“…Innovative treatments using combination NPs have emerged as a promising approach for improving the management of AD through intranasal delivery, which offers higher drug accumulation in the brain compared to equivalent drug solution formulations and systemic approaches [ 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Among these approaches, derivatives of the chitosan (Cs) polymer, such as N , N , N -trimethyl chitosan (TMC), have garnered attention due to their positive biological features, including high mucosal absorption capacity, low toxicity, and ease of NP formation through ionic gelation [ 43 , 44 ]. In comparison to Cs, TMC exhibits excellent mucoadhesive properties and solubility in aqueous solutions across a wide pH range [ 15 ].…”