Preparation of ionically cross-linked polyphosphazene microspheresy by coacervation
 A method is provided for preparing polyphosphazene microspheres wherein the polyphosphazene microspheres are produced by coacervation. A solution containing a polyphosphazene is admixed with a solution containing a salt of a monovalent ion such as a salt of a Group I element (for example, NaCl) to form a dispersion containing polyphosphazene coacervate microdroplets. The dispersion then is admixed with a solution containing a salt of a multivalent ion, such as a salt of a Group II element (for example, CaCl.sub.2) to form a suspension of polyphosphazene microspheres. The polyphosphazene microspheres then are recovered from the suspension. Such method enables one to obtain high yields of microspheres having a controlled size distribution. Polyphosphazene microspheres containing biological material can be produced by providing a biological material in the polyphosphazene solution that is mixed with the solution containing a salt of a monovalent ion. The biological material may be an antigen or other biological material selected from proteins, nucleic acids, polysaccharides and synthetic compounds having biological activity. 
Virus Research Institute, Inc.
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A61K A61K A61K A61P A61K C12N A61P Y10S C07F A61P A61P Y02A C08G A61K A61P Y10T A61P
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Alexander K. Jianping
Andrianov Chen