Biological materials such as vaccines can be stabilised in certain glassy
materials soluble in water. It has been proposed to form these glassy
materials as a powder suspended in a non-aqueous liquid for injection
into a patient. This method is complicated by the need to find suitable
compatible liquids and to stop the glassy particles from congregating in
liquid. These problems have been obviated by supporting the glassy
material on a porous membrane remote from the eluant. When the biological
material requires administration, the eluant can be passed across the
membrane dissolving the glass and causing the substance to be carried by
the liquid into the patient.