Polyethylenimine: A versatile, multifunctional non-viral vector for nucleic acid delivery.

Polyethylenimine (PEI) has recently been widely studied for the design of nucleic acid delivery vehicles. Gene delivery using PEI involves condensation of DNA into compact particles, uptake into the cells, release from the endosomal compartment into the cytoplasm, and uptake of the DNA into the nucleus. PEIs being positively charged, linear or branched polymers are able to form nanoscale complexes with small RNAs, leading to RNA protection, cellular delivery, and intracellular release. This review highlights the important properties of various PEIs with regard to their use for nucleic acid delivery. Brief discussion on cellular uptake mechanism of non-viral vector is included to understand its utility for gene delivery. Applications of modified PEI for increased efficacy, altered pharmacokinetic properties; improved biocompatibility and targeted delivery have also been discussed. An overview of simulation studies which can help in understanding the underlying complexation mechanism has also been included. The review provides a brief discussion about clinical trials and patents related to nucleic acid delivery using PEI based systems.