Biomimetic scaffold for bone regeneration
Described herein are novel methods of producing collagen-apatite (Col-Ap) scaffolds that exhibit a unique, anisotropic multi-level lamellar structure in which nano and submicron pores in each lamellae and macro pores are co-aligned.
1. A method of producing a structural protein-calcium phosphate scaffold with an anisotropic lamellar pore structure, comprising
providing a structural protein-calcium phosphate hydrogel comprising mineralized structural protein fibrils;
compressing the structural protein-calcium phosphate hydrogel to increase the structural protein density in the hydrogel;
freezing the hydrogel with a temperature gradient in a transverse direction across the hydrogel; and
drying the frozen hydrogel to produce the structural protein-calcium phosphate scaffold with an aligned lamellar structure.
2. The method of claim 1 , wherein compression is unconfined self-compression.
3. The method of claim 2 , wherein self-compression is performed at a temperature of 4 to 45° C.
4. The method of claim 1 , wherein the freezing temperature is −197° C. to −10° C.
5. The method of claim 4 , wherein the freezing takes place over 0.5 to 4 hours.
6. The method of claim 1 , wherein the structural protein is collagen Type I, II, III, or V.
7. The method of claim 6 , wherein the calcium phosphate is hydroxylapatite.
8. The method of claim 1 , wherein the structural protein-calcium phosphate scaffold with an anisotropic lamellar pore structure has a structural protein content of 40 to 99 wt %.
9. The method of claim 1 , further comprising crosslinking the structural protein-calcium phosphate scaffold after drying.
10. The method of claim 1 , wherein the structural protein-calcium phosphate hydrogel is formed by
forming an aqueous system comprising a structural protein, a weak acid, water, Ca 2+ , HPO 4 2− , a buffer system, and optionally one or more of Mg 2+ , Na + , K + , Cl − , SO 4 2− ; or HCO 3 − ;
wherein the aqueous system has an initial pH of about 6.0 to about 8.0, in a container; and
allowing the structural protein-calcium phosphate hydrogel to form in the container at a temperature of 4-45° C. and a time of greater than one hour.
11. The method of claim 10 , wherein the hydrogel is formed in a period of greater than 10 hours.
12. The method of claim 10 , wherein
the structural protein is collagen Type I present in an amount of 1 g/L to 10.0 g/L of the aqueous system;
Ca 2+ is present in an amount of 0.1 to 30.0 mM;
Mg 2+ is present in an amount of 0.05 to 10.0 mM;
Na + is present in an amount of 5.0 to 300.0 mM;
K + is present in an amount of 0.1 to 20.0 mM;
Cl − is present in an amount of 5.0 to 300.0 mM;
SO 4 2− is present in an amount of 0 to 5.0 mM;
HPO 4 2− is present in an amount of 0.05 to 20.0 mM; and
HCO 3 − is present in an amount of 0.5 to 50.0 mM.
13. The method of claim 1 , wherein the transverse temperature gradient is formed from the outer edges to the center of the hydrogel.
14. The product of the process of claim 1 .
15. A biomimetic structural protein-calcium phosphate scaffold with an anisotropic lamellar pore structure produced by the process of claim 1 ,
wherein at the macro-level, the scaffold comprises an anisotropic lamellar pore structure and a co-aligned macro-pore size of 10 to 350 micrometers, and
at the micro-level each lamella of the lamellar structure comprises uniaxial aligned layers of structural protein fibers mineralized with the calcium phosphate having a pore size of less than 1 micrometer.
16. The biomimetic structural protein-calcium phosphate scaffold of claim 15 , wherein the scaffold protein is collagen and the calcium phosphate is hydroxyl apatite.
17. The biomimetic structural protein-calcium phosphate scaffold of claim 16 , wherein the wall thickness of the lamellar layers is 2 to 30 micrometers.
18. The biomimetic structural protein-calcium phosphate scaffold of claim 15 , further comprising a drug.
19. A method of bone repair, comprising contacting the scaffold of claim 15 with osteoprogenitor cells, bone marrow cells, or both, under conditions suitable to repair bone.
20. The method of claim 19 , wherein bone repair comprises new bone formation, bone-redistribution, bone-host integration, scaffold degradation, or a combination thereof.