Bioabsorbable Polymer Stent with Thin Struts
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Solution Overview
Problem
The development of fully bioabsorbable polymer stents faces challenges in achieving structural strength and integrity similar to metal stents without the drawbacks of thicker struts, which can lead to larger profiles, reduced flexibility, and longer degradation times.
Innovation Solution
A tubular scaffold comprising interconnected bioabsorbable polymer struts with circumferentially aligned polymer chains, incorporating a macrolide immunosuppressant in crystalline form and a bioabsorbable coating polymer, with an average strut thickness of no more than 120 µm, maintaining structural integrity and flexibility while ensuring bioabsorbability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thicker struts are used to achieve structural strength similar to metal stents, then strength is improved, but profile size increases and flexibility decreases
Solution Approach 1:
The patent changes the material parameter from metal to bioabsorbable polymer, enabling thin strut design while achieving required structural strength through material selection and optimized polymer composition. The polymer material allows thin struts to maintain adequate strength during the critical early healing period while being absorbed over time.
Solution Approach 2:
The patent employs composite structure with multiple polymer layers including a drug-eluting coating layer and a structural polymer layer. This composite approach allows thin struts to achieve both structural integrity and drug delivery functionality, resolving the contradiction between thin profile and adequate strength.
2Strength
If thicker struts are used to achieve structural strength similar to metal stents, then strength is improved, but degradation time increases
Solution Approach 1:
The patent controls degradation time by selecting specific polymer compositions and molecular weight parameters. The bioabsorbable polymer is engineered to maintain structural strength for the required period (typically 6-12 months) and then degrade at a controlled rate, eliminating the direct correlation between thickness and degradation time that exists in metal stents.
Solution Approach 2:
The patent provides adequate structural strength for the critical early healing period without over-engineering the strut thickness. The thin struts provide sufficient support during the period when the vessel needs reinforcement, then degrade appropriately, avoiding excessive degradation time that would occur with thicker designs.
3Ease of operation
If thinner struts are used to improve flexibility and reduce profile, then ease of operation is improved, but structural strength decreases
Solution Approach 1:
The patent compensates for reduced cross-sectional area of thin struts by using high-strength bioabsorbable polymer materials with optimized mechanical properties. The polymer composition and molecular structure are selected to maximize strength-to-weight ratio, enabling thin struts to achieve adequate structural performance.
Solution Approach 2:
The patent employs curved and arc-shaped strut designs rather than straight rigid structures. The curved geometry provides structural reinforcement while maintaining flexibility, allowing thin struts to achieve both ease of operation and adequate strength through optimized shape rather than increased thickness.
4Reliability
If fully bioabsorbable polymer material is used, then bioabsorbability is improved, but structural strength and integrity decrease
Solution Approach 1:
The patent selects specific bioabsorbable polymer materials with controlled degradation rates and optimized mechanical properties. The polymer composition parameters (molecular weight, crystallinity, cross-linking density) are adjusted to ensure adequate structural strength is maintained during the critical early healing period while ensuring complete bioabsorbability over time.
Solution Approach 2:
The patent provides enhanced structural support during the early healing period when the vessel wall is most vulnerable, then gradually reduces support as the vessel heals and the polymer degrades. This temporal matching of structural support with physiological needs resolves the contradiction between bioabsorbability and structural strength.
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 allows for a stent that maintains at least 50% of its nominal luminal cross-sectional area under pressure loads and is fully bioabsorbed within 1-2 years, offering improved flexibility and controlled drug release.
Implementation Method 1
the polymer struts comprises a gel-spun polymer material
Implementation Method 2
the tubular scaffold includes polymer chains that are circumferentially aligned along a center axis of the tubular scaffold, so that the tubular scaffold has an average axial elastic modulus along a center axis of the tubular scaffold and an average circumferential elastic modulus orthogonal to the center axis of the tubular scaffold, the average circumferential elastic modulus being greater than the average axial elastic modulus
Implementation Method 3
a pharmaceutical agent incorporated to the tubular scaffold, wherein at least a portion of the tubular scaffold is covered with a coating comprising the pharmaceutical agent which is a macrolide immunosuppressant in crystalline form
Implementation Method 4
a coating comprising the pharmaceutical agent which is a macrolide immunosuppressant in crystalline form and a bioabsorbable coating polymer
Data Source
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AI summary
A bioabsorbable biomedical implant is disclosed. The implant includes a tubular scaffold comprising a plurality of interconnected polymer struts. The interconnected polymer struts defines a plurality of deformable cells. The polymer struts have an average strut thickness of no more than about 120 μιη. Methods for making the bioabsorbable biomedical implant, including the methods for making the polymer materials for the tubular scaffold, are also disclosed.