2-(dimethylamino)ethyl methacrylate based (co)polymers as gene transfer agents

Abstract

Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) is a water-soluble cationic polymer, which is able to bind to DNA by electrostatic interactions. At a polymer/plasmid ratio above 2 (w/w) positively charged complexes were formed with a size around 0.2 μm. The transfection efficiency of polymer/plasmid complexes was evaluated in cell culture (COS-7 and OVCAR-3 cells) using a pCMV-lacZ plasmid, encoding for β-galactosidase, as a reporter gene. The optimal transfection efficiency was found at a PDMAEMA/plasmid ratio of 3–5 (w/w). Under these conditions 3–6% of the cells were actually transfected. Like other cationic polymers, PDMAEMA is slightly cytotoxic. This activity was partially masked by complexing the polymer with DNA. A pronounced effect of the molecular weight of the polymer on the transfection efficiency was observed. An increasing molecular weight resulted in an increasing number of transfected cells. Dynamic light scattering experiments showed that high molecular weight polymers ( M w>300 kDa) were able to condense DNA effectively (particle size 0.15–0.20 μm). In contrast, when plasmid was incubated with low molecular weight PDMAEMA, large complexes were formed (size 0.5–1.0 μm). Copolymers of DMAEMA with methyl methacrylate (MMA), ethoxytriethylene glycol methacrylate (triEGMA) or N-vinyl-pyrrolidone (NVP) also acted as transfection agents. A copolymer with 20 mol % of MMA showed a reduced transfection efficiency and a substantial increased cytotoxicity compared with a homopolymer of the same molecular weight. A copolymer with triEGMA (48 mol %) showed both a reduced transfection efficiency and a reduced cytotoxicity, whereas a copolymer with NVP (54 mol %) showed an increased transfection efficiency and a decreased cytotoxicity as compared to a DMAEMA homopolymer.