SBIR-STTR Award

Terminal sterilization of tendon allografts to the same levels called for in medical devices is currently all but non-existent. Terminal sterilization using ethylene oxide gas leaves toxic residues and negatively impacts the probability of positive outcomes following ACL surgeries. Gamma irradiation is used to sterilize grafts but at the irradiation levels sufficient to achieve sterilization the tendon is rendered unusable because separation of collagen bundles and denatured proteins result in significant weakening of the graft. An ideal method for sterilization of tendon allograft material would be one that is terminal, non-toxic, retains the essential properties of the allograft, and is validated to achieve sterility assurance level of 10-6 (the same level required for medical devices). Our preliminary experiments indicate that sterilization by our supercritical CO2 process represents a viable solution to answer the pressing need to terminally sterilize tendon allograft material. We request support to develop a validated terminal sterilization process for tendon allografts utilizing supercritical CO2. The specific aims of this proposal are (1) To develop a procedure for terminal sterilization of tendon tissues with supercritical carbon dioxide; (2) To analyze post-sterilization tendon tissue samples for potential biomechanical alterations and compare them with untreated. The long-term objective of this project is to develop a commercially viable terminal sterilization method that would be compatible with human soft tissues and would eventually add a terminal sterilization component to current tissue bank practices. Phase II studies will consist of comprehensive testing to verify inactivation of viral and fungal contaminates in tendon as well as tests using animal models to evaluate histological and biomechanical changes in supercritical CO2 sterilized implanted allograft tendons through the phases of graft necrosis, revascularization, fibroblast invasion and collagen synthesis. Furthermore this technology may be expanded for use in other tissues where donor cell viability is not a concern.

Thesaurus Terms:
antisepsis, carbon dioxide, disease /disorder prevention /control, homologous transplantation, technology /technique development, tendon, tissue /cell preparation, transplantation disease transmission biomechanics, structural biology, tissue resource /registry human tissue

Currently, most tissue banks use a two step process to sterilize soft tissue allografts. The initial step reduces the bioburden with the second step in sterilization resulting in "terminal sterilization". The direct result of Phase 1 funding has been the development of a terminal sterilization technology using supercritical CO2 and a proprietary additive that will allow tissue banks to easily process soft tissue allografts to a sterility assurance level equal to that called for in medical devices (SAL6) in a one step process. Sterilization was confirmed according to the standards in AMI/ISO 11737-1 and 2. The sterilization technology is capable of inactivating a wide variety of microorganisms at concentrations of greater than 106 colony forming units (CFUs) in a half cycle. Utilizing sterilization times as determined from D-value calculations according to the methods of Stumbo-Murphy-Cochran (terminal sterilization at 2.5 hours and overkill at 4 hours) we assessed the affect of our supercritical CO2 process on the biomechanical properties of bone-tendon-bone (BTB) patellar tendon allografts. Biomechanical data obtained revealed no significant difference between the supercritical CO2 sterilized and control group (ANOVA statistical analysis and paired T-testing). The technology developed in Phase 1 will offer an alternative to methods of sterilization of soft tissue allografts used by tissue banks. Musculoskeletal conditions (diseases and disorders) have a tremendous impact on society. In the United States alone, musculoskeletal conditions cost society an estimated $254 billion yearly with 1 out of every 7 Americans reporting a musculoskeletal impairment. Each year, 28.6 million Americans incur a musculoskeletal injury with approximately 7.5 million musculoskeletal procedures performed by physicians. The importance of allograft tissue in the treatment of orthopedic patients has grown rapidly during the last decade. Tendon, ligament and joint injuries represent 45% of the musculoskeletal injuries each year. Tendon injuries are especially common, requiring surgical repair to replace shoulder rotator cuff tendons (51,000/year), achilles tendon (44,000/year), and the patellar tendon (42,000/year) to name a few. Concomitant with the increased demand for tissue has been the increase potential of exposures to pathogens. There is high potential for bacterial or viral contamination of allograft tissue without adequate secondary sterilization processing. Thus, the safety of allograft tissue has become a primary focus for the tissue bank industry, clinicians, and the FDA. Phase II funding will allow us to further optimize the sterilization process by addressing packaging (double packaging and header packs) as recommended by tissue banks and orthopedic surgeons. This packaging will result in a terminally sterilized product ready for direct transfer for transplant. The importance of allograft material in the treatment of orthopedic patients has grown rapidly during the last decade, which leads to a growing concern for an increased potential of exposure to pathogens. Viral and bacterial contamination of allograft tissue without adequate secondary sterilization processing remains an issue. Thus, the safety of allograft tissue has become a primary focus for the tissue bank industry, clinicians and the FDA. The tissue bank industry and processing centers have invested numerous hours and a large amount of money into methods of processing to achieve a high quality and safe. By providing a one step terminal sterilization process (sterilized grafts in final packaging), our company would be adding value and safety to the processing that occurs in the tissue bank industry. The only two processes capable of terminal sterilization of allografts are ethylene oxide and gamma irradiation which suffer from major drawbacks if used at a concentration to achieve SAL6 thus requiring a two step process to minimize the dosage. Terminal sterilization using our supercritical CO2 process has the potential to add a one step validated terminal sterilization process to tissue banking while decreasing the costs of processing and generating a safer product. Funding for Phase I has allowed us to show the feasibility of supercritical CO2 as a method of overcoming the current limited sterilization options. Funding of phase II will allow us to take the next steps towards successful commercialization by further optimization of packaging design (allowing for a terminally sterilized product of various sizes) and other pathogenic inactivation in soft tissue allografts