ABSTRACT
Other techniques, such as gamma sterilization or aseptic procedures, can be chosen. Gamma sterilization techniques have been applied to the sterilization of biodegradable microspheres or implants. A decrease in the molecular weight of the polymer is usually observed after gamma irradiation [121]. Similar observations have been presented by Lemoine et al. [40], who reported a decrease of 28% in the molecular weight of PLGA nanoparticles after a 21,000 Gy irradiation dose. A decrease of the polymer molecular weight may totally change the in vitro, and consequently the in vivo, release profile of the incorporated drugs. After a 2.5 Mrad dose, Alleman et al. reported the dramatic increase of the dissolution rate of savopexine from poly(DL-lactic acid) nanoparticles [38]. This is apparently due to a dramatic decrease in the number-average molecular weight at sterilization doses above 0.1 Mrad. The degradation of the polymer during sterilization and its influence on important product characteristics, such as drug release and biodegradation, has yet to be characterized in detail.
