Controlled release delivery coating formulation for bioactive substances

The present invention relates to a bioactive composition having a controlled, sustained release delivery pattern when contacted with a suitable surrounding media. The composition comprises a pharmaceutically, insecticidally, herbicidally or fertilizing bioactive material core, soluble in a given surrounding media, the core present in an amount at least sufficient for a total dosage during a specified treatment period; a first coating enveloping the bioactive material core comprising a polymer or a blend of polymers, said polymer or blend of polymers being swellable upon penetration by the surrounding media; and a second coating enveloping the first coating, the second coating comprising a polymer or a blend of polymers being water-insoluble and forming a semi-permeable barrier to the inward diffusion of the surrounding media and the outward diffusion of the bioactive material dissolved in the surrounding media.