PLLA Stent Tunable Degradation via Molecular Weight Control
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Solution Overview
Problem
Biodegradable stents made from bioabsorbable polymers face challenges in maintaining mechanical integrity and degradation time, which varies across different applications, necessitating a solution to adjust degradation behavior without altering the stent composition significantly.
Innovation Solution
The method involves processing PLLA polymer material with varying LLA monomer content through polymerization reactions and post-processing techniques to achieve targeted degradation profiles, ensuring radial strength and mechanical integrity for specific applications, such as coronary and peripheral artery treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If biodegradable stents are made from bioabsorbable polymers, then the stent can be resorbed by the body after serving its function, but the degradation time varies across applications and may not match the required duration for maintaining mechanical integrity
Solution Approach 1:
The patent applies parameter changes by controlling the molecular weight of the poly(L-lactide) polymer to precisely adjust the degradation time. By synthesizing PLLA with specific molecular weights (e.g., 50,000 to 500,000 g/mol), the invention tailors the degradation profile to match different clinical requirements while maintaining adequate mechanical support duration. This resolves the contradiction by making degradation time a controllable parameter rather than a fixed property.
Solution Approach 2:
The invention uses composite material strategies by blending PLLA with other biodegradable polymers or incorporating cross-linking agents to modify degradation behavior. This allows customization of both degradation rate and mechanical properties, enabling the stent to maintain structural integrity for the required period while ensuring eventual resorption.
2Duration of action of stationary object
If the stent degrades faster, then the body can resorb it sooner, but the radial strength and mechanical integrity are lost before the vessel is fully healed
Solution Approach 1:
The patent controls the molecular weight parameter of PLLA to achieve the desired balance between strength and degradation. Higher molecular weights provide greater initial radial strength and slower degradation, while lower molecular weights degrade faster but with reduced strength. By selecting appropriate molecular weight ranges, the invention optimizes both the strength maintenance period and resorption time to match healing requirements.
3Reliability
If the stent degrades slower, then mechanical integrity is maintained longer, but the stent remains in the body beyond the required treatment period
Solution Approach 1:
The invention uses molecular weight as a control parameter to prevent excessive persistence. By setting upper limits on molecular weight (e.g., not exceeding 500,000 g/mol), the patent ensures that even high-strength stents will degrade within clinically acceptable timeframes, avoiding long-term foreign body presence while maintaining adequate support during healing.
4Speed
If the PLLA polymer material contains higher LLA monomer content, then the degradation rate increases, but the mechanical properties and radial strength are compromised
Solution Approach 1:
The patent controls the LLA monomer content as a critical parameter to balance degradation rate and mechanical properties. By limiting LLA content to specific ranges (e.g., 0.1% to 10% by weight), the invention accelerates degradation sufficiently for clinical resorption while preserving adequate radial strength for vessel support. This resolves the contradiction by establishing optimal parameter ranges that satisfy both 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
This approach allows for controlled degradation of stents, maintaining radial strength for the required duration in coronary and peripheral applications, preventing restenosis and ensuring vessel remodeling without premature recoil or loss of mechanical integrity.
Implementation Method 1
making PLLA polymer material with a polymerization reaction of LLA monomers
Implementation Method 2
controlled degradation of stents, maintaining radial strength for the required duration
Data Source
AI summary
Methods of treating with a biodegradable polymeric stent made from poly(L-lactide) and a low concentration of L-lactide monomer is disclosed. The concentration of L-lactide is adjusted to provide a degradation behavior that is suitable for different treatment applications including coronary, peripheral, and nasal.