The gallium analogue of the soluble Prussian blue with the formula KGa[Fe(CN)(6)]center dot nH(2)O is synthesized and structurally characterized. A simple aqueous synthetic procedure for preparing nanoparticles of this novel coordination polymer is reported. The stability, in vitro ion exchange with ferrous ions, cytotoxicity, and cellular uptake of such nanoparticles coated with poly(vinylpyrrolidone) are investigated for potential applications of delivering Ga3+ ions into cells or removing iron from cells.