Targeting of Liposomes to the Blood-Brain Barrier in Rats

The delivery of hydrophilic drugs, peptides, and proteins to the brain is restricted by tight junctions between the endothelial cells of the cerebral capillaries which contribute to the blood–brain barrier (BBB). Injection of liposomes as drug delivery vehicles is re-ported to enhance the uptake of certain drugs into the brain. We demonstrate that liposomes with diameters of less than 1000 Å covalently coupled to Fab' fragments of the OX-26 monoclonal antibody, which recognizes the transferrin receptor in rat brain capillary, can bind significantly to brain capillaries following intracarotid infusion in rats. Liposomes covalently coupled to insulin were not effective in targeting to the BBB. Our study indicates that liposomes coupled to antibodies for brain capillary receptors may be effective as drug delivery vehicles to the brain.