manual: LKB 2013 Miniphor Submarine Electrophoresis Unit 1985, Chapter 6). The solution was incubated with 1 μg lamda-DNA for 1 hour at 37° C. Electrophoresis of the incubation mixture was then carried out on Q.5% agarose gel in Tris/borate buffer in standard manner. The DNA breakdown bands observed on the gel corresponded exactly with those of a control run with a fresh enzyme solution.

EXAMPLE 4

A solution containing 100 mg/ml NADH and 33 mg/ml pyruvate was prepared. 0.4 ml of this solution were incorporated into 4 g of a sucrose glass and the mixture processed, as described in Example 2. The mixed glass was stored in 20 mg quantities in spectrophotometer cuvettes which were closed with sealing film and kept in a laboratory where the temperature fluctuated between 20 and 35° C. The glass was stored for 14 days.

For purposes of assay, the contents of a cuvette were dissolved in 2.7ml of 0.01M phosphate buffer (pH 7.0) and 0.1 ml of a LDH solution containing 1 unit/ml was added. The absorbance at 340 nm was recorded at 30 second intervals for a total period of 3 minutes and the temperature of the solution was measured. The apparent LDH enzyme activity was determined from the period during which the absorbance change was linear with time. The activity was calculated as in Example 1. A control assay was carried out with fresh solutions of NADH and pyruvate. The apparent activity obtained using the dissolved glass closely matched the control value.

EXAMPLE 5

The active material was glutamate dehydrogenase. 532 mg of Ficoll 400 DL as used to Example 1 was added to 20 ml of a glutamate dehydrogenase solution, containing 13.3 mg/ml protein. The protein:Ficoll ratio was therefore 1.2. The sample was then divided into eighty 0.25 ml portions and dried at 37° C. under reduced pressure (about 80% of atmospheric) for 24 hours. The sample was then divided into two batches of 40 vials. One batch was heated under reduced pressure for a further two hours at 60° C. The batches were then further subdivided and stored under a range of conditions (see below). Vials were periodically rehydrated by adding 2.23 ml of 50 mM Tris/HCl buffer at pH 7.5, containing 0.3 mM EDTA to give a solution which, assuming no loss of activity, would have contained 100 units of enzyme per ml. This was serially diluted to 1 unit/ml in the same buffer. The actual activity of the recovered enzyme was determined. The assay procedure for recovered enzyme made use of the following solutions:

Solutions

• • 1. 50 mM Tris/HCL pH 7.5+0.3 mM EDTA
  • 2. 4.5 mg/ml NADH in solution 1
  • 3. 4.0125 g NH₄Cl in 25 ml H₂O
  • 4. 97 mg α-ketoglutarate (disodium salt) in 50 ml solution 1.

To carry out the assay 2.6 ml of solution 4.0.2 ml of solution 3 and 0.1 ml of solution 2 were mixed in a 3 ml cuvette. 0.1 ml of the recovered enzymes solution was added. The absorbance at 340 nm was observed over 5 minutes and the activity of the enzyme calculated from the change (ΔA) in absorbance during the 5 minute period. Activity was calculated using the following formula: $\text{Activity (units/ml)}=\frac{\Delta A\times 3}{5\times 0.622}$

The results obtained are set out in the following Table in which “initial activity” denotes the activity of enzyme which was recovered after only a minimal period of storage. The activities are quoted as percentages of the theoretical value of activity assuming this had been retained fully. A quantity of a commercially freeze-dried glutamate dehydrogenase (whose activity before freeze drying was stated by the supplier) was divided into several portions and stored at 25° C. for varying periods and assayed in the same way. Its activity is also quoted as percentages of the theoretical activity. The results for this material ar included in the Table.

Process	Storage
Temp-	Temp-	Initial	Duration of Storage (weeks)
erature	erature	Activity	1	2	3	4	6	12
37° C.	ambient	97%	95%	99%		98%	86%
37° C.	35° C.	97%	78%	82%		87%	84%
37° C.	25° C.	130%	122%	121%	83%	69%		74%
60° C.	ambient	103%	109%	96%		85%	98%	97%
60° C.	35° C.	103%	102%	105%		96%	116%
60° C.	25° C.	121%	114%	125%	84%	81%		89%
Freeze-	25° C.	56%	40%	35%	33%	36%
dried

As can be seen from these results, experimental error gives rise to some variation in FIGURES, but these do nevertheless show very substantial retention of activity over prolonged storage and much better retention of activity than with freeze-dried material.

