The central nervous system (CNS) has developed various barriers, with the blood-brain barrier (BBB) being the most dominant one preventing foreign substances from entering the brain through the blood circulation; therapeutics and their carriers are also subject to rapid clearance by the circulation of cerebrospinal fluid (CSF) and brain interstitial fluid. A polymeric nanoparticle delivery system for drug delivery to the brain was developed in this thesis. Poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymer was covalently conjugated with three selected peptide ligands with different functions: LRVRLASHLRKLRKRLL (denoted as COG), TGNYKALHPHNG (denoted as TGN), and RXRRBRRXRRBRXB (denoted as RXR). Nanoparticles with size around 100-200 nm in diameter and positive su...[ Read more ]

The central nervous system (CNS) has developed various barriers, with the blood-brain barrier (BBB) being the most dominant one preventing foreign substances from entering the brain through the blood circulation; therapeutics and their carriers are also subject to rapid clearance by the circulation of cerebrospinal fluid (CSF) and brain interstitial fluid. A polymeric nanoparticle delivery system for drug delivery to the brain was developed in this thesis. Poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) copolymer was covalently conjugated with three selected peptide ligands with different functions: LRVRLASHLRKLRKRLL (denoted as COG), TGNYKALHPHNG (denoted as TGN), and RXRRBRRXRRBRXB (denoted as RXR). Nanoparticles with size around 100-200 nm in diameter and positive surface charge were formed with these materials. Effects of these peptide ligands, either separately or in combination, were investigated in three aspects: 1) crossing the BBB, 2) retention in the brain, and 3) cellular uptake. In vivo data in mice showed that nanoparticles modified with single ligand COG or TGN could both successfully penetrate the BBB, and nanoparticles modified with ligand TGN could be retained in the brain for at least 24 hours. Nanoparticles modified with multiple ligands – with 1/3 the amount of each single ligand – however, exhibited lower retention in the brain compared with nanoparticles modified with ligand TGN alone, despite their effective penetration across the BBB. In vitro studies were also conducted to examine possible uptake mechanisms in different cell lines. In conclusion, ligands COG and TGN could assist the polymeric nanoparticles cross the BBB, while ligand TGN could further promote retention in the brain; both ligands COG and RXR could facilitate cellular uptake, depending on different types of cells, however, ligand RXR did not present significant ability in crossing the BBB. Two peptide inhibitors, P3V8 and QBP1, were also encapsulated into the nanoparticles and added to cells with induced RNA and protein toxicities. The results showed that nanoparticles modified with multiple ligands could suppress cell death after 72 hours, while solutions of free peptide inhibitors and nanoparticles without ligand modification failed to rescue the cells. This shows the potential as an efficient carrier for targeted drug delivery to the brain.