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This sterilisation technique is suitable for?thermolabile products, which include liposomes, since it does not involve any form of heating nor conditions that can result in the formation of degradation products or leakage of?liposomal contents associated with the other terminal sterilisation techniques. One drawback of this technique is that filtration must be performed under aseptic conditions and is a relatively expensive method since it requires equipment to work under high pressure, which could be above 25?kg/cm2[13]. Some may contend that the size restriction limits the applicability of this terminal sterilisation technique. However, this limitation is insignificant [http://www.selleckchem.com/products/MLN-2238.html selleck chemical] in manufacturing liposomes for parenteral usage since a small vesicle size (of [http://www.selleckchem.com/products/gsk-j4-hcl.html this website] between 200 and 300?nm, the formulations can be heated above the phase transition temperature so that they can pass through the filter pores in their less rigid spherical conformations [14]. Filtration sterilisation is relatively time-consuming and not efficient for removal of viruses [15]. The choice of tight filter holders and filtration units are essential to the sterility of the preparations, since the external pressure exerted on the liposomal dispersion might displace the filter holders slightly causing the assembly to be leaky. Studies have shown that polycarbonate membranes are less effective in ensuring the sterility of the preparations, as compared to Milex? and Minisart? filtration units [http://en.wikipedia.org/wiki/Ribosomal_s6_kinase S6 Kinase] [14]. The limitations of this technique have prompted research of the other sterilisation techniques. Unfortunately, all the other conventional techniques result in the formation of degradation products via the aforementioned degradation pathways. This sterilisation technique achieves microbial death primarily through the degradation of microbial DNA and disruption of the microbial membranes via free radical formation. Although ��-irradiation is an effective sterilisation method for certain medicaments and surgical equipment, it cannot be used in liposome sterilisation. By the aforementioned mechanism of free radical formation, the unsaturated phospholipids of liposomes are subjected to peroxidation and destabilised under irradiation at the recommended dose of 25?kGy. More specifically, ��-irradiation of cholesterol produces OH , while irradiation of phospholipids produces O2??[5]. In addition to lipid peroxidation, irradiation-induced liposomal degradation is also attributed to the free radical phospholipid fragmentation [16].