Highly porous crosslinked poly(ester-anhydride) microspheres with high loading efficiency

Abstract

Microparticles with diameter within the range of D n = 26–38 μm were prepared from functional poly(esteranhydride)s with different amount of allyl groups in the side chains, using emulsion solvent evaporation technique. Porous structure was obtained as the effect of photocrosslinking of allyl groups. 2,2-Dimetoxy-2-phenylacetophenone (DMPA) (0.5 wt%–10 wt%) was used as a photoinitiator. The crosslinking was carried out by UV irradiation during the solvent evaporation. Effectiveness of the crosslinking was characterized by the content of insoluble part of samples and it was in the range of 18%–75%. Porosity of microparticles (in the range of 76%–88%) depended on the functionality of poly(esteranhydride) s and amount of the photoinitiator used. The most porous particles were obtained with use of 0.5 wt% of DMPA. Their flow ability expressed by Carr’s index was excellent, and their theoretical mass mean aerodynamic diameters were acceptable for use in pulmonary drug delivery. The most porous particles were loaded with p-nitroaniline, theophilline or doxycycline. The loading efficiencies of drugs in porous microspheres were higher compared to nonporous ones. The porosity of loaded microparticles was slightly decreased, however their flow ability was still very good.