In Vitro and In Vivo Study of Vitamin E TPGs Coated Immunoliposomes for Sustained and Targeted Delivery of Docetaxel

Abstract

In this study a novel formulation of docetaxel loaded herceptin conjugated liposomes with TPGS (d-alpha tocopheryl polyethylene glycol 1000 succinate) coating has been prepared and their effect was compared with non-conjugated TPGS coated liposomes and Taxotere® for targeted chemotherapy on breast cancer cells. To facilitate the conjugation of herceptin, carboxyl group terminated TPGS has been synthesized and used in the preparation of herceptin conjugated liposomes. Docetaxel or Coumarin-6 loaded liposomes were prepared by solvent injection method and characterized for their size and size distribution, surface charge, surface chemistry and drug/dye encapsulation efficiency and invitro drug release profile. SKBR-3 cells were employed as an invitro model for HER2 positive breast cancer and assessed for their cellular uptake and cytotoxicity of the coumarin-6 and docetaxel loaded immunoliposomes respectively. The particle size of these liposomes ranged between 140-220 nm. High resolution field emission transmission electron microscopy (FETEM) was used to visualize the morphology and surface coating of TPGS on the liposomes. X-ray photoelectron spectroscopy (XPS) and FTIR data confirmed the presence of herceptin conjugated on the surface of liposomes. Differential scanning Calorimetry was used to investigate the molecular arrangement of TPGS-COOH and docetaxel with the lipid bilayer. In vitro cellular uptake was studied by confocal microscopy and higher uptake was observed with immunoliposomes. The IC50 value, which is the drug concentration needed to kill 50 % cells in a designated time period, was found to be 20.23 ± 1.95, 3.74 ± 0.98, 0.08 ± 0.4 µg/ml for the Taxotere®, TPGS coated liposomes and herceptin conjugated liposomes respectively after 24 h incubation with SKBR-3 cells. In vivo PK experiments showed that i.v. administration of herceptin conjugated liposomes achieves 1.9 and 10 times longer half-life respectively than PEG coated liposomes and Taxotere¿. The relative bioavailability of docetaxel was increased by 3.47 fold by the herceptin conjugated liposomes. Thus the herceptin conjugated Vitamin E TPGS coated liposomes showed greater potential for sustained and targeted chemotherapy in the treatment of HER2 over expressing breast cancer.