Treatment of
neurodegenerative disorders such as
Alzheimer's disease is hampered by the blood-brain barrier (BBB). This tight cerebral vascular endothelium regulates selective diffusion and active transport of endogenous molecules and
xenobiotics into and out of the brain parenchyma. In this study,
glutathione targeted PEGylated (GSH-PEG)
liposomes were designed to deliver
amyloid-targeting
antibody fragments across the BBB into the brain. Two different formulations of GSH-PEG
liposomes based on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (
DMPC) and egg-yolk
phosphatidylcholine (EYPC) were produced. Both formulations encapsulate 15kDa
amyloid beta binding llama
single domain antibody fragments (VHH-pa2H). To follow the biodistribution of VHH-pa2H rather than the
liposome, the
antibody fragment was labeled with the
radioisotope indium-111. To prolong the shelf life of the construct beyond the limit of radioactive decay, an active-loading method was developed to efficiently radiolabel the
antibody fragments after encapsulation into the
liposomes, with radiolabeling efficiencies of up to 68% after purification. The radiolabeled
liposomes were administered via a single intravenous bolus injection to APPswe/PS1dE9 double transgenic mice, a mouse model of
Alzheimer's disease, and their wildtype littermates. Both GSH-PEG
DMPC and GSH-PEG EYPC
liposomes significantly increased the standard uptake values (SUV) of VHH-pa2H in the blood of the animals compared to free VHH-pa2H. Encapsulation in GSH-PEG EYPC
liposomes resulted in the highest increase in SUV in the brains of transgenic animals. Overall, these data provide evidence that GSH-PEG
liposomes may be suitable for specific delivery of
single domain antibody fragments over the BBB into the brain.