Posted by Ellen on October 15, 2002 at 10:22:53:
United States Patent 6,465,226
Zimmermann October 15, 2002
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Preparing small microcapsules containing high concentration of cells or tissue
Abstract
Biologically active substances such as cells or tissue are microencapsulated by methods that provide a high proportion of microcapsules containing a core of the biologically active substance as compared to microcapsules not containing the biologically active substance. Microcapsules are obtained having a maximum diameter of 300 micrometers and a high concentration of biologically active substance. A solution of encapsulating material such as alginate containing dispersed biologically active substance is passed through an inner channel of a two-channel spray nozzle to form droplets containing a core of the biologically active substance. Air flow from an outer channel of the nozzle causes the droplets to break off from the nozzle. Conditions of air flow and flow rate of solution are selected to obtain droplets having a volume of 1.5 to 4 times the volume of the biologically active substance that forms the core. The droplets are passed to a precipitation bath containing polycations such as barium ions where the encapsulating material is gelled to form microcapsules containing a core of the biologically active substance and empty microcapsules not containing the biologically active substance. The microcapsules are passed to a density centrifugal separator where the empty microcapsules are separated to obtain the microcapsules containing the biologically active substance. In an alternative method, an electrostatic field is used to separate the droplets from the nozzle.
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Inventors: Zimmermann; Ulrich (Pfarrer-Frohlich-Strasse 17, D-97295, Waldbrunn, DE)