Development of an apolipoprotein E mimetic peptide–lipid conjugate for efficient brain delivery of liposomes

Abstract

Liposomes are versatile carriers that can encapsulate various drugs; however, for delivery to the brain, they must be modified with a targeting ligand or other modifications to provide blood–brain barrier (BBB) permeability, while avoiding rapid clearance by reticuloendothelial systems through polyethylene glycol (PEG) modification. BBB-penetrating peptides act as brain-targeting ligands. In this study, to achieve efficient brain delivery of liposomes, we screened the functionality of eight BBB-penetrating peptides reported previously, based on high-throughput quantitative evaluation methods with in vitro BBB permeability evaluation system using Transwell, in situ brain perfusion system, and others. For apolipoprotein E mimetic tandem dimer peptide (ApoEdp), which showed the best brain-targeting and BBB permeability in the comparative evaluation of eight peptides, its lipid conjugate with serine–glycine (SG)₅ spacer (ApoEdp-SG-lipid) was newly synthesized and ApoEdp-modified PEGylated liposomes were prepared. ApoEdp-modified PEGylated liposomes were effectively associated with human brain capillary endothelial cells via the ApoEdp sequence and permeated the membrane in an in vitro BBB model. Moreover, ApoEdp-modified PEGylated liposomes accumulated in the brain 3.9-fold higher than PEGylated liposomes in mice. In addition, the ability of ApoEdp-modified PEGylated liposomes to localize beyond the BBB into the brain parenchyma in mice was demonstrated via three-dimensional imaging with tissue clearing. These results suggest that ApoEdp-SG-lipid modification is an effective approach for endowing PEGylated liposomes with the brain-targeting ability and BBB permeability.

Keywords:

• Apolipoprotein E mimetic peptide
• blood–brain barrier
• brain-targeting
• liposomes
• tissue clearing

Acknowledgments

This study was partially supported by Nagai Memorial Research Scholarship from the Pharmaceutical Society of Japan (NK). This study used research equipment shared by the MEXT Project to promote the public utilization of advanced research infrastructure (Program for supporting the introduction of the new sharing system; grant number JPMXS0422500320).

Disclosure statement

The author reports no conflicts of interest in this work.

Ethical Approval statement

All animal experiments were performed in accordance with the Guide for Animal Experimentation of Nagasaki University (Approval number, 1812251497-7).

Additional information

Funding

This study was partially supported by JSPS KAKENHI grant number 20H04540 (HA), Grant-in-Aid for JSPS Fellows JP20J21334 (NK), and Center for Clinical and Translational Research of Kyushu University Hospital (SK).