Microstructure and morphology of nimesulide/crospovidone nanocomposites by Raman and electron microscopies

In the present work the arrangement of nanostructured nimesulide embedded inside crospovidone microparticles is experimentally studied. The analysis was carried out by observing cross-sections of the microparticles with electron and Raman microscopes. Scanning electron microscopy (SEM) gave a morphological picture of the cross-sections, energy dispersive X-ray spectroscopy (EDS) allowed to investigate the nimesulide distribution at molecular level in- and outside the crospovidone matrix, and microRaman spectroscopy (μRaman) shed some light on the nimesulide phase composition. The drug resulted to be constrained by crospovidone into three main arrangements: an amorphous phase dispersed into the molecular cross-linked network of the polymer, nanocrystals wrapped up by the polymer, and drug layers, made of micro- and nanocrystals, segregated onto the popcorn-like surface of the polymer. According to X-ray diffraction data, the micro- and nanocrystals are highly disordered and made of crystallites with an average diameter of 17 nm.