Urea entrapment in cellulose acetate microparticles obtained by electrospraying

Urea is a widely used source of nitrogen, but its rapid solubilization in water leads to significant wastage on application. Thus, the quest for an efficient and economical polymeric matrix able to encapsulated urea is a long-standing challenge. In this paper, we present a simple and economical method for urea entrapment in cellulose acetate (CA) microparticles produced by the electrospraying process. The morphology and diameter of the microparticles were optimized experimentally by evaluating the solvent composition (binary mixture) and polymer concentration. The electrospraying process parameters, such as particle collection distance, applied voltage and flow rate, were also evaluated. The particle diameter was determined by scanning electron microscopy (SEM) and the CA microparticle characteristics, urea incorporation and in vitro release profile were determined by Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The morphological characteristics (shape and porosity) of the CA microparticles were affected by the diffusion rate and CA solubility due to solvent evaporation in the electrospraying process. The SEM images showed monodispersed and spherical CA microparticles with a diameter size of 2.2 +/- 0.3 mu m. The FTIR spectra and SEM images verified the urea entrapment in the CA microparticles (100 mg/g), and the particle morphology did not appear to be affected. The release of urea from the CA microparticles showed a maximum of 79% after 7 h, which is a significant difference in relation to in vitro urea release. The results obtained using the electrospray technology represent a step forward in the search to improve the incorporation of urea into CA microparticles.