Amphiphilic polyethylenimine polymers mediate efficient delivery of DNA and siRNA in mammalian cells

Abstract

Recently, non-viral gene delivery vectors have shown promising results in the treatment of inherited as well as infectious diseases. Among various cationic polymers, branched polyethylenimine (bPEI, 25 kDa) has been the most widely used vector and is known as a gold standard in gene delivery. However, in vivo applications of PEI have been hampered by its charge-associated toxicity. Here, in order to address the toxicity concern as well as to enhance the transfection efficacy of bPEI, it has been modified by tethering a hydrophobic and positively charged 6-(N,N,N′,N′-tetramethylguanidinium chloride)-hexanoic acid (TH) linker (II) using water soluble coupling reagent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDAC). A small series of 6-(N,N,N′,N′-tetramethylguanidinium chloride)-hexanoyl-polyethylenimine (THP) polymers was synthesized by varying the amounts of TH-linker (II). These modified polymers were subsequently characterized by spectroscopic techniques and evaluated for their buffering capacity, transfection efficiency and cytotoxicity on HeLa, HEK293 and CHO cells and the results were compared with those obtained with the standard transfection reagent, Lipofectamine™. From these studies, it was observed that one of the formulations, the THP2–DNA complex, exhibited significantly higher transfection efficiency (∼1.5–3.6 folds) and cell viability, outcompeting native bPEI and Lipofectamine™ in the absence and presence of serum. Further, to establish the superiority of THP2, it was examined for its ability to bind and deliver plasmid DNAs (pDNAs) of different molecular weight, provide protection against nucleases present in the cellular milieu and also deliver siRNAs (GFP- and GAPDH-specific). Taken together, the results show the potential of THP polymers as promising carriers of nucleic acids for in vivo applications.