Purpose: The objective of this study was to develop an efficient vasculature-targeted liposomal combretastatin A4 (CA4), by the modification of the sterically stabilized liposomes (SSL) with a ligand of integrins and to explore the possibility of such system for the treatment of choroidal neovascularization (CNV).
Methods: CA4-loaded liposomes were prepared by thin-film dispersion method. The linear arginine-glycine-aspartic acid tripeptide (RGD) with affinity for integrins such as alphavbeta3 expressed on rapidly proliferative vascular endothelial cells was coupled to the distal end of polyethylene glycol (PEG) connected on the surface of SSL. The liposome delivery system was characterized in terms of size and size distribution profiles by dynamic light scattering method, entrapment efficiency, and leakage properties by high-performance liquid chromatography (HPLC). The uptake efficiency by human umbilical vein endothelial cells (HUVECs) was evaluated by confocal microscopy. The therapeutic efficacy was quantitatively assessed by choroidal flat mounts.
Results: CA4-loaded RGD-SSL (RGD-SSL-CA4) was obtained with an entrapment efficiency over 70% and an average diameter of approximately 120 nm. The leakage property of RGD-SSL-CA4 was similar with SSL-CA4, both were slower than CA4 ethanol solution. Confocal microscopy studies revealed that RGD-SSL could facilitate the liposomes' uptake into HUVECs. Rats treated with two intravenous injections of 7 mg/kg RGD-SSL-CA4 resulted in a significant reduction in the area of CNV compared with control group (P < 0.05).
Conclusions: RGD-modified SSL loaded with CA4 can be successfully prepared, and the vasculature-targeted liposome system would increase the uptake of HUVECs and improve the therapeutic efficacy of CA4 on CNV compared with the control formulations.