Journal
INTERNATIONAL JOURNAL OF PHARMACEUTICS
Volume 446, Issue 1-2, Pages 119-129Publisher
ELSEVIER
DOI: 10.1016/j.ijpharm.2013.02.026
Keywords
Liposomes; Poly(ethylene glycol); Circulation persistence; Post-insertion; Complement
Categories
Funding
- National Heart, Lung and Blood Institute [R01HL104286]
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We report synthesis and characterization of a novel PEG(2000)-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 mu M. 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 Tc-99m radionuclide and administered in rats. Tc-99m-HDAS-PEG-liposomes showed prolonged persistence in blood as compared to that shown by Tc-99m-plain liposomes. After 24 h of administration, <1% of Tc-99m-plain liposomes remained in blood, whereas approximately 28% of injected Tc-99m-HDAS-PEG-liposomes were present in blood. In comparison, only 4.8% of Tc-99m-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. (C) 2013 Elsevier B. V. All rights reserved.
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