[Ultrasound enhances microbubble-mediated gene transfection without affecting the cytoskeletons of endothelial cells].

Objective: To investigate the effect of therapeutic ultrasound on enhancing albumin microbubble-mediated gene delivery and evaluate the cytoskeletal damages in endothelial cells (ECs).

Methods: The ECs cultured in 6-well plates were transfected with the plasmid eGFP in the presence or absence of the microbubbles at different concentrations, followed by ultrasound exposure for 30 to 180 s at 2 MHz, with the mechanical index (MI) of 0.5-1.8. The gene transfection efficiency was evaluated by observing the green fluorescence of the cells, and the cytoskeletal damage was assessed using immunofluorescence staining 24 to 48 h after ultrasound exposure.

Results: Within the MI range of ultrasound exposure between 0.50 and 1.00, the gene transfection efficiency was positively correlated to MI (P<0.001), and further increment of the MI failed to further increase the transfection efficiency. The duration of ultrasound exposure, within the range of 30-90 s, was also positively correlated to the gene transfection efficiency and microtubule fluorescence intensity(P<0.001), and prolonged exposure did not further enhance the effects. Variation of the MI and ultrasound exposure time within the above ranges did not cause significant changes in the florescence intensity of the microfilaments (P>0.05).

Conclusion: Albumin microbubbles in the presence of ultrasound exposure can substantially enhance the gene transfection efficiency due to therapeutic ultrasound-mediated microbubble destruction without causing obvious damage of the cytoskeletons, and allows safe and efficient nonviral gene delivery in gene therapy.