Gene transfer with echo-enhanced contrast agents: Comparison between Albunex, Optison, and Levovist in mice - Initial results

PURPOSE: To determine if commercially available echo-enhanced microbubble contrast agents could be used to increase gene transfection efficiency by means of relatively low-intensity ultrasound-mediated microbubble destruction in skeletal muscles. MATERIALS AND METHODS: Three types of ultrasound microbubble contrast agents (0.01 mL of albumin [Albunex] and human albumin [Optison] and 10 mg/mL of SH U 508A [Levovist]) were each separately mixed with the reporter plasmid DNA (25 mug) encoding green fluorescent protein (GFP) prior to intramuscular injection into the quadriceps muscle of a mouse thigh bilaterally (seven mice per contrast agent). One of the muscle sites that was injected with plasmid DNA was irradiated with low-intensity therapeutic ultrasound (1 MHz) at an intensity of 2.0 W/cm(2) for 2 minutes. Mice were sacrificed 7 days after ultrasound treatment for gene expression assay. The number of GFP-expressing muscle fibers was counted. Statistical significance was determined with a two-tailed Student t test. P <.05 was considered to indicate statistically significant difference. RESULTS: Muscle tissue exposed to ultrasound with air-filled Albunex or Levovist microbubbles revealed no difference in the number of GFP-expressing muscle fibers compared with the control non-ultrasound exposed muscle. Albumin-coated octafluoropropane gas-filled Optison microbubbles showed a 10-fold increase in the number of GFP-expressing fibers (P < .05). CONCLUSION: Low-intensity ultrasound with echo-enhanced Optison induced efficient gene transfer unlike that with Albunex or Levovist. (C) RSNA, 2003.