Development and evaluation of Sargassum polysaccharides–algal oil nanoemulsion for intranasal treatment of allergic rhinitis

Allergic rhinitis (AR) is a prevalent inflammatory disorder of the upper respiratory tract, affecting 20-40% of the global population and severely impairing quality of life. Given the limitations and adverse effects associated with conventional pharmacotherapy, naturally derived bioactives with low toxicity are gaining prominence as alternative interventions. In this study, we developed a bioresource-based nanoemulsion (NE) by integrating Sargassum polysaccharides (SP) into algal oil (AO) to enhance intranasal delivery and therapeutic efficacy against AR. Structural analysis confirmed that SP comprised sulfated polysaccharides enriched in fucose, glucose, and galactose. The optimized SP-AO NE, formulated with Tween 80 and prepared via ultrasonic emulsification, exhibited uniform spherical droplets (53.4 ± 1.8 nm), a low polydispersity index (0.3 ± 0.1), and a negative zeta potential (- 29.1 ± 2.8 mV), indicating high colloidal stability and effective oxidative protection of AO during refrigerated storage. In an ovalbumin-induced AR mouse model, intranasal administration of SP-AO NE significantly alleviated nasal rubbing, epithelial hypertrophy, goblet cell hyperplasia, mast cell infiltration, and pulmonary inflammation. Intranasal SP-AO NE treatment decreased IgE levels in serum, nasal lavage, and bronchoalveolar lavage fluids, while enhancing mucosal IgA. In addition, SP-AO NE downregulated IL-4 and TNF-α expression and upregulated TGF-β1, demonstrating a robust immunomodulatory effect. Overall, this work presents a stable, biocompatible, and functional NE that improves intranasal delivery of algal bioactives, offering a promising natural therapeutic strategy for the management of AR.