A method for preparing exosomes or exosome-like vesicles packaged with a nucleic acid of interest is provided. In certain embodiments, the method may comprise: introducing into an exosome-producing cell a nucleic acid construct comprising the nucleic acid sequence of interest incorporated in a pre-miR-451 structural mimic, and allowing the cell to produce exosomes. Nucleic acid constructs, compositions, and uses thereof are also provided.