Cells or tissue coated with non-fibrogenic alginate less than 200 .mu.m thick
First Claim
1. Coated cells for transplanting wherein the cells have a smooth, uniform and continuous coating less than 200 μ
- m thick, consisting essentially of a non-fibrogenic alginate, said coated cells produced by a process comprising the steps;
(a) dispersing the cells in an aqueous solution of the non-fibrogenic alginate containing less than 1 wt. % fucose, less than 0.5 wt. % sulfate, less than 0.01 wt. % phloroglucinol and being free from fibrinogenic concentration of protein, and having a mannuronate to guluronate ratio of from 1.2 to 6, to form a suspension;
(b) discharging the suspension of step (a) from a reservoir and through an orifice of an electrostatic apparatus in a continuous attenuated stream forming droplets in an electrostatic field created by said electrostatic apparatus, said droplets expelled from the orifice placed above an electroconductive liquid capable of gelling the polymer;
(c) applying a first electrostatic continuous DC voltage on the orifice and a second electrostatic continuous DC voltage on the electroconductive liquid of step (b) generating a continuous constant electrical potential while the suspension is being discharged from the orifice in the continuous stream, the electrical potential being sufficient to continuously attenuate the stream of suspension to form a continuous stream of droplets having the same size; and
(d) collecting the formed droplets in the electroconductive liquid capable of gelling the alginate to form a continuous, smooth and uniform coating on the cells less than 200 μ
m thick resulting in formation of said coated cells;
wherein the alginate solution of step (a) has a viscosity of from about 30 to about 250 centipoises;
wherein the orifice of step (b) has a diameter of from about 0.1 to 2 mm; and
wherein the electroconductive liquid of step (b) comprises an aqueous electrolyte solution containing a concentration of alkaline earth metal ions sufficient to gel the alginate.
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Abstract
An electrostatic process is used for coating a biological material with a uniform, continuous polymer layer by discharging a suspension of the biological material in a gelable coating polymer solution in a continuous stream through an orifice into an electrostatic field. The stream is attenuated to form droplets by maintaining an electrostatic voltage between the needle and the gelling solution which is sufficient to maintain an attraction of at least 1×10-6 newtons on the stream of liquid leaving the needle, and the droplets are collected in a gelling solution. A preferred product is pancreatic islets having a continuous, smooth coating of high polymannuronate non-fibrogenic alginate having a thickness less than 200 μm such as about 20-200 μm. The alginate preferably contains less than 1 wt. % fucose, less than 0.5 wt. % sulfate and less than 0.01 wt. % phloroglucinol, is free of fibrinoogenic concentration of protein, and has a mannuronate to guluronate ratio of from 1.2 to 6. Preferably, the electrostatic field is formed by applying an electrostatic continuous DC voltage to each the needle and gelling solution so that the needle and solution have opposite charges.
24 Citations
18 Claims
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1. Coated cells for transplanting wherein the cells have a smooth, uniform and continuous coating less than 200 μ
- m thick, consisting essentially of a non-fibrogenic alginate, said coated cells produced by a process comprising the steps;
(a) dispersing the cells in an aqueous solution of the non-fibrogenic alginate containing less than 1 wt. % fucose, less than 0.5 wt. % sulfate, less than 0.01 wt. % phloroglucinol and being free from fibrinogenic concentration of protein, and having a mannuronate to guluronate ratio of from 1.2 to 6, to form a suspension; (b) discharging the suspension of step (a) from a reservoir and through an orifice of an electrostatic apparatus in a continuous attenuated stream forming droplets in an electrostatic field created by said electrostatic apparatus, said droplets expelled from the orifice placed above an electroconductive liquid capable of gelling the polymer; (c) applying a first electrostatic continuous DC voltage on the orifice and a second electrostatic continuous DC voltage on the electroconductive liquid of step (b) generating a continuous constant electrical potential while the suspension is being discharged from the orifice in the continuous stream, the electrical potential being sufficient to continuously attenuate the stream of suspension to form a continuous stream of droplets having the same size; and (d) collecting the formed droplets in the electroconductive liquid capable of gelling the alginate to form a continuous, smooth and uniform coating on the cells less than 200 μ
m thick resulting in formation of said coated cells;wherein the alginate solution of step (a) has a viscosity of from about 30 to about 250 centipoises; wherein the orifice of step (b) has a diameter of from about 0.1 to 2 mm; and wherein the electroconductive liquid of step (b) comprises an aqueous electrolyte solution containing a concentration of alkaline earth metal ions sufficient to gel the alginate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- m thick, consisting essentially of a non-fibrogenic alginate, said coated cells produced by a process comprising the steps;
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9. A coated pancreatic islet tissue for transplanting coated with a smooth, uniform and continuous coating less than 200 μ
- m thick, consisting essentially of a non-fibrogenic alginate, said coating produced by a process comprising the steps;
(a) dispersing the pancreatic islet tissue in an aqueous solution of the non-fibrogenic alginate containing less than 1 wt. % fucose, less than 0.5 wt. % sulfate, less than 0.01 wt. % phloroglucinol and being free from fibrinogenic concentration of protein, and having a mannuronate to guluronate moiety ratio of from 1.2 to 6, to form a suspension; (b) discharging the suspension of step (b) from a reservoir and through an orifice of an electrostatic apparatus in a continuously attenuated stream forming droplets in an electrostatic field created by the apparatus, said droplets expelled from the orifice placed above an electroconductive liquid capable of gelling the polymer; (c) applying a first electrostatic continuous DC voltage on the orifice and a second electrostatic continuous DC voltage on the electroconductive liquid of step (b) generating a continuous constant electrical potential while the suspension is being discharged from the orifice in the continuous stream, the electrical potential being sufficient to continuously attenuate the stream of suspension to form a continuous stream of droplets having the same size; and (d) collecting the droplets in the electroconductive liquid capable of gelling the alginate and forming a continuous, smooth and uniform coating on the pancreatic islet tissue less than 200 μ
m thick resulting in formation of said coated pancreatic islet tissue;wherein the solution of step (a) has a viscosity of from about 50 to about 150 centipoises; wherein the orifice of step (b) has a diameter of from about 0.1 to 2 mm; and wherein the electroconductive liquid of step (b) comprises an aqueous electrolyte solution containing a concentration of alkaline earth metal ions sufficient to gel the alginate. - View Dependent Claims (10, 11, 12, 13, 14, 15)
- m thick, consisting essentially of a non-fibrogenic alginate, said coating produced by a process comprising the steps;
- 16. The coated pancreatic islet tissue is wherein the electrostatic continuous DC voltage of step (c) is from 1 to 400 KV.
Specification