Brain Targeting Study Of Stearate Grafted Chitosan Micellar Drug Delivery System

The blood brain barrier restricts the entry of most therapeutic molecules into brain and results in lack of efficiency in treatment. With the growing of various CNS diseases, aggressive research work has been given on the development of brain targeting drug delivery system. However, little achievement is made. Therefore, how to overcome the barrier and deliver drug more effectively to CNS has been the most emergent and challenging task at present.Chitosan (CSO) and stearic acid (SA) are both bio-compatible and biodegradable materials. Chitosan is hydrophbically modified by stearic acid using EDC as coupling reagant and thus stearic acid grafted chitosan (CSO-SA) is synthesized. In this research, the potential of CSO-SA on brain targeting drug delivery is studied. The amino substitute degree of synthesize CSO-SA was 26.9±1.08%. The micelles distributed 81.35±5.16 nm with a surface potential of 36.4±0.71 mV. Using bEnd.3 as the model cell, micelles was internized by most cells after 6 h incubation, which indicated excellent celluar uptake ability of CSO-SA. The IC50 against bEnd.3 was 237.6±6.61μg·mL-1 by MTT assay. It was comfirmed that CSO-SA was a safe material that could be applied on brain targeting drug delivery system.Doxorubicin (DOX) was chosen as the model drug and was entrapped into self-assembled micelles by dialysis method. It revealed that micellar size decreased after loading drug. Drug entrapment effeciency reached 81.35% with a cumulative release up to 70% in 48h in vitro. The in vivo imaging result showed that CSO-SA could transport across BBB rapidly and into the brain using DiR as the tracker. In vivo drug extraction method was established and doxorubicin was detectd by a HPLC system with fluorescence. Drug distribution in brain peaked at 15 minutes after administration, which was 1.01%/g. It maintained above 0.45%/g within 1 h. Meanwhile, free DOX·HC1 could not transport across BBB and was not detectable in brain. In the pharmacokinetics study, the AUC of drug loaded micelles was increased by 4.1 times compared with DOX·HC1. In other major tissues, drug was mainly distributed in liver, spleens and lung. The amount of DOX in heart was reduced a half. Thus side effect and toxicity of DOX was reduced.Angiopep-2 was acted as an active brain targeting ligand. Using PEG as the linker, angiopep-2 modified CSO-SA polymer was obtained. The drug level in brain of angiopep-2 modified CSO-SA polymer was investigated. After modification with angiopep-2, micellar size increased and drug loading ability deceased without significant change in in-vitro release. For quantatitive analysis, increase of DOX in brain was observed and the AUC of DOX was increased by about 17.5 times.