The Research Of Targeted Liposome Embedding Brain Derived Neurotrophic Factor Through The Blood-brain Barrier

bjective:Adopting liposomes encapsulated brain derived neurotrophic factor (BDNF) and making the appropriate modification to observe BDNF entering the brain across the BBB provide the experimental basis for the realization of targeted drug in the brain.Methods:The experiment adopts the method of injecting the well-constructed targeting liposomes, Tf-pGFAP-BDNF-PEG, Tf-pCMV-BDNF-PEG and Tf-H2O-PEG into the male rats respectively in the different potions of10μg/kg and2μg/kg. The60SD male rats that are in weight of (180±30)g and at the age of6-8weeks should be grouped randomly into the Tf-pGFAP-BDNF-PEG group, Tf-pCMV-BDNF-PEG group, Tf-H2O-PEG as the control group. Every group is divided into high-dose group (10μg), low-dose group (2μg), in total of six groups with10in each group. The experimenters inject three different liposomes into the rats across the tail vein. Then48hours later, the experimenters remove their brains and livers to observe the distribution and BDNF expression respectively through the immunofluorescence staining,reverse transcription-PCR(RT-PCR) and immunohistochemistry method.Results:(1)Compared with Tf-H2O-PEG group, Tf-pGFAP-BDNF-PEG and Tf-pCMV-BDNF-PEG can effectively cross the BBB. And in different parts of brain tissue, BDNF distributes differently and mostly lies in the cortex,but its expression in the white matter and the hippocampus is not obvious.(2)The different BDNFs encapsulated by different liposomes as the vectors have the significant differences in the expression levels of the cerebral cortex, where the expression level of the positive cells in Tf-pGFAP-BDNF-PEG group is obviously higher than that of Tf-pCMV-BDNF-PEG group and Tf-H2O-PEG group (P<0.05).(3)Meanwhile, the comparison between the liposomes with same vectors but different doses shows that there are differences in the expression of Tf-pGFAP-BDNF-PEG and Tf-pCMV-BDNF-PEG groups. The high-dose group is significantly higher than the low-dose group in terms of BDNF content across the BBB(P<0.05). However, the groups of different doses in the Tf-H2O-PEG are with no significant difference (P>0.05).(4)The BDNF expression in liver of Tf-pCMV-BDNF-PEG group is significantly higher than that of Tf-pGFAP-BDNF-PEG group (P<0.05), while Tf-H2O-PEG group has no obvious BDNF expression in liver.Conclusion:When connected to the brain-specific GFAP promoters, the liposomes modified by Tf and PEG can realize in-brain transfection of the exogenous genes. Besides, they also can reduce the capture of peripheral organs to increase the expression of the exogenous genes in brain and to some degree, improve liposomes’ target, which provides the experimental basis for the treatment to the central nervous system diseases.