Chemistry: molecular biology and microbiology – Micro-organism – per se ; compositions thereof; proces of... – Preserving or maintaining micro-organism
Reexamination Certificate
2002-02-08
2004-11-30
Prats, Francisco (Department: 1654)
Chemistry: molecular biology and microbiology
Micro-organism, per se ; compositions thereof; proces of...
Preserving or maintaining micro-organism
C530S345000, C159S004010, C424S093100, C424S093450, C424S094100, C435S188000
Reexamination Certificate
active
06825031
ABSTRACT:
This invention relates to the stabilisation and storage of materials. The principal envisaged field of application is materials employed in the biochemical field and some pharmaceuticals.
A few biologically active materials (e.g. some proteins) are sufficiently stable that they can be isolated, purified and then stored in solution at room temperature. For most materials however this is not possible and some more elaborate form of stabilisation/storage procedure must be used.
As discussed in our co-pending European application published as EP-A-383569 a number of storage techniques are known but are not universally applicable to materials which give rise to a storage problem.
That pending application discloses the storage of materials by incorporating them into a water-soluble or water-swellable substance which is in an amorphous, glassy or (much less preferably) rubbery state.
That application discloses the preparation of storable compositions by preparing a solution of the substance(s) to be stored and a water-soluble or swellable substance, then evaporating water from the solution at room temperature or with some heating. Temperatures of 37° C. and 60° C. are exemplified. The solutions were simply held in a stationary container during drying.
It is of course considered prudent to minimise the application of heat when drying a material which is not particularly stable. Freeze drying is a prime example of this.
Spray drying is a known process for drying a solution or suspension to a solid, particulate form. The process entails delivering the solution or suspension into a flow of preheated gas, usually air, whereupon water rapidly evaporates from the droplets. It is widely used in the manufacture of detergent powders and in that field it is well known that certain materials are not stable to spray-drying conditions.
Spray drying has been used to kill microbial cells, for instance in dairy products as disclosed by A. Chopin et al, Can J. Microbiol 23, 716 (1977). EP-A-366303 discloses the use of spray drying to dry a cell composition with the intention that the cells will be killed but cell components such as enzymes will be recoverable from the dried composition. Spray drying has been used in attempts to dry microbial cells to a state of suspended animation from which viable cells can be recovered, but even in a relatively favourable case losses of 97% were recorded after 30 days storage at room temperature as disclosed by I. A. Abd el Gawad et al Egyptian Journal of Dairy Science, 17 273 (1989).
Surprisingly, we have now found that spray drying can be used to make storable compositions by drying mixtures of the material(s) to be stored and aqueous solutions of a water-soluble or water-swellable substance which forms a glassy (or possibly rubbery) state on drying.
According to this invention, therefore, we provide a process of rendering a material suitable for storage comprising spraying into a hot gas stream, an aqueous mixture of the material and a carrier substance which is water-soluble or water-swellable, thereby drying the mixture to particles in which the said carrier substance is in a glassy or rubbery state, and separating the particles from the gas stream.
This process is of course also a process for preparing a storable composition.
The aqueous mixture of the material for storage and the carrier substance will generally be formed by mixing the material with the carrier substance in the presence of water. However, it is possible that the material to be stored will be provided as a solution which already contains a substance which is able to form a glass and so is suitable as a carrier substance, so that deliberate addition of a carrier substance is unnecessary.
As will be explained in more detail below it is preferred that the composition produced by the drying procedure displays a glass transition temperature of at least 20° C., preferably at least 30° C. and possibly well above this e.g. at least 50° C.
The invention may be utilised for stable storage of a single material, or for a mixture of materials which have little or no effect on each other.
However, a further possibility is that the invention is used to produce a composition which contains a plurality of materials which (when in contact with water) form part or all of a reacting system. These materials may be fairly simple chemicals.
Yet another possibility is that the material comprises viable biological cells.
Material Stored (i) Inanimate Materials
The material(s) stabilised for storage may potentially be any of a wide range of materials which are ordinarily liable to undergo chemical reaction, and so are not stable during storage at ambient temperature of 20° C.
One category of materials to which the invention is applicable is proteins and peptides, including derivatives thereof such as glycoproteins. Such proteins and peptides may be any of: enzymes, transport proteins, e.g. haemoglobin, immunoglobulins, hormones, blood clotting factors, other blood plasma components and pharmacologically active proteins or peptides.
Another category of materials to which the invention is applicable comprises nucleosides, nucleotides, dinucleotides, oligonucleotides (say containing up to four nucleotides) and also enzyme cofactors, whether or not these are nucleotides. Enzyme substrates in general are materials to which the invention may be applied.
The material for stabilisation and storage may be isolated from a natural source, animal, plant, fungal or bacterial, may be produced by and isolated from cells grown by fermentation in artificial culture, or may be produced by chemical synthesis. Such cells may or may not be genetically transformed cells.
The material will need to be soluble in aqueous solution, at least to the extent of forming a dilute solution which can be used for incorporation into the carrier substance.
As mentioned above, a possibility is to store more than one component of a reacting system in a glass. This can be useful for materials which will be required to be used together in, for example, an assay or a diagnostic kit.
Storing the materials as a single glassy preparation provides them in a convenient form for eventual use. For instance, if an assay requires a combination of one or more substrates, and/or a cofactor and an enzyme, two or all three could be stored in a glass in the required concentration ratio and be ready for use in the assay.
If multiple materials are stored, they may be mixed together in an aqueous solution and then incorporated together into a glass. Alternatively they may be incorporated individually into separate glasses which are then mixed together.
When multiple materials are stored as a single composition (which may be two glasses mixed together) one or more of the materials may be a protein, peptide, nucleoside, nucleotide or enzyme cofactor. It is also possible that the materials may be simpler species. For instance a standard assay procedure may require pyruvate and NADH to be present together. Both can be stored alone with acceptable stability. However, when brought together in aqueous solution they begin to react. If put together in required proportions in the glassy state they do not react and the glass can be stored.
Material to be Stored (ii) Cells
In a significant development of this invention we have found that the material which is stored may comprise viable biological cells. The composition obtained by spray drying can then contain the cells in a state of suspended animation, and viable cells can be recovered from storage. Cells which may be placed in a storable condition by the method of the invention will preferably be existing as single cells, being either a single cell organism or being cells which are in culture as individual, undifferentiated cells. In particular the cells may be a bacterial culture, which may be isolated from nature or may be a laboratory or industrial bacterial strain including genetically transformed bacteria. The cells may be eukaryotic cells, notably including yeasts but also other fungal cultures. Again the cell culture may be a n
Franks Felix
Hatley Ross Henry
Mathias Sheila Frances
Coe Susan D.
Evans Susan T.
Nektar Therapeutics
Prats Francisco
LandOfFree
Storage of materials does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Storage of materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Storage of materials will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3339243