Kinetics of silver nanoparticle release from chitosan spheres

The kinetics of silver nanoparticles release from chitosan spheres is addressed experimentally and theoretically in this work. From the experimental viewpoint, the study of silver nanoparticles release is performed by measuring the time-dependent UV-Vis spectra of solutions where spheres were dispersed. The UV-VIS spectra intensity reflects the concentration of nanoparticles in the solution. Despite simple expressions for drug release are found in the literature, as those that relate the amount of drug release with the square root of time, a proper modeling might require the inclusion of several phenomena such as the presence of stagnant layers, swelling or erosion of the matrix, accumulation of particles in the medium, amongst others. The experiments show that chitosan/silver nanoparticles complexes are actually released, indicating that both swelling and erosion of the matrix takes place during the release process. The simplest model for drug release, i.e., the Higuchi’s model, fits the observed results surprisingly well, which is a relevant result due to the lack of mathematical modeling for the release of nanoparticles.