Liposome-Encapsulated Polyethylenimine/Oligonucleotide Polyplexes Prepared by Reverse-Phase Evaporation Technique

Abstract

Abstract. Liposome-encapsulated polyplex system represents a promising delivery system for oligonucleotide-based therapeutics such as siRNA and asODN. Here, we report a novel method to prepare liposome-encapsulated cationic polymer/oligonucleotide polyplexes based on the reverse-phase evaporation following organic extraction of the polyplexes. The polyplexes of polyethylenimine and oligonucleotide were first formed in aqueous buffer at an N/P ratio of 6. The overall positively charged polyplexes were then mixed with the anionic phospholipids in overall organic media. The overall organic environment and electrostatic interaction between anionic phospholipids and positively charged polyplexes resulted in inverted micelle-like particles with the polyplexes in the core. After phase separation, the hydrophobic particles were recovered in organic phase. Reverse-phase evaporation of the organic solvent in the presence of hydrophilic polymer-grafted lipids resulted in a stable aqueous dispersion of hydrophilic lipid-coated particles with the polyplex in the core. Transmission electron microscopy visualization revealed spherical structures with heavily stained polyplex cores surrounded by lightly stained lipid coats. The lipid-coated polyplex particles showed colloidal stability, complete protection of the loaded oligonucleotide molecules from enzymatic degradation, and high loading efficiency of more than 80%. Thus, this technique represents an alternative method to prepare lipid-coated polyplex particles as a delivery system of oligonucleotide therapeutics.

Folate-Targeted Liposome Encapsulating Chitosan/Oligonucleotide Polyplexes for Tumor Targeting

“…This liposomal nanocarrier was characteristically very similar to the pegylated liposomes encapsulating polyethylenimine/oligonucleotide, which were previously reported (11,12). However, it differs from the previous one in the ways that low molecular weight chitosan (LMWC) is used instead of PEI and folate ligands are introduced into the surface, which would provide the nanocarrier with some properties critical for in vivo application, i.e., low toxicity and enhanced tumor targeting.…”

“…Nevertheless, polyplexes between PEI and nucleic acids have not shown significant therapeutic efficacy for in vivo application due to their rapid plasma clearance and accumulation by reticuloendothelial system (RES) sites. In an effort to improve the poor in vivo stability and pharmacokinetic behavior of the polyplex systems, we previously reported a procedure to prepare liposomes encapsulating polyethylenimine/oligonucleotide polyplexes within PEG-stabilized liposomes by rehydrating anionic lipid film in an aqueous buffer containing preformed polyethylenimine/oligonucleotide polyplexes (11) or reversephase evaporation technique (12). Our previously established procedure offers a simple method for combining polyplex systems with liposomal gene carrier systems, with a very high loading efficiency.…”

Three‐Layered Biodegradable Micelles Prepared by Two‐Step Self‐Assembly of PLA‐PEI‐PLA and PLA‐PEG‐PLA Triblock Copolymers as Efficient Gene Delivery System

“…PEGylation of the polyplex surface has been shown to have minimal effect on the stability towards competing polyanions . However, the complete shielding of the polyplex using a barrier that is impermeable for polyanions has been shown to dramatically increase polyplex stability . In our system, the hydrophobic PLLA inner shell provides this impermeable barrier and increases micelle stability in neutral pH.…”

Combinatorial therapeutic approaches with RNAi and anticancer drugs using nanodrug delivery systems

“…However, if the carrier liposome is anionic or neutrally charged, siRNAs may be encapsulated in the aqueous core [48]. Proper packaging of nucleic acid in liposomes can also occur through condensation using cationic polymers like protamine [48] or PEI [49], which enhances siRNA stability. Depending on the solubility, chemotherapy drugs are either encapsulated in the aqueous core or embedded in the lipid bilayer during liposome preparation.…”