Radiation sterilization of polymeric implant materials

Abstract

High-energy irradiation sterilization of medical devices and implants composed of polymeric biomaterials that are in contact with tissue and/or blood, may adversely affect their long-term mechanical and/or biological performance (tissue and/or blood compatibility). Since many polymeric implants may contain trace quantities of catalysts and/or other additives, the effect of high-energy radiation on these additives, and possible synergistic effects with the polymer chains under the influence of high-energy radiation, must be considered. It is essential to indicate whether polymeric implants are used in short-term (acute) or long-term (chronic) applications. Relatively small changes in their physicochemical, mechanical, and biological properties may be tolerable in the short term, whereas similar changes may lead to catastrophic failures in long-term applications. Therefore, polymeric implants which are to be sterilized by high-energy irradiation should be carefully evaluated for long-term property changes which may be induced by the radiation.

Formation and Elution of Toxic Compounds From γ-Ray-Sterilized Medical Products and the Ames Test of Eluted Components

“…This was thought to be due to the rare possibility of simultaneous cleavage occurring at two successive urethane linkages forming MDA Shintani, 1991b, 1994 It has been reported that PU was cross-linked byray irradiation Bruck and Muller, 1988;Wall, 1955 ; however, the authors have no evidence of cross-linking in chain-extended PU such as Pellethane R 2363 when subjected to -ray irradiation Shintani, 1990 . The author's data, however, indicated clear evidence of degradation in -ray irradiated chain-extended thermoplastic PU and predominant crosslinking in nonchain-extended thermoplastic PU Shintani, 1990 .…”

“…These compounds as well as gaseous chemical residues, i.e. ethylene oxide and formaldehyde, require careful evaluation to estimate the risk factor to patients and recipients exposed Shintani, 1995;Golberg, 1986 . -ray irradiation sterilization is an alternative, but does not provide an effective depth of sterilization compared with -ray irradiation Bruck and Muller, 1988;Gardner, 1986 . It has been reported that MDA Figure 1 lowest , a carcinogen and mutagen, is formed in autoclavesterilized chain-extended thermoplastic PU and is detectable at a level of a few ppb to a few hundred ppb in aqueous extract, depending on the period of autoclaving or material O'Mara et al, 1984;Ernes and Hanshumaker, 1983;Mazzu and Smith, 1984 . Other than the author's report, there has been so far an absence of reports describing the formation of MDA and other toxic and mutagenic compounds in sterilized thermoplastic and thermosetting PUs when subjected to gamma-ray irradiation or autoclave sterilization…”

“…One was nonchain-extended thermoplastic PU Figure 1 upper figure and the other was chain-extended PU Figure 1 middle figure . Chain-extended PU was fabricated by reacting MDI with an excess of PTMG chemical sterilization Shintani, 1989aShintani, , b, 199la, 1995Golberg, 1986;Bruck and Muller, 1988;Gardner, 1986;Nystrom, 1991 . The Delany clause in the U.S.A. prohibits the manufacture or sterilization of medical devices exhibiting a potential for the production of toxic compounds: therefore, the formation and elution of N,N-methylenedianiline MDA, Figure 1 and other unidentified toxic compounds require evaluation.…”

Formation and Elution of Toxic Compounds from γ-Ray Sterilized Medical Products: Toxic Compound Formation and Ames test of Eluted Components

“…Accepted sterilization procedures for medical devices are γ-ray irradiation, β-ray irradiation, steam autoclaving, or ethylene oxide or formaldehyde gaseous chemical sterilization [8][9][10][11][12][13]. The Delany clause in the U.S.A. prohibits the manufacture or sterilization of medical devices exhibiting a potential for the production of toxic compounds, therefore the formation and elution of N,N-methylenedianiline (MDA, Figure 1) and other unidentified toxic compounds require evaluation.…”

“…The author has previously reported that during γ-ray or autoclave sterilization, toxic and low molecular weight compounds have been formed in PU as a result of degradation [9,14,15] formaldehyde, require careful evaluation to estimate the risk factor to patient and recipients exposed [10,11]. β-ray irradiation sterilization is an alternative, but does not provide an effective depth of sterilization compared with γ-ray (Bruck and Muller, 1988;Gardner, 1986).…”