Nanoporous layers using thermal dealloying
The present invention relates generally to medical devices with therapy eluting components and methods for making same. More specifically, the invention relates to implantable medical devices having at least one porous layer, and methods for making such devices, and loading such devices with therapeutic agents. A mixture or alloy is placed on the surface of a medical device, then one component of the mixture or alloy is generally removed without generally removing the other components of the mixture or alloy. In some embodiments, a porous layer is adapted for bonding non-metallic coating, including drug eluting polymeric coatings. A porous layer may have a random pore structure or an oriented or directional grain porous structure. One embodiment of the invention relates to medical devices, including vascular stents, having at least one porous layer adapted to resist stenosis or cellular proliferation without requiring elution of therapeutic agents. The invention also includes methods, devices, and specifications for loading of drugs and other therapeutic agents into nanoporous coatings.
1 . A stent for insertion into a body structure, comprising:
a tubular member having:
a first end and a second end,
a lumen extending along a longitudinal axis between the first end and the second end,
an ablumenal surface,
a lumenal surface; and
at least one porous layer, the porous layer comprising an interstitial structure and an interstitial space;
wherein the interstitial space is generally configured by the removal of at least a portion of at least one sacrificial material by a thermal dealloying process from a mixture comprising at least one sacrificial material with one or more structural materials that comprise the interstitial structure of the porous layer; and
wherein the porous layer is adapted to receive and release at least one therapeutic agent.
2 . The stent for insertion into a body structure as in claim 1 , wherein at least one sacrificial material is selected for its boiling point.
3 . The stent for insertion into a body structure as in claim 1 , wherein at least one sacrificial material is selected for its vapor pressure.
4 . The stent for insertion into a body structure as in claim 1 , wherein the thermal dealloying process comprises the application of a heat source.
5 . The stent for insertion into a body structure as in claim 4 , wherein the heat source is a light source.
6 . The stent for insertion into a body structure as in claim 5 , wherein the light source is a laser.
7 . The stent for insertion into a body structure as in claim 5 , wherein the light source is an infrared light source.
8 . The stent for insertion into a body structure as in claim 5 , wherein the light source is an ultraviolet light source.
9 . The stent for insertion into a body structure as in claim 4 , wherein the heat source is an inductive heat source.
10 . The stent for insertion into a body structure as in claim 4 , wherein the heat source is an ultrasound source.
11 . The stent for insertion into a body structure as in claim 1 , wherein at least one sacrificial material comprises a form of magnesium.
12 . The stent for insertion into a body structure as in claim 4 , wherein the application of a heat source is performed in a vacuum of about 10 −5 torr or less.
13 . The stent for insertion into a body structure as in claim 12 , wherein the application of a heat source is performed in a vacuum of about 10 −6 torr or less.
14 . The stent for insertion into a body structure as in claim 13 , wherein the application of a heat source is performed in a vacuum of about 10 −9 torr or less.
15 . The stent for insertion into a body structure as in claim 4 , wherein the heat source is capable of heating a portion of the mixture in a temperature of at least about 400° Celsius.
16 . The stent for insertion into a body structure as in claim 15 , wherein the heat source is capable of heating a portion of the mixture in a temperature of at least about 500° Celsius.
17 . The stent for insertion into a body structure as in claim 16 , wherein the heat source is capable of heating a portion of the mixture in a temperature of at least about 600° Celsius.
18 . The stent for insertion into a body structure as in claim 1 , wherein the pores of the porous layer are modified by the application of an etchant to the porous layer.
19 . The stent for insertion into a body structure as in claim 18 , wherein the etchant has anisotropic properties.
20 . The stent for insertion into a body structure as in claim 18 , wherein the etchant has isotropic properties.
21 . A therapy-eluting medical device, comprising:
at least one component of a medical device having at least one therapy-eluting surface comprising an interstitial structure and an interstitial space, wherein the interstitial space is configured generally by the removal of at least a portion of one sacrificial material by a thermal dealloying process from a mixture comprising at least one sacrificial material and one or more structural materials that comprise the interstitial structure of the porous layer; and
wherein the therapy-eluting surface is adapted to receive and release at least one therapeutic agent.
22 . A method for manufacturing a medical device with at least one non-polymeric porous layer, comprising the steps of:
providing at least a component of a medical device having at least one surface;
depositing a layer of a material onto at least a portion of the surface; the layer of material comprising at least one sacrificial component and at least one structural component and at least one component is not a polymer or therapeutic agent; and
thermally removing at least a portion of at least one sacrificial component to form an interstitial space.
23 . The method for manufacturing a medical device with at least one non-polymeric porous layer as in claim 22 , further comprising increasing the interstitial space with an etchant.
24 . The method for manufacturing a medical device with at least one non-polymeric porous layer as in claim 23 , wherein the etchant has isotropic properties.
25 . The method for manufacturing a medical device with at least one non-polymeric porous layer as in claim 23 , wherein the etchant has anisotropic properties.
26 . The method for manufacturing a medical device with at least one non-polymeric porous layer as in claim 22 , wherein the thermally removing step is performed in a vacuum.
27 . The method for manufacturing a medical device with at least one non-polymeric porous layer as in claim 22 , wherein the thermally removing step is performed using a laser.