Microencapsulation process and products therefrom

• US 5,407,609 A
• Filed: 05/17/1993
• Issued: 04/18/1995
• Est. Priority Date: 05/04/1989
• Status: Expired due to Term

• Current Assignee: Brookwood Pharmaceuticals Inc (Surmodics Incorporated)
• Original Assignee: Southwest Research Institute
• Inventors: Tice, Thomas R., Gilley, Richard M.
• Primary Examiner(s): Stoll, Robert L.
• Assistant Examiner(s): COVERT, JOHN
• Application Number:
  US08/062,696
• Time in Patent Office: 701 Days
• Field of Search: 264/4.1, 264/4.6, 427/213.3, 427/213.36, 424/490, 424/491, 424/497, 428/402.21, 428/402.22, 428/402.24
• US Class Current: 264/4.6
• CPC Class Codes: A61K 9/1694 resulting in granules or microspheres of the matrix type containing more than 5% of excipient
• CPC Class Codes: A61K 9/5089 Processes
• CPC Class Codes: B01J 13/12 removing solvent from the wall-forming material solution

Abstract

A method of microencapsulating an agent to form a microencapsulated product, having the steps of dispersing an effective amount of the agent in a solvent containing a dissolved wall forming material to form a dispersion, combining the dispersion with an effective amount of a continuous process medium to form an emulsion that contains the process medium and microdroplets having the agent, the solvent and the wall forming material and adding rapidly the emulsion to an effective amount of an extraction medium to extract the solvent from the microdroplets to form the microencapsulated product.

Claims

1. An emulsion-based method of microencapsulating an agent to form a microencapsulated product, comprising the steps of:

a) dissolving or dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of a continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction media.

2. The method of claim 1, wherein said adding step comprises the addition of said emulsion to said extraction medium within 3 minutes.

3. The method of claim 1, wherein said dispersing step comprises dissolving said agent in said solvent.

4. The method of claim 1, wherein said solvent is immiscible with said process medium.

5. The method of claim 1, wherein said process medium is water.

6. The method of claim 1, wherein said process medium is an organic solvent.

7. The method of claim 1, wherein said process medium is an oil.

8. The method of claim 1, wherein said process medium contains a surfactant.

9. The method of claim 8, wherein said surfactant is present in the process medium from about 0.1% to about 20% by weight.

10. The method of claim 1, and further comprising the step of saturating said process medium with said solvent prior to said step of adding said dispersion to said continuous process medium.

11. The method of claim 1, and further comprising the step of preventing the evaporation of said solvent from said microdroplets.

12. The method of claim 1, wherein said extraction medium is water.

13. The process of claim 1, wherein said extraction medium is an organic solvent.

14. The method of claim 1, wherein said extraction medium is an oil.

15. The method of claim 1, and further comprising the step of dissolving an effective amount of a salt in said extraction medium to adjust its ionic strength.

16. The method of claim 1, and further comprising the step of controlling the pH of said extraction medium by adding an acid or base.

17. The method of claim 1, and further comprising the step of separating said microencapsulated product from said extraction medium.

18. The method of claim 1, wherein said agent is a highly water soluble compound.

19. The method of claim 1, wherein said agent has a solubility of greater than 10 milligrams per milliliter in said continuous process medium.

20. The method of claim 1, wherein the ratio of said agent to said wall forming material in said dispersion is high to affect the porosity of said microencapsulated product.

21. The method of claim 1, wherein the percentage of said agent to said wall forming material in said dispersion is greater than 20 wt. %.

22. The method of claim 1, wherein the percentage of said agent to said wall forming material in said dispersion is from about 20 wt. % to about 80 wt. %.

23. The method of claim 1, wherein the percentage of said agent to said wall forming material in said dispersion is low to affect the porosity of said microencapsulated product.

24. The method of claim 1, wherein the percentage of said agent to said wall forming material in said dispersion is less than 20 wt. %.

25. The method of claim 1, wherein said continuous process medium is soluble in said solvent to control the porosity of said microencapsulated product.

26. The method of claim 1, wherein said continuous process medium has a solubility of from about 2% to about 25% in said solvent to provide said microencapsulated product with a high porosity.

27. The method of claim 1, wherein said continuous process medium has a solubility of less than about 2% in said solvent.

