Medical device disinfection by dense carbon dioxide

Polyisocyanopeptide Hydrogels Are Effectively Sterilized Using Supercritical Carbon Dioxide

Adequate sterilization procedures for soft biomaterials such as hydrogels are known to be challenging. These materials are delicate in structure, making them sensitive to harsh conditions and prone to damage. In this study, a suitable sterilization method for hydrogels composed of tri(ethylene glycol)-functionalized polyisocyanopeptides (PIC) was explored. These high biomimetic hydrogels are temperature and strain sensitive and have been presented as novel cell culturing matrices, wound dressings, and drug carriers. The methods that were investigated include autoclaving, γ-irradiation, ultraviolet (UV) light irradiation, and supercritical CO₂ (scCO₂) treatment. The results show that autoclaving and γ-irradiation have deleterious effects on the gelation behavior and mechanical characteristics of PIC. For γ-irradiation, cooling the gels on dry ice alleviated this negative impact, but not sufficiently enough to make the method viable. In contrast, UV light and scCO₂ treatment do not affect the mechanical properties of the PIC gels. Studies with gels inoculated with 10⁷ CFU/mL Gram-positive bacteria Staphylococcus aureus show that only scCO₂ is capable of successfully sterilizing PIC hydrogels by achieving a 6-log reduction in bacterial load. It was concluded that, within the range of tested techniques, the sterilization of PIC is limited to scCO₂.

A new era for sterilization based on supercritical CO2 technology

The increasing complexity in morphology and composition of modern biomedical materials (e.g., soft and hard biological tissues, synthetic and natural-based scaffolds, technical textiles) and the high sensitivity to the processing environment requires the development of innovative but benign technologies for processing and treatment. This scenario is particularly applicable where current conventional techniques (steam/dry heat, ethylene oxide, and gamma irradiation) may not be able to preserve the functionality and integrity of the treated material. Sterilization using supercritical carbon dioxide emerges as a green and sustainable technology able to reach the sterility levels required by regulation without altering the original properties of even highly sensitive materials. In this review article, an updated survey of experimental protocols based on supercritical sterilization and of the efficacy results sorted by microbial strains and treated materials was carried out. The application of the supercritical sterilization process in materials used for biomedical, pharmaceutical, and food applications is assessed. The opportunity of supercritical sterilization of not only replace the above mentioned conventional techniques, but also of reach unmet needs for sterilization in highly sensitive materials (e.g., single-use medical devices, the next-generation biomaterials, and medical devices and graft tissues) is herein unveiled.

Supercritical CO2 technology: The next standard sterilization technique?

Sterilization of implantable medical devices is of most importance to avoid surgery related complications such as infection and rejection. Advances in biotechnology fields, such as tissue engineering, have led to the development of more sophisticated and complex biomedical devices that are often composed of natural biomaterials. This complexity poses a challenge to current sterilization techniques which frequently damage materials upon sterilization. The need for an effective alternative has driven research on supercritical carbon dioxide (scCO₂) technology. This technology is characterized by using low temperatures and for being inert and non-toxic. The herein presented paper reviews the most relevant studies over the last 15 years which cover the use of scCO₂ for sterilization and in which effective terminal sterilization is reported. The major topics discussed here are: microorganisms effectively sterilized by scCO₂, inactivation mechanisms, operating parameters, materials sterilized by scCO₂ and major requirements for validation of such technique according to medical devices' standards.