Ultrasound assisted siRNA delivery using PEG-siPlex loaded microbubbles

Abstract

Short interfering RNA (siRNA) attracts much attention for the treatment of various diseases. However, its delivery, especially via systemic routes, remains a challenge. Indeed, naked siRNAs are rapidly degraded, while complexed siRNAs massively aggregate in the blood or are captured by macrophages. Although this can be circumvented by PEGylation, we found that PEGylation had a strong negative effect on the gene silencing efficiency of siRNA-liposome complexes (siPlexes). Recently, ultrasound combined with microbubbles has been used to deliver naked siRNA but the gene silencing efficiency is rather low and very high amounts of siRNA are required. To overcome the negative effects of PEGylation and to enhance the efficiency of ultrasound assisted siRNA delivery, we coupled PEGylated siPlexes (PEG-siPlexes) to microbubbles. Ultrasound radiation of these microbubbles resulted in massive release of unaltered PEG-siPlexes. Interestingly, PEG-siPlexes loaded on microbubbles were able to enter cells after exposure to ultrasound, in contrast to free PEG-siPlexes, which were not able to enter cells rapidly. Furthermore, these PEG-siPlex loaded microbubbles induced, in the presence of ultrasound, much higher gene silencing than free PEG-siPlexes. Additionally, the PEG-siPlex loaded microbubbles only silenced the expression of genes in the presence of ultrasound, which allows space and time controlled gene silencing.

Self-assembled liposome-loaded microbubbles: The missing link for safe and efficient ultrasound triggered drug-delivery

“…We showed that in combination with ultrasound, such microbubbles strongly improved both doxorubicin (DOX) cytotoxicity and pDNA [16,22] and siRNA [23] delivery to cells in vitro. However, the complex microbubble preparation method, the immunogenic nature of the avidin-biotin chemistry used to link the liposomes/lipoplexes to the microbubbles and the successive washing steps, made this material not ideal for easy clinical use.…”

Optimization and apoptosis induction by RNAi with UTMD technology in vitro

“…Among non-viral techniques, ultrasound-targeted microbubble destruction (UTMD) has evolved as a new, promising tool for site-specific drug and gene delivery in vitro and in vivo, targeting delivery via a process called sonoporation, allowing for direct transfer into the cells (14)(15)(16). Significant efforts have been made to demonstrate the application of siRNA mediated by UTMD to block gene expression in vitro and in vivo (17)(18)(19)(20). Wang et al (21) found that UTMD was capable of delivering survivin siRNA into SKOV-3 cells, which inhibited survivin expression and induced apoptosis.…”

Spatiotemporally controlled single cell sonoporation

“…Without the need to use viral vectors, sonoporation enables the delivery of a wide range of bioactive agents with minimal inflammatory and immunological responses for both in vitro studies and in vivo applications (12)(13)(14)(15)(16). In addition, ultrasound application can be targeted to a specific volume of tissue in vivo noninvasively.…”