The aim of this study was to investigate the value of microbubble destruction using low-frequency ultrasound for enhancing gene delivery to skeletal muscles of laboratory animals.

Lac-Z gene was injected into 21 mouse anterior tibialis muscles. Seven muscles received the gene only, and seven each received either 20-kHz ultrasound exposure or ultrasound-PESDA (perfluorocarbon-exposed sonicated albumin) destruction, respectively, following the injection; the extent of Lac-Z expression was then compared. Luciferase gene was injected into the muscles (N=80). The muscles were divided into two groups according to the mixture; in the first group saline was used as the mixture solute, with PESDA used in the second group. The groups were subdivided into two groups, one receiv 10 seconds of ultrasound at the injection site after injection, and the other that received no further intervention. Luciferase activities were measured and compared.

The proportions of Lac-Z stained cells were 0, 5.7±1.2 and 7.7±1.7%, respectively, showing a significant stepwise increase microbubble destruction (p<0.05). Luciferase activities were as follows: Luciferase only (Group 1, N=17), 5727±2178 RLU/mg; luciferase plus PESDA (Group 2, N=17), 1170±470.7 RLU/mg; luciferase plus ultrasound (Group 3, N=17), 16480±5239 RLU/mg; and luciferase plus PESDA destruction (Group 4, N=17), 49910±16500 RLU/mg. The activity in group 4 was significantly higher than in group 1 (p<0.01), showing an 8.7-fold increase in gene delivery due to microbubble destruction.

Microbubble destruction using low-frequency ultrasound is an efficient method for increasing the efficacy of direct gene delivery to skeletal muscles.