Controlled release of biological response modifiers. Production and characterization of particulate delivery systems: liposomes, microspheres for gene therapy. In particular, new formulations, have been designed and produced for Natural and Peptide (PNA) Nucleic Acids, based on cationic polymeric sub-micron particles constituted by Eudragit RS 100 plus different cationic surfactants such as dioctadecyl-dimethyl-ammonium bromide (DDAB18) and diisobutylphenoxyethyl dimethylbenzyl ammonium chloride (DEBDA).