siRNA delivery mediated by copolymer nanoparticles, phospholipid stabilized sulphur hexafluoride microbubbles and ultrasound.

The combination of ultrasound (US) and microbubbles (MB) is a promising physical method for improving the nanoparticles (NPs) delivery efficiency. However, few concerns over comparable delivery effect of the passive or active targeting property's NPs mediated by US and MB have limited their translation towards further application. For this, we prepared small interfering RNA (siRNA)-loaded mPEG-PLGA-PLL (siRNA/mPPP) NPs with passive targeting property and siRNA-loaded mPEG-PLGA-PLL-cRGD (siRNA/mPPPR) NPs with active targeting property, and evaluated the effect of US and MB for their delivery efficiency. The experimental results demonstrated that US and MB effectively enhance the siRNA delivery efficiency of the mPPP NPs compared with the mPPP NPs alone. In contrast, an improved delivery efficiency of siRNA was not observed in PC-3 cells treated with the mPPPR NPs mediated by US and MB, suggesting that the delivery efficiency of NPs mediated US and MB also depend on its targeting properties.