Liposomal composition tuning improves intranasal brain drug delivery: Role of cholesterol and formulation rheology

While nose-to-brain drug delivery is promising, there is limited research on optimizing formulation. Universal design guidelines could enhance intranasal delivery of diverse therapeutics. Therefore, we systematically investigated how lead lipid effect (positive, negative, and polyphenol lipids), lipid composition ratio, and cholesterol content affect nose-to-brain drug delivery efficiency.

Positively charged liposomes trended toward delivering more drug than negatively charged or polyphenol-based formulations; however, this difference was not significant. Notably, lowering the lipid composition ratio and cholesterol markedly enhanced fluorescent-drug delivery by 1.9- and 4.3-fold, respectively. These improvements were associated with stronger mucin interactions, a longer linear viscoelastic region supporting stable nasal coating, and a favorable viscosity that enables efficient polymer mobility along the nose-to-brain route. Mechanistic analysis revealed that the optimized formulation with reduced cholesterol and lipid content (11cholND) led to significantly higher cellular uptake. Inhibitor assays identified macropinocytosis and cholesterol-dependent endocytosis as key routes for drug entry, while cell-surface zeta-potential profiling indicated that charge complementarity contributed to uptake preference. Encapsulating urocortin into this optimized formulation resulted in clear therapeutic benefits in a rat intracerebral hemorrhage model: intracerebral hemorrhage lesion volume was reduced by 30% compared to the untreated group, and neurological function improved significantly, as evidenced by decreases of 34.5% and 37.5% in the modified Neurological Severity Score on days 1 and 3, respectively.

Lowering the lipid ratio and cholesterol content enhances the effectiveness of nose-to-brain drug delivery through improved rheological properties and cellular interactions, offering a strong therapeutic platform for intranasal neuropharmacology.