Radiochemical sterilization

To minimize or eliminate reliance on ethylene oxide and exploit reliability of assured sterility using radiation for absorbable polymers and particularly those used in tissue engineering, Shalaby and co-workers developed the radiochemical sterilization (RC-S) process. The RC-S process represents a novel approach to the sterilization of certain mechanical devices, such as those made of absorbable polyesters, that are sensitive to high-energy radiation delivered at the traditional dose of 25 kGy. RC-S is a hybrid process encompassing the attributes of chemical high-energy radiation sterilization without the drawbacks associated with the use of the parent processes. RC-... 

S entails the use of about 5 to 7.5 kGy of gamma radiation and a polyformaldehyde package insert capable of a radiolytic, controlled release of formaldehyde in a hermetically sealed package imder dry nitrogen. The process has been applied successfully to absorbable sutures without compromising their clinically relevant properhes, such as their in vivo breaking strength retention. Typical BSR data of radiochemically sterilized suture braids and controls are reported by Anneaux and co-workers. ... 

Anneaux, B. L., Atkins, G. G., Linden, D. E., Corbett, J. T., Fulton, L. K. and Shalaby, S. W, In vivo breaking strength retention of radiochemically sterilized absorbable braided sutures, Trans. Soc. Biomater., 24, 157, 2001. 

Prior to in vivo evaluation of the suture breaking strength retention, some of the sutures were subjected to radiochemical sterilization using a 5-kGy dose.i° This sterilization process has been described briefly in Chapter 1 and can be used to achieve suture sterility without compromising its breaking strength. This is contrary to what is known to occur when absorbable sutures are radiation-sterilized using the traditional dose of about 25 kCy. 

In a study by Carpenter and co-workers, three polymers (I, III, and IV) were made using TMP to prepare the respective polymeric initiators, as described in Section 3.23P In an effort to produce compliant monofilaments, these polymers were extruded to monofilaments and processed under slightly different conditions from those used in preparing their counterparts in section 3.2.3. One of the polymers (I) was used to prepare a second set of monofilaments for studying the effect of radiation dose, under a typical radiochemical sterilization process (RC-S) on their in vitro breaking strength retention (BSR). 

The composition and thermal data of typical polymers and tensile properties of their respective nonsterile monofilaments are summarized in Tables 3.3 and 3.4, respectively. The monofilaments were then radiochemically sterilized using 5 and 7.5 kGy gamma radiation and a polyformaldehyde package insert as described earlier by Correa et al. ° The tensile properties of typical sterile monofilament sutures and their BSR profiles were determined after incubation in a phosphate buffer at 37°C and pH 7.4 to simulate their in vivo profile. The tensile properties and BSR data of a typical radiochemically sterilized monofilament suture are summarized in Table 3.5. 

Typical In Vitro BSR Data of a Radiochemically Sterilized Monofilament Suture ... 

Effect of Composition on the Breaking Strength Retention (BSR) of Radiochemically Sterilized Sutures... 

S. W., Radiochemical sterilization of polyglycolide sutures. Sixth World Biomaterials Congress, Trans. Soc. Biomater., II, 992, 2000. 

Abstract Biotextile sterilization presents unique challenges. The chapter describes the principles of sterilization and the way in which sterility assurance levels are defined and demonstrated.Traditional thermal, chemical and radiation sterilization methods are described, as well as newer methods such as plasma and microwave sterilization, and applications for which each is suitable. The advantages of the emerging technology of radiochemical sterilization are described, together with some of its successful applications, such as surgical sutures and tissue adhesive and the results of recent comparative studies of radiochemical and other sterilization methods for absorbable materials. Projected future trends in sterilization technology are also outlined. 

Radiochemical sterilization (RCS) is an emerging technology. It is based on low-dose radiation sterilization in a dry environment at low temperatures in conjunction with the use of radiolytically and controllably generated formaldehyde gas at low levels. Details of the RCS process are described in the following excerpt from Shalaby, S.W., Doyle, Y., Anneaux, B.L., Carpenter, K.A., Schiretz, F.R. Radiochemical Sterilization and its use for Sutures (Nuclear Instruments and Methods in Physics Research B (2003) 110-114) ... 

Table 6.5 Absorbable suture radiochemical sterilization using package inserts ...

Tate, E, Anneaux, B., Vaughn, M.A. and Shalaby, S.W, Use of radiochemically sterilized, absorbable tissue adhesive for rabbit kidney repair . Transactions of the Society for. Biomaterials, 2(2), (2006) 433. 

---