Tailoring quaternized starch as a non-viral carrier for gene delivery applications

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 (c) 2014 John Wiley & Sons, Ltd.