Radio sterilization

Barbarin, N. Rollmann, B. Tilquin, B. Role of residual solvents in the formation of volatile compounds after radio sterilization of cefotaxime. Int. J. Pharm. 1999, 178, 203-212. 

By comparison with earlier methods, numerous advantages are admitted for the radio-sterilization.The process ... 

The major disadvantage of radio-sterilization is the peculiarity of the radiation chemistry induced simultaneously to sterilization, which requires a special study the irradiated drug is thus considered as a "new" drug. While micro organisms are killed, various products of degradation of the main compounds may appear in traces amounts though they are often the same as in thermal sterilization. 

The HPLC-UV-DAD was used for the analysis of final products results showed that many related compounds of cefotaxime were present prior to irradiation. Some of them had maxima around 320-380 nm and could be responsible for the change in color of the dissolved irradiated drug. The radiolytic products (25 kGy) were present in traces and were all below the qualification limit of0.1%.TheHPLC-UV-MS results showed that some radiolytic products detected were impurities already present in the non-irradiated cefotaxime and increased after irradiation. The other products were unique to radio-sterilization [14]. 

At the radio-sterilization doses, simulation predicts a greater loss than in the experimental results, possibly because some radiolytic products react with the water radiolysis radicals thus protecting the drug solute [16]. The simulations also predict similar solute concentrations without dose rate effects for E-beam or gamma irradiations whereas the opposite isfound in experimental results [17].The complexity ofthe radiolysis mechanisms at sterilization doses appears with the increase ofthe analytical efficiency. 

All these recommendations are summarized in the Decision trees for the selection of sterilization methods, edited by the EMEA [23] (Fig. 1).Two cases are considered on one hand, the aqueous products and on the other hand, the non-aqueous liquid, semi-solid and dry powder products. Figure 1 shows the order of preference of the sterilization methods for the second group. The terminal ones are ranked in the first place. Among them, thermal sterilization is still referred as the best choice, radio-sterilization ranking right after. Since gas sterilization is excluded and non-terminal methods are listed as the last choice, radiosterilization now precedes all these methods. It is deemed as the recommended alternative method to thermal sterilization. 

Terryn H., Maquille A., Houee-Levin C., Tilquin B., Irradiation of human insulin in aqueous solution first step towards radio-sterilization, Int. J. Pharm., 2007,343,4-11. 

Jacobs. G. P. (1985). A review Radiation sterilization of phannaceuticals. Radio-tion Physics and Chemistry 26 133. 

I - Non-passivated, TFGD-treated, polished machined flats II - Non-passivated, unsterilized, polished machined flats III - Passivated, dry-heat-sterilized, polished machined flats IV - Passivated, dry-heat-sterilized, polished coined flats V - Passivated, dry-heat-sterilized, unpolished flats C - Composite (includes all liquids) P - only polar liquids D - only dispersive liquids. RFGD - Radio Frequency Glow Discharge. 

These examples underscore the wide range of material physical characteristics that remain to be explored to improve fibrous implantable medical devices and make them even smarter for each intended application. While some of these smart characteristics could be easily identified, such as radio-opacity, radioresistance, and resistance to sterilization, wettability, the fibrous material area is a vast exploratory field that is not as well known and described as the fibrous stmctures area. 

---