Treatment of bioprosthetic tissues to mitigate post implantation calcification

• US 20030125813A1
• Filed: 01/03/2002
• Published: 07/03/2003
• Est. Priority Date: 01/03/2002
• Status: Active Grant

• Current Assignee: Edwards Lifesciences Corporation
• Original Assignee: Edwards Lifesciences Corporation
• Inventors: Carpentier, Alain F., Carpentier, Sophie M.
• Granted Patent: US 6,878,168 B2
• Time in Patent Office: Days
• US Class Current: 623/23.72
• CPC Class Codes: A61L 2400/02 Treatment of implants to prevent calcification or mineralisation in vivo
• CPC Class Codes: A61L 27/3604 characterised by the human or animal origin of the biological material, e.g. hair, fascia, fish scales, silk, shellac, pericardium, pleura, renal tissue, amniotic membrane, parenchymal tissue, fetal tissue, muscle tissue, fat tissue, enamel
• CPC Class Codes: A61L 27/3687 characterised by the use of chemical agents in the treatment, e.g. specific enzymes, detergents, capping agents, crosslinkers, anticalcification agents
• CPC Class Codes: B65B 63/08 for heating or cooling articles or materials to facilitate packaging

Abstract

Bioprosthetic tissues are treated by immersing or otherwise contacting fixed, unfixed or partially fixed tissue with a glutaraldehyde solution that has previously been heat-treated or pH adjusted prior to its contact with the tissue. The prior heat treating or pH adjustment of the glutaraldehyde solution causes its free aldehyde concentration to decrease by about 25% or more, preferably by as much as 50%, and allows a “stabilized” glutaraldehyde solution to be obtained at the desired concentration and pH for an optimal fixation of the tissue at high or low temperature. This treatment results in a decrease in the tissue'"'"'s propensity to calcify after being implanted within the body of a human or animal patient. The heat-treated or pH adjusted glutaraldehyde solution may, in some cases, also be used as a terminal sterilization solution such that the calcification-decreasing treatment with the previously treated glutaraldehyde and a terminal sterilization may be carried out simultaneously and/or in a single container.

Claims

1. A method for mitigating post-implantation calcification of a bioprosthetic material, said method comprising the steps of:

(a) heating a glutaraldehyde solution to a first temperature for a first period of time;

(b) adjusting the temperature of the glutaraldehyde solution to a second temperature; and

,

(c) after the temperature of the glutaraldehyde solution has been adjusted to the second temperature, contacting a quantity of biological tissue that contains connective tissue protein with the glutaraldehyde solution for a second period of time.

2. A method according to claim 1, wherein the first temperature is maintained for a period of time until a predetermined end point is reached, said predetermined end point being indicated by at least one indicator selected from:

a decrease of about 25% or more in the free aldehyde content of the solution;

a fall in the pH of the solution from about 7.4 to about 6.0;

a fall in the pH of the solution by about 20%; and

,

a change in the color of the solution to yellow or brown.

3. A method according to claim 2 wherein the first temperature is about 20-90°

C.

4. A method according to claim 2 wherein the first temperature is about 60-80°

C.

5. A method according to claim 2 wherein the first temperature is about 70±

5°

C.

6. A method according to claim 2 wherein the second temperature is less than the first temperature.

7. A method according to claim 6 wherein the second temperature is about 30-70°

C.

8. A method according to claim 6 wherein the second temperature is about 40-60°

C.

9. A method according to claim 6 wherein the second temperature is about 50±

°

C.

10. A method according to claim 1 wherein the first temperature is no lower than about 70°

C. and the second temperature is no higher than about 60°

C.

11. A method according to claim 10 wherein the first period of time is one hour to six months.

12. A method according to claim 10 wherein the second period of time is shorter than the first period of time.

13. A method according to claim 1 wherein the tissue is at least partially fixed prior to the performance of Step (c).

14. A method according to claim 1 wherein the tissue is fixed after the performance of Step (c).

15. A method according to claim 1 wherein the tissue is fixed concurrently with the performance of Step (c).

16. A method according to claim 15 wherein the tissue is fixed concurrently with the performance of Step (c) by immersing the tissue in a solution that contains the glutaraldehyde that was heat-treated in Step (a) as well as a fixative agent.

17. A method according to claim 16 wherein the fixative agent is non-heat-treated glutaraldehyde.

18. A method according to claim 17 wherein the fixative agent is selected from the group of fixative agents consisting of:

(a) aldehydes;

(b) polyglycidyl ethers;

(c) heterologous multifunctional crosslinkers; and

(d) combinations of aldehydes, polyglycidyl eithers and heterologous multifunctional crosslinkers.

