Brain delivery and cellular internalization mechanisms for transferrin conjugated biodegradable polymersomes.

Transferrin conjugated biodegradable polymersomes (Tf-PO) were exploited for efficient brain drug delivery, and its cellular internalization mechanisms were investigated. Tf-PO was prepared by a nanoprecipitation method with an average diameter of approximately 100 nm and a surface Tf molecule number per polymersome of approximately 35. It was demonstrated that the uptake of Tf-PO by bEnd.3 was mainly through a clathrin mediated energy-dependent endocytosis. Both the Golgi apparatus and lysosomes are involved in intracellular transport of Tf-PO. Thirty minutes after a 50mg/kg dose of Tf-PO or PO was injected into rats via the tail vein, fluorescent microscopy of brain coronal sections showed a higher accumulation of Tf-PO than PO in the cerebral cortex, the periventricular region of the lateral ventricle and the third ventricle. The brain delivery results proved that the blood-brain barrier (BBB) permeability surface area product (PS) and the percentage of injected dose per gram of brain (%ID/g brain) for Tf-PO were increased to 2.8-fold and 2.3-fold, respectively, as compared with those for PO. These results indicate that Tf-PO is a promising brain delivery carrier.