Donepezil and Embelin Loaded Nanostructured Lipid Carriers for Direct Brain Delivery as An Intervention for Alzheimer’s Disease: Formulation Design, Optimization and Evaluation

Donepezil hydrochloride (DPL) and Embelin (EMB) loaded Nanostructured Lipid Carriers (NLCs) have been developed and optimized to achieve optimal drug loading, safer nasal delivery, effective neuronal/cell uptake, enhanced brain accessibility, controlled release, and desired therapeutic effect. Molecular docking studies demonstrated that both drugs bind effectively to AchE with interaction energies of -48.5319 and − 65.7525, respectively, indicating a synergistic approach. The hydrophobic interactions with target proteins facilitate the transportation of drugs through brain hydrophobic channels to provide a desired pharmacological response. N2a cell line investigation advised a 1:1 ratio of DPL and EMB to have the greatest possible synergistic effect based on the MTT assay. NLCs were fabricated by hot emulsification probe sonication method and optimized using QbD-based Central Composite Rotatable Design (CCRD). Optimized NLCs with a diameter of 180.2 nm were suitable for axonal uptake. A low Polydispersity index (PDI) score of 0.37 and Zeta Potential (ZP) of -12 mV indicated a uniform monodisperse system with persistent and stable dispersion properties. The NLCs demonstrated sustained drug release, DPL released at 90.72 ± 1.00%, and EMB at 81.30 ± 0.52% in 24 h. The Korsemeyer-Peppas model proved to be the most accurate fit due to its strong correlation. Ex vivo permeation and CLSM studies revealed superior goat nasal mucosa penetration of NLCs over suspension with a higher fluorescence level, up to 35 μm. NLCs treated nasal mucosa exhibited no erosion or interstitial gaps in the histopathological study. Moreover, NLCs were nontoxic and non-irritating, with a HET CAM score of 0.68 ± 0.05, indicating safe nasal delivery. The cellular uptake study showed a preponderance of the NLCs in the Cell’s cytoplasm, indicating ready uptake by N2a cells. Hence, intranasal therapy with the DPL and EMB-loaded NLCs could be a practical and promising implementation. Further in vivo, and clinical studies will be required to establish the formulation’s efficacy in treating Alzheimer’s disease (AD).