Nanostructure-coated diclofenac-loaded microparticles: preparation, morphological characterization, in vitro release and in vivo gastrointestinal tolerance

This work reports the preparation and characterization of polymeric nanostructure-coated diclofenac-loaded microparticles. After spray-drying, powders presented 80% of yield and encapsulation efficiency of 83%. SEM analyses showed nanostructures adsorbed onto the surface of microparticles presenting surface area (BET) and pore volumes (BJH) (83 m² g-1, 0.10 cm³ g-1) smaller than the uncoated-core (163 m² g-1, 0.25 cm³ g-1). In vitro drug release experiments at pH 5.0 and 7.4 showed dissolution efficiencies of 34% and 78% (uncoated-core), 74% and 83% (physical mixture of raw materials), and 58% and 85% (nanostructure-coated microparticles), respectively. Mathematical modeling of the dissolution profiles fitted a biexponential model at pH 5.0 and a monoexponential model at pH 7.4. Regarding the digestive tolerance experiments, the total lesional indexes were 156.1 ± 48.5 for sodium diclofenac aqueous solution, 132.4 ± 45.7 for uncoated-core, 109.1 ± 35.8 for physical mixture and 29.9 ± 12.1 for microparticles showing a protective effect of these microparticles against the mucosal diclofenac damage. This strategy of coating presents a potential use for oral administration of drugs.