Biocompatibility of human bone allograft powder processed by supercritical CO2

Purpose Bone allografts have long been used as a natural substitute to repair skeletal defects. Long bone allografts come from some brain death donors; although the numbers are very few, they are often used in large segmental allograft form for tumor and joint reconstruction surgery. To promote and facilitate its clinical use, microlization of allograft is the first step. We try to use the effect of delipidation and sterilization of supercritical CO2 (SCCO2) to process allograft powder extraction. After passing through the biocompatibility test, these extracted allograft powder can be used clinically. Methods The allograft powder is extracted by SFX 2-10 supercritical fluid extractor, which controls CO2 with pressure (P) to 400 bar and temperature (T) to 45°C. All specimens will receive bacterial culture test after extraction, both aerobically and anaerobically, in a Chinese National Laboratory Accreditation (ISO 15189) qualified laboratory. Intracutaneous irritation test, skin sensitization study, and cytotoxicity study will be performed for its biocompatibility. When all tests results achieve the ISO 10993 (Biological evaluation of medical devices) criteria, we begin to process allograft bone powder transplantation to some patients. The indications of transplantation are patients who have senile fracture. Results After SCCO2 extraction, all specimen showed no growth of bacterial culture, both aerobically and anaerobically. All of the biocompatibility tests fulfill the ISO 10993 criteria. In this small preliminary clinical trial series, we found the extracted allograft powder may promote the fracture union without any infection or rejection of implantation. Conclusions Through SCCO2 extraction, we can sterilize and remove the lipid components of allograft powder in a single procedure. Bone allograft powder, unlike synthetic medicinal product, is produced from processing untreated human tissue. It is necessary to inactivate and remove any harmful agents from the bone to reduce the risk of disease transmission. Screening donor’s underlying disease carefully before further processing with SCCO2 may be a simple and safe method to process human bone allograft powder.