IE61012B1 - Container for freeze drying under sterile conditions - Google Patents

Abstract

For the freeze-drying of, in particular, biological or pharmaceutical material under sterile conditions, the material to be dried is placed in a container whose sides are at least partly composed of a hydrophobic, porous, germproof membrane which is permeable to water vapour, the container is closed pressure-tight and then the material is freeze-dried in the closed container under usual conditions.

Description

The present invention is concerned with a container for freeze drying under sterile conditions, especially for the drying of biological and/or pharmaceutical material.

In the case of biological and pharmaceutical materials, it is frequently necessary to store the materials completely dry until they are used. These sensitive substances are mostly only obtainable by freeze drying,. Furthermore, as a rule, it is necessary to keep these substances completely free from microorganisms not only because of the decomposition of biological substances brought about by micro-organisms but also in order to prevent possible infections in the case of their use.

The freeze drying of biological and pharmaceutical materials is generally known (see also Ullmanns Enzyklopadie der Technischen Chemie, 3rd edition, Vol. I, p. 556 et seq.). In order to avoid a contamination of the dried material with micro-organisms and other contaminants, laborious apparatus and processtechnical measures have to be made.

In the case of drying pharmaceutical preparations in ampoules or small bottles, the procedure is, for example, to provide small bottles which contain the frozen material with a bacterial filter and to dry the material in the small bottles in a first drying step to -310 Τ ) 25 such an extent that the sublimation of the frozen solvent is concluded.

Subsequently, in a second drying stage, i.e. the so-called post or residual drying», the still remaining residual moisture is removed from the material. Since this second drying step is usually carried out in a special apparatus- the ampoules or vials must be removed from the first drying apparatus in a further working step which is prone to contamination and introduced into the second drying apparatus. For this purposes the bacterial filter is removed and replaced by an aluminium cap provided with a rubber diaphragm and a hollow needle. After a residual drying for several days depending upon the nature of the material to be drieds the drying chamber is filled with an inert gas and with slight overpressure and the diaphragm opening closed as vapour-tightly as possible by a grouting mass.

Since the speed of sublimation in the case of this type of freeze drying is only about half as great as that of openly spread out material, the freeze drying of biological and pharmaceutical material is also carried out on plates under sterile conditions.

A solution of the material to be dried is thereby first sterilised5 for example by filtration over a sterile filters subsequently poured under sterile conditions on to plates and freeze dried by means of known methods. -4However, a prerequisite of this process is that the whole of the freeze drying plant can be sterilised. Furthermore, it is also necessary to keep the surroundings of the drying plant free from micro-organisms.

After drying has taken place, it is necessary to remove the material in the drying plant itself or in its surroundings with mechanical processes from the plates under sterile conditions and to fill it into also sterile storage containers. This process requires laborious plant and sterile chambers, as well as an especially careful working with the material to be dried or already dried until it is confectioned ready for use.

From GB-A-995930, ic was already known to freezedry radio-active aqueous solutions in vapour-permeable bags and thereby to make available for the sublimation a larger surface area than in the case of drying in bottles. The problem of a microbial contamination of the material co be dried thereby does not arise..

It is an object of the present invention to overcome the above-mentioned disadvantages and to provide a simple container with the help of which freeze dried material can be obtained without the abovementioned laborious sterility requirements for the drying plant, as well as for the space surrounding this.

Thus, according to the present invention, there is provided a container for freeze drying of especially biological or pharmaceutical material under sterile conditions., characterised in chat its sides consist at least partly of two walls connected hermetically and pressure» proof with one another on their edges, one wall of which is made from liquid-tight material and che ocher wall of a hydrophobic,, porous,, germ-tight water vapourpermeable material. -5The present invention is based on the surprising finding that, contrary to expectations, the vapour flow resulting by the sublimation of solvent molecules, which flows from the material to be dried to a condenser is hindered only to a small extent by the membrane used in the process according to the present invention.

