Validating a Low Dose Gamma Irradiation Process for Sterilizing Allografts Using ISO 11137 Method 2B
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Cell and Tissue Banking (2005) 6:271–275 DOI 10.1007/s10561-005-7364-6
Validating a low dose gamma irradiation process for sterilizing allografts using ISO 11137 Method 2B Thomas F. Baker*, Chad J. Ronholdt and Simon Bogdansky AlloSource 6278 S. Troy Circle, Centennial, CO 80111; *Author for correspondence (e-mail: tbaker@ allosource.org; phone: +720-873-0213; fax: +720-873-0212) Received 30 November 2004; accepted in revised form 17 May 2005
Key words: Allograft tissue, Bioburden, Gamma 60Co radiation, Sterility assurance level, Sterilization dose, Validation
Abstract This paper describes the validation of an allograft sterilization method specifically designed for the processing methods used at AlloSource in Centennial, CO. The methods used for this validation followed ISO Standard 11137, Method 2B. Three hundred allografts, collected from three defined production batches were dosed using a series of five incremental doses, beginning at 1 kGy and increasing by 1 kGy until 5 kGy was achieved. Following sterilization dosing, each allograft test article was analyzed using a sterility test to identify any viable microorganisms. The number of positive sterility samples was used to calculate the verification dose (1.27 kGy), which was then verified by an additional batch of 100 allografts. The results from this validation indicate that sterility (10 6 SAL) on human allograft tissue using gamma 60Co radiation can be achieved when a dose of at least 9.2 kGy is employed.
Introduction Recently, the tissue banking industry has been undergoing a complex metamorphosis from a clinical hospital environment to a much more structured and regulated industry. This metamorphosis has been fueled by regulatory pressure and the public’s expectation regarding the safety of allografts. Most tissue banks use a series of aseptic processing steps consisting of various chemical, mechanical and detergent steps to clean and inactivate microorganisms from musculoskeletal allografts. Aseptic processing is defined by the American Association of Tissue Banks (AATB) as, ‘the processing of tissue using methods to prevent, restrict, or minimize contamination with microorganisms from the environment, processing personnel, and/or equipment’ (Woll and Kasprisin
2002). Although these methods are effective in reducing the inherent microbial bioburden present on incoming cadaveric tissue, they are not capable of sterilizing the allografts. The recent adverse reactions associated with musculoskeletal allograft transplantation have prompted several governmental and public health institutions to recommend the development and utilization of technologies that sterilize musculoskeletal allograft tissue (Centers for Disease Control and Prevention 2003; Hartill et al. 2003; Malinin et al. 2003; Kainer et al. 2004; Crawford et al. 2005). Several published studies support the use of terminal sterilization for allograft tissue (De Deyne and Haut 1991; Godette et al. 1996; Vangsness et al. 1996; Crawford et al. 2005) and conversely, there are an equivalent number of publ
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