Bioabsorbable Stent Coating Molecular Weight Control
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Solution Overview
Problem
Current drug-eluting stents face challenges with compromised coating integrity due to ethylene oxide sterilization and crimping processes, leading to issues like polymer deformation and adhesion to delivery balloons, as well as suboptimal mechanical properties and prolonged absorption periods of aliphatic polyesters like PLLA.
Innovation Solution
A bioabsorbable stent coating comprising a D,L-PLA polymer with a number average molecular weight below 60,000 Daltons, a thickness of less than 5 micrometers, and a primer layer of high molecular weight polymer, which completely absorbs within 3 to 6 months, along with the option of lactide monomers and oligomers, and a bioactive agent like novolimus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a completely amorphous bioabsorbable polymer is used for coating a stent, then the coating can be applied, but the coating integrity is compromised during ETO sterilization or crimping due to polymer deformation and adhesion
Solution Approach 1:
The patent changes the molecular weight parameter of the D,L-PLA polymer to below 60,000 Daltons and controls the coating thickness to less than 5 micrometers. These parameter changes modify the polymer's physical properties to reduce deformation and adhesion during sterilization and crimping while maintaining coating integrity.
Solution Approach 2:
The patent creates a composite coating system combining D,L-PLA polymer with novolimus drug, where the polymer matrix provides structural integrity and the drug reservoir provides therapeutic function. This composite approach allows the coating to maintain integrity during processing while delivering drug benefits.
2Object-affected harmful factors
If PLLA is used as the polymer material, then the coating is biodegradable and biocompatible, but the mechanical properties are compromised after fabrication and deployment
Solution Approach 1:
The patent changes the molecular weight parameter of the D,L-PLA polymer to below 60,000 Daltons, which modifies the mechanical properties by reducing brittleness and improving flexibility while maintaining biodegradability and biocompatibility of the PLLA material.
3Duration of action of stationary object
If PLLA is used as the polymer material, then the coating is biodegradable, but the absorption period is relatively long
Solution Approach 1:
The patent changes the molecular weight parameter of the D,L-PLA polymer to below 60,000 Daltons, which accelerates the hydrolysis and degradation rate of the polymer, thereby reducing the absorption period from several months to 3-6 months while maintaining complete biodegradability.
4Productivity
If the coating thickness is reduced to improve drug delivery, then the drug delivery efficiency increases, but the coating becomes more susceptible to damage during processing
Solution Approach 1:
The patent optimizes the coating thickness parameter to less than 5 micrometers, which is thin enough to allow efficient drug diffusion and delivery while being thick enough to maintain structural integrity during ETO sterilization and crimping processes when combined with the low molecular weight D,L-PLA polymer.
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 coating provides enhanced mechanical properties and reduced absorption time, preventing occlusion and thrombosis, while maintaining effective drug delivery and biocompatibility, thereby addressing the limitations of existing stent coatings.
Implementation Method 1
The coating has an absorption period from about three months to about six months during which the coating is completely or substantially completely absorbed upon implantation in a human body
Data Source
AI summary
The present invention provides an absorbable coating for an implantable device and the methods of making and using the same.