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.

Accelerated Blood Clearance (ABC) Phenomenon Favors the Accumulation of Tartar Emetic in Pegylated Liposomes in BALB/c Mice Liver

Tartar emetic (TE) was the first drug used to treat leishmaniasis. However, its use was discontinued due to high toxicity. Association of TE with liposomes is a strategy to reduce its side effects. Pegylated liposomes (Lpeg) present lower rates of uptake by macrophages and prolonged circulation compared to their nonpegylated counterparts. However, repeated administration of Lpeg can cause an Accelerated Blood Clearance (ABC) phenomenon, whereby recognition of liposomes by antibodies results in faster phagocytosis. This work evaluated the effect of TE administration on histopathological aspects and the effect of the ABC phenomenon on targeting and toxicity in mice. Our results show that treatment with free or liposomal TE had no effect on the erythrocyte count, on liver and spleen weight, and on hepatic, splenic, and cardiac histology in mice. Severe lesions were observed on the kidneys of animals treated with a single dose of free TE. Treatment with TE in Lpeg after induction of ABC phenomenon caused a significant increase in Sb level in the liver without toxicity. Furthermore, mice treated with TE in liposomes showed normal renal histopathology. These results suggest site-specific targeting of Sb to the liver after induction of ABC phenomenon with no toxicity to other organs.

Zwitterionic stealth peptide-protected gold nanoparticles enable long circulation without the accelerated blood clearance phenomenon

Poly(ethylene glycol) (PEG), which is considered as a gold standard for surface modification of nanoparticles in biomedical applications, has been reported to encounter the accelerated blood clearance (ABC) phenomenon after repeated administration.