P01 超音波照射による脂質二重膜の酸化の研究

抄録

Ultrasound is often used in the preparation of size-controlled liposome, which is used as drug delivery carrier. The effects of sonicating liposome have a lot of questions to be resolved. In this work, we investigated the oxidation of unsaturated phospholipid by sonication, particularly focusing on the effects of irradiation time, frequency, and intensity of the ultrasound. The phospholipid we used is egg yolk phosphatidylcholine. Phospholipid solution was sonicated with a horn type homogenizer (20kHz) and a bath-type ultrasonic reactor (490kHz), both of which have a thermostatting system which kept the sample solutions 25℃. The sonication times are from 0 to 2 hours, and the effective power of the ultrasound, which is determined by a calorimetric method, are 9W, 21W and 33W for 490kHz experiments, and 21W for 20kHz sonication. We determined the amount of double bond and bisallyl hydrogen in phospholipid from the area of their characteristic peaks by NMR, and the amount of TBARs, which are the product of the reactions of aldehydes and lipid peroxides with 2-thiobarbituric acid, were determined by a TEA assay. As a result, it was revealed that the sonication brought about decreases in the amount of double bond and bisallyl hydrogen, and increase in that of TBARs. It indicates that the lipid was oxidized by sonication. From the change of the amount of these species, the sonication of higher intensity caused stronger lipid peroxidation, and lower frequency ultrasound has more powerful oxidation effect than higher frequency one. We measured the amount of OH radical generated by sonication with a KI method, and we found higher frequency sonication is more efficient to product OH radical. Therefore our experimental results suggest that the rate of OH radical production is not the only mechanism that affects the ultrasound-induced peroxidation of lipids.