Nanocapsules, nanoemulsion and nanodispersion containing melatonin: preparation, characterization and stability evaluation

In a previous work, we have demonstrated that melatonin-loaded polymeric nanoparticles provided an important increase in the antioxidant effect of melatonin against lipid peroxidation. Hence, in this work, the aim was to study the stability of nanocapsules containing melatonin (1.5 mg/mL) prepared by interfacial deposition, using different polymers. For comparison, the stability of the nanoemulsion and nanodispersion was also evaluated. These nanoparticulated systems had diameters between 134 and 325 nm. The associated melatonin concentrations ranged from 29% to 50%, depending on the composition of the nanocarriers. The stability evaluation of formulations was preformed at room temperature and protected from or exposed to the natural light or at 50 degrees C and protected from the light. The stability of the nanocarriers was evaluated in terms of the macroscopic aspects, the total contents of melatonin, associated melatonin concentrations, pH and sizes of particles. The compositions of the nanocarriers and the condition of storage influenced the stability of melatonin.