Development and evaluation of naproxen-loaded sericin/alginate beads for delayed and extended drug release using different covalent crosslinking agents.

Different polymer matrix compositions based on sericin and alginate blend (using or not the covalent crosslinking agents dibasic sodium phosphate, polyvinyl alcohol and polyethylene glycol) were evaluated to entrap naproxen. Sericin has been shown to be essential for improving incorporation efficiency. Comparing the formulations with and without crosslinking agent, the best results were obtained for that composed only of sericin and alginate, with satisfactory values of entrapment efficiency (>80%) and drug loading capacity (>20%). In this case, delayed release (<10% in acid medium) and prolonged release (~360 min) were achieved, with a complex release mechanism involving swelling and polymer chain relaxation. The incorporation of the drug could be confirmed by the techniques of characterization of X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), as well as drug compatibility with the polymer matrix. In addition, particles of suitable size for multiparticulate systems were obtained and with higher thermal stability when compared to the pure drug.