Parylene-Lined Drug Capsules for Moisture-Sensitive Payloads
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Solution Overview
Problem
Existing drug delivery vehicles, such as capsules, fail to adequately prevent moisture and vapor ingress, leading to degradation of hygroscopic and moisture-sensitive pharmaceutical ingredients, and commercial enteric coatings leave residues that interfere with payload deployment.
Innovation Solution
The development of capsules with a parylene moisture-barrier layer and an enteric coating that minimizes moisture ingress and residue, allowing for effective deployment of mechanical actuators like microneedle systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydroxypropyl methylcellulose capsules are used, then the capsule structure is simple and easy to manufacture, but moisture can still ingress and degrade hygroscopic APIs
Solution Approach 1:
The patent uses a composite capsule structure combining HPMC outer shell with parylene inner lining. The HPMC provides biocompatibility and dissolution properties while the parylene layer provides superior moisture barrier properties. This composite approach achieves reliable moisture protection while maintaining reasonable structural complexity.
Solution Approach 2:
The patent implements a nested capsule structure where the parylene layer is positioned inside the HPMC capsule shell. This nested configuration allows the inner parylene layer to provide enhanced moisture protection to the API while the outer HPMC shell maintains capsule integrity and dissolution characteristics.
2Reliability
If additional drying processes are applied after filling, then moisture content is reduced, but the filling process is extended and yield decreases
Solution Approach 1:
The patent incorporates moisture-absorbing desiccants inside the capsule during the filling process itself, rather than applying additional drying processes after filling. This preliminary action removes moisture at the source during manufacturing, eliminating the need for extended post-filling drying steps and thereby maintaining high productivity.
Solution Approach 2:
The patent introduces desiccants as intermediary moisture-trapping elements within the capsule structure. These desiccants act as mediators that actively remove moisture from the environment inside the capsule during storage and delivery, providing reliable moisture control without requiring additional manufacturing process steps.
3Reliability
If enteric coatings are applied to protect against moisture, then moisture protection is improved, but residues are left that interfere with payload deployment
Solution Approach 1:
The patent modifies the enteric coating composition by incorporating specific polymers and plasticizers that enable complete dissolution. By changing the chemical parameters of the coating formulation, the patent achieves moisture protection while ensuring the coating dissolves completely in the gastrointestinal tract without leaving residues that would interfere with payload deployment.
Solution Approach 2:
The patent designs the enteric coating to be temporarily protective but fully biodegradable. The coating performs its moisture barrier function during transit through the stomach and then completely dissolves and is excreted in the gastrointestinal tract, discarding the protective function when no longer needed without leaving harmful residues.
4Reliability
If moisture-sensitive APIs are formulated, then drug efficacy is maintained, but special protective pathways and additional resources are required
Solution Approach 1:
The patent places moisture-sensitive APIs inside a nested protective structure with the parylene layer positioned directly against the API compartment. This nested configuration provides targeted moisture protection exactly where the API is located, maintaining API stability without requiring complex formulation changes throughout the entire capsule structure.
Solution Approach 2:
The patent introduces desiccants as intermediary moisture-trapping elements positioned within the capsule next to the API. These desiccants act as protective mediators that actively absorb moisture from the environment, creating a low-humidity microenvironment for the moisture-sensitive API without requiring complex formulation modifications.
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 capsules effectively prevent moisture and vapor ingress, ensuring payload stability and enabling rapid dissolution with minimal residue, facilitating efficient deployment of mechanical actuators in the gastrointestinal tract.
Implementation Method 1
a parylene layer that prevents moisture and vapor from entering the interior volume of the capsule
Implementation Method 2
an enteric coating that dissolves rapidly in the gastrointestinal tract
Implementation Method 3
treating an outer surface of the parylene layer with oxygen plasma
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
The present disclosure is related to a method of producing a capsule. The method includes providing a mold, depositing parylene on the mold to form a parylene layer, scoring the parylene layer, and coating the parylene layer with a polymer to produce a capsule.