Implantable Stent with Differentiated Surface Energies
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Solution Overview
Problem
Existing implantable medical devices face challenges in effectively delivering bioactive agents without causing inflammation, thrombosis, or the need for containment matrices, which can lead to adverse reactions and reduced efficacy.
Innovation Solution
The medical device is treated to have differentiated abluminal and luminal surfaces, with abluminal surfaces optimized for bioactive agent retention through functionalization and without a polymer matrix, and luminal surfaces coated with carbon to reduce thrombosis risk, eliminating the need for containment layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polymer containment matrix is used to hold the bioactive agent, then drug dosing and adherence are improved, but inflammation and neointimal proliferative response are caused
Solution Approach 1:
The patent removes the polymer containment matrix from the device design. Instead of using a polymer layer to hold and release the drug, the invention directly coats the bioactive agent onto the metal stent surface through specialized surface treatment and coating processes, thereby eliminating the source of inflammation and neointimal proliferation while maintaining drug delivery functionality
Solution Approach 2:
The patent employs a composite coating structure consisting of multiple layers: a primer layer for adhesion, a pharmacoeffective layer containing the bioactive agent, and optionally a protective layer. This composite approach allows direct drug coating on metal without polymer matrices, achieving both reliable drug delivery and biocompatibility
2Reliability
If a polymer coating is applied to deliver the bioactive agent, then drug retention is improved, but thrombotic response is enhanced
Solution Approach 1:
The patent eliminates polymer coatings entirely from the device design. The bioactive agent is directly coated onto the metal stent surface using a multi-layer coating system with primer and pharmacoeffective layers, removing the thrombogenic polymer material while preserving drug retention through direct metal-coating adhesion
Solution Approach 2:
The patent changes the surface energy and chemical properties of the metal stent through surface treatment (such as anodization or plasma treatment) to enable direct adhesion of the bioactive agent coating. This parameter change allows the metal surface to function as a drug carrier without requiring polymer intermediaries, thereby reducing thrombotic response
3Reliability
If the luminal surface is made highly adhesive for drug delivery, then bioactive agent retention is improved, but thrombosis risk increases
Solution Approach 1:
The patent applies different surface properties to different regions of the stent: the abluminal surface (facing the vessel wall) is treated to be highly adhesive for optimal bioactive agent retention, while the luminal surface (facing the blood flow) is kept with native metal properties or specially treated to be non-thrombogenic. This spatial differentiation of surface quality allows simultaneous achievement of drug retention and thrombosis prevention
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances bioactive agent adhesion and retention on the device, reduces thrombosis risk, and avoids foreign body reactions, providing a more effective and safer long-term delivery of therapeutic agents.
Implementation Method 1
the luminal surfaces which are intended to minimise thrombosis... the at least one luminal surface has a much lower surface energy and such as to exhibit significantly reduced adhesion characteristics
Implementation Method 2
the abluminal surfaces which are optimised for carrying a therapeutic agent such as a bioactive agent... the at least one abluminal surface has a surface energy sufficient to hold therapeutic agents, such as bioactive agents, such as drugs, thereto
Data Source
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AI summary
There are disclosed implantable medical devices (100) and apparatus for treating implantable medical devices during production, so as to cause the implantable medical devices (100) to have abluminal surfaces and luminal surfaces with different functional characteristics and in particular surface energies. The luminal surfaces of the medical device (100) 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.