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.

Liposome Encapsulation of the Palmitoyl–KTTKS Peptide: Structural and Functional Characterization

“…On the other hand, an enhanced interaction with cell membrane structure is promoted by liposomes favoring the biological effect of the peptide. A strategy to encapsulate lipopeptides in liposome vesicles has been successfully adopted in other studies for the delivery of vaccines [ 32 ] or for the transport of drugs through the Brain–Blood Barrier [ 33 ]. Interestingly, as can be observed in Figure 3 and Figure 4 , plain liposomes (TLE and REV samples) were also shown to be able to induce collagen production, although with a less potent effect compared to the pal-KTTKS-loaded liposomes.…”

Lipid-Based Nanoparticle Functionalization with Coiled-Coil Peptides for In Vitro and In Vivo Drug Delivery

“…R8-RGD increased the cellular uptake 2-fold and nearly 30-fold compared to separate R8 and RGD, respectively, and in vivo studies in mice showed that R8-RGD-liposomes could be efficiently delivered into the brain and selectively accumulated in the glioma foci . Further examples showed that the functionalization with a peptide called ApoEdp (CFG­GGL­RKL­RKR­LLL­RKL­RKR­LL) yields 3.9-fold higher accumulation in the brain compared to the nonmodified liposome formulation …”

“…53 Further examples showed that the functionalization with a peptide called ApoEdp (CFGGGLRKLRKRLLLRKLRKRLL) yields 3.9-fold higher accumulation in the brain compared to the nonmodified liposome formulation. 47 Uhl et al demonstrated that the modification of liposome surfaces with a cell-penetrating peptide (cyclic R9 peptide) allows mucosal permeation. Therefore the cyclic R9 (cR9) peptide was conjugated to a PEG12 linker containing a maleimide group, which was bound to a thiol-modified phospholipid to achieve a construct of lipid-PEG12-cR9.…”

“…To overcome physiological and cellular barriers and/or to achieve successful targeting, a huge variety of nanoparticles have been functionalized with CPPs and CTPs, including liposomes, lipid nanoparticles (LNPs), polymeric nanoparticles, gold/metal nanoparticles, and silica quantum dots. − …”

“… 53 Further examples showed that the functionalization with a peptide called ApoEdp (CFGGGLRKLRKRLLLRKLRKRLL) yields 3.9-fold higher accumulation in the brain compared to the nonmodified liposome formulation. 47 …”