Process for the preparation of a biomimetic bone substitute and its uses
The object of the present invention is a process for obtaining a bone substitute of given chemical and physical characteristics and entirely similar to those of the mineral portion of natural bone tissue. The process substitutes Ca ions with Mg ions in a porous matrix; the process comprises a phase of contacting the matrix with a saline aqueous solution containing an effective quantity of Mg ions at a pressure greater than or equal to 1 bar.
1. A process for the preparation of a biomimetic bone substitute comprising:
(a) providing a preformed solid three-dimensional porous scaffold comprising hydroxyapatite or carbonate-hydroxyapatite;
(b) contacting extracorporeally said scaffold with a saline aqueous solution containing an effective concentration of Mg 2+ ions at a pressure greater than or equal to 1 bar, whereby during said contacting step Ca 2+ ions in the scaffold are substituted with Mg 2+ ions and the concentration of Mg 2+ ions in the scaffold is increased; and
(c) obtaining a biomimetic bone substitute comprising magnesium-hydroxyapatite or magnesium-carbonate-hydroxyapatite having a content of Mg 2+ ions in the range of 0.2% to 1.5% by weight and a total porosity of 50% to 90% by volume, with respect to the total volume of the bone substitute, wherein both the total porosity and the porosity distribution of the bone substitute is the same as the total porosity and the porosity distribution of said three-dimensional porous scaffold.
2. The process according to claim 1 , wherein said bone substitute has a total porosity of from 75% to 85% by volume.
3. The process according to claim 1 , wherein said saline aqueous solution comprises said Mg 2+ ions at a concentration of from 0.1M to 4M.
4. The process according to claim 3 , wherein said saline aqueous solution comprises said Mg 2+ ions at a concentration of from 0.2M to 3M.
5. The process according to claim 4 , wherein said saline aqueous solution comprises said Mg 2+ ions at a concentration of from 0.5M to 2.5M.
6. The process according to claim 1 , wherein said Mg 2+ ions are present as MgCl 2 .
7. The process according to claim 1 , wherein said porous scaffold and said saline aqueous solution are present in a weight ratio in the range from 1/3000 to 1/50.
8. The process according to claim 1 , wherein the pressure is from 1 bar to 5 bar.
9. The process according to claim 1 , wherein the pressure is from 1.5 bar to 3.5 bar.
10. The process according to claim 1 , wherein said process is performed at a temperature ranging from 100° C. to 150° C.
11. The process according to claim 10 , wherein the temperature is from 120° C. to 140° C.
12. The process according to claim 11 , wherein the temperature is from 130° C. to 138° C.
13. The process according to claim 1 , wherein step (b) is carried out in an autoclave over a time of from 10 minutes to 80 minutes.
14. The process according to claim 13 , wherein step (b) is carried out in an autoclave over a time of from 15 minutes to 60 minutes.
15. The process according to claim 1 , wherein the quantity of Mg 2+ ions is from 0.3% to 1.0% by weight with respect to that of the bone substitute.
16. The process according to claim 15 , wherein the quantity of Mg 2+ ions is from 0.4% to 0.7% by weight with respect to that of the bone substitute.