The present invention describes a synthetic non-viral vector composition for gene therapy and the use of such compositions for in vitro, ex vivo and/or in vivo transfer of genetic material. The invention proposes a pharmaceutical composition containing 1) a non-cationic amphiphilic molecule or macromolecule and its use for delivery of nucleic acids or 2) a cationic amphiphilic molecule or macromolecule that transforms from a cationic entity to an anionic, neutral, or zwitterionic entity by a chemical, photochemical, or biological reaction and its use for delivery of nucleic acids. Moreover this invention describes the use of these non-viral vector compositions in conjunction with a surface to mediate the delivery of nucleic acids. An additional embodiment is the formation of a hydrogel with these compositions and the use of this hydrogel for the delivery of genetic material. A further embodiment of this invention is the use of a change in ionic strength for the delivery of genetic material.