Effects of frequency and power of ultrasound on the size reduction of liposome.

The solutions of liposome made of l-alpha-dilauroyl phosphatidylcholine are sonicated at various powers and frequencies (43-480kHz), and the resultant change in the size of liposome is measured by the dynamic light scattering method. The ultrasonic power dissipated into the solution is determined by the calorimetric method in order to compare the effects of ultrasound of different frequencies. The faster reduction of the mean size of liposome is achieved at the lower frequency. Comparing at the same frequency and total energy, short-time irradiation of strong ultrasound is more efficient than long-time irradiation of weak ultrasound. These results indicate that the small number of cavitation events with stronger physical disturbance on liposome can reduce the size of the liposome more efficiently than the large number of cavitation events with weaker disturbance.