Dissertation > Medicine, health > Pharmacy > Pharmacy

Studies on RGD-Mediated Brain-Target Ferulic Acid Liposome

Author QinJing
Tutor ChenDaWei
School Shenyang Pharmaceutical University
Course Pharmacy
Keywords Brain-targeting RGD peptide Liposome Ferulic acid calcium acetate gradient body distribution pharmacokinetics pharmacodynamics ischemia reperfusion antioxidant activity
Type PhD thesis
Year 2007
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Inflammatory response plays an important role in the pathogenesis of neurodegenerative diseases such as ischemia in the brain, Alzheimer’s and Parkinson’s. Leukocytes including monocytes and neutrophils can cross an intact blood-brain barrier (BBB) and be delivered to the site of injury or infection in the brain. RGD peptide (Arg-Gly-Asp) can combine with integrin receptors which are expressed on the surface of leukocytes (neutrophils and monocytes). Then, RGD-liposomes can be devised for selective and preferential presentation to blood monocytes/neutrophils, and taken into the brain in response to the inflammation recruitment. Thus, in the present study, FA was used as model drug and loaded into liposomes. RGD peptide was coupled with FA liposomes for binding to monocytes and neutrophils in peripheral blood for brain targeting in response to leukocyte recruitment. The pharmacodynamic of FA in vivo was greatly enhanced and brain targeted delivery was achieved.FA was loaded into liposome via calcium acetate gradient with 80.2% entrapment efficiency (EE) and 80% FA released form liposomes within 5h. However, the application of the pH gradient theory to account for the remote loading of the calcium acetate gradient did not appear to be satisfactory. Hence, the potentiometric technique and EPR were used to investigate the interactions between drugs and liposomes. The chemical potential gradient and electrical potential were used to account to the mechanism of loading drugs. The EEs of salicylic acid liposomes via a variety of salt gradients was determined to verify the explanation. It was found that high solubility in interior could contribute to high EE.The CHS was used as coupling arm according to the affinity ability to leukocytes with 2.5% coupling density. 72.4% of RGD-liposomes could combine with integrin receptors which were expressed on the surface of leukocytes. The temperature, pH, lipid concentration were studied where it was found that 98% of RGD peptide was coupled with liposomes within 2h. The drug leakage and liposome aggregation were not observed. The physicochemical properties of RGD-liposome were valued and morphology was observed by freeze-fracture electron microscopy. A good stability and high EEs were obtained and unilamellar vesicles were present in the micrographs.The rats were subjected to intrastriatal microinjections of 100μl of human recombinant IL-1βto produce brain inflammation to study the body distribution. For RGD coated liposomes, the concentration of FA in brain was 6-fold higher than that of FA solution and 3-fold higher than that of uncoated liposomes. The half life was prolonged with 2.6-fold compared to FA solution and 1.43-fold in comparison with FA liposome. Thus, the uptake of RGD FA liposome into liver and spleen was avoided. Furthermore, the rats were subjected to an administration of fluorescence-labeled RGD-liposome. The result of fluorescent microscopy showed that RGD-liposome could be mediated into brain and accumulated in the focus of infection.Mitochondrial transmembrane potential alternation, cell viability assay and morphology were assayed to value the antioxidant activity of RGD-FAL. It was found that FA liposomes exhibited greater antioxidant activity than FA solution on U937 cell.Animal model of ischemia/reperfusion was set up to value the antioxidant activity in vivo and the activity of SOD, T-AOC and the content of MDA were used as index. The results of pharmacodynamic studies had a good correlation with that of body distribution. The antioxidant activity in vivo of RGD-FAL was significantly greater than that of FA injection, liposomal FA and Ligustrazine. Thus, this strategy is a promising approach due to it can deliver drug directly to the inflammatory site in the brain following the recruitment of leukocytes and allow a better protective effect in vivo.

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