From Phage Display to Nanoparticle Delivery: Functionalizing Liposomes with Multivalent Peptides Improves Targeting to a Cancer Biomarker

Abstract

Phage display is commonly used to isolate peptides that bind to a desired cell type. While chemical synthesis of selected peptides often results in ligands with low affinity, a multivalent tetrameric presentation of the peptides dramatically improves affinity. One of the primary uses of these peptides is conjugation to nanoparticle-based therapeutics for specific delivery to target cell types. We set out to optimize the path from phage display peptide selection to peptide presentation on a nanoparticle surface for targeted delivery. Here, we examine the effects of peptide valency, density, and affinity on nanoparticle delivery and therapeutic efficacy, using the αvβ6-specific H2009.1 peptide as a model phage-selected peptide and liposomal doxorubicin as a model therapeutic nanoparticle. Liposomes displaying the higher affinity multivalent H2009.1 tetrameric peptide demonstrate 5-10 fold higher drug delivery than liposomes displaying the lower affinity monomeric H2009.1 peptide, even when the same number of peptide subunits are displayed on the liposome. Importantly, a 6-fold greater toxicity is observed towards αvβ6-expressing cells for liposomes displaying tetrameric verses monomeric H2009.1 peptides. Additionally, liposomal targeting and toxicity increase with increasing concentrations of H2009.1 tetrameric peptide on the liposome surface. Thus, both the multivalent peptide and the multivalent liposome scaffold work together to increase targeting to αvβ6-expressing cells. This multi-layered approach to developing high affinity targeted nanoparticles may improve the utility of moderate affinity peptides. As tetramerization is known to increase affinity for a variety of phage-selected peptides, it is anticipated that the tetrameric scaffold may act as a general method for taking peptides from phage display to nanoparticle display.

α-Enolase–binding peptide enhances drug delivery efficiency and therapeutic efficacy against colorectal cancer

“…Peptide phage display is a powerful method used to identify peptides capable of binding to a specific cell type by whole-cell panning; the ability of the identified peptides to be internalized enables their use as a drug delivery vehicle when conjugated to nanoparticles (15). Although numerous tumor-targeting peptides have been isolated using in vitro panning against cultured cells, several challenges still remain in this field (16).…”

“…Although numerous tumor-targeting peptides have been isolated using in vitro panning against cultured cells, several challenges still remain in this field (16). In particular, experimental approaches for systematic target identification are still lacking (15); this is a key problem, because accurate identification of peptide-targeted molecules is very important for basic and clinical research. Conventional receptor identification focuses on membrane protein extraction and affinity purification, followed by mass spectrometric (MS) identification of the purified protein.…”

Ligation Strategies for Targeting Liposomal Nanocarriers

“…More recently, monomeric and tetrameric H2009.1 peptides for targeting integrins α v β 6 expressed on non-small cell lung cancer cells were attached to the surface of preformed liposomes containing DSPE-PEG 2000 -maleimide [45]. Three liposome formulations varying in the concentration of DSPE-PEG-maleimide were investigated.…”

Global liposome research in the period of 1995–2014: a bibliometric analysis

“…(4) Cancer therapy: Success of Doxil promotes the research and development of liposomes carrying anticancer drug. Further understanding of how actively targeted liposomes behave in vivo and subsequent optimization of liposome design could translate into successful applications of targeted liposomes in the clinic, providing the potential for substantial breakthroughs in cancer therapeutics (Qhattal and Liu 2011;Gray et al 2013;Deshpande et al 2013;Yao et al 2013). Taken together, nanotechnology, drug delivery, siRNA and cancer therapy are trends of liposome.…”