In accordance with the present invention, it has been discovered that the uptake of charged molecules into cells can be enhanced by noncovalently associating such molecules with molecular entities comprising an amphiphilic core with oppositely charged arms. The molecular entities form well defined stoichiometric complexes with charged molecules. Various compositions and methods for stabilizing anionic charged molecules and for enhancing the cellular uptake of any anionic charged molecules, e.g. double-stranded or hairpin nucleic acid, are provided.