DNA nano-carriers from biodegradable cationic branched polyesters are formed by a modified solvent displacement method

Abstract

DNA nano-carriers were formulated relying on biodegradable polyesters consisting of amine-modified poly(vinyl alcohol) (PVAL) backbones grafted with PLGA, based on the Marangoni effect thus avoiding detrimental shear or ultrasonic forces. These amine modified high molecular weight biodegradable polyesters combine specific characteristics, such as electrostatic interactions between DNA and cationic branched polyesters facilitating loading of NP with DNA. The resulting DNA containing NP showed hydrodynamic diameters in the range of 175–285 nm and highly positive ξ-potentials, depending on the nitrogen to phosphate (N/P) ratio used for the particle formation. Atomic force microscopy (AFM) demonstrated well-defined spherical particle morphologies. DNA was released from NP upon incubation in PBS buffer in its intact supercoiled form. Agarose gel electrophoresis demonstrated that DNA within the NP was protected from enzyme degradation. The biological efficiency of the DNA delivery by this nano-carrier was demonstrated by an in vitro transfection assay using four cell lines. Reporter gene delivery of the amine-modified polymers was higher than naked DNA (Control) and raised with increasing degree of amine substitution. Also type of amine and distance of cationic charge from the backbone play an important role. Further, this feature was shown by Luciferase expression of the pCMV-Luc plasmid with PEI 25 kDa/DNA polyplexes and NP prepared with amine modified polyesters with a grafted PLGA chain length of 10 monomers compared at equal N/P ratios. DNA loaded NP from P(68)-10 showed 8× higher transfection efficiencies than the PEI 25 kDa at an N/P ratio of 9 for both preparations. These novel DNA nano-carriers merit further investigations in particular for DNA vaccination under in vivo conditions.