Two-stage microparticle-based therapeutic delivery system and method

A system for delivery of a therapeutic agent to a site in mucosal tissue is provided. The system includes a porous, mucoadhesive polymeric matrix having a first and a second opposed surfaces. The matrix is formed by a composition including chitosan. The composition may also include any or all of a hydration promotor, a microparticle adhesion inhibitor, and a microparticle aggregation inhibitor. A plurality of microparticles having an average diameter between 500 nm and 2000 nm are embedded within the matrix. The microparticles contain a therapeutic agent and have a coating around the therapeutic agent. The first surface of the matrix is configured to be attached to the site in the mucosal tissue and the matrix is configured to provide controlled release of the microparticles through the first surface. The coating of the microparticles includes chitosan so as to provide controlled release of the agent from the microparticles.