Modeling Drug-Carrier Interaction in the Drug Release from Nanocarriers
Schematics of drug release from various systems, including core-shell (a–c), porous (d), and monolithic systems (e). (a) A core functions as a drug reservoir while a shell controls release rate. (b) A special core-shell system (e.g., hollow NPs, hollow fibers, hydrophilic drugs encapsulated in liposomes), in which an inner aqueous compartment replaces the excipient in (a) as a reservoir of polymer-insoluble drug. (c) The core-shell system that encapsulates polymer-soluble drug in the shell. For instance, hydrophobic drugs are encapsulated in the lipid bilayers of liposomes. (d) A porous system with polymer-insoluble drug primarily localized in the vicinity of discrete occlusions or pores. (e) A monolithic system. Red dots represent molecularly dispersed drug molecules, while green explosions represent drug crystals/aggregates, adsorbed drug molecules on surfaces, and/or drug molecules forming complexes with the excipient. Although spherical carriers are illustrated, the schematics can apply to drug-carrier systems of fibers and other geometries.