19. A method according to claim 1 wherein the tissue is fixed in the glutaraldehyde solution in Step (c) while the solution is moving relative to the tissue.

20. A method according to claim 1 wherein the method further comprises:

preparing a solution of 0.1-25% by weight glutaraldehyde;

heating the glutaraldehyde solution to about 20-90°

C. in Step (a);

adjusting the second temperature to no greater than about 60°

C.; and

thereafter immersing the tissue in the glutaraldehyde solution in Step (c) while maintaining the temperature of the solution in the range of about 40°

C. to 60°

C. for about 1 day to two months.

21. A method according to claim 20 further comprising the step of adding any desired non-biological components to the tissue and fabricating a bioprosthesis.

22. A method according to claim 20 further comprising the step of subjecting the tissue to a bioburden reduction process.

23. A method according to claim 22 wherein the step of subjecting the tissue to a bioburden reduction process comprises contacting the tissue with a bioburden reduction solution containing a surfactant, an aldehyde and an alcohol.

24. A method according to claim 23 wherein the bioburden reduction solution comprises:

25. A method according to claim 20 further comprising the steps of:

adding any desired non-biological components to the tissue and fabricating a bioprosthesis; and

,

sterilizing the bioprosthesis.

26. A method according to claim 1 further comprising the steps of:

removing the tissue from the heat-treated glutaraldehyde solution;

subjecting the tissue to a first bioburden reduction process;

adding any desired non-biological components to the tissue and fabricating a bioprosthesis;

subjecting the tissue to a second bioburden reduction process; and

,

sterilizing the bioprosthesis.

27. A method according to claim 1 further comprising the step of sterilizing the tissue.

28. A method according to claim 27 wherein the sterilization of the tissue comprises:

contacting the tissue with a terminal sterilization solution and heating said terminal sterilization solution to a temperature between about 20 to 50°

C. for a period of time sufficient to ensure the sterility of the bioprosthesis until the time of implantation.

29. A method according to claim 28 wherein the sterilization is carried out in a sealed container and further comprises allowing the tissue to remain within said sealed container until the time of implantation.

30. A method according to claim 28 wherein the sterilization is carried out in a moving glutaraldehyde solution.

31. A method according to claim 28 wherein said terminal sterilization solution comprises an aqueous solution of 0.2-1.0% by weight glutaraldehyde buffered to a pH of approximately 7.4.

32. A method according to claim 28 wherein the terminal sterilization solution comprises osmotically balanced salt solution in combination with at least one chemical sterilant.

33. A method according to claim 28 wherein the terminal sterilization solution comprises at least one component selected from i) a denaturant, ii) a surfactant, and iii) a crosslinking agent.

34. A method according to claim 28 wherein the sterilization solution comprises the previously heated and cooled glutaraldehyde solution prepared in Steps (a) and (b) of claim 1 and wherein the tissue treatment of Step (c) is carried out concurrently with the sterilization step of claim 27.

35. A method according to claim 1 wherein the tissue is sterilized after Step (c) by an in-container terminal sterilization process comprising the steps of:

providing a container which contains a quantity of a terminal sterilant solution comprising 0.2-1.0% by weight glutaraldehyde buffered to a pH of approximately 7.4;

immersing the tissue in said terminal sterilant solution within said container;

sealing said container;

heating said container, and the terminal sterilant solution and bioprosthesis contained therein, to a temperature of about 37-50°

C. for a period of about six hours to six days;

cooling said container, and the terminal sterilant solution and bioprosthesis contained therein, to room temperature; and

,

allowing said container to remain sealed until it is desired to implant the bioprosthesis in a mammalian patient.

71. A bioprosthesis according to claim 65 wherein the terminal sterilization solution is the glutaraldehyde solution that was heat-treated and cooled in Steps (a) and (b) of claim 1 and wherein the treatment of the tissue of Step (c) is carried out concurrently with the terminal sterilization of the bioprosthesis.

36. A bioprosthesis comprising tissue that has been subjected to a calcification mitigation treatment comprising the steps of:

(a) heating a glutaraldehyde solution to a first temperature for a first period of time;

(b) adjusting the temperature of the glutaraldehyde solution to a second temperature; and

,

(c) after the temperature of the glutaraldehyde solution has been adjusted to the second temperature, contacting the glutaraldehyde solution with a quantity of biological tissue that contains connective tissue protein for a second period of time.

37. A bioprosthesis according to claim 36 wherein the bioprosthesis comprises a tissue selected from the group of tissues consisting of:

cardiac valves;

blood vessels;

skin;

dura mater;

pericardium;

ligaments;

tendons;

small intestinal submucosa; and

,

combinations of cardiac valves, blood vessels, skin, dura mater, pericardium, ligaments, tendons, and small intestinal submucosa.

