Gamma Irradiation of Liposomal Phospholipids
Suna ERDOĞAN*, A. Yekta ÖZER*^,°, Melike EKİZOĞLU**, Meral ÖZALP**, Şeyda ÇOLAK***, Mustafa KORKMAZ***
* Hacettepe University, Faculty of Pharmacy, Department of Radiopharmacy, 06100 S›hh›ye-Ankara, Turkey
** Hacettepe University, Faculty of Pharmacy, Department of Pharmaceutical Microbiology, 06100 S›hh›ye-Ankara, Turkey
*** Hacettepe University, Faculty of Engineering, Department of Physics Engineering, Beytepe-Ankara, Turkey

^oCorresponding Author

Summary

Gamma irradiation is becoming more and more accepted as a sterilization method of pharmaceuticals, particularly for those showing heat-sensitivity during autoclaving. Particulate drug delivery systems such as liposomes and niosomes are complex products usually containing lipids and/or polymers with glass transition temperatures below the temperature required for heat sterilization. Consequently, these products would break down if subjected to heat sterilization. From this point of view, gamma irradiation seems to be a suitable sterilization technique for liposomes and niosomes. In previous studies, excessive degradation of liposomal phospholipids was found after gamma irradiation of
aqueous liposome dispersions with a dose of 25 kGy (the suggested dose by pharmacopoeias for gamma sterilization). In this study, solid phospholipids/lipids were sterilized prior to liposome production and lower radiation dose was used for sterilization to decrease the radiation-induced degradation of phospholipids/lipids. According to IR and NMR spectra, DSC thermograms and ESR studies, radiation of raw materials used in liposome and niosome dispersions did not cause meaningful changes in the structure of the materials. Further experiments are still required to determine the changes in the physical behavior of the subsequently produced liposomes and niosomes and the interaction of the irradiated substances with biological systems.

Key Words :
Gamma irradiation, phospholipids, surfactant,stearylamine, dicetyl phosphate, cholesterol, chemical stability.