Nose-to-brain delivery of riluzole-loaded nanoemulsion in a controlled cortical impact-induced traumatic brain injury: Insights fromIn vitro,Ex vivo, andIn vivostudies.

Traumatic brain injury (TBI) triggers oxidative stress, neuroinflammation, and functional impairments, yet effective brain-targeting therapies remain limited. The current study reports the development and evaluation of an intranasal (IN) riluzole-loaded mucoadhesive nanoemulsion (RLZ-MNE) to enhance nose-to-brain delivery and therapeutic efficacy in TBI. The optimized RLZ-MNE exhibited a mean globule size of 21.24 ± 0.5 nm and spherical morphology. The formulation showed nasal-compatible pH and excellent spreading behavior, as reflected by a reduced contact angle (30.691 ± 0.1 °). Ex vivo permeation studies depicted significantly enhanced flux (10.98 ± 0.79 µg/cm2/h) and permeability coefficient (3.66 × 10-3 ± 0.0003 cm/h) compared to pristine drug, with histological evidence of preserved mucosal integrity. In vitro studies in H2O2-induced SH-SY5Y cells confirmed neuroprotection, evidenced by improved cell viability, reduced nitrosative stress and reactive oxygen species, and restoration of mitochondrial membrane potential. Pharmacokinetic evaluation revealed a ∼2.8- and ∼3.85-fold enhancement in brain Cmax following RLZ-MNE IN rather than RLZ-IN and RLZ-IV, respectively. Additionally, enhanced N2B transport was confirmed by increased drug targeting efficiency (%DTE, ∼5.4-fold) and direct transport percentage (%DTP, ∼4.81-fold) compared to RLZ-IN. In vivo, IN administration of RLZ-MNE at high and low doses significantly reduced neurological severity scores (⁓6-fold and 7.6-fold vs. CCI), improved motor coordination in the rota-rod test (*p < 0.05), enhanced preference index (****p < 0.0001; **p < 0.01), and discrimination index (*p < 0.05) relative to the CCI group. RLZ-MNE markedly decreased brain water content (***p < 0.001), indicating attenuation of cerebral edema. The pro-inflammatory cytokines were also considerably reduced compared to the CCI. Immunohistochemical analysis demonstrated the downregulation of p-NF-κB expression, and RT-PCR results depicted the restoration of EAAT2 mRNA expression following treatment with RLZ-MNE. Histopathological evaluation further corroborated these findings by demonstrating reduced lesion severity and preservation of neuronal architecture in RLZ-MNE-treated groups. Overall, RLZ-MNE demonstrated superior nasal permeation, antioxidant capacity, and neuroprotective efficacy, highlighting its promise as an efficient IN brain delivery approach for the management of TBI.