Box-Behnken design optimization of mucoadhesive chitosan-coated nanoemulsions for rosmarinic acid nasal delivery—In vitro studies

Mucoadhesive chitosan-coated nanoemulsions for rosmarinic acid (RA) nasal delivery were optimized. The optimum ratio between the formulation components that led to minimum droplet size and PDI, and maximal ζ-potential and RA content was obtained using Box-Behnken design (BBD). Optimized conditions were 8.5% oil phase (w/v), 3:10 lecithin to oil phase ratio (w/w), and 0.1% chitosan final concentration (w/v). Physicochemical characterization, mucoadhesion measurement, in vitro release and permeation/retention were performed. Optimized chitosan-coated RA nanoemulsions presented adequate physicochemical characteristics, high mucoadhesive potential, prolonged drug release, and long-lasting permeation time with a higher RA penetration/retention through porcine nasal mucosa. Cell viability and death by necrosis in fibroblasts cells were also evaluated to investigate the formulations safety. Formulations did not induce cytotoxicity following 24 h (3.125–50 μM) or 48 h (3.125–25 μM) of treatments. Overall results demonstrated that optimized chitosan-coated nanoemulsion showed to be a suitable carrier for RA nasal delivery aiming neuroprotective therapies.