A tumor vasculature targeted liposome delivery system for combretastatin A4: Design, characterization,; in vitro evaluation
The objective of this study was to develop an efficient tumor vasculature targeted liposome delivery system for combretastatin A4, a novel antivascular agent. Liposomes composed of hydrogenated soybean phosphatidylcholine (HSPC), cholesterol, distearoyl phosphoethanolamine-polyethylene-glycol-2000 conjugate (DSPE-PEG),; DSPE-PEG-maleimide were prepared by the lipid film hydration; extrusion process. Cyclic RGD (Arg-Gly-Asp) peptides with affinity for ?v?3-integrins expressed on tumor vascular endothelial cells were coupled to the distal end of PEG on the liposomes sterically stabilized with PEG (long circulating liposomes, LCL). The liposome delivery system was characterized in terms of size, lamellarity, ligand density, drug loading,; leakage properties. Targeting nature of the delivery system was evaluated in vitro using cultured human umbilical vein endothelial cells (HUVEC). Electron microscopic observations of the formulations revealed presence of small unilamellar liposomes of ?120 nm in diameter. High performance liquid chromatography determination of ligand coupling to the liposome surface indicated that more than 99% of the RGD peptides were reacted with maleimide groups on the liposome surface. Up to 3 mg/mL of stable liposomal combretastatin A4 loading was achieved with ?80% of this being entrapped within the liposomes. In the in vitro cell culture studies, targeted liposomes showed significantly higher binding to their target cells than non-targeted liposomes, presumably through specific interaction of the RGD with its receptors on the cell surface. It was concluded that the targeting properties of the prepared delivery system would potentially improve the therapeutic benefits of combretastatin A4 compared with nontargeted liposomes or solution dosage forms.
Ramakrishna Nallamothu1Email:rnallamo@utmem.edu?George C. Wood1?Christopher B. Pattillo2?Robert C. Scott2?Mohammad F. Kiani2?Bob M. Moore4?Laura A. Thoma1
[1] Parenteral Medications Laboratories, Department of Pharmaceutical Sciences, University of Tennessee Health Sciences Center, TN, 26 S Dunlap St, Room 214, 38163 Memphis, TN ;[2] Department of Mechanical Engineering, Temple University, Philadelphia, PA ;[3] Department of Radiation Oncology, Temple University, Philadelphia, PA ;[4] Department of Pharmaceutical Sciences, University of Tennessee Health Sciences Center, Memphis, TN
