1帝京大学薬学部薬物送達学研究室, 2日本学術振興会特別研究員PD, 3Faculty of Science, Utrecht University
1Laboratory of Drug & Gene Delivery Research, Faculty of Pharma-Sciences, Teikyo University, 2Research Fellow, JSPS, 3Faculty of Science, Utrecht University
【Purpose】 To develop a novel bubble formulation for ultrasound（US）imaging and therapy with small particle size and a good stability and test the formulation as US imaging contrast agent and for gene delivery in vitro and in vivo. 【Methods】 Lipid-stabilized bubbles were prepared by homogenization of a lipid dispersion in the presence of perfluoropropane gas. Different phospholipid compositions were tested and evaluated. After bubble formation the bubbles were freeze-dried so that a dry sample containing bubbles was formed. After re-constitution of the samples they were analyzed for size, gas content and US signal intensity. The bubbles were also evaluated as contrast agents in vivo, and for US activated gene delivery of luciferase pDNA in vitro on cell culture and in vivo in mice. 【Results and discussion】 Bubbles were in the size range 500-800 nm and could be re-constituted by simple addition of water to the dry sample. Changes in the lipid composition had a big impact on the bubbles properties. A mixture of three different lipids in the stabilizing layer resulted in the most stable bubbles. In vivo imaging of B16BL6 tumours in mice, using the most stable bubbles showed circulation times longer than for the commercial bubble Sonazoid®. Also, the bubbles were well suited for visualization of tumour neovasculature. Bubbles together with pDNA and US exposure increased the luciferase activity by about 300 times in vitro and 2000 times in vivo, compared to only pDNA+US. We believe this new formulation shows great promise for both diagnostic and therapeutic applications thanks to its good stability, relatively small bubble size and the simplicity of handling.