Implantable medical device with differentiated luminal and abluminal characteristics
There are disclosed implantable medical devices and apparatus for treating implantable medical devices during production, so as to cause the implantable medical devices to have abluminal surfaces and luminal surfaces with different functional characteristics and in particular surface energies. The luminal surfaces of the medical device are preferably coated with carbon, so as to have a low surface energy, which reduces the risk of thrombi forming when implanted into a patient's vessels. The abluminal surfaces are treated so as to have a high surface energy, such that a therapeutic, preferably bioactive, material, such as a drug, can adhere to the abluminal surfaces and preferably without any need for a containment layer such as polymer or other matrix material. Once the therapeutic material has been delivered into the tissue wall, the stent can remain within the patient's vessel without leaving any delivery artefacts, as occurs with some prior art drug eluting medical devices.
1. An implantable medical device including a support structure having at least one abluminal surface having a first surface energy, at least one luminal surface having a second surface energy, and a therapeutic material disposed on the at least one abluminal surface;
wherein the second surface energy is less than the first surface energy;
wherein the at least one luminal surface includes a coating of or comprising carbon,
wherein the coating of carbon on the at least one luminal surface is an innermost surface of the medical device
wherein the at least one luminal surface of the support structure includes an oxide layer, the coating of carbon being disposed over of the oxide layer;
wherein the support structure is a stent,
wherein the at least one abluminal surface is on a tubular outer surface of the stent, and
wherein the at least one luminal surface is on a tubular inner surface of the stent.
2. An implantable medical device according to claim 1 , wherein the at least one abluminal surface is a functionalised surface.
3. An implantable medical device according to claim 1 , wherein the abluminal surface is free of polymer and matrix materials.
4. An implantable medical device according to claim 1 , wherein the abluminal surface is free of containment and time release elements.
5. An implantable medical device according to claim 1 , including a therapeutic material coating disposed directly on the at least one abluminal surface so as to overlie the at least one abluminal surface, the therapeutic material coating attaching to the at least one abluminal surface as a result of the first surface energy thereof.
6. An implantable medical device according to claim 1 , wherein the abluminal surface is functionalised by at least one polar acid or by at least one polar base component, so as to be a functionalised surface.
7. An implantable medical device according to claim 6 , including a therapeutic material coating disposed directly on the at least one abluminal surface so as to overlie the at least one abluminal surface, the coating being a conjugate base or including a conjugate base component of the polar acid or being a conjugate acid or including a conjugate acid component of the polar base.
8. An implantable medical device according to claim 7 , wherein the therapeutic material coating disposed directly on the at least one abluminal surface so as to overlie the at least one abluminal surface is free of containment or time release materials.
9. An implantable medical device according to claim 1 , wherein the therapeutic material is a bioactive material.
10. A method of preparing an implantable medical device according to claim 1 , including the steps of:
treating the at least one abluminal surface of the stent to increase the surface energy of the at least one abluminal surface relative to the at least one abluminal surface, said treatment step not being carried out on the at least one luminal surface.
11. A method according to claim 10 , including the steps of subjecting the at least one abluminal surface to a treatment or functionalisation agent while keeping the at least one luminal surface apart from the treatment or functionalisation agent.
12. A method according to claim 10 , wherein the at least one luminal surface is covered during treatment or functionalisation of the at least one abluminal surface.
13. A method according to claim 10 , wherein the at least one abluminal surface is passed through a bath of functionalising solution while the at least one luminal surface is kept remote from the functionalising solution.
14. A method according to claim 10 , including the step of washing the entire support structure in an alcohol, sealing the at least one luminal surface and plasma cleaning the at least one abluminal surface.
15. A method according to claim 14 , wherein the alcohol is ethanol.
16. A method according to claim 10 , wherein at least the abluminal surface or surfaces are plasma cleaned.
17. A method according to claim 10 , wherein both the abluminal and luminal surfaces are plasma cleaned.
18. A method according to claim 10 , wherein at least the abluminal surface or surfaces are cleaned by UV Ozone.