Exploring the potential to enhance drug distribution in the brain subregion via intranasal delivery of nanoemulsion in combination with borneol as a guider

The number of people with Alzheimer's disease (AD) is increasing annually, with the nidus mainly concentrated in the cortex and hippocampus. Despite of numerous efforts, effective treatment of AD is still facing great challenges due to the blood brain barrier (BBB) and limited drug distribution in the AD nidus sites. Thus, in this study, using vinpocetine (VIN) as a model drug, the objective is to explore the feasibility of tackling the above bottleneck via intranasal drug delivery in combination with a brain guider, borneol (BOR), using nanoemulsion (NE) as the carrier. First of all, the NE were prepared and characterized. In vivo behavior of the NE after intranasal administration was investigated. Influence of BOR dose, BOR administration route on drug brain targeting behavior was evaluated, and the influence of BOR addition on drug brain subregion distribution was probed. It was demonstrated that all the NE had comparable size and similar retention behavior after intranasal delivery. Compared to intravenous injection, improved brain targeting effect was observed by intranasal route, and drug targeting index (DTI) of the VINNE group was 154.1%, with the nose-to-brain direct transport percentage (DTP) 35.1%. Especially, remarkably enhanced brain distribution was achieved after BOR addition in the NE, with the extent depending on BOR dose. VIN brain concentration was the highest in the VIN-1-BOR-NE group at BOR dose of 1 mg/kg, with the DTI reaching 596.1% and the DTP increased to 83.1%. BOR could exert better nose to brain delivery when administrated together with the drug via intranasal route. Notably, BOR can remarkably enhance drug distribution in both hippocampus and cortex, the nidus areas of AD. In conclusion, in combination with intranasal delivery and the intrinsic brain guiding effect of BOR, drug distribution not only in the brain but also in the cortex and hippocampus can be enhanced significantly, providing the perquisite for improved therapeutic efficacy of AD.