Self-Buffering Medical Implants

• US 20100222873A1
• Filed: 03/02/2010
• Published: 09/02/2010
• Est. Priority Date: 03/02/2009
• Status: Active Grant

• Current Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Scimed (Boston Scientific Corporation)
• Inventors: Genovese, Frank, Amey, Michael S., Feng, James Q., Flanagan, Aiden, Weber, Jan, Holman, Tom, Atanasoska, Liliana, Shippy, James Lee III, Schoenle, Victor
• Granted Patent: US 8,267,992 B2
• Time in Patent Office: Days
• US Class Current: 623/1.420
• CPC Class Codes: A61L 2300/416 Anti-neoplastic or anti-proliferative or anti-restenosis or anti-angiogenic agents, e.g. paclitaxel, sirolimus
• CPC Class Codes: A61L 2300/604 Biodegradation
• CPC Class Codes: A61L 2400/12 Nanosized materials, e.g. nanofibres, nanoparticles, nanowires, nanotubes; Nanostructured surfaces
• CPC Class Codes: A61L 2420/04 Coatings containing a composite material such as inorganic/organic, i.e. material comprising different phases
• CPC Class Codes: A61L 27/34 Macromolecular materials
• CPC Class Codes: A61L 27/446 with other specific inorganic fillers other than those covered by A61L27/443 or A61L27/46
• CPC Class Codes: A61L 27/54 Biologically active materials, e.g. therapeutic substances A61L27/227 takes precedence
• CPC Class Codes: A61L 27/58 Materials at least partially resorbable by the body
• CPC Class Codes: A61L 31/10 Macromolecular materials
• CPC Class Codes: A61L 31/128 containing other specific inorganic fillers not covered by A61L31/126 or A61L31/127
• CPC Class Codes: A61L 31/148 Materials at least partially resorbable by the body
• CPC Class Codes: A61L 31/16 Biologically active materials, e.g. therapeutic substances A61L31/047 takes precedence
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence

Abstract

A medical implant includes a bioerodible portion that includes a bioerodible polymer and a bioerodible metal. The bioerodible polymer matrix degrades under physiological conditions to form acidic degradation products. The bioerodible metal degrades under physiological conditions to form basic degradation products. The acidic degradation products and the basic degradation products buffer at least a portion of the medical implant. In one aspect, the bioerodible portion includes a bioerodible polymer matrix and a bioerodible metal within the bioerodible polymer matrix. In another aspect, the medical implant can include a body, a plurality of discrete deposits of the bioerodible polymer on the body, and a plurality of discrete deposits of the bioerodible metal on the body.

Claims

1. A medical implant comprising a bioerodible portion comprising:

a bioerodible polymer matrix that degrades under physiological conditions to form acidic degradation products; and

a bioerodible metal within the bioerodible polymer matrix, wherein the bioerodible metal degrades under physiological conditions to form basic degradation products, the acidic degradation products and the basic degradation products buffering at least a portion of the medical implant.

2. The medical implant of claim 1, wherein the bioerodible portion comprises a plurality of particles of the bioerodible metal within the bioerodible polymer matrix.

3. The medical implant of claim 2, wherein the plurality of particles comprise nanoparticles.

4. The medical implant of claim 1, wherein the bioerodible polymer comprises a plurality of fibers comprising the bioerodible polymer metallized with the bioerodible metal.

5. The medical implant of claim 1, wherein the bioerodible metal is selected from the group consisting of magnesium, iron, calcium, and alloys thereof.

6. The medical implant of claim 5, wherein the bioerodible metal comprises magnesium or an alloy thereof.

7. The medical implant of claim 5, wherein the bioerodible metal comprises calcium.

8. The medical implant of claim 1, wherein the bioerodible polymer is selected from the group consisting of polylactic acid, poly(lactic-co-glycolic acid), poly(propylene-ram-ε

-caprolactone carbonate), polycaprolactone, poly-L-lactic-acid, poly(3-hydroxybutyrate), and a combination thereof.

9. The medical implant of claim 8, wherein the bioerodible polymer is polylactic acid.

10. The medical implant of claim 8, wherein the bioerodible polymer is poly(lactic-co-glycolic acid.

11. The medical implant of claim 1, further comprising a therapeutic agent.

12. The medical implant of claim 11, wherein the therapeutic agent is incorporated in the bioerodible polymer matrix and elutes as the bioerodible polymer degrades under physiological conditions.

13. The medical implant of claim 11, wherein the therapeutic agent comprises paclitaxel.

14. The medical implant of claim 1, wherein the medical implant consists essentially of the bioerodible portion.

15. The medical implant of claim 1, wherein the medical implant is bioscaffolding, an aneurysm coil, an orthopedic implant, an identification tag, a pacemaking electrode, or a bone screw.

16. The medical implant of claim 1, wherein the medical implant is a stent.

22. The stent of claim 1, wherein the micro or nano particles comprise a calcium compound selected from the group consisting of calcium dihydrogenphosphate, calcium hydrogenpohosphate, calcium phosphate, calcium carbonate, hydroxyapatite, wollastonite, and combinations thereof.

23. The stent of claim 1, wherein the micro or nano particles comprise bioglass.

24. The stent of claim 1, wherein the micro or nano particles comprise titanium oxide.

25. The stent of claim 1, wherein the micro or nano particles comprise citric acid or a salt thereof.

17. A medical implant comprising:

a body;

a plurality of discrete deposits of a bioerodible polymer on the body, wherein the plurality of bioerodible polymer deposits degrade under physiological conditions to form acidic degradation products; and

a plurality of discrete deposits of a bioerodible metal on the body, wherein the plurality of bioerodible metal deposits degrade under physiological conditions to form basic degradation products, wherein each deposit of the plurality of deposits of the bioerodible metal is adjacent to at least one deposit of the bioerodible polymer.

18. The medical implant of claim 17, wherein the discrete deposits of the bioerodible polymer and the discrete deposits of the bioerodible metal each have an average diameter of no greater than 50 microns.

19. The medical implant of claim 17, wherein the body comprises stainless-steel, platinum-enhanced stainless steel, a cobalt-chromium alloy, a nickel-titanium alloy, or a combination thereof.

20. The medical implant of claim 17, wherein the medical implant is a stent.

21. A stent comprising a bioerodible portion comprising:

a bioerodible polymer matrix that degrades under physiological conditions to form acidic degradation products; and

micro or nano particles within the bioerodible polymer matrix, wherein mirco or nano particles degrades under physiological conditions to form basic degradation products, the acidic degradation products and the basic degradation products buffering at least a portion of the stent.