The present invention provides an anionic nanoparticle formed from an anionic polymer and an anionic small molecule drug and further comprising a cation, wherein said anionic polymer is selected from an anionic natural polysaccharide or a derivative thereof, and an anionic synthetic polymer. The present invention further provides uses of the anionic nanoparticle for the deliver} 7 of the anionic small molecule drugs into cells and in methods for treating a disease, disorder or condition selected from cancer, metabolic, neurodegenerative, cardiovascular, infectious and inflammatory diseases or disorders, and methods for preparation of the nanoparticle. The present invention also provides a nanoparticle comprising a divalent cation and an anionic small molecule drug and lacking an anionic polymer, and methods for its production.
