Engineering of green sterilization technology to obtain biocompatible aerogels: Supercritical CO2 versus ethylene oxide and gamma radiation

The growing relevance of aerogels in biomedicine demands the choice of compatible sterilization techniques with these materials. Conventional methods, such as ethylene oxide (EO) and gamma radiation (γ-rays) sterilization, have significant drawbacks while facing important environmental restrictions. In this study, supercritical CO₂ (scCO₂) sterilization is tested for polysaccharide (starch and alginate) aerogels as an eco-friendly alternative to conventional procedures. Three post-processing treatments under different CO₂ exposure regimes (static, dynamic and combined) and in the presence of H₂O₂ as additive were developed and assessed to reach sterility assurance levels (SAL) below 10^-6. After sterilization, a vacuum treatment was implemented to ensure a low residual presence of H₂O₂ in the aerogels so that the material biocompatibility was not compromised according to in vitro cell tests with fibroblasts. The residual adsorbed H₂O₂ was quantified for the first time in aerogels by nuclear magnetic resonance spectroscopy. The effects of the supercritical sterilization treatments on the textural and chemical properties of the aerogels were evaluated and compared to those treated with EO and γ-rays. Results highlight the unique efficiency of scCO₂ sterilization as a post-processing method that preserves the aerogel structure while offering an eco-sustainable potential for producing sterile and biocompatible materials.