Cationic polymer optimization for efficient gene delivery.

The polyplexes which are formed between cationic polymers and DNA through electrostatic interactions and thus known as polycation/DNA complexes, are by far the most widely used non-viral gene delivery vectors. Many factors such as molecular weight, surface charge, charge density, hydrophilicity and the structure of cationic polymers affect gene transfection efficiency of cationic polymers. Therefore, optimization of cationic polymers is necessary to improve the gene transfection efficiency. Currently several important cationic polymers were used as cationic vectors for gene delivery which included PEI, PLL, Chitosan and PAMAM. Their most advantages and the rational design are introduced in this article. However, these systems are much less efficient in gene transfer experiments compared with viral systems. Some strategies such as PEGylation, combination and multifunctional modification were developed in the cationic polymeric vectors for gene delivery. Hereby, this article will review various kinds of copolymers with higher stability but biodegradable, bioresponsive and easy refined molecular weight which could be easily modification. Especially, the multifunctional modified polyplexes and polymersomes will be further discussion due to their ability to conjugate biologically active ligands, which can be used as potential nanostructured biomaterials for future in vivo gene delivery.