Biodegradable Stent Crosslinked Polymer Shape Recovery
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Solution Overview
Problem
Self-expandable stents face issues with incomplete apposition due to slow shape recovery, leading to potential stent thrombosis and movement under blood flow, and existing biodegradable stents lack sufficient radial force and strain resistance.
Innovation Solution
A self-expandable stent composed of a crosslinked polymer with a rigid biodegradable constitutional unit (A) having a glass transition temperature of 40 °C or more, a rubber-like biodegradable constitutional unit (B) with a glass transition temperature of 30 °C or lower, and a crosslinking agent (C) in amounts between 10% to 60% by weight, ensuring rapid shape recovery and sufficient radial force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a biodegradable polymer is used to form a self-expandable stent, then the radial force decreases over time to improve medium to long-term clinical outcomes, but the shape recovery speed becomes slow causing incomplete stent apposition
Solution Approach 1:
The patent uses a copolymer composed of a rigid biodegradable polymer (providing strength and radial force) and a rubber-like biodegradable polymer (providing elasticity and fast shape recovery). This composite material structure allows the stent to achieve both slow radial force degradation for long-term benefits and rapid shape recovery to prevent incomplete apposition, resolving the contradiction between these two requirements.
2Speed
If the rubber-like polymer content is increased to improve elastic properties and reduce inward recoil, then the shape recovery speed increases, but the radial strength decreases
Solution Approach 1:
The patent optimizes the compositional parameters of the copolymer, specifically controlling the rubber-like polymer content to be 5-50 mol% of the total copolymer. This parameter optimization achieves a balance where sufficient elastic properties and shape recovery speed are obtained while maintaining adequate radial strength, resolving the contradiction between speed and strength.
3Force
If a nickel-titanium alloy is used to provide strong radial force, then the expansion retention force is maintained, but major adverse cardiac events occur in medium to long-term outcomes
Solution Approach 1:
The patent employs a biodegradable polymer material that gradually degrades and loses its radial force over time, unlike permanent nickel-titanium alloys. This 'temporary support' approach provides sufficient radial force during the critical healing period and then naturally degrades, allowing the vessel to remodel without long-term foreign body presence, thereby reducing major adverse cardiac events while maintaining expansion retention force when needed.
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 stent achieves rapid shape recovery within seconds to minutes, maintains radial force for effective expansion, and reduces incomplete apposition and long-term adverse cardiac events by degrading over time.
Implementation Method 1
a constitutional unit (B) derived from a monomer to constitute a rubber-like biodegradable polymer which is a homopolymer having a glass transition temperature (Tg) of 30 °C or lower
Implementation Method 2
a self-expandable stent formed of a super-elastic alloy, such as a nickel-titanium alloy, is commercially available in Europe
Implementation Method 3
US Patent Application Publication No. 2010/0262223 discloses a method of producing a stent, the method including crosslinking a biodegradable polymer by a crosslinking agent to form a base material
Implementation Method 4
Since a biodegradable material is gradually degraded in a living body, it is supposed that the radial force of the stent decreases over time to improve the medium to long-term clinical outcomes
Implementation Method 5
a constitutional unit (A) derived from a monomer to constitute a rigid biodegradable polymer
Data Source
Figure 1(A)~1(B)
Figure 2~3
Figure 4
AI summary
Provided is a self-expandable stent which has sufficient radial force, has good flexural properties, and recovers the shape from a diameter in a contracted state to a diameter before contraction in a short period of time around body temperature (37°C). The self-expandable stent of the present invention is a self-expandable stent that includes a crosslinked polymer including a constitutional unit (A) derived from a monomer to constitute a rigid biodegradable polymer, a constitutional unit (B) derived from a monomer to constitute a rubber-like biodegradable polymer, and a constitutional unit (C) derived from a crosslinking agent, the constitutional unit (C) being contained in an amount of 10% by weight or more and less than 60% by weight based on the total amount of the constitutional unit (A) and the constitutional unit (B).