Polysialic Acid Modified Liposomes for Improving Pharmacokinetics and Overcoming Accelerated Blood Clearance Phenomenon

Poly (ethylene glycol) (PEG) modified nanocarriers are being used widely in the drug delivery system (DDS). However, the “accelerated blood clearance (ABC) phenomenon” was induced upon repeated administration of PEG-modified liposomes, resulting in reduced blood circulation time, and increased accumulation in liver and spleen. To avoid the unexpected phenomenon, polysialic acid (PSA) was selected to modify liposomes. PSA is a natural, highly hydrophilic polysaccharide polymer for which no receptors exists in the body. It is non-immunogenic, biodegradable and endows the conjugated bioactive macromolecule and drugs with increased circulation time in vivo. In the present study, the in vivo evaluation showed that PSA modified liposomes (PSA-Lip) afford extended blood circulation in wistar rats and beagle dogs. Moreover, the ABC phenomenon did not occur and the IgM antibody was not induced after repeated injections of PSA-Lip. These results strongly suggest that PSA modification represents a promising strategy to afford good stealth of the liposomes without evoking the ABC phenomenon.