Crystalline Limus Coating for Stent Proliferation Inhibition
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Solution Overview
Problem
Current medical devices coated with limus substances for preventing vasoconstriction and cell proliferation have limited efficacy due to slow tissue absorption and short retention, which is inferior to paclitaxel-coated devices, and there is a lack of comparison studies with uncoated devices.
Innovation Solution
Medical devices with a coating of non-encapsulated crystalline limus substances applied from a solution or suspension using water-miscible organic solvents, with controlled crystallization and drying to enhance tissue retention and bioavailability, and optionally including antioxidants and excipients for improved adhesion and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If limus substances are applied locally to medical devices, then cell proliferation is inhibited and vasoconstriction is prevented, but tissue absorption is slow and retention is short
Solution Approach 1:
The patent changes the physical state parameter of the limus substance from amorphous to crystalline form. This parameter change fundamentally alters the dissolution kinetics, enabling the substance to remain on the device surface longer while maintaining therapeutic efficacy. The crystalline structure provides controlled release characteristics that extend tissue retention time without compromising the anti-proliferative effect.
Solution Approach 2:
The patent creates a composite coating system combining limus substance crystals with specific excipients including fatty acid salts (0.5-50 wt%), antioxidants (0.1-5 wt%), and other pharmaceutical excipients. This composite formulation enhances both the stability and retention of the limus substance on the medical device surface, addressing the short retention time issue while maintaining therapeutic reliability.
2Ease of manufacture
If limus substances are applied from non-polar organic solvents, then coating is achieved, but water-miscibility and controlled release are compromised
Solution Approach 1:
The patent changes the solvent parameter from non-polar organic solvents to water-miscible organic solvents. This parameter change ensures the coating solution can be easily applied while the resulting crystalline limus substance provides controlled release. The water-miscible nature of the solvent system maintains biocompatibility and enables predictable dissolution kinetics in the aqueous physiological environment.
3Duration of action of stationary object
If limus substances are applied in crystalline form, then tissue retention is extended, but manufacturing precision is required for controlled crystallization
Solution Approach 1:
The patent utilizes controlled changes in temperature and solvent composition parameters to guide crystallization. By adjusting these parameters during the coating process, consistent crystalline structures are formed with predictable release characteristics. This parameter control approach transforms a potentially imprecise crystallization process into a reliable manufacturing method.
Solution Approach 2:
The patent employs self-assembly crystallization where the limus substance naturally forms crystalline structures when exposed to water-miscible organic solvents under controlled conditions. This self-organizing process reduces the need for complex external control mechanisms, achieving consistent crystalline coatings with acceptable manufacturing precision through the inherent properties of the material system.
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 achieves faster and more complete tissue absorption, longer retention, and enhanced efficacy in inhibiting neointima proliferation, with a sustained effect comparable to paclitaxel-coated devices, while being locally tolerable and stable.
Implementation Method 1
the at least one crystalline non-encapsulated limus substance was applied directly from a solution together with a water-miscible organic solvent or a mixture of water-miscible organic solvents and water
Implementation Method 2
with controlled crystallization and drying to enhance tissue retention and bioavailability
Implementation Method 3
The limus substances are usually applied to coronary stents, slowly released therefrom and transferred to the directly adjacent tissue
Data Source
AI summary
In order to provide medical devices having a coating for local prophylaxis and treatment of undesirable cell proliferation and vasoconstriction, a medical device comprising a coating on at least a portion of the surface is proposed, said coating comprising at least one limus substance in non-encapsulated crystalline form, wherein the at least one non-encapsulated limus substance is applied directly from a solvent mixture of at least one organic solvent and water. The formation of crystals of the limus substance can be brought about or enhanced by slowing down the evaporation of the solvent mixture.In addition, a method for preparing the medical devices is proposed.