Methods and compositions for selectively removing potassium ions from the mammalian gastrointestinal tract

A method of removing potassium ions from a mammalian gastrointestinal tract, the method comprising: administering a core-shell particle to the mammal, wherein the core-shell particle comprises a core component and a shell component, wherein the core component is a polymer having a capacity to bind potassium ions and the shell Component is a permselective polymer for potassium ions over magnesium ions, Passing the core shell particle through the mammalian gastrointestinal tract, wherein the permselectivity of the core shell particle for potassium ion to magnesium ions persists during passage of the core shell particle through the small intestine and the colon, the core Shell particles preferentially bind and retain potassium ions to sodium ions in a lower colon of the gastrointestinal tract, and Removing a therapeutically effective amount of potassium ions from the mammalian gastrointestinal tract.