Liquids Containing Suspended Glass Particles
Present proposals to use perfluorocarbons as a medium to suspend glass particles presents the problem of aggregation of the particles within the suspending medium. Overcoming this problem requires careful particle sizing and density matching techniques. An additional disadvantage of the large scale use of perfluorocarbons is their contribution to global warming. The inventor has realised that by replacing perfluorocarbons with the more environmentally friendly fluorinated ethers such as hydrofluoroethers or hydrofluoropolyethers a long lasting suspension of glass particles can be achieved without the need for such rigorous particle sizing or density matching processes.
1 . A formulation comprising an active ingredient preserved in glassy or amorphous particles, the particles being suspended in a liquid in which at least one component comprises a hydrofluoroether, perfluroether, hydrofluroamine, perfluoroamine, hydrofluorothioether, perfluorothioether hydrofluoropolyether, perfluorpolyether or a general formula
R1-X—R2 or
R1-X-(CF2Y) n (CF2CF2Z) m -R2 or
R1-[(X—CF—R2) n -(X—CF2) m ]OR3
where X, Y and Z are defined as O (oxygen), and ether, NR3 (N=nitrogen), an amine or S (sulphur); and each of R1, R2 and R3 are defined as a non-fluorinated, partially fluorinated or fully fluorinated alkyl, cycloalkyl, aryl or arylalkyl group or an organic functional group, halogen group or cyano group.
2 . A formulation according to claim 1 in which the particles contain a sugar glass or a glass which is a mixture of sugar, metal carboxylate, amino acid or calcium phosphate or any combination of these.
3 . A formulation according to claim 1 in which the particles have a density which is matched to the density of the liquid sufficiently closely that the particles will remain in suspension under normal conditions.
4 . A formulation according to claim 1 in which the liquid contains different components specified in claim 1 mixed in proportions to give a required density.
5 . A formulation according to claim 1 in which the liquid contains a perfluorocarbon mixed with one or more components specified in claim 1 .
6 . A formulation according to claim 1 in which the active ingredient is a vaccine.
7 . A formulation according to claim 1 in which the particles are made by spray drying.
8 . A formulation according to claim 1 in which the particles are made by freeze drying.
9 . A formulation according to claim 1 in which the particles are made by grinding.
10 . A method of making a formulation according to claim 4 including the step of selecting liquids to give the required density matching properties and mixing them with the particles.
11 . A formulation comprising an active ingredient preserved in glassy or amorphous particles, the particles being suspended in a liquid comprising a hydrofluoroether.