超音波照射によるマイクロカプセルの破壊及び内包物放出過程の観測

摘要

This report investigates the destruction property of biocompatible poly-L-lactic acid (PLLA) microcapsules under ultrasound irradiation, and the release of inner substance through the capsule destruction is quantitatively evaluated. PLLA microcapsules with the diameter of 1 to 45 μm were fabricated by double emulsion method. The capsules have trilaminar structure: an air bubble coated with a red fluorescent dye, which is substitute for drug, is surrounded by a PLLA spherical shell. The shell thickness was distributed from 100 nm to 3 μm and the hollow rate of capsules was estimated to be 75% to 97%. The frequency dependence of the capsule destruction was investigated in water tank by irradiating continuous sound wave with 400 kPa at several frequencies from 700 kHz to 2 MHz. The capsules with the resonance size were significantly destroyed: they were 30, 25, and 20 μm at 700 kHz, 1, and 2 MHz, respectively. Through the capsule destruction by the high-intensity ultrasound, the inner dye was gradually released and most of the inner dye has been released for 60 seconds. The vibration of the inner bubble synchronized with the driving ultrasound will assist the release of the inner dye form the ruptured shell.%ポリ乳酸を膜材質とする中空カプセルを作製し，超音波照射下におけるカプセルの破壊特性及び，内包物の放出を評価した.作製したカプセルの粒径は1～45μmであり，ダブルエマルション法を用いて作製した.周囲膜内部には模擬薬物である蛍光色素(acid red 52)と空気が封入されており，三層構造を持つ.膜厚は100nm～3μmであり，中空率は75～97%である.実験容器内を脱気水で満たし，周波数700kHz,1,2 MHzの連続正弦波，音圧400kPaでカプセルの破壊実験を行った.各周波数におけるカプセルの共振径はそれぞれ30,25,20μmであった.カプセル破壊後，内包物は60秒間にわたり放出がなされた.カプセル内部の気体の振動が内包物の放出に影響を与えると考えられる.