Identification of Peptide Ligands for Targeting to the Blood-Brain Barrier

Abstract

PurposeTransport of drugs to the brain is limited by the blood-brain barrier. New, specific brain endothelium ligands can facilitate brain-specific delivery of drugs.MethodsWe used phage display in an in situ brain perfusion model to screen for new brain endothelium peptide ligands.ResultsTwo phage clones, displaying 15 amino acid-peptides (GLA and GYR) that were selected for brain binding in the mouse model, showed significant binding to human brain endothelium (hCMEC/D3), compared to a random control phage. This binding was not seen for other human endothelial cells (HUVEC). Binding to hCMEC/D3 cells was dose dependent. When phage GLA and GYR were individually perfused through the murine brain, their ability to bind to the brain was 6-fold (GLA) and 5-fold (GYR) higher than the control phage. When compared to lung perfusion, phage showed an 8.5-fold (GYR) and 48-fold (GLA) preference for brain over lung compared to the control.ConclusionsThese results indicate that two new peptide ligands have been identified that may be used for specific targeting of drugs to the blood-brain barrier.

Combinatorial Approaches for the Identification of Brain Drug Delivery Targets

“…For example, they can be presented as linear peptides from 7 to 15 amino acids long [28, 29], or presented as conformationally constrained peptides through cysteine cyclization [30]. Peptide libraries are especially useful because of the ease of production and their correspondingly high diversity.…”

“…In this situation, a putative binding or transporting phage clone with a low representation in the original library could be completely removed from the blood stream before it ever gets to the brain, thereby effectively reducing the diversity of the library. One approach to circumvent this problem was employed by Van Rooy et al [29] where a 15 amino acid peptide phage display library was administered to the mouse by in situ brain perfusion as opposed to intravenous injection. In this particular form of in situ brain perfusion, the phage display library is introduced into the left heart ventricle where it then travels through the aorta and ultimately to the brain.…”

Strategies for drug delivery to the central nervous system by systemic route

“…GLA is positively charged and can bind electrostatically with negatively charged cell membrane. But GYR, which is negatively charged, also shows good binding to BBB (van Rooy et al, 2010). However, when liposomes where spiked with synthetically synthesized GLA and GYR peptides, binding was less significant.…”

Blood-to-Brain Drug Delivery Using Nanocarriers

“…These antibodies have been used to produce the so-called Trojan horse liposomes for the delivery of plasmid DNA or antisense gene therapy (Pardridge 2010 ). Peptide targeting vectors for the delivery of liposomal drugs to the brain include COG133 (an ApoE-mimetic peptide), Angiopep-2 (with high affi nity for the LRP receptor on brain endothelial cells), or GLA peptide (selected through phage display with brain uptake through a yet unknown mechanism) (van Rooy et al 2010 ). Recently, van Rooy et al ( 2012 ) have shown the importance of peptide conformation for the ability of GLA to improve drug targeting to the brain (van Rooy et al 2012 ), a fi nding that may hold true for other (peptide) targeting ligands as well.…”