Optimization of Chitosan-α-casein nanoparticles for improved gene delivery: characterization, stability, and transfection efficiency

Among non-viral vectors, the cationic polymer chitosan has gained attention as a gene delivery system. We hypothesized that the addition of casein into the nanoparticle’s structure would facilitate a proper gene transfer. The work herein presented aimed to optimize the production method of chitosan-casein nanoparticles (ChiCas NPs) and to test their ability as a gene delivery system. ChiCas NPs formulation optimization was carried out by analyzing several characteristics such as NP size, zeta potential, and chitosan and casein incorporation efficacy. The best formulation developed presented small and homogenous particle size (around 335 nm) and positive zeta potential (≈ + 38 mV), and showed to be stable for 34 weeks both, at 4°C and 20°C. The particles were further used to entrap or to adsorb DNA and form NPs-DNA complexes. In vitro transfection studies, carried out in COS-7 cells, suggested a low transfection efficiency of the different NPs:DNA ratios tested, comparatively to the positive control. Nonetheless, we could observe that the complexes with larger sizes presented better transfection results than those with smaller diameters. To conclude, ChiCas NPs have great technological potential since the preparation process is very simple, and the DNA incorporation efficacy is very high and shows to be physically very stable. The NPs:DNA ratio still needs to be optimized with the aim of achieving better transfection results and being able to anticipate a high gene expression on DNA-based vaccination studies.