A stable and soapless latex of 2-diethyl-aminoethyl (DEAE)-dextran-methyl methacrylate (MMA) graft copolymer (DDMC) was developed for nonviral gene delivery vectors (complex between polycation and nucleic acid). DDMC was newly prepared using MMA and DEAE-dextran. Following a transfection protocol, transfection of HEK 293 cells by DDC1, DDC2, and DDC3 samples was carried out using plasmid DNA. With the transfection efficiency determined using the X-Gal staining method, a higher value of 5 times or more was confirmed for DDMC samples DDC1 and DDC2 (but not for DDC3) than for the starting DEAE-dextran hydrochloride. The absorption spectrum shift at around 3400 cm(-1) of the complexes between DDMC and DNA may support the formation of more compact structures by a Coulomb force between the phosphoric acid of DNA and the DEAE group of DEAE-dextran, concluding in DNA condensation. The specifically designed molecular structure of DDMC to ensure easy entry of DNA into cells needs not only a positive charge and a hydrophilic-hydrophobic microseparated domain but also more compact structures for transfection steps. (c) 2005 Wiley Periodicals, Inc.