Gamma radiation is known to reduce the strength of tissue by disrupting, or denaturing, the collagen building block. Although lyophilized tissue or the addition of radioprotectants have shown some strength preservation in various types of bone, their use often requires an additional processing step, further lengthening tissue process times. The NovaSterilis process requires no additional steps beyond standard tissue cleaning protocols to achieve a SAL6 in a terminally sterilized product.
A recent 2012 publication in Cell Tissue Bank by the group of William Walsh established the effect of 25 kGy gamma, 10 kGy gamma, and SCCO2 sterilization on bone. In this study they used 3 point bending, 4 point bending and torsion to analyze the mechanical changes to bone post-sterilization. This paper confirmed 25 kGy radiation had a significant effect in all tests, and 10kGy showed moderate changes in 3 point and 4 point bending but statistically significant effects in torsion testing. SCCO2 showed no measurable effect in all three areas providing valuable evidence in maintenance of mechanical properties.
Multiple studies have demonstrated similar results in soft tissue including tendon, acellular dermis and amnion. NovaSterilis's process provides a safe and effective sterilization process for allograft, xenograft and other delicate materials maintaining vital physical and biochemical properties while achieving SAL6 in final packaging.
In addition, gamma radiation is challenged by many viruses, even at high levels of radiation that are otherwise damaging to biological tissue. Viruses do not significantly challenge the NovaSterilis process, and bacterial endospores remain the reference organism for inactivation studies.
Ethylene oxide sterilization is a chemical process consisting of four primary variables: gas concentration, humidity, temperature and time. Ethylene oxide is an alkylating agent that disrupts the DNA of microorganisms, which prevents them from reproducing. Ethylene Oxide (EO) is a carcinogenic, mutagenic and highly flammable/explosive chemical that is used in sterilization of many medical products. It is highly effective for sterilization but residual EO in many products, for example allografts, limits its use. The EO process is significantly longer than SCCO2 and may reach temperatures that are slightly higher than what is acceptable for some biopolymers.
Supercritical CO2 combined with NovaSterilis proprietary sterilization additive NovaKill™ provides a fast low temperature alternative to EO. NovaKill™ is used in extremely low quantities and most residual NovaKill™ is removed in the out gassing process, what residual is not removed will quickly biodegrade to 2 harmless products. A typical cycle time for SCCO2 varies from a ½ hour to 6 hours based on the material, and there is no long outgassing process in the chamber. By 2015, over 70,000 allograft tissues have been transplanted using NovaSterilis's SCCO2 process with no adverse reports to date, adding real life support for this green process. NovaSterilis is a 2007 Recipient of the Presidential Green Chemistry Award presented by the EPA. This process is safe for employees, patients, and the environment.