A method for intracellular delivery of isolated naked nucleic acids into a biological tissue or organ, that includes (a) contacting the tissue or organ with an efficient amount of at least one active corticosteroid, and (b) contacting the tissue or organ treated in step b with an efficient amount of isolated naked nucleic acids, wherein step (a) is carried out for a period of time ranging from at least five minutes to at most two hours and being immediately followed by step (b).
