Biological materials such as vaccines can be stabilised in certain glassymaterials, soluble in water. It has been proposed to form these glassymaterials as a powder suspended in a non-aqueous liquid for injection into apatient. There is a problem in maintaining the suspension because theparticles tend to sink to the bottom. The problem is solved by adding ablowing agent into a solution for which the glass is formed. The blowing agentdecomposes as the solution evaporates thereby forming cavities in theresulting glass structure, reducing its density to match that of the liquid inwhich it is to be suspended. Other uses for the invention are in compositionsintended for inhalation and for rapid dissolution in aqueous solutionsimmediately before use.
