Proton Sponge Trick for pH-Sensitive Disassembly of Polyethylenimine-Based siRNA Delivery Systems

Abstract

Small interfering RNAs offer novel opportunities to inhibit gene expression in a highly selective and efficient manner but depend on cytosolic translocation with synthetic delivery systems. The polyethylenimine (PEI) is widely used for plasmid DNA transfection. However, the water-soluble PEI does not form siRNA polyplexes stable enough in extracellular media for effective delivery. We previously showed that rendering PEI insoluble in physiological media, without modifying drastically its overall cationic charge density, by simple conjugation with natural hydrophobic alpha-amino acids, can lead to effective siRNA delivery in mammalian cells. In here, we comprehensively investigated the mechanism behind the excellent efficacy of the leading PEIY vector. Our data revealed that the underlining proton sponge property is key to the effectiveness of the tyrosine-polyethylenimine conjugate as it may allow both endosomal rupture and siRNA liberation via an optimal pH-sensitive dissolution of the PEIY self-aggregates. Altogether, these results should facilitate the development of novel and more sophisticated siRNA delivery systems.

Enhancing microparticle internalization by nonphagocytic cells through the use of noncovalently conjugated polyethyleneimine

“…We anticipated that using PEI, microparticles would be found in the cytosol, because it has been previously reported that the capability of protonation of PEI results in the disruption of endosomes. [29][30][31] Authors that have covalently attached PEI to microparticles 20 have reported that these particles can be found free in the cytosol as early as 4-6 hours posttransfection when using PEI 70 KDa but not when using PEI 25 KDa. Kobayashi et al 21 demonstrated that the use of free cationic lipids increases the internalization of microparticles and that once in the endosomes compartment, they escape in a few minutes.…”

Dual Responsive, Stabilized Nanoparticles for Efficient In Vivo Plasmid Delivery

“…Polymeric vectors that are effective for plasmid delivery often have to be modified in order to efficiently deliver siRNA. [39][40][41] In this case, the ternary block-statistical copolymer that showed highest gene transfer was also most effective at siRNA delivery without the need for additional modifications. The triblock copolymers in contrast display an insignificant silencing effect.…”

Synthetic vectors for gene delivery: An overview of their evolution depending on routes of administration.

“…When endocytosis of polyplexes was mediated by clathrin-dependent endocytosis, pDNA can escape the endosomal compartment and reach the cytosol by exploiting the protonation capacity of the polymers. In addition to the role played by their cationic groups in condensing pDNA, the polyplexes also carried acid-protonable groups such as secondary amines [101,102] or imidazole rings [103]. It is of note that when they route via the caveolea-dependent pathway, polyplexes can also reach the clathrin-dependent pathway [104].…”