Heparin-Polymer Conjugate Coating for Stent Thrombosis Prevention
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Solution Overview
Problem
Current drug-eluting stents face challenges in preventing restenosis and thrombosis, with existing coatings either being ineffective in reducing restenosis or increasing the risk of thrombosis, and there is a need for a coating that can stabilize therapeutic agents while preventing blood coagulation and burst release.
Innovation Solution
A conjugate between heparin and a comb-type bioabsorbable polymer with a free carboxyl end group is used, where the heparin is oriented away from the hydrophobic agent, forming a stable outer layer that prevents thrombosis and modulates the release kinetics of the inner drug layer, ensuring extended release and reduced burst release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drug-loaded polymeric coating is applied to prevent restenosis, then restenosis is inhibited, but thrombosis risk increases
Solution Approach 1:
The coating is divided into two distinct layers: an inner layer containing the anti-restenotic drug and an outer layer containing the anti-thrombotic agent heparin. This segmentation allows each layer to perform its specific function independently, with the inner layer preventing restenosis and the outer layer preventing thrombosis, thereby resolving the contradiction between restenosis prevention and thrombosis risk
Solution Approach 2:
Different regions of the coating have different functional properties: the inner layer is designed with drug-loading capacity for anti-restenotic therapy, while the outer layer is designed with heparin for anti-thrombotic protection. This local differentiation of quality ensures that each part of the coating addresses specific pathological concerns without interfering with the other function
2Object-affected harmful factors
If heparin is conjugated to the polymer, then thrombosis is prevented, but drug release stability is compromised
Solution Approach 1:
The heparin conjugate is placed in a separate outer layer rather than being mixed with the drug in the inner layer. This spatial segmentation prevents heparin from interfering with the drug release kinetics while still providing thrombosis prevention functionality, thus maintaining both thrombosis protection and drug release stability
Solution Approach 2:
The outer layer of heparin-conjugated polymer acts as an intermediary protective layer that prevents thrombosis without directly interacting with the inner layer drug. This intermediary structure allows the drug to release according to its intended kinetics while the outer layer provides its independent anti-thrombotic function
3Device complexity
If a single-layer coating is used, then device complexity is reduced, but dual functionality (anti-restenotic and anti-thrombotic) cannot be achieved
Solution Approach 1:
The coating is segmented into two functional layers, each with specific composition and purpose. The inner layer contains the anti-restenotic drug in a biodegradable polymer matrix, while the outer layer contains heparin-conjugated polymer for anti-thrombotic protection. This segmentation enables dual functionality while maintaining a relatively simple overall structure that can be applied in a sequential manner
Solution Approach 2:
The multi-layer coating structure provides multi-functionality: the inner layer delivers anti-restenotic therapy while the outer layer provides anti-thrombotic protection. Together, they create a universal coating system that addresses multiple pathological concerns (restenosis and thrombosis) simultaneously, making the device adaptable to complex clinical requirements
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
The solution effectively inhibits thrombosis and sub-acute device thrombosis while maintaining the therapeutic efficacy of the biologically active agents, providing a stable and prolonged release of drugs, thus addressing the limitations of existing coatings.
Implementation Method 1
The outmost layer of the coating comprises the conjugate of the present invention, which prevents the formation of thrombosis
Implementation Method 2
The release mechanism of the drug from the polymeric materials depends on the nature of the polymeric material and the drug to be incorporated. The drug diffuses through the polymer to the polymer-fluid interface and then into the fluid
Implementation Method 3
The stent is then subjected to a drying process, during which the solvent is evaporated, and the polymeric material, with the drug dispersed therein, forms a thin film layer on the stent
Implementation Method 4
The degradation of the polymeric material may occur through hydrolysis or an enzymatic digestion process, leading to the release of the incorporated drug into the surrounding tissue
Data Source
AI summary
An implantable device having a coating comprising a comb-type anti-thrombotic conjugate to prevent or reduce the formation of thrombosis on the surface of the device. The device includes a frame expandable from a first diameter to a second diameter wherein the frame has an inner surface and an outer surface, a plurality of structural features disposed along the frame and a plurality of polymer anti-thrombotic conjugate particles situated with the plurality of structural features. The particle can be created utilizing the comb type polymer and heparin conjugate as a carrier for a therapeutic agent within its polymer matrix. The structural features allow for particles having differing properties to be placed at various locations along the device. Moreover, particles having at least two different agents can be located within the same structural feature.