38. A bioprosthesis according to claim 36 wherein the glutaraldehyde contacted with the biological tissue in step (c) is prepared by heating glutaraldehyde, in the absence of the biological tissue, until a predetermined end point is reached said predetermined end point being indicated by at least one indicator selected from:

a decrease of about 25% or more in the free aldehyde content of the solution;

a fall in the pH of the solution from about 7.4 to about 6.0;

a fall in the pH of the solution by about 20%; and

,

a change in the color of the solution to yellow or brown.

39. A bioprosthesis according to claim 36 wherein the first temperature is about 20-90°

C.

40. A bioprosthesis according to claim 36 wherein the first temperature is about 60-80°

C.

41. A bioprosthesis according to claim 36 wherein the first temperature is about 70±

5°

C.

42. A bioprosthesis according to claim 36 wherein the second temperature is less than the first temperature.

43. A bioprosthesis according to claim 42 wherein the second temperature is about 30 to 70°

C.

44. A bioprosthesis according to claim 42 wherein the second temperature is about 40 to 60°

C.

45. A bioprosthesis according to claim 42 wherein the second temperature is about 50±

5°

C.

46. A bioprosthesis according to claim 36 wherein the first temperature is no lower than about 70°

C. and the second temperature is no higher than about 60°

C.

47. A bioprosthesis according to claim 39 wherein the first period of time is one hour to six months.

48. A bioprosthesis according to claim 46 wherein the second period of time is shorter than the first period of time.

49. A bioprosthesis according to claim 48 wherein the first temperature is about 70-80°

C., the first period of time is about one day to two months and the second period of time is about 5 to 10 days.

50. A bioprosthesis according to claim 36 wherein the second period of time is less than the first period of time.

51. A bioprosthesis according to claim 36 wherein the tissue is at least partially fixed prior to the performance of Step (c).

52. A bioprosthesis according to claim 36 wherein the tissue is fixed after the performance of Step (c).

53. A bioprosthesis according to claim 36 wherein the tissue is fixed concurrently with the performance of Step (c).

54. A bioprosthesis according to claim 53 wherein the tissue is fixed concurrently with the performance of Step (c) by immersing the tissue in a solution that contains the glutaraldehyde that was heat-treated in Step (a) as well as a fixative agent.

55. A bioprosthesis according to claim 54 wherein the fixative agent is non-heat-treated glutaraldehyde.

56. A bioprosthesis according to claim 55 wherein the fixative agent is selected from the group of fixative agents consisting of:

aldehydes;

polyglycidyl eithers;

heterologous multifunctional crosslinkers; and

combinations of aldehydes, polyglycidyl eithers, and heterologous multifunctional crosslinkers.

57. A bioprosthesis according to claim 36 wherein the method by which the bioprosthesis is treated further comprises:

preparing a solution of 0.1-25% by weight glutaraldehyde;

heating the glutaraldehyde solution to 20-90°

C. in Step (a);

adjusting the temperature of the glutaraldehyde solution to a temperature no greater than about 60°

C. and buffering the pH of the solution at that adjusted temperature to approximately 7.4; and

thereafter immersing the tissue in the glutaraldehyde solution in Step (c) while maintaining the temperature of the solution in the range of about 40°

C. to 60°

C. for about 1-15 days.

58. A bioprosthesis according to claim 57 wherein the method by which the bioprosthesis is treated further comprises the step of adding any desired non-biological components to the tissue and fabricating a bioprosthesis.

59. A bioprosthesis according to claim 57 wherein the method by which the bioprosthesis is treated further comprises the step of subjecting the tissue to a bioburden reduction process.

60. A bioprosthesis according to claim 59 wherein the step of subjecting the tissue to a bioburden reduction process comprises contacting the tissue with a bioburden reduction solution containing a surfactant, an aldehyde and an alcohol.

61. A bioprosthesis according to claim 60 wherein the bioburden reduction solution comprises:

62. A bioprosthesis according to claim 36 wherein the method by which the bioprosthesis is treated further comprises the steps of:

adding any desired non-biological components to the tissue and fabricating a bioprosthesis; and

,

sterilizing the bioprosthesis.

63. A bioprosthesis according to claim 36 wherein the method by which the bioprosthesis is treated further comprises the steps of:

removing the tissue from the heat-treated glutaraldehyde solution;

subjecting the tissue to a first bioburden reduction process;

adding any desired non-biological components to the tissue and fabricating a bioprosthesis;

subjecting the tissue to a second bioburden reduction process; and

,

sterilizing the bioprosthesis.