Thus, surprisingly, the freeze drying of material which is enclosed by the membrane proceeds almost equally quickly as the freeze drying of the same material when open and non-packed.

The membranes used according to the present invention are hydrophobic membranes which contain pores which, on the one hand, are permeable for water vapour buts on the other hand, are so small that microorganisms can no longer pass through. Such pores preferably have a size of <$ 0,5 pm. and especially of < 0.2 pm. Membranes are preferably used which, under the particular process conditions., are also tearproof even in a wet state. However, the container according to the present invention can also be used with less stable membranes provided that these are strengthened with a carrier -6material or are not excessively mechanically stressed.

The particularly selected proportion of the membrane on the wall surface of che container according to che present invention depends upon the particular selected conditions and the drying period and can easily be ascertained by means of simple experiments. In one embodiment preferred according to the present inventions the whole wall surface consists of the membrane film and in a further preferred embodiment about one half of the wall surface consists of che membrane film. The container according co the present invention can also be advantageously carried out when the wall surface also only consists of up co 10% of the membrane film.

In particular, there are suitable semi-permeable papers of cellulose and usual cellulose derivatives, such as cellulose acetate.

Membranes of films of polymer compounds, for example polytetrafluoroethylene or polypropylene, can also be advantageously used. Films of sterilisation paper according to German Industrial Standard DIN 58 953 are also quite especially useful as water vapour-permeable membranes. In further preferred embodiments of the present invention^ Goretex and similar membranes or also commercially available film tubes can be used. 7In principle, any film membrane can be useds regardless of its componentss provided that they fulfil the requirements with regard to micro-organism impermeability, air permeability and especially strength given in German Industrial Standard DIN 58 953.

In a preferred embodiment» the .container according to the present invention consists of a bag or tube which consists of two walls hermetically and tightly connected with one another on their edges» one wall of which consists of a liquidtight material and the other wall of the membrane.

The membrane is preferably welded or glued with the vessel. According to the present invention» troughs are especially preferred as the vessels.

In a further preferred embodiments the trough consists of liquid-impermeable synthetic resin and preferably has a wall thickness of 0.5 to 1 mm.

The most favourable drying conditions., such as pressure, temperature and amount, depend upon the particular material to be dried and the thickness of the membrane, as well as upon the size and number of the pores thereof and must be determined by usual and simple experimentation for the particular material and the packing.

The following Examples are given for the purpose of illustrating the present invention? -8Example 1.

The testing of the micro-organism impermeability of a membrane was so carried out according to German Industrial Standard DIN 58 953 that micro-organisms in water drops were applied to test pieces and,, after drying the water drops, it was ascertained whether micro-organisms have passed through to the under side of the test pieces.

The membrane film to be tested was cut up into squares of about 50 mm. edge length and the test pieces were sterilised and dried. Each test piece of the sterilised membrane was placed on a sterilised substrate with the side which can be contaminated in the case of use upwardly and inoculated with 5 drops each of 0.1 ml. (corresponding to 10θ to 10? micro-organisms).

The test pieces were stored at a temperature of 20 to 25°C. under a relative atmospheric humidity of 40 to 60%. The drops must be completely dried within 6 hours.

Each test piece was placed with the inoculated surface upwardly on the surface of a blood agar plate (1.5% agar) so that the whole film surface came into contact with the agar. After 5 to 6 seconds, the paper was removed and the plates were incubated for 16 to 25 hours at 37°C. If the agar plates treated with such film samples show no growths the film is regarded as being C sufficiently impermeable to micro-organisms. Further statements regarding the testing of the impermeability -9of membranes to micro-organisms and especially the preparation of test micro-organism suspensions, can be taken from part 6 of German Industrial Standard DIN 58 953.

Example 2.

A nutrient solution was produced which consisted of 10 g. peptone? 5 g. glucose. 5 g. sodium chloride,» 0.084 g. monopotassium dihydrogen phosphates 0.187 g. disodium hydrogen phosphate dihydrate and pyrogen-free water ad 1.0 litre and which had been adjusted to pH 7.0. Subsequently,, it was end-sterilised in a closed, piercable bottle.

