Disclosed are particular 3-dimensional structural matrices containing nucleic acids, various fabrication processes and methods for the prolonged release of nucleic acids in various biological environments. The nucleic acid-matrix materials are created such that they maintain a defined space, allowing cellular migration, transfection and proliferation to occur in a controlled manner. The fabrication processes provide for both high incorporation efficiencies and control over the sustained nucleic acid release. The resultant nucleic acid-containing structural matrices are thus particularly useful in in vivo cell transfection and gene expression in the context of gene therapy.