Polymer Stent Molecular Weight Stabilization After E-Beam Sterilization
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Solution Overview
Problem
The challenge in manufacturing polymeric stents lies in maintaining radial strength, stiffness, and toughness while ensuring product consistency over time, as radiation sterilization can lead to changes in molecular weight and free radical generation, affecting the stent's properties during storage.
Innovation Solution
Exposing polymeric stent scaffolding to E-beam radiation in an oxygen-containing environment during or after sterilization, followed by storage in an inert gas atmosphere, to quench free radicals and stabilize molecular weight, thereby maintaining the stent's mechanical properties over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric stent scaffolding is sterilized using radiation, then sterilization is achieved, but molecular weight changes and free radical generation occur, affecting stent properties during storage
Solution Approach 1:
The patent applies preliminary action by exposing the polymeric stent scaffolding to oxygen-containing gas immediately during or after radiation sterilization. This pre-empts the harmful effects of free radical generation by having oxygen ready to quench the radicals before they can cause molecular weight changes. The oxygen exposure is timed to occur before the stent enters storage, preventing composition instability from developing during the storage period.
Solution Approach 2:
The patent converts the harmful effect of radiation-induced free radical generation into a beneficial process. Instead of trying to prevent free radical formation, the method allows radicals to form during sterilization but then uses oxygen to quench them, converting the potentially damaging free radicals into beneficial peroxyl radicals that terminate the chain reactions. This transforms the harmful radiation effect into a controlled process that actually stabilizes the polymer composition.
2Stability of the object's composition
If polymeric stent scaffolding is stored in oxygen-containing environment, then free radicals are quenched and molecular weight is stabilized, but oxidation of polymer may occur
Solution Approach 1:
The patent applies preliminary action by performing oxygen exposure during or immediately after sterilization, before the stent enters long-term storage. This timing is critical because it quenches free radicals when they are most abundant, preventing molecular weight changes. By completing the oxygen exposure step before storage begins, the patent avoids prolonged oxygen exposure that would cause oxidation, while still achieving the benefit of free radical quenching.
Solution Approach 2:
The patent provides beforehand cushioning by introducing oxygen-containing gas as a protective measure during the sterilization process. This oxygen acts as a cushion against the harmful effects of free radicals by quenching them before they can cause damage. The oxygen exposure serves as a protective buffer that prevents molecular weight degradation without requiring prolonged exposure that would lead to oxidation during storage.
3Object-affected harmful factors
If polymeric stent scaffolding is stored in inert gas atmosphere, then oxidation is prevented, but free radicals persist and cause molecular weight changes over time
Solution Approach 1:
The patent applies preliminary action by exposing the stent to oxygen-containing gas during or immediately after sterilization, before inert gas storage begins. This preliminary oxygen exposure quenches free radicals at the source, preventing the molecular weight changes that would otherwise occur during storage. By performing this quenching step beforehand, the patent enables subsequent inert gas storage without the harmful effects of persistent free radicals.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining free radical quenching capability throughout the sterilization and transition to storage. The oxygen exposure during sterilization creates a continuous protective effect that carries through into the storage phase. This continuous action prevents free radical persistence and molecular weight changes, while the subsequent inert gas atmosphere maintains oxidation prevention, achieving both benefits continuously.
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 method effectively stabilizes the molecular weight and mechanical properties of polymeric stents, reducing variability and ensuring consistent performance and resorption profiles, even after extended storage periods.
Implementation Method 1
the oxygen in the gas quenches free radicals generated by the radiation exposure and stabilizes the molecular weight of the scaffolding polymer
Implementation Method 2
exposing the scaffolding to E-beam radiation for sterilization
Data Source
AI summary
Methods of stabilizing the molecular weight of polymer stents scaffolds after E-beam sterilization are disclosed. The molecular weight of the polymer of the irradiated scaffolds is stabilized through exposure to gas containing oxygen.