Protective Polymer Layer for Implantable Medical Device Coatings
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Solution Overview
Problem
Existing implantable medical devices face challenges in minimizing infection risk at the implantation site, particularly due to the degradation and absorption of antibiotic coatings before implantation, and the need for controlled drug release post-implantation.
Innovation Solution
An implantable medical device with a protective polymeric layer comprising polylactic acid, polyglycolic acid, or a lactic acid/glycolic acid copolymer is used, which protects the antibiotic coating during handling and implantation, and dissolves or degrades upon exposure to body fluids to facilitate rapid drug release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an antibiotic coating is applied to the medical device surface, then infection risk is reduced, but the coating degrades and absorbs moisture before implantation, compromising its integrity
Solution Approach 1:
A protective polymer layer is applied over the antibiotic coating before implantation to prevent degradation and moisture absorption during storage and handling. This preliminary protective action ensures the coating remains intact until the moment of implantation, at which point the protective layer dissolves to release the antibiotic.
2Reliability
If a protective polymer layer is added to protect the antibiotic coating, then coating integrity is maintained, but drug release may be delayed
Solution Approach 1:
The protective layer uses a polymer with low molecular weight (not more than 40,000) and specific composition (polylactic acid, polyglycolic acid, or lactic acid/glycolic acid copolymer) that dissolves rapidly upon contact with body fluids. This parameter selection ensures the protective layer maintains the coating during storage but dissolves quickly post-implantation to enable rapid antibiotic release.
3Reliability
If the protective layer thickness is increased to improve protection, then coating stability is enhanced, but drug release speed decreases
Solution Approach 1:
The protective layer thickness is optimized to provide sufficient protection during handling while maintaining rapid dissolution characteristics. The specific polymer composition and molecular weight ensure that even at protective thicknesses, the layer dissolves quickly in body fluids to enable timely drug release.
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 protective layer effectively shields the antibiotic coating from degradation and moisture absorption, ensuring its integrity before implantation and enabling a controlled, rapid release of the drug post-implantation, thereby reducing infection risk and enhancing tissue interaction.
Implementation Method 1
The protective layer can be displaced after the device has been implanted, allowing drug in the coating to be absorbed. Displacement of the protective layer can involve degradation or dissolution or both as a result of contact with body fluids on implantation.
Implementation Method 2
Displacement of the protective layer can involve adsorption of body fluids so that the water content of the polymer matrix increases. The adsorbed water can allow migration through the protective layer of a hydrophilic drug.
Implementation Method 3
Displacement of the protective layer can involve degradation or dissolution or both as a result of contact with body fluids on implantation.
Data Source
AI summary
An implantable medical device, which comprises a device substrate, a coating on the substrate which includes a drug, and a protective layer which overlies the coating. The protective layer comprises a polymer selected from the group consisting of polylactic acid, polyglycolic acid and a lactic acid/glycolic acid copolymer having a weight average molecular weight of not more than 40,000.