Supercritical CO2 Sterilization of Hydrogel Scaffolds
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Solution Overview
Problem
Current sterilization methods for biopolymers, such as moist heat steam autoclaves, ethylene oxide gas, and gamma irradiation, are inadequate as they can degrade thermally sensitive materials and compromise biocompatibility, necessitating a new low-temperature, biocompatible sterilization process for medical devices and pharmaceuticals.
Innovation Solution
Supercritical CO2 (SC-CO2) technology is employed at pressures of 4 MPa to 30 MPa and temperatures of 5° C to 75° C for treating biocompatible hydrogel polymers, potentially including hydrogen peroxide, to effectively sterilize without degrading the material's properties, achieving a 90% or higher kill rate of bacteria like S. aureus and E. coli.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sterilization methods (moist heat steam autoclaves, ethylene oxide gas, gamma irradiation) are used on biopolymers, then sterilization is achieved, but the biopolymers are degraded and biocompatibility is compromised
Solution Approach 1:
The invention changes the physical state and parameters of CO2 to supercritical conditions (pressure above 7.38 MPa and temperature above 304.2 K), creating a fluid with unique properties that enable effective sterilization at low temperatures, thus preserving biopolymer integrity while achieving reliable sterilization
Solution Approach 2:
The invention utilizes the phase transition of CO2 to supercritical state and its subsequent expansion to gas phase. The supercritical fluid penetrates the biopolymer structure effectively, and the phase transition to gas allows for easy removal without residual damage to the biopolymer, resolving the contradiction between sterilization effectiveness and material preservation
2Reliability
If high temperature sterilization is applied, then sterilization effectiveness is improved, but thermally sensitive biopolymer materials are degraded
Solution Approach 1:
The invention changes CO2 to supercritical state which allows sterilization to occur at low temperatures (above 304.2 K but well below conventional sterilization temperatures). The supercritical fluid's enhanced diffusivity and penetrability at these low temperatures enable effective sterilization without thermal degradation of sensitive biopolymers
3Reliability
If toxic or oxidative chemical agents are used for sterilization, then sterilization effectiveness is improved, but biocompatibility of biopolymers is lowered
Solution Approach 1:
The invention uses CO2 in its supercritical state, which is chemically inert and non-toxic. This inert environment provides effective sterilization through physical mechanisms rather than chemical reactions, eliminating the harmful effects of toxic or oxidative agents while maintaining biopolymer biocompatibility
Solution Approach 2:
The CO2 used in the process is readily available, inexpensive, and can be easily removed after sterilization by simple pressure release. The temporary presence of supercritical CO2 achieves sterilization without leaving harmful residues, making it a safe alternative to persistent toxic chemical agents
4Stability of the object's composition
If supercritical CO2 is used for sterilization, then biocompatibility and material properties are maintained, but the process requires high pressure equipment
Solution Approach 1:
The invention employs CO2 which serves multiple functions: it acts as the sterilizing agent, the heating medium, and the expanding gas for easy removal. This multi-functionality simplifies the overall system design despite the need for high-pressure equipment, as one substance performs multiple roles in the sterilization process
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 SC-CO2 process effectively kills bacteria while maintaining the physical and chemical properties of hydrogel polymers, ensuring biocompatibility and functionality, thus providing a promising alternative for sterilizing thermally sensitive biomedical materials.
Implementation Method 1
CO2 exhibits a liquid-like density (0.6-1.0×10−3 kg·m−3) but gas-like diffusivity (10−7-10−8 m2s−1) and viscosity (3-7×10−5 N·s·m−2). Because there is no vapor-liquid interface for pure SC-CO2, there are no surface tension considerations. These properties allow CO2 to penetrate porous structures easily.
Implementation Method 2
When heated and compressed above its critical point (7.38 MPa and 304.2 K) CO2 exhibits a liquid-like density (0.6-1.0×10−3 kg·m−3) but gas-like diffusivity (10−7-10−8 m2s−1) and viscosity (3-7×10−5 N·s·m−2).
Implementation Method 3
The biocidal and sterilizing effects of high-pressure CO2 mixtures have been quantified for various species of bacteria. Research has shown that compressed CO2 kills many clinically relevant gram-positive vegetative bacteria (e.g. Listeria monocytogenes, Staphylococcus aureus, and Enterococcus faecalis) and gram-negative vegetative bacteria (e.g. Salmonella typhimurium, E. coli, and Pseudomonas aeruginosa).
Data Source
AI summary
Methods for sterilizing a biocompatible hydrogel polymer are provided via treating the biocompatible hydrogel polymer with a supercritical CO2 treatment composition at a treatment pressure of about 4 MPa to about 30 MPa and a treatment temperature of about 5° C. to about 75° C. The supercritical CO2 treatment composition can be substantially pure CO2 or may further include hydrogen peroxide (e.g., in an amount of about 10 ppm to about 1,000 ppm). In certain embodiments, the biocompatible hydrogel polymer can be treated with the supercritical CO2 treatment composition for about 30 minutes to about 5 hours. According to these methods, treating the biocompatible hydrogel polymer can kill about 90% or more of any S. aureus and E. coli present in the biocompatible hydrogel polymer.