Removing endotoxin from metallic biomaterials with compressed carbon dioxide-based mixtures

Bacterial endotoxins have strong affinity for metallic biomaterials because of surface energy effects. Conventional depyrogenation methods may not eradicate endotoxins and may compromise biological properties and functionality of metallic instruments and implants. We evaluated the solubilization and removal of Escherichia coli endotoxin from smooth and porous titanium (Ti) surfaces and stainless steel lumens using compressed CO2-based mixtures having water and/or surfactant Ls-54. The CO2/water/Ls-54 ternary mixture in the liquid CO2 region (25 °C and 27.6 MPa) with strong mixing removed endotoxin below detection levels. This suggests that the ternary mixture penetrates and dissolves endotoxins from all the tested substrates. The successful removal of endotoxins from metallic biomaterials with compressed CO2 is a promising cleaning technology for biomaterials and reusable medical devices.