Abstract: A composition for the sequestration and sustained delivery of an active ingredient in the form of porous particles, the composition comprising the product of the controlled dehydration of particles formed by the reaction of a polymeric anionic material with a polyvalent cation. The composition may be loaded with an active ingredient by soaking the particles in a solution of the active ingredient; and may then be dehydrated. They may then be soaked in a solution of a polymeric cationic material, to form particles providing the controlled release of the active ingredient.