Nanoembedded Microparticles for Stabilization and Delivery of Drug-Loaded Nanoparticles

Nanoparticle-based pharmaceutical products are currently finding their way onto the market as a popular strategy to improve the therapeutic efficacy of numerous drugs, hereunder medications for a targeted treatment of severe diseases (e.g., cancer). Drug-loaded polymer and lipid nanoparticles are typically produced via solvent-based methods and result in colloidal suspensions, which often suffer from physical and chemical instability (e.g., formation of aggregates) resulting in loss of functionality. There are various ways to stabilize such nanoparticle-based formulations including addition of ionic materials to provide electrostatic repulsion or polymer materials forming a steric barrier between the particles. However, for long-term stability often water needs to be removed to obtain a dry product. For this purpose atomization-based techniques such as spray-drying and spray freeze-drying are frequently used to remove water from the nanoparticle suspensions and to form tailored powder products (e.g., nanoembedded microparticles (NEMs)). NEMs provide an excellent vehicle for both stabilization of nanoparticles and delivery of the nanoparticles to their intended site of action. Excipients such as sugars and biocompatible polymers are used to prepare the surrounding, stabilizing matrix. Further, these "Trojan" vehicles are compatible with a wide range of therapeutic molecules, nanocarriers and applications for different routes of administration. The preparation, properties and stability of these NEMs are described in this review and their application and future development are discussed.