Stent Radiation Sterilization via Cryogenic Cooling
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Solution Overview
Problem
Radiation sterilization of stents can alter the properties of polymers, leading to embrittlement, cracking, and reduced drug loading due to temperature increases during exposure, which affects the mechanical properties and drug delivery efficacy.
Innovation Solution
Cooling the stent to a sterilization temperature below ambient temperature before, during, and after radiation exposure to maintain the polymer properties and reduce adverse effects, using methods such as cooling fluids, cold media, and radiation barriers to control temperature and radiation dose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radiation sterilization is performed at ambient temperature, then sterilization effectiveness is achieved, but polymer embrittlement and cracking occur
Solution Approach 1:
The patent applies parameter changes by lowering the temperature parameter during radiation sterilization from ambient temperature to reduced temperatures (e.g., -80°C to 0°C). This temperature parameter change modifies the polymer's response to radiation, preventing embrittlement and cracking while maintaining sterilization effectiveness. The cooled polymer matrix becomes more resistant to radiation-induced chain scission and cross-linking that would otherwise compromise mechanical strength.
Solution Approach 2:
The patent implements preliminary action by cooling the stent to reduced temperatures before exposing it to radiation sterilization. This pre-cooling step prepares the polymer material to withstand the subsequent radiation exposure without suffering embrittlement or structural damage. The cooling is performed in advance of the sterilization process, establishing protective conditions before the harmful radiation effect occurs.
2Reliability
If radiation sterilization is performed at ambient temperature, then sterilization is completed, but drug loading capacity is reduced
Solution Approach 1:
The patent changes the temperature parameter during radiation sterilization to reduced temperatures, which protects the drug substance from radiation-induced degradation. At lower temperatures, the drug molecules remain more stable and retain their loading capacity on the stent surface or within the polymer matrix, while still achieving complete sterilization through the radiation exposure.
3Strength
If cooling medium is added to control temperature, then polymer properties are maintained, but device complexity increases
Solution Approach 1:
The patent introduces a cooling medium as an intermediary substance between the radiation source and the stent polymer. This cooling medium (e.g., liquid nitrogen, dry ice, or cold gas) serves as a thermal mediator that absorbs excess heat generated during radiation exposure and maintains the stent at reduced temperatures. The cooling medium can be applied in various forms (spray, immersion, or circulating fluid) and does not chemically interact with the stent, simply providing thermal management to preserve polymer properties during sterilization.
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
This approach minimizes the adverse effects of radiation sterilization on stent materials, reducing cracking and maintaining drug loading, thereby enhancing the mechanical properties and drug delivery performance of the stents.
Implementation Method 1
cooling a stent to a sterilization temperature below ambient temperature
Implementation Method 2
conveying a cooling fluid at or adjacent to a stent to reduce the temperature of the stent
Implementation Method 3
exposing the cooled stent to a dose of radiation
Implementation Method 4
exposing the stent to radiation sterilization
Data Source
AI summary
Methods and systems for reduced temperature radiation sterilization of stents are disclosed.