Effect of gamma irradiation on the physical stability of DPPC liposomes

Unilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) were prepared by the reverse-phase evaporation method and extrusion through a polycarbonate membrane filter. Liposomes at 0.7 mg/mL lipid concentration in deionized water were exposed to gamma irradiation at a dose in the range 0.5 to 25 kGy. Gamma irradiation of liposomes resulted in the degradation of DPPC lipids into free fatty acids, lysophosphatidylcholine and 1,2-palmitoyl-phosphatidic acid (DPPA). The effect of gamma irradiation towards the physical stability of liposomes was investigated by means of dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential analysis. From the DLS analysis, no significant changes were observed in the hydrodynamic size of liposomes. TEM images indicate that the liposomes surface became smoother and rounder as higher irradiation doses were applied. Zeta potential analysis showed that gamma irradiation of DPPC liposomes at radiation doses as low as 0.5 kGy resulted in a drastic rise in the magnitude of the zeta potential. The results also demonstrate that gamma irradiation of liposomes suspension enhanced the overall stability of liposomes. Hence, it can be concluded that gamma irradiation on DPPC liposomes may potentially produce liposomes with higher stability

Effect of silver nanoparticle addition on the structure and characteristics of radio-photoluminescence glass dosimeter

A series of silver-activated phosphate glass was prepared by melt quenching method. The effect of silver nanoparticle addition on the phosphate glass microstructure, composition and chemical characteristics was investigated using x-ray diffraction, fourier transform infrared and photoluminescence spectroscopy. Other physical property such as density was also evaluated. The density increased when the amount of silver ions were increased, due to the enhanced formation of non-bridging oxygen. In this study, we discuss the emission mechanism of two radio-photoluminescence peaks at 460 nm and 620 nm, where the electrons and holes produced by γ-irradiation a re-trapped by Ag+ ions to produce Ag0 and Ag2+ ions respectively, when the Ag+-doped phosphate glass is exposed to γ-ray. We proposed that an emission mechanism of 460 and 620 nm radio-photoluminescence peaks with these Ag2+ and Ag0 ions. Furthermore, a correlation between the investigated properties and glass composition is discussed