Introduction: Packaging of Muscolo-Skeletal Tissues (MST) stored at −80°C must assure safety and sterility in order to minimize any risk of bacterial contamination and/or mechanical failure. Polymeric bags demonstrated problem of integrity at −80°C; gamma ray sterilisation induce oxidation decreasing mechanical properties, whereas Ethylene Oxide (EtO) does not. Antioxidant biocompatible additive, as Vitamin E, could improve mechanical resistance.
Objectives: Based on a previous paper presented at EATB 2005 congress, to analyse mechanico-chemical properties of plastic bags routinely used in MST Banks and new samples in order to identify and solve possible problems arising from the chemical composition and/or sterilisation.
Materials and Methods: Five different polymeric sterile bags used in three International Banks (three gamma and two EtO sterilised) and four experimental sample, manufactured on purpose from a Linear Low Density PolyEthylene (LLDPE) 150 microns thick films (EtO and e-beam sterilised), two added of Vitamin E, were analysed. Impact resistance was evaluated both on frozen and unfrozen material (in oven at 37°C); results were related to chemical composition, Tg, sterilisation and Fourier Transformed InfraRed Spectroscopy (FTIR).
Results: Three samples routinely used (one gamma and one EtO) showed severe macroscopic modification (glassy behaviour) at frozen temperature with no resistance to any mechanical stress Two samples (EtO) did not resist to mechanical tests at frozen state. The four experimental LLDPE, EtO and e-beam sterilised, resisted to mechanical tests. FTIR analysis confirmed the chemical composition declared by the commercial film: pure LLDPE, without any toxic additive and LLDPE with vitamin E.
Discussion: Packaging must use polymers with adeguate glass transition temperature (Tg) in order to maintain at −80° the rubbery state, not stiff nor fragile (not to pass to glassy state). High energy radiation oxidize polymer and decrease their mechanical resistance. LLDPE combine low Tg of the amorphous phase and low crystallinity, resulting in good mechanical properties at working temperature and at −80°C. Addition of Vitamin E protect against oxidation. EtO sterilisation does not modify the structure.
Conclusion: A LLDPE added of Vitamin E, sterilised by EtO and e-beam could improved packaging and storage of tissues at −80°C, with increased resistance to oxidation.