EXAMPLE 6

2.50 ml of ascorbate oxidase (21.25 mg protein) solution was prepared. To this was added 2.50 ml of Tris buffer pH 7.6 containing 21.25 mg Ficoll 400, giving a protein:Ficoll weight ratio of 1:1. This was then divided into ten 0.5 ml portions and dried at 37° C. under reduced pressure of about 80% of atmospheric for 24 hours. The samples were next heated, still under reduced pressure, for a further two hours at 60° C. Storage was on a laboratory shelf (temperature fluctuations between 17 and 28° C.). After varying periods of storage, samples were rehydrated by addition of 2.5 ml of 0.4 mM Na₂HPO₄ containing 0.5% Bovine serum albumin. It was then serially diluted to more of the same solution so that its activity would be 0.2 units/ml, if activity had been fully retained, and assayed. The activity relative to the starting value was determined.

Assay was carried out using a standard assay procedure published by Boeringer Mannheim. The assay monitors the decrease in absorbance at 245 nm as the enzyme catalyses the oxidation of a known solution of ascorbic acid. Enzyme which had been stored for 2 months at 35° C. was found, within the limits of experimental error, to have the same activity as enzyme which was stored for only a very short time.

EXAMPLE 7

Lactate dehydrogenase was incorporated into Ficoll 400 using the procedure of Example 5. The Ficoll:enzyme ratio was 0.23:0.26. Samples were stored for various periods and then recovered by adding 0.01M phosphate buffer in a quantity which would give a theoretical activity of 1 unit/ml, assuming full retention of activity. The recovered solutions were assayed using the procedure set out in Example 1. The measured activity of recovered material, as a percentage of the theoretical activity was:

Before	Storage period (days)
Drying	1	14	21	28	35	180
100%	91%	81%	91%	112%	97%	98%

EXAMPLE 8

Cytochrome C reductase was incorporated into Ficoll 400 by the procedure of Example 5. The ratio of enzyme:Ficoll was 1:1. Samples were subjected to an accelerated test, viz. stored for 14 days at 35° C., and then recovered by adding 4 ml of 0.2M KHCO₃ to give a solution with a theoretical activity of 0.87 unit/ml assuming full retention of activity. The recovered material was assayed using a procedure given in “Methods in Enzymology” by Mahler, Volume II 1955 p. 688. It was found that the recovered material had an activity of 88% of the theoretical value.

EXAMPLE 9

Glycerol-3-phosphate dehydrogenase was incorporated into Ficoll 400 by the procedure of Examples. The ratio of enzyme:Ficoll was 1:2. Samples were subjected to an accelerated storage test by storage at 35° C. After 7 days storage the material was recovered by adding 0.05M Tris/HCl buffer at pH 7.6. This also contained 2 mg/ml albumin and 0.74 mg/ml EDTA. The recovered material was assayed using a procedure published by Biozyme Laboratories in which the enzyme catalyses the reaction: ##STR00001##
and the oxidation of NADH is followed spectrophotometrically at 340 nm.

It was found that after 7 days storage at 35° C. the activity was 96% of the activity of a control sample which was rehydrated immediately after being incorporated into Ficoll.

EXAMPLE 10

Alpha-glucosidase was incorporated into Ficoll 400 using the procedure of Example 5. The Ficoll:enzyme ratio was 1:1. As an accelerated test, samples were stored for various periods at 35° C. and then recovered by adding 4 mls of 0.067M phosphate buffer at pH 7.0 to give a solution whose theoretical activity, assuming full retention of activity, was 2 units/ml. The recovered solutions were assayed by a procedure described by H. Halvorson, Methods in Enzymology 8 559 (1966). The actual activity of recovered material relative to the theoretical value was:

Before	Storage period (days at 35° C.)
Drying	1	4	11	90
100%	100%	103%	95%	70%

EXAMPLE 11

Pyruvate: 5 g of Ficoll 400 was added to 20 ml of 10 mM sodium pyruvate solution. The solution was then divided into 40 portions, each containing 0.25 ml portions and processed in the manner described for Example 5 to give glasses.

