Integrated processes (HPSE+scCO₂) to prepare sterilized alginate-gelatine-based aerogel

Biopolymers application in biomedical areas has been limited due to the physicochemical degradation that occurs using conventional processing/sterilization methods (e.g., steam heat, γ-radiation, ethylene oxide). Aiming to avoid/minimize degradation and preserve their properties, supercritical carbon dioxide (scCO₂) has been proposed as an alternative sterilization method for such materials. ScCO₂ can simultaneously be used as a drying method to produce aerogels (i) and sterilize them (ii). However, a solvent exchange is required to prepare the alcogel from hydrogel, achievable through high-pressure solvent exchange (HPSE) (iii). This study integrated three processes: HPSE, scCO₂ drying, and sterilization to prepare alginate-gelatine sterilized aerogels. Two scCO₂ sterilization methods were tested. Results showed that sterilization did not compromise the aerogels' chemical, thermal and swelling properties. Conversely, Young's Modulus increased, and BET surface area decreased, due to the structural changes caused by the fast pressurization/depressurization rates applied during sterilization. Regarding the sterilization efficiency, results showed a reduction in contamination throughout the process, achieving a SAL of 10^-4. The sterilized aerogels were non-cytotoxic in vitro and showed improved wound-healing properties. The innovative integrated process produced decontaminated/sterile and ready-to-use aerogels reducing process time by 75 %, from 2 days up to 12 h without compromising the aerogel's properties.