For the reception of the sterile nutrient solution to be lyophilised, there was prepared a trans15 parent sterile bag consisting of a transparent film and an appropriate paper. For this purpose, a piece with a length of 800 mm. was cut off from a commercially available roll of transparent sterilisation bag film of the firm Wipak Medical, type Steri-King R 47 which is available in the form of a tube, i.e. is welded on both sides but is otherwise open, the roll having a width of 400 mm. This tube was welded on both of the open sides with a commercially available film-welding apparatus to form a bag. Subsequently, this bag was sterilised in an autoclave with filter programme at 123°C. and 2 bar vapour pressure, the sterile bag was placed with the transparent film downwardly for better -10handling in a non-sterile sheet metal trough (VA sheet metal3 dimensions: length 800 mm., breadth 400 mm., height 30 mm.) and opened in a laminar flowbox under sterile conditions with disinfected scissors by cutting off of a corner. Through this opening of about 30 mm. between the film and the paper was introduced 1.5 litres of sterile nutrient solution via a sterile tube pushed into the opening. The so filled bag was again closed in the laminar flowbox under sterile conditions by means of a commercially available film welding device by welding over the corner.

The whole assembly (sheet metal trough, bag and sterile nutrient solution) was applied to a plate pre-cooled to -45°C. of a commercially available, nonsterilisable freeze drying apparatus of the firm Edwards + Kniese with a total positioning surface of 2 1.5m and the solution frozen in. After complete freezing in of the solution under non-sterile conditions, it was freeze dried at a pressure of 10-^ mm.Hg and a plate temperature of 22°C. and the product _3 post-dried at 10 mm.Hg, again under non-sterile conditions. The total drying time was about 72 hours.

The so obtained freeze-dried material, present as a pale brown powder in the transparent sterilisation bag, was subsequently introduced into a laminar flowbox and dissolved in 1.5 litres of sterile water. For this purpose, the intended puncturing point was disinfected -11with alcohol on the paper side, by means of a sterile canula and appropriate sterile syringe a total of 1.5 litres of sterile water was introduced into the bag, the dried material dissolved and the solution transferred into a sterile bottle. This solution was incubated for 4 days at 37°C. and subsequently the micro-organism count of the incubated solution determined by the membrane filter method.

It was shown that no micro-organisms had been 10 entrained by the freeze drying.

Claims (11)

1. „ Container for freeze drying of especially biological or pharmaceutical material under sterile conditions, characterised in that its sides consist at least 5 partly of two walls connected hermetically and pressureproof with one another on their edges, one wall of which is made from liquid-tight material and the other wall of a hydrophobic, porous s germ-tight water vapourpermeable material. 10

2. , Container according to claim 1, characterised in that the pores of the membrane have a size of <^0-5 pm,.

3. Container according to claim 2 S characterised in that the pores of the membrane have a size of <· 0,.2 pm,,

4. Container according to one of claims 1 to 3,. 15 characterised in that the membrane is a film with the properties according to DIN 58 953»

5. » Container according to one of claims 1 to 4, characterised in that the membrane consists of semipermeable paper.«, preferably of cellulose and cellulose 20 derivatives.

6. ,, Container according to claim 5,, characterised in that the membrane consists of cellulose acetate.

7. Container according co claim 1 co 4 # , characterised in that the membrane is β film of a polymer compound „ 25 preferably of polytetrafluoroethylene or polypropylene.

8. Container according to claim 1 to characterised in that it is formed as tube or bag. P - 13

9. Container according to claim 1 to 7 1 , characterised in that it is formed as flask, ampoule or vial which is closed with the membrane.

10. Container according to claim 1 to 7, characterised 5 in that it is forced as trough which is connected pressure-proof with the membrane as covering.

11. A container according to claim 1 f substantially as hereinbefore described and exemplified.