It has been discovered that the uptake of anionic charged species into cells can be enhanced by noncovalently associating such species with specifically modified forms of cyclodextrin. The invention modified forms of cyclodextrin form well defined stoichiometric complexes with anionic charged molecules. This discovery enables one to produce various compositions containing anionic charged molecules and facilitates methods for enhancing the cellular uptake of double-stranded or hairpin nucleic acid.