Keywords: polymeric nanoparticles, nanospheres, SAXS, diffusion, release, mathematical modelling, indomethacin ester, antiedematogenic activity, rats, nanotechnology, nanoprecipitation, pharmacological response
Structural model of polymeric nanospheres containing indomethacin ethyl ester and in vivo antiedematogenic activity
The aim of this work was to establish a structural model for describing the organisation, at a molecular level, of nanospheres prepared by nanoprecipitation using poly(ε-caprolactone), sorbitan monostearate and polysorbate 80. Therefore, different techniques were employed to characterise the systems such as dynamic and static light scattering, small angle X-ray scattering and release profile evaluations. The indomethacin ethyl ester that is insoluble in water and presents in vitro anti-inflammatory activity was encapsulated in the nanospheres. Furthermore, the antiedematogenic activity has been studied in rats. The unloaded and loaded nanosphere suspensions presented particle diameters of 186 nm and 208 nm, polydispersity lower than 0.2, ζ-potentials of ?40.7 mV and ?45.3 mV and pH 5.0 and 5.2, respectively. The depolarisation ratio showed constant values that were lower than 0.015 indicating that nanospheres in suspensions are isotropic, then being considered spherically shaped. SAXS analyses showed a partial organisation of the sorbitan monostearate and no peak relative to the crystallinity of the polymer, suggesting that this surfactant is retained in the polymer matrix of nanospheres. The structural organisation, at a molecular level, of those nanospheres corresponds to particles in which aggregates of sorbitan monostearate are stabilised by the polymeric chains. Additionally, the indomethacin ethyl ester-loaded nanospheres presented antiedematogenic activity after oral administration in rats, indicating that even though the ester is insoluble in gastric or intestinal media, those nanospheres were able to deliver it for a pharmacological response.