Ultrasound-triggered microbubble destruction in combination with cationic lipid microbubbles enhances gene delivery

This study aimed to examine the preparation of cationic lipid microbubble (CLM), and evaluate its physical and chemical properties and toxicity, measure the gene transfection efficiency by ultrasound triggered microbobble destruction (UTMD) in combination with CLM. The CLM was prepared by the method of the thin film hydration, and its morphology was observed under the electron microscopy at 1st, 3rd, 7th, 10th, and 14th day after preparation, respectively. The size, Zeta potential and stability of CLM were tested. The acute toxicity of CLM was assessed. The green fluorescent protein gene (EGFP) transfection efficiency was evaluated. The experiment grouping was as follows: naked plasmid group (P group), ultrasonic irradiation plus naked plasmid group (P-US group), naked plasmid plus CLM group (P-CLM group), naked plasmid plus ultrasound and CLM group (UTMD group). The expression of EGFP was detected by fluorescent microscopy and flow cytometry. The results showed that CLMs were spherical in shape, with the similar size and good distribution degree under the light and electron microscopies. The size of CLMs was varied from 250.4±88.3 to 399.0±99.8 nm and the Zeta potential of CLMs from 18.80±4.97 to 20.1±3.1 mV. The EGFP expression was the strongest in the UTMD group, followed by the P-CLM group, P-US group and P group. Flow cytometry results were consistent with those of fluorescent microscopy. The transfection efficiency was substantially increased in the P-US group, P-CLM group and UTMD group as compared with that in the P group, almost 7 times, 10 times and 30 times higher than that in the P group respectively. It is suggested that CLMs prepared by the method of thin film hydration are uniform in diameter, and proved non-toxic. UTMD combined with CLM can significantly increase the transfection efficiency of EGFP to targeted cells.