Breaking down the barriers: siRNA delivery and endosome escape

Abstract

In vivo deliveryPreclinical experiments have demonstrated the effectiveness of synthetic siRNAs as potent inhibitors of a variety of diseaseassociated genes. However, the physicochemical properties of siRNAs -including their small size, hydrophilicity, net negative charge and sensitivity to nuclease degradation -pose challenges Summary RNA interference (RNAi)-based technologies offer an attractive strategy for the sequence-specific silencing of disease-causing genes. The application of small interfering (si)RNAs as potential therapeutic agents requires safe and effective methods for their delivery to the cytoplasm of the target cells and tissues. Recent studies have shown significant progress in the development of targeting reagents that facilitate the recognition of and siRNA delivery to specific cell types. However, most of these delivery approaches are not optimized to enable the intracellular trafficking of the siRNAs into the cytoplasm where they must associate with the RNA-induced silencing complex (RISC) to direct the cleavage of mRNAs bearing complementary binding sites. In particular, the trafficking of siRNAs from endosomes into the cytoplasm represents a major rate-limiting step for many delivery approaches. This Commentary focuses on novel strategies designed to enhance endosomal escape and thereby increase the efficacy of siRNA-mediated gene silencing.

Multiparametric approach for the evaluation of lipid nanoparticles for siRNA delivery

“…The low LNP pK a of some formulations can be predicted based on lipid structure. For example, lipid structures with electron-withdrawing groups neighboring the amine in the head group are weak bases (13,20,28,29, and 30) and may thus lead to low LNP pK a 's. Other formulations were less predictable.…”

“…Challenges to efficient delivery include nanoparticle dissociation via serum proteins (10,11), cellular uptake (12), endosomal escape (13), and appropriate intracellular disassembly (14,15). To address some of these challenges, single-parameter studies that evaluate the effect of chemical structure on a single biological property or on delivery performance have been carried out (16)(17)(18)(19)(20)(21).…”

Uptake and impact of natural diet-derived small RNA in invertebrates: Implications for ecology and agriculture

“…142,143 Once endocytosed, sRNA can be recycled back to the extracellular space, can be degraded in the lysosome, or can exit the endosome via opaque mechanisms. 144,145 Further definition of the processes governing this decision for endogenous extracellular sRNA is warranted to provide a better understanding of the potential handling of diet-derived sRNA.…”

siRNA-based Nanoparticles for Cancer Therapy: Hurdles and Hopes

“…Once inside the target cells, the nanoparticulate RNAi must escape the endosomal enzymes in the lysosome to avoid degradation. Fusogenic peptides and lipids, pHsensitive polyplexes and lipoplexes, have been used to improve endosomal escape [15].…”