28. The method of claim 1, wherein said solvent is selected from the group consisting of ethyl acetate, diethyl carbonate, chloroform and methylene chloride and said continuous process medium is water.

29. The method of claim 1, wherein said agent is soluble in said continuous process medium.

30. The method of claim 1, wherein said agent has a solubility greater than 100 mg/mL in said continuous process medium.

31. The method of claim 1, and further comprising the step prior to step b) of mixing a water soluble auxiliary compound with said agent.

32. The method of claim 31, wherein said auxiliary compound has a solubility greater than 100 mg/mL in said continuous process medium.

33. The method of claim 31, wherein said auxiliary compound has a solubility greater than 1 gram/mL in said continuous process medium.

34. The method of claim 31, wherein said agent is a solid compound.

35. The method of claim 34, wherein said microcapsule exhibits zero-order release kinetics.

36. The method of claim 31, wherein said auxiliary compound has a solubility greater than 100 mg/mL in said extraction medium.

37. The method of claim 31, wherein said auxiliary compound has a solubility greater than 1 gram/mL in said extraction medium.

38. The method of claim 1, wherein said agent is a solid compound.

39. The method of claim 1, wherein said agent is a liquid.

40. The method of claim 1, wherein the percentage of wall forming material to solvent in said dispersion is between about 3 wt. % and 40 wt. %.

41. The method of claim 1, wherein said agent is removed from said microencapsulated product during or after said extraction of said solvent from said microdroplets to provide a microbubble.

42. The method of claim 41, wherein said agent is a solid having a solubility over 1 gram/mL in said continuous process medium.

43. The method of claim 41, wherein said agent is a liquid.

44. The method of claim 43, wherein said liquid is mannitol dissolved in water.

45. The method of claim 1, wherein said wall-forming material is present at a concentration greater than 20 wt. % in said solvent.

46. The method of claim 45, wherein said agent is a solid having a solubility over 1 gram/mL in said extraction medium.

47. The method of claim 1, wherein said wall-forming material is present at a concentration less than 20 wt. % in said solvent.

48. The method of claim 1, wherein said agent has a solubility of greater than 10 milligrams per milliliter in said extraction medium.

49. The method of claim 1, wherein said agent has a solubility greater than 100 mg/mL in said extraction medium.

50. The method of claim 1, wherein said method comprises a continuous process.

51. The method of claim 1, wherein the microencapsulated agent is an analgesic, anesthetic, anorexic, antiarthritic, antiasthmatic, antibiotic, antifungal, antiviral, anticancer agent, anticoagulant, anticonvulsant, antidepressant, antihistamine, hormone, tranquilizer, antispasmodic, vitamin, mineral, cardiovascular agent, enzyme, peptide, protein, prostaglandin, nucleic acid, carbohydrate, fat, narcotic, psychotherapeutic, antimalarial, L-dopa, diuretic, antiulcer drug, or immunological agent.

52. The method of claim 1, wherein the microencapsulated agent is an adhesive, pesticide, fragrance, antifoulant, dye, salt, oil, ink, cosmetic, catalyst, detergent, curing agent, flavor, food, fuels, herbicides, metal, paint, photographic agent, biocide, pigment, plasticizer, propellant, solvent, stabilizer or polymer additive.

53. The method of claim 1, wherein the wall-forming material is poly(lactide), poly(glycolide), poly(caprolactone), poly(hydroxybutyrate) or copolymers thereof.

54. The method of claim 1, wherein the microencapsulated product comprises a central core comprising said agent surrounded by an outer membrane.

55. The method of claim 1, wherein the diameter of said microencapsulated product ranges from nanoparticles to about 2 millimeters.

56. The method of claim 1, wherein the diameter of said microencapsulated product ranges from about 1 μ

m to about 10 μ

m.

57. The method of claim 1, wherein the diameter of said microencapsulated product ranges from about 1 μ

m to about 5 μ

m.

58. The method of claim 1, wherein the diameter of said microencapsulated product ranges from about 5 μ

m to about 10 μ

m.

59. The method of claim 1, wherein the diameter of said microencapsulated product ranges from about 45 μ

m to about 250 μ

m.

