Examining Functionalized Vesosomes as Drug Delivery Vehicles

Unilamellar vesicles have been used as drug delivery vehicles for many years although a major limitation was the rapid in vivo breakdown of the vesicle phospholipid bilayer, resulting in premature release of contents. By encapsulating multiple vesicles within a second phospholipid bilayer, multi-compartmental "vesosomes" were created, extending drug retention time by two orders of magnitude. The vesosome phospholipid bilayer was functionalized to further enhance the efficiency of drug therapy through targeted delivery, enhanced release control, and improved resistance to physiological clearance mechanisms. The focus of this project was to qualify and quantify the efficiency of various functionalization formulations both in buffer and in vivo. Vesicles were created using 1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine (DPPC) tagged with the fluorescently-labeled lipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, triethylammonium salt (NBD-PE) and hydrated in Phosphate Buffered Saline (PBS). Vesosomal bilayers were created using DPPC, tagged with Texas Red© 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, triethylammonium salt (Texas Red© DHPE), functionalized using 1,2-Diacyl-sn-Glycero-3-Phosphoethanolamine-N -[Methoxy(Polyethylene glycol)-2000] (mPEG 2000 PE, "PEG"), and hydrated in PBS. The vesosome formulations were analyzed using confocal microscopy, cryogenic transmission electron microscopy (Cryo-TEM), freeze-fracture transmission electron microscopy (FF-TEM), and fluorimetry. The initial analysis confirmed that the synthesis of functionalized vesosomes successfully produced encapsulated vesicles and that different vesosomal formulations resulted in different behavior both in vivo and in buffer, necessitating future experimentation focusing on refinement and quantification of functionalization.