A method for manufacturing a therapeutic agent delivery system includes forming a first mixture with a plurality of microparticles, the microparticles containing a therapeutic agent and having a coating around the therapeutic agent, the coating including chitosan. The method also includes forming a second mixture from ingredients including the first mixture, chitosan, a hydration promoter, a microparticle adhesion inhibitor, and a microparticle aggregation inhibitor, freezing the second mixture in a bath containing an aqueous alcoholic solution at a temperature above the freezing temperature of the aqueous alcoholic solution and at most −40° C., to form a frozen layer precursor, and drying the frozen layer precursor to form a porous polymeric matrix with microparticles embedded within the matrix.
