Sterilizing Bioabsorbable Stents via Supercritical CO2
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Solution Overview
Problem
Traditional sterilization methods for medical devices, such as dry heat, steam autoclave, ethylene oxide, gamma radiation, and hydrogen peroxide vapor, are ineffective for temperature-sensitive and complex-geometry devices like bioabsorbable polymeric stents and catheters, as they can cause mechanical property deterioration and lack penetration into device lumens.
Innovation Solution
A method combining ethylene oxide sterilization at a temperature range of 38°-50° C with relative humidity of 20%-80%, followed by vaporized hydrogen peroxide sterilization at below 60° C and 50%-60% concentration, and optionally using nitrous oxide sterilization at room temperature, along with the use of 0.2 µm pore filters and a mandrel for isolating and maintaining sterility within catheter lumens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sterilization methods (dry heat, steam autoclave, ETO) are used, then sterilization effectiveness is improved, but mechanical properties of temperature-sensitive polymeric devices deteriorate
Solution Approach 1:
The patent changes the physical-chemical parameters of the sterilization process by using supercritical carbon dioxide instead of traditional high-temperature methods. The temperature is maintained below 50°C and pressure is controlled at 73-300 atm, which preserves the mechanical properties of temperature-sensitive polymeric devices while achieving effective sterilization through the unique properties of supercritical CO2
Solution Approach 2:
The patent replaces thermal sterilization mechanisms with a supercritical fluid-based sterilization mechanism. Instead of using heat to achieve sterilization, the invention uses the penetrating and disinfecting properties of supercritical carbon dioxide, substituting thermal energy with a phase-change fluid system that operates at low temperatures
2Object-affected harmful factors
If VHP sterilization is used, then material compatibility is improved, but penetration into device lumens is insufficient
Solution Approach 1:
The patent utilizes the properties of supercritical carbon dioxide to penetrate through porous and tubular structures. The supercritical fluid can penetrate deep into catheter lumens and complex device geometries, overcoming the penetration limitation of VHP while maintaining excellent material compatibility
Solution Approach 2:
The patent uses supercritical carbon dioxide as an intermediary substance that can penetrate device lumens and deliver sterilization effect. The supercritical CO2 acts as a mediator that combines the benefits of liquid penetration capability with gas-phase sterilization effectiveness, solving both the penetration and material compatibility issues
3Reliability
If gamma or E-beam radiation sterilization is used, then sterilization effectiveness is improved, but polymer structure changes occur
Solution Approach 1:
The patent replaces radiation sterilization with supercritical fluid sterilization. Instead of using ionizing radiation that causes polymer degradation, the invention uses supercritical carbon dioxide which sterilizes through physical dissolution and disruption of microorganisms without causing chemical changes to the polymer structure
Solution Approach 2:
The patent changes the sterilization mechanism from high-energy radiation to low-energy supercritical fluid interaction. By controlling temperature below 50°C and pressure at 73-300 atm, the supercritical CO2 achieves sterilization without the harmful effects of radiation on polymer molecular structure
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 effectively preserves the mechanical properties of bioabsorbable polymeric stents and ensures complete sterilization of catheter lumens without compromising the stent's structure, maintaining sterility and mechanical integrity throughout the sterilization process.
Implementation Method 1
Hydrogen Peroxide is an oxidizing agent that effects sterilization thru oxidation of key cellular components (e.g. membrane lipids, DNA, and other essential constituents)
Implementation Method 2
Hydrogen Peroxide is an oxidizing agent that effects sterilization thru oxidation of key cellular components (e.g. membrane lipids, DNA, and other essential constituents)
Implementation Method 3
The one or more filters may, for example, be 0.2 μm pore filters
Data Source
Figure 1~2
Figure 3A~4B
Figure 5A~6B
AI summary
Sterilization methods for implantable prostheses are described where a polymeric stent may be sterilized, e.g., via ETO sterilization, at a temperature below a glass transition temperature of the stent. A separate delivery catheter may be sterilized separately and the stent and delivery catheter may then be combined in an aseptic or semi-aseptic environment and sterilized as an assembled system such that the requirements for sterilizing the system are relatively lower. Additionally and/or alternatively, valve and filter assemblies may be used with an optional mandrel assembly for maintaining sterility of the internal components of a catheter system.