Development of "leaky" liposome triggered by radiation applicable to a drug reservoir and a simple radiation dosimeter

Akamatsu, Ken

Effects of lipid compositions and the content ratios on the membrane permeability of liposome have been investigated using soft X-rays as ionizing radiation (IR) sources. Three-component liposome constituted from an unsaturated phosphatidyl choline (PC), a saturated PC, and cholesterol was selected in a series of the study. As the results, following characteristics of IR-sensitive liposome were discovered: (1) A PC with bis-allylic hydrogen is essential as a component of unsaturated PC., (2) Dilinoleoyl PC (DLOPC) is optimal as a component of unsaturated PC., (3) Either distearoyl PC (DSPC) or dipalmitoyl PC (DPPC) is optimal as a component of saturated PC., (4) Lower dose- rate makes the liposome more IR-sensitive., (5) Lower concentration of liposome makes the liposome more IR-sensitive., (6) There is a region for optimal DLOPC content ratio for the IR-sensitive liposome around 5 20 mol%., and (7) There is a region for optimal cholesterol content ratio for preparing a stable liposome around 30 60 mol%. These fundamental laws for IR-sensitive liposome will contribute to understanding of biomembrane damage by IRs and developing a new-conceptual pharmaceutical available in radiotherapies.