Sterilization of biomedical devices and biomaterials is required prior to invasive surgical procedures.  The FDA defines sterilization as 6-log (99.9999%) reduction of bacterial spores.  This project examines the killing of B. atrophaeus spores inoculated on typical fibrous biomaterials, i.e. cotton threads and polyester sutures. Both substrates were treated with supercritical CO₂ with trace levels of H₂O₂.  The sterilization process was also tested with the polyester sutures placed inside a 1/8-inch diameter lumen (tube), representative of an endoscope.  Treated substrates were assayed for killing efficiency using a pour plating technique.  We can claim at least 5.24-log reduction of spores on cotton threads, and 4.55-log reduction of spores on polyester sutures.  However, turbidity tests of treated threads and sutures showed no growth of spores after 24-hours, indicating a complete spore killing.  Sutures treated within a 2 foot lumen indicated 4.24-log kill; additional replication of results is required.  B. atrophaeus threads and sutures can be used in future work to test sterilization by securing substrates within biomedical devices, and sterilizing the devices using SC-CO₂ + H₂O₂.