¹The Faculty of Biotechnology and Food Engineering, The Technion -Israel Institute of Technology, Haifa, Israel

Correspondence: Dr M Machluf, The Laboratory of Cancer Drug Delivery & Mammalian Cell Technology, Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa 32000, Israel. E-mail: machlufm@tx.technion.ac.il

Received 1 May 2006; Revised 4 October 2006; Accepted 18 October 2006; Published online 12 January 2007.

Abstract

Therapeutic ultrasound (TUS) is a promising non-viral clinical approach for the delivery of genes. This study demonstrates the efficient delivery and localization of DNA in subcutaneous tumors facilitated by TUS application and examines the contribution of ultrasound contrast-agent (USCA) addition on transfection. The study addresses the importance of in vivo optimization when using long-term TUS and USCA based on data achieved in vitro. In vitro results showed that transfection of TrampC2 prostate cancer (Pca) cells using genes encoding for luciferase and green fluorescent protein was enhanced when DNA and Optison were added together and TUS was applied for 20 or 30 min. In vivo results showed that the highest transfection was achieved when Optison and DNA were co-injected intratumoraly, and TUS was applied for 20 min. Using Optison significantly increased protein distribution in the tumor. However, in vivo expression level was decreased by two and four fold at 7 and 14 days, respectively, post-TUS. The study establishes the potential of intratumoral delivery of DNA–Optison, followed by TUS as an effective, non-toxic, gene delivery method that could provide a safe, clinical alternative to current viral gene delivery approaches where short-term gene expression is needed.