Rapamycin-Cilostazol Stent Coating for Restenosis Prevention
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Solution Overview
Problem
Current methods for preventing restenosis after percutaneous transluminal coronary angioplasty are ineffective, as systemic pharmacologic agents fail to achieve therapeutic concentrations without causing toxicity, and existing stents induce neointimal hyperplasia, leading to continued vascular narrowing and thrombosis.
Innovation Solution
Development of medical devices with coatings containing rapamycin and cilostazol, combined with polymeric materials for controlled elution, to inhibit smooth muscle cell proliferation and platelet deposition, reducing restenosis and thrombosis through local drug delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If systemic pharmacologic agents are used to prevent restenosis, then therapeutic effect is achieved, but toxicity occurs due to inability to maintain therapeutic concentrations
Solution Approach 1:
The patent applies local quality by coating the stent surface with drugs (rapamycin and/or cilostazol) that are released locally at the site of vascular injury. This ensures high drug concentration where needed (at the injured vessel wall) while avoiding systemic circulation and associated toxicity. The stent acts as a localized delivery system, concentrating therapeutic effect precisely where restenosis prevention is required.
Solution Approach 2:
The stent coating serves as an intermediary carrier that mediates drug delivery from the implantable device to the surrounding tissue. The polymeric coating material acts as a reservoir and controlled-release mechanism, transferring drugs directly to the injured vessel wall without requiring systemic circulation. This intermediary system bridges the gap between the stent structure and the target tissue, enabling localized therapeutic action.
2Reliability
If conventional stents are used to maintain vessel patency, then vascular opening is achieved, but neointimal hyperplasia occurs leading to restenosis
Solution Approach 1:
The stent is pre-coated with anti-proliferative drugs (rapamycin and/or cilostazol) before implantation. These drugs are released immediately upon deployment to preemptively inhibit smooth muscle cell proliferation and neointimal hyperplasia. The preliminary presence of the drug coating counteracts the proliferative response that would otherwise be triggered by the stent implantation and vascular injury, preventing restenosis before it can develop.
Solution Approach 2:
The stent combines multiple materials and functions: the metallic stent structure provides mechanical support and vessel patency, while the polymeric drug-containing coating provides pharmacological protection against restenosis. This composite structure integrates the mechanical function of the stent with the biological function of the drug delivery system, creating a multi-functional device that simultaneously maintains patency and prevents hyperplastic response.
3Reliability
If drug coatings are applied to stents, then local drug delivery is achieved, but control over elution rate is challenging
Solution Approach 1:
The drug delivery system is segmented into distinct functional layers: a primary polymeric coating containing the drugs (rapamycin and/or cilostazol) and a secondary outer coating layer. This segmentation allows different layers to perform different functions - the inner layer provides drug reservoir and initial release, while the outer layer controls the elution rate and provides additional protection. The segmented structure simplifies the control mechanism by using physical layering rather than complex chemical or mechanical systems.
Solution Approach 2:
The stent coating uses composite polymeric materials with different properties to achieve controlled drug release. The combination of different polymers (e.g., polyurethane, polyester, polyamide) with varying degradation rates, porosity, and drug affinity creates a composite structure that naturally regulates elution kinetics. The composite material system provides controlled release through the inherent properties of the polymer blend rather than requiring external control mechanisms.
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 combination of rapamycin and cilostazol on drug-eluting stents effectively reduces neointimal growth and thrombosis, providing sustained anti-restenotic and anti-thrombotic effects, enhancing vascular patency and reducing the risk of restenosis and inflammation.
Implementation Method 1
a second coating, including a second polymeric material, affixed to the first coating for controlling the elution rate of the rapamycin and the cilostazol
Implementation Method 2
controlling the elution rate of the rapamycin and the cilostazol
Data Source
AI summary
Medical devices, and in particular implantable medical devices, may be coated to minimize or substantially eliminate a biological organism's reaction to the introduction of the medical device to the organism. The medical devices may be coated with any number of biocompatible materials. Therapeutic drugs, agents or compounds may be mixed with the biocompatible materials and affixed to at least a portion of the medical device. These therapeutic drugs, agents or compounds may also further reduce a biological organism's reaction to the introduction of the medical device to the organism. In addition, these therapeutic drugs, agents and/or compounds may be utilized to promote healing, including the formation of blood clots.