WO1996009157B1

WO1996009157B1 - Carbon containing vascular graft and method for making same

Info

Publication number: WO1996009157B1
Application number: PCT/US1995/011731
Authority: WO
Filing date: 1995-09-15
Publication date: 1996-06-06
Anticipated expiration: 1997-03-23

Abstract

A method for making a carbon lined vascular graft wherein a polymeric carbon compound and a polymeric compound are co-extruded through a mandrel and die assembly to form a vascular graft having carbon as an integral component of its intraluminal or exterior surface is presented, along with the carbon containing graft which results from the method. A divided preformer comprising two hollow concentrical cylinders is used to form a dual compound billet for extrusion. Alternatively, the polymeric carbon compound may be used to fill both cylinders of the divided preformer to form a single compound billet which is extruded to present a carbon containing polymeric graft having uniform carbon polymeric material throughout the wall of the graft. A preformer having multiple dividers which thereby forms a billet having multiple layers wherein one of the layers contains a carbon element way also be used as part of the inventive method. A time-releasable bioactive substance may be incorporated into the vascular grafts resulting from the inventive method.

Claims

AMENDED CLAIMS

[received by the International Bureau on 25 March 1996 (25.03.96); original claims 7-11, 13 and 16-24 cancelled; original claims 1-3,

12, 14, 15, 25 and 26 amended; remaining claims unchanged (5 pages)] 1. A method for making a tubular carbon-containing vascular graft comprising the steps of:

a) molding a concentrically-plied, cylindrical preform billet having a solid inner cylindrical portion formed of a substantially homogeneous admixture of polytetrafluoro-ethylene and a carbon component selected from activated charcoal or activated carbon and graphite and a solid outer cylindrical portion formed of polytetrafluoroethylene

surrounding said solid inner cylindrical portion;

b) co-extruding the cylindrical preform billet through a die to form a hollow, tubular extrudate having a carbon-containing luminal surface;

c) expanding the tubular co-extrudate; and d) sintering the expanded tubular extrudate.

2. The method of Claim 1 wherein said step cf molding a preform billet comprises the steps of:

a) providing an vertically-oriented cylindrical preform barrel which is divided into inner and outer hollow cylindrical sections by an upright hollow cylindrical divider concentrically positioned within the cylindrical preform barrel;

b) compounding a polytetrafluoroethylene resin, a carbon component selected from activated charcoal or activated charcoal and graphite, and a lubricant to form a substantially homogeneous polytetrafluoroethylene-carbon admixture;

c) pouring an amount of the polytetraflucroethylene- carbon admixture into the inner cylindrical section of said preform barrel such that it fills said inner cylindrical section;

d) pouring a quantity of a polytetrafluoroethylene- lubricant admixture into the outer cylindrical section of the preform barrel such that it fills the outer cylindrical section; e) compacting the inner and outer cylindrical sections within the preform barrel under an applied positive pressure to form a cylindrical extrusion billet having

concentric inner and outer layers; and

f) removing the extrusion billet from the preform barrel.

3. The method of Claim 2 wherein the carbon component is present at approximately 3% to 20% by weight of the

polytetrafluoroethylene resin.

4. The method of Claim 3 wherein said carbon component is an activated charcoal powder.

5. The method of Claim 2 further characterized by the step of incorporating a time-releasable bioactive substance within the carbon containing vascular graft subsequent to the step of sintering the expanded tubular extrudate.

6. The method of Claim 5 wherein said bioactive

substance comprises at least one of an anticoagulant, an anti-microbial agent, an anti-inflammatory, a growth factor, a smooth muscle inhibitor, an antithrombogenic agent, an

antiplatelet agent, and a non-steroidal anti-inflammatory drug.

7. Canceled,

8. Canceled.

9. Canceled.

10. Canceled.

11. Canceled.

12. A tubular vascular graft characterized by concentric luminal and abluminal layers, the luminal layer being composed of a substantially homogenous admixture of a carbon component selected from activated charcoal or activated charcoal and graphite and polytetrafluoroethylene and the abluminal layer being composed of polytetrafluoroethylene, the

polytetrafluoro-ethylene having a microporous microstructure of nodes interconnected by fibrils, with the fibrils being oriented substantially parallel to a longitudinal axis of the tubular vascular graft, and further including a bioactive substance adsorbed within the carbon component and

physiologically releasable therefrom in vivo.

