Amino poly(glycerol methacrylate)s for oligonucleic acid delivery with enhanced transfection efficiency and low cytotoxicity

Abstract

To improve the transfection activity and reduce cell cytotoxicity of polycations with antisense oligonucleotide (AON), poly(glycidyl methacrylate)s (PGMAs) were modified with different amines, i.e., methylethylamine (MEA), 2-amino-1-butanol (2-ABO) and 4-amino-1-butanol (4-ABO). The structures of resulting polymers were well characterized and their thermal properties were studied by differential scanning calorimetry (DSC). The amino PGMA could self-assemble with AON in a Tris buffer solution, resulting in narrowly distributed polymer/AON complexes with a size of 0.1–0.3 μm at an amine-group-of-polymer/phosphate-group-of-nucleotide ratio (N/P ratio) of 0.5–3. Spherical nanoparticles of the complexes were visualized using atomic force microscopy (AFM), and the gel electrophoresis and zeta potential assay evidenced the formation of complexes at relatively low N/P ratios. Stability of the complexes towards dissociation was tested using ethidium bromide displacement assay. Protection of the incorporated AON against DNase I degradation was also evaluated. An increased charge ratio and a synergistic effect of hydrogen bonding in this system contributed to the increased stability of the complex, which prevents the incorporated AON from nuclease degradation. In vitro cytotoxicity experiments on COS-7 cells showed that all amino PGMAs displayed lower toxicity compared to the control PEI25k, except for the polymers with a relatively high molecular weight (30 kDa). In addition, the MEA modified linear and star-shaped PGMA (M_n in the range of 15–20 kDa) as well as 4-ABO modified linear PGMA complexes exhibited higher transfection efficiencies in vitro, compared to PEI25k. These results demonstrated that amino PGMAs with suitable amine groups and molecular weight can be used as safe and efficient AON delivery polymers.