Unchul Shin

GOAL: The Sonophoresis, which utilizes ultrasound for transdermal drug delivery (TDD), can improve the efficiency of drug delivery for a variety of drugs predominantly due to caviation effect. In order to increase the efficacy of sonophoresis, we propose an alternative cavitation seed specialized for sonophoresis, which can be concentrated on the skin surface by gravity adapting perfluorohexane as core. METHODS: An in vitro and in vivo experiments were conducted to assess the effect of the specialized cavitation seed. High performance liquid chromatography was used for in vitro experiments on porcine skin with ferulic acid and an optical imaging system was used for in vivo experiments on rat model with fluorescein isothiocyanate-dextran (FD, 150 kDa), respecitively. RESULTS: The amount of ferulic acid delivered by sonophoresis with the proposed cavitation seed was approximately 1,700 times greater than the amount delivered by diffusion. FD could be delivered to a depth of 500 ¼m under the skin, and the average total flux in the region of interest was increased 6.4-fold for the group using sonophoresis with the cavitation seed compared to the group using diffusion. CONCLUSION: Conclusively, sonophoresis with the proposed cavitation seed demonstrated significant improvement in TDD and the possibility of macromolecule delivery into the skin. SIGNIFICANCE: This approach has potential to be a main TDD method for variety of applications including medicine and cosmetics.

Ultrasound Contrast Agents (UCAs) were developed to maximize reflection contrast so that organs can be seen clearly in ultrasound imaging. UCAs increase the signal to noise ratio (SNR) by linear and non-linear mechanisms and thus help more accurately visualize the internal organs and blood vessels. However, the UCAs on the market are not only expensive, but are also not optimized for use in various therapeutic research applications such as ultrasound-aided drug delivery. The UCAs fabricated in this study utilize conventional lipid and albumin for shell formation and perfluorobutane as the internal gas. The shape and density of the UCA bubbles were verified by optical microscopy and Cryo SEM, and compared to those of the commercially available UCAs, Definity® and Sonovue®. The size distribution and characteristics of the reflected signal were also analyzed using a particle size analyzer and ultrasound imaging equipment. Our experiments indicate that UCAs composed of spherical microbubbles, the majority of which were smaller than 1 um, were successfully synthesized. Microbubbles 10 um or larger were also identified when different shell characteristics and filters were used. These laboratory UCAs can be used for research in both diagnoses and therapies.

Abstract Ultrasound contrast agents (UCAs), which are groups of engineered microbubbles, have been recently studied for drug delivery applications, since the cavitation of bubbles can increase the temporary permeability of nearby cells. However, the internal volume of UCAs is generally filled with gas, hence loading drug molecules into UCAs is limited. In this study, an echogenic liposome with a liquid and gas core is proposed as an alternative carrier of genetic material for ultrasound‐mediated drug delivery. The structure of the synthesized echogenic liposome was analysed via transmission electron microscopy and confocal microscopy with fluorescent labels. The protection of siRNA by the echogenic liposomes was also verified by exposure to RNase. The results indicate that at least 10% of the total siRNA used in the experiment was successfully protected by the proposed echogenic liposome. Additionally, the release of siRNA from the liposomes could be successfully achieved with 1 W/cm 2 ultrasound sonication at 1 MHz; parameters low enough to be used in generic ultrasound therapeutic systems. Although further studies to clarify the responses to incident ultrasound fields and to quantitatively analyse the internal liquid volume for drug loading are required, the proposed echogenic liposome has great potential for ultrasound‐mediated gene delivery.

Supercoiling DNA (folding DNA into a more compact molecule) from open circular forms requires significant bending energy. The double helix is coiled into a higher order helix form; thus it occupies a smaller footprint. Compact packing of DNA is essential to improve the efficiency of gene delivery, which has broad implications in biology and pharmaceutical research. Here we show that low-intensity pulsed ultrasound can pack open circular DNA into supercoil form. Plasmid DNA subjected to 5.4 mW/cm(2) intensity ultrasound showed significant (p-values <0.001) supercoiling compared to DNA without exposure to ultrasound. Radiation force induced from ultrasound and dragging force from the fluid are believed to be the main factors that cause supercoiling. This study provides the first evidence to show that low-intensity ultrasound can directly alter DNA topology. We anticipate our results to be a starting point for improved non-viral gene delivery.

Sonphoresis can increase skin permeability to various drugs in transdermal drug delivery (TDD) and cavitation is recognized as the predominant mechanism of sonophoresis. In order to increase cavitation activity on the skin surface, dense liquid phase gas core cavitation seed was designed instead of commercially available ultrasound contrast agents (UCAs). The effect of specialized cavitation seed in sonophoresis was quantitatively analyzed with high performance liquid chromatography. Ferulic acid was used as target drug molecule to be delivered into porcine skin. The results indicate that specialized cavitation seed can increase the amount of delivered ferulic acid approximately 2,000 folds while a commercial UCA does not improve the efficiency of TDD. We expect the developed specialized cavitation seeds could be used widely for various skin related applications.