Multilayer Coatings for Controlled Drug Release
Solution Overview
Problem
Designing coatings that stably entrap and control the release of highly water-soluble drugs is challenging due to rapid 'burst effect' when in contact with body fluids, as small defects in coatings can lead to rapid release.
Innovation Solution
Multilayer coatings with a hydrophobic encasing layer that conforms to the water-soluble drug layer, providing controlled release without leakage, even with cuts or fissures, and does not require binder materials, allowing for high drug loading and flexible application on various substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a coating contains a hydrophilic or lipophilic drug, then the drug can be delivered to the body, but the drug elutes very fast initially causing a burst effect
Solution Approach 1:
The coating is divided into multiple layers: a drug-containing layer and a separate topcoat layer. This segmentation allows the drug to be contained in one layer while the topcoat provides controlled release, preventing the burst effect by separating the drug reservoir from the release interface.
Solution Approach 2:
The topcoat acts as an intermediary layer between the drug-containing layer and the body fluid. It mediates the release process by providing a controlled pathway for drug diffusion, preventing direct contact between the hydrophilic drug and bulk water that would cause rapid elution.
2Reliability
If a topcoat is used to control drug release, then release can be modulated, but small defects like cracks, abrasions and cuts lead to rapid burst release
Solution Approach 1:
The topcoat is formulated as a flexible, elastic layer that can deform and seal around defects such as cracks, abrasions, and cuts in the underlying drug-containing layer. This flexibility allows the coating to maintain its barrier function even when the substrate or drug layer is compromised, preventing rapid drug release through defect sites.
Solution Approach 2:
The elastic topcoat provides a protective cushioning effect that anticipates and compensates for potential defects. When defects occur, the flexible nature of the topcoat allows it to conform and seal around them, providing a secondary barrier that prevents burst release before the defect can cause significant drug loss.
3Adaptability or versatility
If water is absorbed by the topcoat, then the coating becomes more compliant with body environment, but this leads to rapid burst release of hydrophilic drugs
Solution Approach 1:
The coating system exhibits different properties in different layers: the topcoat is designed to be water-absorbing and compliant with body tissue, while the drug-containing layer maintains its drug-loading capacity. This local differentiation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
By separating the water-absorbing function (topcoat) from the drug-containing function (inner layer), the system allows the topcoat to absorb water and become compliant with body tissue while the inner layer retains the drug. The segmented structure prevents water from the topcoat from directly dissolving and releasing the hydrophilic drug rapidly.
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 multilayer coatings ensure controlled release of hydrophilic drugs over extended periods, maintaining therapeutic efficacy while minimizing drug loss, even when compromised, and simplify the formulation process by eliminating the need for binder materials.
Implementation Method 1
a hydrophobic encasing layer that conforms to the water-soluble drug layer
Implementation Method 2
allows controlled release of a water soluble drug
Data Source
AI summary
The present disclosure relates to multilayer coatings that include a hydrophobic encasing layer and allow controlled release of a water soluble drug. The encasing layer encases water soluble, or hydrophilic, drugs with a flexible layer and comes in good intimate contact with the water soluble drug layer. Thus, the encasing layer conforms to the water soluble drug and can control the release of the drug. Advantageously, major cuts or fissures in the coating do not cause the water soluble drug to leak or burst out; rather, the encasing layer continues to provide modulated release of the drug. The present disclosure also includes methods of making the multilayer coatings, methods of using the multilayer coatings, and articles that include the multilayer coatings.