Cell-Penetrating Peptide-Modified Block Copolymer Micelles Promote Direct Brain Delivery via Intranasal Administration

In order to develop non-invasive and effective nose-to-brain delivery of drugs, we synthesized Tat analog-modified methoxy poly(ethylene glycol) (MPEG)/poly(epsilon-caprolactone) (PCL) amphiphilic block copolymers through the ester bond. We evaluated the brain distribution of coumarin, acting as a model chemical, after intravenous or intranasal administration of MPEG-PCL. In addition, cellular uptake of coumarin by rat glioma cells transfected with coumarin-loaded MPEG-PCL or MPEG-PCL-Tat was determined. Finally, we determined the brain distribution and biodistribution after intranasal administration of coumarin-loaded MPEG-PCL-Tat. The amount of coumarin in the brain after intranasal administration was significantly higher than that after intravenous administration. In addition, cellular uptake of coumarin using MPEG-PCL was the lowest, while cellular uptake of coumarin using Tat-modified MPEG-PCL (MPEG-PCL-Tat) was higher than that of MPEG-PCL. Therefore, the brain distribution of coumarin administered using MPEG-PCL-Tat was significantly greater than that using MPEG-PCL. Then, the coumarin distribution after MPEG-PCL-Tat administration in non-targeted tissues (lung, liver, heart, kidney and spleen) was lower than that after coumarin administration without nanomicelles. We have demonstrated that utilization of nano-sized micelles modified with Tat can facilitate direct intranasal brain delivery.