Intranasal delivery of rapamycin via brain-targeting polymeric micelles for Alzheimer's disease treatment.

Alzheimer's disease (AD) is a long-term neurological disorder associated with neuroinflammation and amyloid-beta (Aβ) aggregation, which leads to a decline in cognitive and behavioral changes. Rapamycin (Rapa) is an immunosuppressive drug effective in preventing organ rejection after a kidney transplant. In the last few years, orally delivered Rapa has emerged as a potential candidate for improving cognitive function in patients with AD. However, it is evident that long-term oral treatment of Rapa causes systemic toxicity, and although controversial, it may even trigger the aggregation of Aβ deposition. This study investigated the therapeutic potential of intranasally delivered brain-targeting polymeric micelles carrying Rapa. We successfully prepared Fibronectin CS1 peptide-conjugated poly(ethylene glycol)-block-poly(D, L-lactic acid) (FibCS1-PEG-b-PLA) micelles carrying Rapa, which were 98.08 ± 1.15 nm in particle size with a polydispersity index of 0.21 ± 0.01. FibCS1-PEG-b-PLA micelles showed a significant improvement for nasal permeation of Rapa across RPMI-2650 epithelial cells. Behavioral studies such as corner, novel object recognition and Morris Water Maze tests showed promising results towards the improvement of cognitive function in a 3xTg-AD mice model when treated with intranasal FibCS1-PEG-b-PLA micelles carrying RAPA at a dose of 0.2 mg/kg (q4dx5). The western blot and ELISA results of the brain tissues of 3xTg-AD mice treated with intranasal FibCS1-PEG-b-PLA micelles carrying Rapa showed significant reductions in Aβ and two pro-inflammation markers (e.g. interleukin (IL)-1β, tumor necrosis factor (TNF)-α). Here, we conclude that brain-targeting FibCS1-PEG-b-PLA micelles carrying Rapa were effective in reaching the brain via intranasal route, reduced pro-inflammatory markers and Aβ, and improved cognitive function in AD-induced mice.