Self-aggregating 1.8 kDa polyethylenimines with dissolution switch at endosomal acidic pH are delivery carriers for plasmid DNA, mRNA, siRNA and exon-skipping oligonucleotides

Abstract

Efficiency of polyethylenimine (PEI) for nucleic acid delivery is affected by the size of the carrier and length of the nucleic acids. For instance, PEIs with molecular weights between 10-30kDa provide optimal DNA delivery activity whereas PEIs with molecular weights below 1.8kDa are ineffective. The activity of PEI is also severely diminished by substitution of DNA for shorter nucleic acids such as mRNA or siRNA. Here, through chemical modification of the primary amines to aromatic domains we achieved nucleic acid delivery by the 1.8kDa polyethylenimine (PEI) particles. This modification did not affect the PEI buffering abilities but enhanced its pH-sensitive aggregation, enabling stabilization of the polyplex outside the cell while still allowing nucleic acid release following cellular entry. The aromatic PEIs were then evaluated for their gene, mRNA, siRNA and 2'O-methyl phosphorothioate oligonucleotide in vitro transfection abilities. The salicylamide-grafted PEI showed to be a reliable carrier for delivering nucleic acids with cytoplasmic activity such as the mRNA and siRNA or nuclear diffusible oligonucleotide. It was then further equipped with polyethyleneglycol (PEG) and the delivery efficiency of the copolymer was tested in vivo for regeneration of dystrophin in the muscle of mdx mouse through a 2'O-methyl phosphorothioate-mediated splicing modulation. Intramuscular administration of polyplexes resulted in dystrophin-positive fibers in a mouse model of Duchenne muscular dystrophy without apparent toxicity. These findings indicate that precise modifications of low molecular weight PEI improve its bio-responsiveness and yield delivery vehicles for nucleic acids of various types in vitro and in vivo.

Design and evaluation of ionizable peptide amphiphiles for siRNA delivery

“…The remarkable effect of tryptophan, and to a lesser extent the tyrosine residue, is reminiscent of the work on decoration of PEI polymer where decoration with aromatic amino acids equally lead to a steep increase of the affinity towards siRNA molecules. [28,29] Our results suggest that a similar triggering effect is seen with the Trp peptide amphiphiles, where π-stacking and pre-organizations is supposed to stabilize the formed amph-R/siRNA complexes. The hydrophobic tryptophan may also act by enhanced membrane interactions as described for Trp containing cell penetrating peptides, especially by triggering glycosaminoglycan-dependent endocytosis.…”

Nanoscale platforms for messenger RNA delivery

“…Through intranasal delivery of this mRNA vaccine, both nasal epithelium and nasal-associated lymphoid tissue displayed dramatic uptake, consequently leading to anti-HIV immune responses in mice (Li, Zhao, Fu, et al, 2016). Since PEI with low molecular weight (<2 kDa) exhibited less cytotoxicity, Chiper, Tounsi, Kole, Kichler, and Zuber (2017) grafted salicylamide with PEI1.8k using an amide linker. This modified PEI was used to deliver diverse DNA and RNA (Chiper et al, 2017).…”

“…Since PEI with low molecular weight (<2 kDa) exhibited less cytotoxicity, Chiper, Tounsi, Kole, Kichler, and Zuber (2017) grafted salicylamide with PEI1.8k using an amide linker. This modified PEI was used to deliver diverse DNA and RNA (Chiper et al, 2017). In addition to chemical conjugation, Choi et al fabricated a complex of graphene oxide (GO)-polyethylenimine (PEI).…”

Biomedical applications of mRNA nanomedicine

“…In another study, 1.8 kDa PEI with its primary amines modified by different aromatic domains was evaluated. Only the salicylamide-modified PEI was a reliable carrier for mRNA delivery in HeLa and U87 cells [104]. As an alternative to PEI, poly (β-amino esters) (PBAEs) exhibit several advantages, such as easy synthesis, relatively low cytotoxicity, and good degradability, and have been demonstrated as an effective delivery system for nucleic acids [105, 106].…”