Medical devices and biomaterials must be clean and free of contaminants prior to use, and this is particularly critical for implants. With increasing complexity of bioengineered constructs, for example tissue engineering scaffolds and multifunctional devices, there is a crucial need to develop processes for proper decontamination. This encompasses cleaning, disinfection, and sterilization. Compressed CO2 (liquid and supercritical) has been identified as a gentle and safe alternative to established decontamination processes, which often involve high temperatures, intense radiation, or harsh chemicals.

This work presents our recent results in several aspects of decontamination using liquid and supercritical CO2 technology. We demonstrate removal of E. coli endotoxins from titanium surfaces. For this application, CO2 solvent capability was enhanced by the addition of CO2-soluble surfactant to create water-in-CO2 microemulsions that dissolve and remove the endotoxins. In another application, high level disinfection of a model hydrogel has been achieved with both liquid and supercritical CO2. The hydrogel, poly (acrylic acid-co-acrylamide) potassium salt, was contaminated with either S. aureus and E. coli. The bacterial killing kinetics and CO2 diffusion limitation were investigated in the hydrogel. Morphological and physiological changes inflicted on bacterial cells were studied using SEM and BacLight fluorescent staining, respectively. Lack of morphological changes confirms the mildness of the CO2 process. BacLight images showed damaged cell membranes, in agreement with our earlier studies of bacterial spore deactivation mechanisms.