13. Canceled.

14. The vascular graft of Claim 12 wherein said

bioactive substance comprises at least one of an

anticoagulant, an anti-microbial agent, an anti-inflammatory, a growth factor, a smooth muscle inhibitor, an

antithrombogenic agent, an antiplatelet agent, and a non-steroidal anti-inflammatory drug.

15. A tubular carbon-containing vascular graft

comprising:

a first layer forming an interior surface of the tubular vascular graft and defining a flow passage

therethrough, the first layer comprising a substantially homogeneous admixture of polytetrafluoroethylene and carbon; and

a second layer concentrically surrounding the first layer wherein the second layer comprising one of

polytetrafluoroethylene or a substantially homogeneous admixture of polytetrafluoroethylene and carbon, wherein the tubular carbon-containing vascular graft is made in accordance with the method of any of Claims 1 to 6.

16. Canceled.

17. Canceled.

18. Canceled.

19. Canceled.

20. Canceled.

21. Canceled.

22. Canceled.

23. Canceled.

24. Canceled.

25. A method for making a tubular carbon-containing vascular graft comprising the steps of:

a) molding a preform billet by the steps of:

(i) providing an upright, cylindrical preform barrel which is divided into at least two concentric

cylindrical sections;

(ii) pouring a substantially homogeneous admixture of polytetrafluoroethylene, carbon and an extrusion aid into a first one of the at least two cylindrical sections;

(iii) pouring one if an admixture of

polytetrafluoroethylene and an extrusion aid or an admixture of polytetrafluoroethylene, carbon and an extrusion aid into a second one of the at least two cylindrical sections; and

(iv) compacting the admixtures in the first and second of the at least two cylindrical sections to form an extrusion billet having inner and outer concentric layers;

b) extruding the extrusion billet through a die to form a tubular extrudate having plied inner and outer

concentric layers corresponding to the first and second cylindrical layers of the extrusion billet;

c) longitudinally expanding the tubular extrudate; and

d) sintering the longitudinally expanded tubular extrudate.

26. A carbon-containing vascular graft made in

accordance with the method of Claim 25 characterized by an inner layer having a carbon component substantially

homogeneously dispersed in the polytetrafluoroethylene and a polytetrafluoroethylene outer layer. STATEMENT UNDER ARTICLE 19

Claims 1-3 have been amended to specify that the preform billet is formed of concentric plied layers with an inner layer formed from a substantially homogeneous admixture of polytetrafluoroethylene and a carbon component, the carbon component being one of activated charcoal or activated carbon and graphite, and the outer layer being

polytetrafluoroethylene. Claim 2 has been amended to clarify that the preform barrel is vertically-oriented and formed as a hollow cylinder. The method recited in Claims 1-6 has been clarified as a method of making a tubular vascular graft. Claim 6 has been emended to replace "antithrombic" with "antithrombogenic."

Claim 12 has been amended to clarify that the vascular graft is tubular and formed of concentric luminal and abluminal layers of material. The luminal layer is made of a

substantially homogenous admixture of a carbon component, selected from activated charcoal or activated charcoal and graphite and polytetrafluoroethylene. Additionally, the bioactive substance is claimed to be adsorbed within the carbon component and is physiologically releasable therefrom in vivo. Claim 14 has been amended to replace "antrthrombic" with "antithrombogenic."

Claim 15 has been amended to include the claim in its entirety, to specifically claim that the inner layer is made of polytetrafluoroethylene and carbon and that the graft is made in accordance with the method of any of Claims 1-6.

Finally, Claim 25 has been amended to specifically claim polytetrafluoroethylene and an admixture of polytetrafluoroethylene, carbon and an extrusion aid used to form the preform billet using an upright cylindrical preform. Claim 25 further claims that the tubular extrudate is longitudinally expanded. Claim 26 has been amended to clarify that the carbon component is substantially homogeneously dispersed in the polytetrafluoroethylene of the inner layer.

Due to cancellation of many claims, the claims are now presented on fewer pages of the application than in the International Application as originally filed. No change has been made to the Abstract.

Applicant respectfully requests that the Claims as amended herein under Article 19 publish with the International Publication.