Enhanced bonding layers on titanium materials
The present invention provides a dense-coverage, adherent phosphorous-based coating on the native oxide surface of a material. Disclosed phosphorous-based coatings include phosphate and organo-phosphonate coatings. The present invention also provides further derivatization of the phosphorous-based coatings to yield dense surface coverage of chemically reactive coatings and osteoblast adhesion-promoting and proliferation-promoting coatings on the native oxide surface of a titanium material.
1. A method of forming a coated article on a metal oxide surface comprising:
a. depositing a layer of a solution of a phosphorous-based acid on a metal oxide substrate;
b. removing solvent from the deposited solution layer so that a film of the phosphorus-based acid forms on the substrate; and
c. heating said metal oxide substrate from step (b) so as to react the phosphorus-based acid with the substrate until said film is bonded thereto,
wherein said phosphorous-based acid is selected from the group consisting of H 3 PO 4 and organo-phosphonic acids and said H 3 PO 4 reacts to form a phosphate bond with said oxide metal substrate thereby providing an inorganic phosphate coating comprising free hydroxyl groups.
2. The method of claim 1 , wherein the metal oxide surface is the native oxide of a titanium material substrate.
3. The method of claim 1 wherein said oxide surface layer is heated to a temperature between about 100 and about 200° C.
4. The method of claim 1 , wherein said phosphorous-based acid moiety is an organo-phosphonic acid containing a hydrocarbon ligand having from about 2 to 40 carbon atoms, said hydrocarbon ligand comprising a linear or branched, saturated or unsaturated, aliphatic or aromatic alkylene moiety.
5. The method of claim 4 , wherein said hydrocarbon ligand comprises an unsaturated alkylene moiety, and the method further comprises the step of polymerizing said unsaturated alkylene moiety.
6. The method of claim 4 , wherein said hydrocarbon ligand contains a pi-electron delocalized structure.
7. The method of claim 6 , wherein said pi-electron delocalized structure is an aromatic ring compound.
8. The method of claim 1 , wherein the organophosphonic acid forms a self-assembled monolayer coating with phosphonate bonds to the metal oxide surface and the organo groups contain reactive sub substituents.
9. The method of claim 8 further comprising the step of reacting said reactive sub stituents with a metal alkoxide reagent having two or more alkoxide ligands, thereby forming a layer comprising said metal alkoxide covalently bonded to said phosphonate coating, said metal alkoxide layer comprising unreacted alkoxide ligands.
10. The method of claim 9 , wherein said metal alkoxide is selected from the group consisting of reagents comprising metals from groups 4-14 ligated with 2 or more alkoxide ligands.
11. The method of claim 10 , wherein said metal alkoxide has the formula M(tert-butoxide) 4 , where M is Zr or Si.
12. The method of claim 11 , wherein said titanium oxide surface is a derivative surface of a polymeric, metallic, or ceramic material with a surface bearing a metal oxide layer.
13. The method of claim 8 , wherein said reactive substituents comprise omega-functional groups selected from the group consisting of hydroxyl, carboxylate, thiol and amino groups for the covalent attachment of bone tissue proteins and the chemical precursors thereof.
14. The method of claim 13 , wherein said omega functional groups are thiol or amino groups.
15. The method of claim 1 , wherein said phosphorus-based acid comprises an organo-phosphonic acid having a hydrocarbon ligand containing from 2 to 40 carbon atoms.
16. The method of claim 15 , wherein said hydrocarbon ligand is a satu-rated or unsaturated, substituted or unsubstituted, aliphatic or aromatic alkylene group.
17. The method of claim 16 , wherein said hydrocarbon ligand is omega-substituted with a substituent selected form the group consisting of hydroxyl, amino, carboxylate or thiol groups.
18. A method for improving the adhesion to bone tissue of implantable medical devices having a titanium oxide surface for contacting said bone tissue, said method comprising coating said surface with phosphoric acid or an organo-phosphonic acid according to the method of claim 1 .
19. A method for attaching an implantable device to bone tissue, said device having a titanium oxide surface for contacting said bone tissue, said method comprising first coating said oxide surface with phorphoric acid or an organo-phosphonic acid according to the method of claim 1 .
20. A method for coating an implantable device for attachment to bone tissue, said device having a titanium oxide surface for contacting said bone tissue, said method comprising coating said surface with phosphoric- or an organo-phosphonic acid according to the method of claim 1 .
21. The method of claim 1 , wherein said removing step comprises evaporating solvent from said solution so that a film of said phosphorus-based acid forms on said substrate.
22. The method of claim 1 , wherein said depositing step comprises dipping said metal oxide substrate into a vessel containing said phosphorus-based acid solution and draining the excess acid solution.