- Non-viral gene delivery systems have become increasingly desirable in both basic research and clinical settings as they overcome some of the problems associated with viral vectors. Presently, non-viral carriers used for gene transfer consist mostly of liposomal formulations and cationic polymers. Starch, which is a biodegradable, biocompatible, non-toxic, and water soluble polysaccharide, was evaluated for its potential as a non-viral gene delivery carrier, after modifying it to cationic starch (Q-starch) by means of quaternization. Q-starch synthesis was assessed by means of nuclear magnetic resonance, Fourier transform infrared spectroscopy, elemental analysis, and Kjeldahl method, demonstrating that all the chemical reactions occurred. The Q-starch potential to condense pDNA was evaluated by gel electrophoresis, dynamic light scattering, atomic force microscopy, and zeta potential, validating the formation of nano-sized, positively charged spherical complexes. Transfection efficiency experiments reveal that there are two barriers for efficient transfection: endosomal escape and complex de-complexation, while the latter appears to be the rate-limiting step. We propose that further improvement in transfection efficiency can be achieved by augmenting carrier lysosomotropic ability, as well as its ability to disconnect from the pDNA. Copyright © 2014 John Wiley & Sons, Ltd.