Hollow Stent Drug Loading via Reverse Fill and Solvent Extraction
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Solution Overview
Problem
Drug-eluting medical devices face challenges in delivering increased quantities of therapeutic agents and controlling the elution rate, with issues such as adverse reactions from remaining polymer material, flaking coatings, and limited drug delivery capacity due to polymer coatings.
Innovation Solution
A method for loading a therapeutic substance into a hollow stent with side openings, allowing for controlled drug delivery through a reverse or forward fill process, followed by solvent extraction to remove the solvent, ensuring only the drug or excipients remain, and a stent cleaning step to prevent exterior residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polymer coatings are used to deliver drugs, then the drug can be delivered to the target site, but the quantity of drug delivered is limited by the coating capacity and device size
Solution Approach 1:
The patent utilizes the hollow internal structure of the stent struts to nest and store therapeutic substances. Instead of relying on external polymer coatings, the drug is delivered from within the hollow lumens of the struts, effectively using the device structure itself as a drug reservoir. This nesting approach dramatically increases the drug carrying capacity without adding external complexity.
Solution Approach 2:
The patent changes the physical state and storage location of the therapeutic substance from being embedded in polymer coatings to being stored in hollow internal lumens. This parameter change from surface-based to volume-based drug storage enables significantly higher drug quantities to be delivered while simplifying the overall device structure by eliminating the need for thick polymer coatings.
2Duration of action of moving object
If polymer coatings are used to control drug elution rate, then drug release can be controlled, but the remaining polymer material causes adverse reactions and clot formation
Solution Approach 1:
The patent extracts and eliminates the polymer coating material from the device design. Instead of using polymer coatings to control drug release, the invention uses the hollow strut structure combined with porous surface treatments to achieve drug elution control without the harmful residual polymer materials that cause adverse reactions and thrombosis.
Solution Approach 2:
The patent employs porous surface treatments on the hollow struts to control drug elution rates. The porous structure allows for controlled drug release through diffusion and capillary action, providing sustained drug delivery without requiring polymer coatings. This approach maintains elution rate control while eliminating the harmful effects of remaining polymer material.
3Reliability
If polymer coatings are applied to device surfaces, then drug delivery is enabled, but the coatings may flake off or be damaged during delivery
Solution Approach 1:
The patent nests the therapeutic substance within the hollow internal lumens of the struts rather than applying it as an external coating. This internal storage configuration protects the drug from mechanical damage and flaking during device delivery, significantly improving drug delivery reliability while eliminating coating integrity issues.
Solution Approach 2:
The patent inverts the conventional approach by moving the drug storage from the external surface (coating) to the internal hollow space of the struts. This inversion protects the therapeutic substance from mechanical stresses during delivery, preventing flaking and damage, thereby enhancing the reliability of drug delivery to the target site.
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 enables controlled and increased delivery of therapeutic agents, avoiding adverse reactions and improving the elution rate control, while maintaining biocompatibility and consistency.
Implementation Method 1
a therapeutic substance or drug in a solution or suspension is loaded into a lumenal space of a hollow wire
Implementation Method 2
The open ends of the hollow stent are sealed and a pressure differential is utilized to force the solution or suspension into the lumenal space
Implementation Method 3
a solvent or dispersion medium extracting step is performed to extract the solvent or dispersion medium from within the lumenal space
Data Source
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AI summary
Methods and apparatus are disclosed for loading a therapeutic substance or drug within a lumenal space of a hollow wire having a plurality of side openings along a length thereof that forms a hollow drug-eluting stent with a plurality of side drug delivery openings. Loading a drug within the lumenal space of the hollow stent includes a drug filling step, in which the drug is mixed with a solvent or dispersion medium. The lumenal space may be filled with the drug solution or suspension in a reverse fill process and/or a forward fill process. After the drug filling step, a solvent or dispersion medium extracting step is performed to extract the solvent or dispersion medium from within the lumenal space such that only the drug remains within the hollow stent. A stent cleaning step may be performed to an exterior surface of the hollow stent.