Fig. 1

Schematic drawing of gene transfection by the combination of US with microbubbles and cross-linked PEIs. On one hand, sonoporation of US allows cross-linked PEI-DNA complexes into the cytoplasm. On the other hand, US can enhance endocytosis. The complexes will escape from the endosome to the cytoplasm. After reaching the cytoplasm, all the complexes will degrade into their low molecular-weight components and release DNA to enter the nucleus for transcription