Porous calcium phosphate networks for synthetic bone material

• US 20050255159A1
• Filed: 04/15/2005
• Published: 11/17/2005
• Est. Priority Date: 04/16/2004
• Status: Active Grant

• Current Assignee: University Of Massachusetts
• Original Assignee: University Of Massachusetts
• Inventors: Hyers, Robert, SanSoucie, Michael
• Granted Patent: US 7,758,896 B2
• Time in Patent Office: Days
• US Class Current: 424/484
• CPC Class Codes: A61K 33/42 Phosphorus; Compounds thereof
• CPC Class Codes: A61L 27/12 Phosphorus-containing materials, e.g. apatite
• CPC Class Codes: A61L 27/56 Porous materials, e.g. foams or sponges

Abstract

A porous composition comprising a hydroxyapatite material, as can be made from a mixture of calcium phosphate, calcium oxide and a removable inorganic porogen. In other embodiments, the present invention provides a method of making such a porous hydroxyapatite material or using a ternary system to prepare a two-phase composition enroute to a biomimetic bone material.

Claims

1. A calcium phosphate composition comprising a first phase comprising hydroxyapatite and tricalcium phosphate, and a second phase comprising a removable inorganic porogen, said second phase substantially interconnected continuously within said first phase, said interconnection of a substantially constant cross-sectional dimension.

2. The composition of claim 1 wherein said removable porogen is a transition metal oxide.

3. The composition of claim 2 wherein said transition metal oxide is selected from iron oxide, nickel oxide, cobalt oxide, manganese oxide and copper oxide.

4. The composition of claim 3 wherein said composition comprises an iron oxide content ranging from about 25 wt. % to about 65 wt. %, a calcium oxide content ranging from about 25 wt. % to about 45 wt. %, and a phosphorous oxide content ranging from about 10 wt. % to about 30 wt. %.

5. The composition of claim 1 wherein said porogen is at least partially removed, said composition a matrix of interconnected pores.

6. The composition of claim 5 wherein said matrix has a porosity ranging from about 30% to about 60%.

7. The composition of claim 6 wherein said pore size ranges from about 3 μ

m to about 700 μ

m.

8. The composition of claim 6 wherein said porosity ranges from about 55% to about 70%

9. The composition of claim 8 wherein said matrix has a pore size selected from a size ranging from about 500 μ

m to about 600 μ

m, a size ranging from about 190 μ

m to about 230 μ

m, and a size ranging from about 3 μ

m to about 30 μ

m.

10. The composition of claim 1 wherein said first and second phases have a wavelength less than about 3 μ

m.

11. A calcium phosphate spinodal decomposition product of a mixture comprising iron oxide, calcium oxide and calcium phosphate, said product within the immiscibility region of a phase diagram of a CaO—

P₂O₅—

FeO_n ternary system.

12. The product of claim 11 comprising an iron oxide content ranging from about 25 wt. % to about 65 wt. %, a calcium oxide content ranging from about 25 wt. % to about 45 wt. %, and a phosphorous oxide content ranging from about 10 wt. % to about 30 wt. %.

13. The product of claim 12 wherein said iron oxide content is about 40 wt. %, said calcium oxide content is about 37.5 wt. % and said phosphorous oxide content is about 22.5 wt. %.

14. The product of claim 11 comprising a Ca/P ratio between about 1.5 and about 2.0.

15. The product of claim 11 having a wavelength of less than about 3 μ

m.

16. The product of claim 11 substantially absent iron oxide and comprising a porous calcium phosphate matrix.

17. The product of claim 16 wherein said calcium phosphate matrix has a porosity ranging from about 55% to about 70%, said pores of a dimension selected from the pore dimension of cancellous bone and cortical bone.

18. A method of using a ternary system to prepare a biomimetic bone material, said method comprising:

providing a mixture of a transition metal oxide, calcium oxide and calcium phosphate components, each said component in an amount sufficient to provide a spinodal decomposition product within the immiscibility region of a phase diagram of a CaO—

P₂O₅-MO ternary system, where MO is selected from the group of transition metal oxides;

heating said mixture over a temperature range and a time sufficient for spinodal decomposition of said mixture; and

removing said MO component from said spinodal decomposition product, to provide a biomimetic bone material.

19. The method of claim 18 wherein said mixture is melted, and cooled at a rate sufficient to affect product microstructure.

20. The method of claim 19 wherein at least one of the amount of said MO and said rate of cooling affects the porosity of said biomimetic bone material.

21. The method of claim 18 wherein said removal comprises contacting said MO component with at least one of an acid and a chelating agent.

22. The method of claim 18 wherein said biomimetic bone material is sterilized.