(360d) Effects of Ultrasonic Stimulation on Release of Internal Hydrophobic Dyes from Pluronic Micelles

In a general chemical industrial process, many reactors, mixture operations, and separation operations are needed, and the design and maintenance become complex. On the other hand, high performance drug carrier has been investigated in the field of drug delivery system. The use of Pluronic block copolymers in experimental medicine and pharmaceutical has been investigated long time. And, the application of ultrasound for drug delivery system has been investigated. In this study, the application of the drug carrier to a chemical reaction process was investigated from the view point of process intensification. Pluronic micelle and hydrophobic dye were used as a model reactant carrier and internal substances, respectively. The effects of ultrasonic irradiation on effluence of dye from Pluronic micelle were investigated. Especially, the relationships between ultrasonic frequency and type of Pluronic were investigated.

Pluronic was used as the micelle and NKX-1595, which is a hydrophobic organic dye, was used as the internal substance. A Pluronic micelle solution containing NKX-1595 was prepared by a dialysis method. The effects of ultrasonic stimulation on the release of NKX-1595 from the Pluronic micelle were investigated. Before ultrasonic irradiation, the Pluronic micelle solution (10 mL) containing NKX-1595 was charged into a reaction vessel. The sample was irradiated with ultrasound for 10 min, and the effects of ultrasonic frequency and power on the release of the dye were investigated. The ultrasonic power in the reactor was measured by calorimetry. To quantitatively evaluate the amount of dye released from the micelle, the absorbance of the sample solution before and after stimulation was measured at a wavelength of 480 nm using a UV–Vis spectrometer.

From the results of ultrasonic stimulation, the internal dye is readily released from the micelle at low ultrasonic frequencies. An ultrasonic physical effect is considered one of the main factors in the release of the hydrophobic dye from the Pluronic micelle. It also can be observed that degree of drug release (DDR) increases with the Pluronic micelle size. The release of the dye from the micelle by ultrasonic stimulation is not only affected by frequency but also by the molecular structure and micelle size. We focused on the inhibition effect when the dye moves to the corona from the core. Under strong ultrasonic physical effects at 22.8 kHz, DDR is not affected by the number of EO units per unit core surface area. However, under a weak physical effect at 490 kHz, DDR changes rapidly when the number of EO units per unit core surface area is approximately 0.4 nm⁻². This phenomenon is owing to the fact that when the internal substance moves to the corona from the core, the inhibition effect decreases with the number of EO units per unit core surface area.