Chemical architecture and functionality play an important role in the physico-chemical properties of cationic polymers with applications as gene vectors. In this study, linear homopolymers of N-ethyl pyrrolidine methacrylamide (EPA), copolymers of EPA with N,N-dimethylacrylamide (DMA) and oligomers of EPA were synthesized, and the resulting structures were evaluated for their transfection efficiency as non-viral gene vectors. Specifically, polymer species with high and low molecular weights (120-2.6 kDa) and different functionalities (tertiary amines as side chains and primary amine as chain end) were prepared as non-crosslinked, linear homopolymers, copolymers and oligomers, respectively. Polymer/DNA complexes (polyplexes) formation was evaluated by agarose gel electrophoresis, showing that all systems complexed with DNA in all P/N ratios with the exception of the EPA homopolymer. Furthermore, light scattering measurements and transmission electronic microscopy (TEM) showed different size (50-450 nm) and morphology depending on the composition and concentration of the polyplex systems. Cell viability and proliferation after contact with polymer and polyplexes were studied using 3T3 fibroblasts, and the systems showed an excellent biocompatibility at 2 and 4 days. Transfection studies were performed with plasmid Gaussian luciferase kit and were found that the highest transfection efficiency in serum free was obtained with oligomers from the P/N ratio of 1/6 to 1/10. Transfection values of the functionalized oligomers with respect to the control linear poly (dimethylaminoethyl methacrylate) [poly (DMAEMA)] are very interesting in the presence of serum. Haemolysis for these polymers values below 1%, which provide attractive potential applications in gene therapy with these non-toxic readsorbable polymers. (C) 2011 Elsevier B.V. All rights reserved.