title: Post-modification of preformed liposomes with novel non-phospholipid poly(ethylene glycol)-conjugated hexadecylcarbamoylmethyl hexadecanoic acid for enhanced circulation persistence in vivo.
abstract: We report synthesis and characterization of a novel PEG2000-conjugated hexadecylcarbamoylmethyl hexadecanoate (HDAS-PEG) as a PEG-phospholipid substitute for enhancing circulation persistence of liposomes. HDAS-PEG showed critical micelle concentration of 4.25 μM. We used post-insertion technique to introduce HDAS-PEG in outer lipid layer of the preformed liposomes. The presence of surface HDAS-PEG was confirmed by altered electrophoretic mobility, confocal microscopy and PEG estimation by ELISA. The post-inserted HDAS-PEG desorbed at approximately half the rate at which post-inserted DSPE-PEG desorbed from the liposome surface. HDAS-PEG significantly reduced liposome-induced complement activation (C4d, Bb and SC5b); HDAS-PEG was more effective than more commonly used DSPE-PEG in this capacity. For studying circulation persistence, the liposomes were labeled with (99m)Tc radionuclide and administered in rats. (99m)Tc-HDAS-PEG-liposomes showed prolonged persistence in blood as compared to that shown by (99m)Tc-plain liposomes. After 24 h of administration, <1% of (99m)Tc-plain liposomes remained in blood, whereas approximately 28% of injected (99m)Tc-HDAS-PEG-liposomes were present in blood. In comparison, only 4.8% of (99m)Tc-DSPE-PEG-liposomes were measured in blood after 24 h. As expected, the clearance route of the liposomes was through liver and spleen. These results demonstrate the potential of a novel non-phosphoryl HDAS-PEG for surface modification of preformed liposomes with a goal of prolonging their circulation persistence and more effective inhibition of complement activation.
authors: Department of Pharmaceutical Sciences, College of Pharmacy, University of Oklahoma Health Sciences Center, 1110 North Stonewall Avenue, Oklahoma City, OK 73117, USA.
authors: Okhil K
authors: OK
authors: Nag
authors: Vivek R
authors: VR
authors: Yadav
authors: Andria
authors: A
authors: Hedrick
authors: Vibhudutta
authors: V
authors: Awasthi
mesh_terms: D000818:Animals; D003167:Complement Activation / Q000187:drug effects; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008081:Liposomes / Q000097:blood / Q000737:chemistry* / Q000494:pharmacology; D019308:Palmitic Acid / Q000737:chemistry* / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D008081:Liposomes; D019308:Palmitic Acid; D011092:Polyethylene Glycols