64. A bioprosthesis according to claim 36 wherein the method by which the bioprosthesis is treated further comprises the step of sterilizing the tissue.

65. A bioprosthesis according to claim 64 wherein the sterilization of the tissue comprises contacting the tissue with a terminal sterilization solution and heating said terminal sterilization solution to a temperature between about 37 to 50°

C. for a period of time sufficient to ensure the sterility of the bioprosthesis until the time of implantation.

66. A bioprosthesis according to claim 65 wherein the sterilization is carried out in a sealed container and further comprises allowing the tissue to remain within said sealed container until the time of implantation.

67. A bioprosthesis according to claim 65 wherein said terminal sterilization solution comprises an aqueous solution of 0.2-1.0% by weight glutaraldehyde buffered to a pH of approximately 7.4.

68. A bioprosthesis according to claim 65 wherein the terminal sterilization solution comprises osmotically balanced salt solution in combination with at least one chemical sterilant.

69. A bioprosthesis according to claim 65 wherein the terminal sterilization solution comprises at least one component selected from i) a denaturant, ii) a surfactant, and iii) a crosslinking agent.

70. A bioprosthesis according to claim 36 wherein the bioprosthesis is sterilized after Step (c) by an in-container terminal sterilization process comprising the steps of:

providing a container which contains a quantity of a terminal sterilant solution comprising 0.2-1.0% by weight glutaraldehyde buffered to a pH of approximately 7.4;

immersing the bioprosthesis in said terminal sterilant solution within said container;

sealing said container;

heating said container, and the terminal sterilant solution and bioprosthesis contained therein, to a temperature of about 37-60°

C. for a period of about six hours to six days;

cooling said container, and the terminal sterilant solution and bioprosthesis contained therein, to room temperature; and

,

allowing said container to remain sealed until it is desired to implant the bioprosthesis in a mammalian patient.

72. A method for mitigating post-implantation calcification of a bioprosthetic material, said method comprising the steps of:

(a) adjusting the pH of a solution selected from the group consisting of a glutaraldehyde solution and a physiologic solution, to a pH in the range of about 5.0 to 7.0;

(b) contacting a quantity of biological tissue that contains connective tissue protein with the solution; and

(c) heating the solution and the tissue to a temperature in the range of about 30 to 70°

C. for a period of time.

73. A method according to claim 72, wherein the pH is adjusted to about 6.0.

74. A method according to claim 72, wherein the temperature is in the range of about 40 to 60°

C.

75. A method according to claim 72, wherein the temperature is about 50°

C.±

5°

C.

76. A method according to claim 72, wherein the period of time is between about one hour and six months.

77. A method according to claim 72, wherein the period of time is between about one day and two months.

87. A method according to claim 72, wherein the solution from Step (a) is used to sterilize the bioprosthetic material in a terminal sterilization step.

88. A method according to claim 87, wherein the solution from Step (a) is used to sterilize the bioprosthetic material during Step (c).

89. A method according to claim 88, wherein the sterilization and heat treatment of Step (c) occurs after the bioprosthetic material has been placed in a final container.

78. A method for mitigating post-implantation calcification of a bioprosthetic material, said method comprising the steps of:

(a) heating a solution selected from the group consisting of a solution comprising a fixative agent, a solution comprising a surfactant, and a physiologic solution, to a first temperature in the range of about 20 to 90°

C. for a first period of time;

(b) adjusting the solution from step (a) to a second temperature in the range of about 30 to 70°

C.; and

(c) then treating the bioprosthetic material with the solution from step (b) for a second period of time.

79. A method according to claim 78, wherein the first temperature is in the range of about 37 to 60°

C.

80. A method according to claim 78, wherein the first temperature is about 45°

C.±

5°

C.

81. A method according to claim 78, wherein the first period of time is between about one hour and six months.

82. A method according to claim 78, wherein the first period of time is between about one day and two months.

83. A method according to claim 78, wherein the second temperature is in the range of about 40 to 60°

C.

84. A method according to claim 78, wherein the second temperature is about 50°

C.±

5°

C.

85. A method according to claim 78, wherein the second period of time is between about one hour and six months.

86. A method according to claim 78, wherein the second period of time is between about one day and two months.

90. A method according to claim 78, wherein the solution from Step (a) is used to sterilize the bioprosthetic material in a terminal sterilization step.

91. A method according to claim 90, wherein the solution from Step (a) is used to sterilize the bioprosthetic material during Step (c).

92. A method according to claim 91, wherein the sterilization and treatment of Step (c) occurs after the bioprosthetic material has been placed in a final container.