Poly(2‐oxazoline)‐Based Polyplexes as a PEG‐Free Plasmid DNA Delivery Platform

Abstract

AbstractThe present study expands the versatility of cationic poly(2‐oxazoline) (POx) copolymers as a polyethylene glycol (PEG)‐free platform for gene delivery to immune cells, such as monocytes and macrophages. Several block copolymers are developed by varying nonionic hydrophilic blocks (poly(2‐methyl‐2‐oxazoline) (pMeOx) or poly(2‐ethyl‐2‐oxazoline) (pEtOx), cationic blocks, and an optional hydrophobic block (poly(2‐isopropyl‐2‐oxazoline) (iPrOx). The cationic blocks are produced by side chain modification of 2‐methoxy‐carboxyethyl‐2‐oxazoline (MestOx) block precursor with diethylenetriamine (DET) or tris(2‐aminoethyl)amine (TREN). For the attachment of a targeting ligand, mannose, azide‐alkyne cycloaddition click chemistry methods are employed. Of the two cationic side chains, polyplexes made with DET‐containing copolymers transfect macrophages significantly better than those made with TREN‐based copolymer. Likewise, nontargeted pEtOx‐based diblock copolymer is more active in cell transfection than pMeOx‐based copolymer. The triblock copolymer with hydrophobic block iPrOx performs poorly compared to the diblock copolymer which lacks this additional block. Surprisingly, attachment of a mannose ligand to either copolymer is inhibitory for transfection. Despite similarities in size and design, mannosylated polyplexes result in lower cell internalization compared to nonmannosylated polyplexes. Thus, PEG‐free, nontargeted DET‐, and pEtOx‐based diblock copolymer outperforms other studied structures in the transfection of macrophages and displays transfection levels comparable to GeneJuice, a commercial nonlipid transfection reagent.