NADH: 5 g of Ficoll 400 was added to 20 ml of a 2 mg/ml NADH solution. This was divided into 40 portions, each containing 0.25 ml, and processed as in Example 5 to give glasses.

At intervals following storage one sample of each reagent was rehydrated and the solutions mixed. They were assayed by the standard method described in Example 4. After 3 months storage at ambient temperature their ability to react in the LDH assay was 100% of the control value obtained at the initiation of storage.

EXAMPLE 12

NADH and pyruvate were processed as in Example 11. Portions of each resulting glass powder were mixed together. One such mixture was at once rehydrated and assayed by the procedure of Example 4. The reaction mixture consisted of 2.8 mls 0.01M phosphate buffer, 0.1 ml of rehydrated NADH/pyruvate mixture, and 0.1 mls of 1 unit/ml enzyme solution. The change in absorbance at 340 nm over three minutes was defined as 100%.

A further mixture was stored for one week and then rehydrated and assayed in the same way. Within the limits of experimental error, its activity was the same. Thus there had been no reaction of the NADH and pyruvate during storage.

EXAMPLE 13

A range of carrier materials were used in a standard procedure in which the stored active material is lactate dehydrogenase. In each case, a solution consisting of 0.05 g of carrier dissolved in 100 ml 0.01M phosphate buffer was prepared. 1 ml of 10 mg/ml lactate dehydrogenase solution was then added to 20 ml of the prepared solution. The solution thus created was divided into 0.5 ml aliquots in glass vials. These were dried under reduced pressure of about 80% atmospheric in a vacuum oven at 36° C. for 24 hours. After drying the vials were sealed and stored at ambient temperature. The product had a carrier:protein ratio by weight of 1:0.22.

Some samples were rehydrated immediately by addition of phosphate buffer. Others were stored for various lengths of time and then rehydrated. The activity of enzyme was determined as in Example 1. Activity of enzyme is expressed, in each case, as activity relative to that of enzyme rehydrated in the first week after drying. Results are set out in the following Table, in which “PVP” denotes polyvinylpyrollidone, “GPS” denotes 6-O-α-D-glucopyranosyl-D-sorbitol. “Palatinit” is a product of Südzucker Aktiengesellschaft, Mannheim-Ochsenfurt. Germany, and consisting of an equimolecular mixture of α-D-glucopyranosyl-1,6-mannitol and α-D-glucopyranosyl-1,6-sorbitol.

	Storage period at 25° C. (weeks)
Carrier	1	2	3	4	5	6	8	10	12	16
Malto-	100	114		91		96	68	71	101	94
trose
Poly-	100	132		123		103	116	146	103
dextrose
Inulin	100	99		91		95	114	98	91
Stachy-	100	122		137		140	109	106	127
ose
Dextran	100	81		71		89	102	91	95	84
Sorbose	100	93	75	76		55	66	65	58	62
Poly-	100	100	80		71		53	62	55	63
acryl-
amide
PVP	100	75		76		70	62
GPS	100	124
Pala-	100	99
tinit

Claims

1. A composition which is storage stable at 20° C. comprising:

i) a carrier substance which is water-soluble or water-swellable and is in a glassy amorpous state;

ii) at least one material to be stored, which is unstable in aqueous solution at room temperature of 20° C. dissolved in said amorphous carrier substance, said composition existing in a glassy state at 20° C.

2. A composition according to claim 1 wherein the material to be stored is selected from proteins, peptides, nucleosides, nucleotides, dimers or oligomers of nucleosides or nucleotides, enzyme cofactors, and derivatives of any of the foregoing having one or more additional moieties bound thereto.

3. A composition according to claim 1 having a water content not exceeding 4% by weight.

4. A composition according to claim 1 wherein the composition displays a glass transition temperature of at least 30° C.

5. A composition according to claim 1 wherein carrier substance is selected from carbohydrates and derivatives thereof which are polyhydroxy compounds.

