Research progress of porous polymer microspheres of pulmonary drug delivery

Pulmonary drug delivery agents deliver drugs directly to the lung tissue to obtain higher local concentration, which is beneficial to the treatment of lung diseases, and may reduce the systemic side effects. Therefore, it has become the preferred drug for the treatment of many lung diseases. However, the drugs entering the lungs are easily cleared by the lung tissues, which reduce the retention time of the drugs in the lungs and affects the efficacy. Although particles with a smaller particle size (1-5 µm) are easily inhaled into the lungs, they are also easily swallowed and cleared by lung macrophages. While the porous polymer microspheres (PPMS) with larger geometric diameter (Dg > 5 µm) and low density (ρ < 0.4 g·cm^-3) can not only effectively avoid the phagocytosis of alveolar macrophages, but also have a high effective deposition rate in the lungs due to the appropriate aerodynamic diameter, moreover, the polymer is biodegradable and non-toxic, so it has become a research hotspot for pulmonary drug delivery carriers. This article combined with the lung clearance mechanism of granules, summarized the preparation materials and methods of PPMS, as well as its quality control, etc. Furthermore, opinions are also put forward for the development of PPMS, to provide a reference for the in-depth study of PPMS.