U-Shaped Stent Strut Drug Coating Design
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Solution Overview
Problem
Drug eluting stents face issues with fragile coatings that can fracture during manufacture, delivery, or deployment, leading to reduced effectiveness and potential hazards due to lost drug and metal strut fatigue, along with concerns over long-term polymer effects in the body.
Innovation Solution
A drug eluting folded stent system featuring U-shaped struts with a recess and drug coating within, designed to release medication at a predetermined rate, manufactured by applying a drug coating to a metal ribbon, folding it into a U-shape, and interconnecting the struts to form a tubular body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exterior coatings are applied to metal struts to deliver drugs, then drug delivery capability is improved, but coating fragility increases leading to fracture and fragmentation during manufacture and use
Solution Approach 1:
The drug coating is extracted from the exterior surface of the metal struts and relocated to the interior surface only. This eliminates the fragility issue of exterior coatings while preserving drug delivery capability through controlled diffusion from the interior coating through the metal strut walls.
Solution Approach 2:
The coating is applied selectively to specific locations - the interior surface of the struts rather than the entire exterior surface. This localized application reduces the total coated area exposed to mechanical stress during deployment, thereby reducing fragmentation risk while maintaining therapeutic effectiveness through controlled drug diffusion.
2Duration of action of moving object
If coating thickness is increased to extend drug elution duration, then drug delivery duration is improved, but coating fragility and fracture risk increase
Solution Approach 1:
By moving the coating to the interior surface, the coating is protected from the mechanical stresses of deployment and blood flow. This allows for thicker coatings to be applied without proportionally increasing fracture risk, as the interior location provides mechanical protection while still enabling controlled drug diffusion through the strut walls over extended periods.
3Strength
If metal struts are used to maintain lumen open, then structural support is improved, but metal fatigue and crack propagation occur leading to strut fracture
Solution Approach 1:
The invention creates a composite structure combining metal struts for mechanical support with an interior polymer coating for drug delivery. This composite approach allows the metal to provide structural strength while the coating provides therapeutic function, potentially reducing stress concentration points that would lead to metal fatigue and crack propagation.
4Quantity of substance
If exterior coatings are used for drug delivery, then drug release capability is improved, but drug loss due to fragmentation during delivery and deployment increases
Solution Approach 1:
Relocating the drug coating from the exterior to the interior surface protects the drug-containing coating from mechanical fragmentation during delivery and deployment. The interior location shields the coating from the harshest mechanical stresses, thereby preserving drug integrity and reducing loss while maintaining the ability to deliver the full drug dose to the tissue.
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 provides a stable and effective drug delivery system that minimizes fragmentation risks, controls drug elution duration, and reduces the risk of metal strut fatigue, while maintaining mechanical integrity and biocompatibility.
Implementation Method 1
The drug release opening is sized to release a drug from the drug coating at a predetermined drug elution rate
Data Source
AI summary
The drug eluting folded stent and a stent delivery system, which includes a stent having a plurality of struts interconnected to form a tubular body. At least one of the struts includes a U-shaped strut having in cross-section a first leg, a second leg, and a closed end connecting the first leg and the second leg, wherein the first leg, the second leg, and the closed end define a recess having a drug release opening opposite the closed end; and a drug coating disposed on the first leg, the second leg, and the closed end within the recess. The drug release opening is sized to release a drug from the drug coating at a predetermined drug elution rate.