Influence of gamma and electron beam sterilization on the stability of a premixed injectable calcium phosphate cement for trauma indications.

Premixed calcium phosphate cements (CPC's) are becoming the material of choice for injectable cements as a result of their effective delivery to the target implantation site. For orthopaedic use, it is of vital importance that the attributes of these CPC's are not compromised by irradiation sterilization. Therefore, the aim of this study is to determine the influence of irradiation sterilization on a range of premixed CPC's, with an emphasis on improving product shelf life through the use of optimal packaging configurations and annealing steps. Electron spin resonance (ESR) confirmed the presence of free radicals in the inorganic phase of the CPC paste following irradiation. The inclusion of a 24-h annealing step was the only successful method in reducing the degree of free radical formation. Based on the results of injectability force testing, it was revealed that an annealing step greater than 24-h significantly altered the viscosity, however; at 24-h the key attributes of the CPC paste were minimally effected. Overall, it was established that vacuum packing the CPC paste, placing the contents into a foil pouch, gamma irradiating at the minimal dose required and using an annealing step of ≤ 24-h, has the potential to extend the shelf life of the cement.

Programmatic Assessment of Potential Induced Radioactivity in Electron Beam Sterilization of Healthcare Products.

ISO 11137-1:2006 Sterilization of Healthcare Products-Radiation requires that the potential for induced radioactivity be evaluated for medical devices irradiated with electrons with energy more than 10 MeV. For a manufacturing operation where new devices are being developed, a practical program for making such an evaluation should be engrained in the process, including the device design phase, where selection of materials can make a difference in the potential for activation to occur as a result of the irradiation process. The program, which is based on general assumptions as to the likely activation processes and generalized process assessments is being implemented in three phases: (1) incorporating materials consideration in the design phase, (2) evaluating potential activation empirically, including measurement at the point of irradiation, and (3) implementing routine procedures for the program, including developing a data base of results for consideration in future design efforts.

Effects of temperature, packaging and electron beam irradiation processing conditions on the property behaviour of Poly (ether-block-amide) blends.

The radiation stability of Poly (ether-block-amide) (PEBA) blended with a multifunctional phenolic antioxidant and a hindered amide light stabiliser was examined under various temperatures, packaging and electron beam processing conditions. FTIR revealed that there were slight alterations to the PEBA before irradiation; however, these became more pronounced following irradiation. The effect of varying the temperature, packaging and processing conditions on the resultant PEBA properties was apparent. For example, rheology demonstrated that the structural properties could be enhanced by manipulating the aforementioned criteria. Mechanical testing exhibited less radiation resistance when the PEBA samples were vacuum packed and exposed to irradiation. MFI and AFM confirmed that the melting strength and surface topography could be reduced/increased depending on the conditions employed. From this study it was concluded that virgin PEBA submerged in dry ice with non-vacuum packaging during the irradiation process, provided excellent radiation resistance (20.9% improvement) in contrast to the traditional method.

Effects of gamma ray and electron beam irradiation on the mechanical, thermal, structural and physicochemical properties of poly (ether-block-amide) thermoplastic elastomers.

Both gamma ray and electron beam irradiation are widely used as a means of medical device sterilisation. However, it is known that the radiation produced by both processes can lead to undesirable changes within biomedical polymers. The main objective of this research was to conduct a comparative study on the two key radiosterilisation methods (gamma ray and electron beam) in order to identify the more detrimental process in terms of the mechanical, structural, chemical and thermal properties of a common biomedical grade polymer. Poly (ether-block-amide) (PEBA) was prepared by injection moulding ASTM testing specimens and these were exposed to an extensive range of irradiation doses (5-200 kGy) in an air atmosphere. The effect of varying the irradiation dose concentration on the resultant PEBA properties was apparent. For instance, the tensile strength, percentage elongation at break and shore D hardness can be increased/decreased by controlling the aforementioned criteria. In addition, it was observed that the stiffness of the material increased with incremental irradiation doses as anticipated. Melt flow index demonstrated a dramatic increase in the melting strength of the material indicating a sharp increase in molecular weight. Conversely, modulated differential scanning calorimetry established that there were no significant alterations to the thermal transitions. Noteworthy trends were observed for the dynamic frequency sweeps of the material, where the crosslink density increased according to an increase in electron beam irradiation dose. Trans-vinylene unsaturations and the carbonyl group concentration increased with an increment in irradiation dose for both processes when observed by FTIR. The relationship between the irradiation dose rate, mechanical properties and the subsequent surface properties of PEBA material is further elucidated throughout this paper. This study revealed that the gamma irradiation process produced more adverse effects in the PEBA material in contrast to the electron beam irradiation process.