6. A composition according to claim 5 wherein the carrier substance is a sugar polymer containing sugar residues linked through ether bridges to bifunctional groups other than carbohydrate.

7. A composition according to claim 1 wherein the carrier substance is a synthetic polymer.

8. A composition according to claim 1 wherein said material to be stored comprises a material which is unstable when alone in aqueous solution at room temperature.

9. A composition according to claim 1 wherein said material to be stored comprises a plurality of materials.

10. A composition according to claim 9 wherein said material to be stored comprises a plurality of materials which react together in aqueous solution.

11. A composition according to claim 1 which can be stored without refrigeration for at least 1 week.

12. A method of rendering a material storage stable a 20° C., which material is unstable in aqueous solution at room temperature of 20° C., comprising dissolving the material in a carrier substance which is water-soluble or water-swellable, or to a solution thereof, so that the material is dissolved in said carrier substance, and forming the resulting mixture into a glassy amorphous state, said mixture existing in said glassy state at 20° C.

13. A method according to claim 12 wherein forming the said mixture into an amorphous state is effected by evaporation under subatmospheric pressure.

14. A method according to claim 13 wherein evaporation is commenced at a temperature of 20 to 40° C. and subsequently continued at a temperature of 40 to 70° C.

15. A method according to claim 13 wherein the subatmospheric pressure is not greater than 90% of atmospheric.

16. In a method of storing a material, which material is unstable in aqueous solution at 20° C., the improvement comprising dissolving the material in a carrier substance which is water-soluble or water-swellable, or in a solution thereof, so that the material is dissolved in said carrier substance, forming the resulting mixture into a glassy amorphous state and storing the mixture in said glassy amorphous state without refrigeration for at least one week.

17. A composition which is storage-stable at 20° C., comprising:

(1) a carrier substance which is water-soluble or water-swellable and is in a glassy state;

(2) at least one material to be stored which is dissolved in said carrier substance;

wherein said composition exists in a glassy state at 20° C.;

wherein said at least one material comprises a purified biologically active material that is unstable in aqueous solution at 20° C.;

wherein said purified biologically active material is selected from the group consisting of peptides, proteins, nucleosides, nucleotides, dimers or oligomers of nucleosides or nucleotides, enzymes, enzyme cofactors and derivatives of any of the foregoing, said derivatives having one or more additional moieties bound thereto;

wherein said composition contains no more than 4 percent by weight of water; and

wherein said biological active material is not rennin.

18. A composition which is storage-stable at 20° C., comprising:

(1) a carrier substance which is water-soluble or water-swellable and

(2) at least one material to be stored which is dissolved in said carrier substance;

wherein said composition has the property that it exists in a glassy state when at 20° C.;

wherein said at least one material comprises a purified biologically active material that is unstable in aqueous solution at 20° C.;

wherein said biologically active material is selected from the group consisting of peptides, proteins, nucleosides, nucleotides, dimers or oligomers of nucleosides or nucleotides, enzymes, enzyme cofactors and derivatives of any of the foregoing, said

with proviso that when said at least one material comprises an enzyme, said enzyme comprises an enzyme selected from restriction enzymes, dehydrogenase enzymes, oxidase enzymes, and reductase enzymes.

19. A composition which is storage-stable at 20° C., comprising:

(1) a carrier substance which is water-soluble or water-swellable and

(2) at least one material to be stored which is dissolved in said carrier substance;

wherein said composition has the property that it exists in a glassy state when at 20° C;

wherein said at least one material comprises a purified biologically active material that is unstable in aqueous solution at 20° C;

wherein said biologically active material is selected from the group consisting of peptides, proteins, nucleosides, nucleotides, dimers or oligomers of nucleosides or nucleotides, enzymes, enzyme cofactors and derivatives of any of the foregoing, said derivatives having one or more additional moieties bound thereto; and

wherein said biologically active material is not freeze stable; and

with proviso that when said at least one material comprises an enzyme, said enzyme comprises an enzyme selected from dehydrogenase enzymes, restriction enzymes, oxidase enzymes, and reductase enzymes.