60. A method of preparing a microencapsulated product having an encapsulating wall exhibiting high porosity, wherein the encapsulated agent is soluble in a continuous process medium, an extraction medium, or both media, comprising the steps of:

a) dissolving or dispersing said agent in a solvent containing a dissolved wall forming material to form a dispersion;

the percentage of said agent to said wall forming material being greater than about 20 wt. %;

b) combining said dispersion with an effective amount of said continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once alter step b) said emulsion to an effective amount of said extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

61. The method of claim 60, wherein said continuous process medium is highly soluble in said solvent.

62. The method of claim 61, wherein said continuous process medium has a solubility of from about 2% to about 25% in said solvent.

63. The method of claim 60, wherein the percentage of said agent to said wall forming material in said dispersion is from about 20 wt. % to about 80 wt. %.

64. A method of preparing a microencapsulated product having an encapsulating wall exhibiting low porosity, wherein the encapsulated agent is soluble in a continuous process medium, and extraction medium, or both media, comprising the steps of:

a) dissolving or dispersing said agent in a solvent containing a dissolved wall forming material to form a dispersion;

the percentage of said agent to said wall forming material being less than about 20 wt. %;

b) combining said dispersion with an effective amount of said continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once after step b) said emulsion to an effective amount of said extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part par 100 parts to about 25 parts per 100 parts in said extraction medium.

65. The method of claim 64, wherein said continuous process medium has a solubility of less than about 2% in said solvent.

66. A method of preparing a microencapsulated product having an encapsulating wall exhibiting high porosity, wherein the encapsulated agent is soluble in a continuous process medium, and extraction medium, or both media, comprising the steps of:

a) dissolving or dispersing said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of said continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material, said continuous process medium having a solubility of from about 2% to about 25% in said solvent; and

c) immediately after the formation of said emulsion, adding all at once after step b) said emulsion to an effective amount of said extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

67. A method of preparing a microencapsulated product having an encapsulating wall exhibiting low porosity, wherein the encapsulated agent is soluble in a continuous process medium, and extraction medium, or both media, comprising the steps of:

a) dissolving or dispersing said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of said continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material, said continuous process medium having a solubility of less than about 2% in said solvent; and

c) immediately after the formation of said emulsion, adding all at once after step b) said emulsion to an effective amount of said extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

68. A method of microencapsulating an agent from media in which said agent is soluble, to form a microencapsulated product, comprising the steps of:

a) dissolving or dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with and effective amount of a continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material, wherein said agent is soluble in said continuous process medium; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said agent is soluble in said extraction medium, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

69. A method of microencapsulating an agent, to form a microencapsulated product, comprising the steps of:

a) dissolving or dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with and effective amount of a continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material, wherein said agent is soluble in said continuous process medium; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

70. A method of microencapsulating an agent from media in which said agent is soluble, to form a microencapsulated product, comprising the steps of:

a) dissolving dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with and effective amount of a continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said agent is soluble in said extraction medium, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

71. An emulsion-based method of microencapsulating an agent that is soluble in a continuous process medium, an extraction medium, or both media, to form a microencapsulated product comprising a central core of said agent surrounded by an outer membrane, comprising the steps of:

a) dissolving or dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of said continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of said extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

72. An emulsion based method of microencapsulating a water-soluble agent to form a microencapsulated product, comprising the steps of:

a) dissolving or dispersing an effective amount of said water-soluble agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of an aqueous continuous process medium to form an emulsion that contains said aqueous process medium and microdroplets comprising said water-soluble agent, said solvent and said wall forming material; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an aqueous extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.

73. An emulsion-based method of microencapsulating an agent that has a propensity to partition within minutes into the continuous phase of the emulsion to form a microencapsulated product, comprising the steps of:

a) dissolving or dispersing an effective amount of said agent in a solvent containing a dissolved wall forming material to form a dispersion;

b) combining said dispersion with an effective amount of a continuous process medium to form an emulsion that contains said process medium and microdroplets comprising said agent, said solvent and said wall forming material, wherein said agent has a propensity to partition within minutes into said continuous process medium; and

c) immediately after the formation of said emulsion, adding all at once said emulsion to an effective amount of an extraction medium to extract said solvent from said microdroplets to form said microencapsulated product, wherein said solvent has a a solubility of from about 1 part per 100 parts to about 25 parts per 100 parts in said extraction medium.