Avidity and Cell Uptake of Integrin-Targeting Polypeptide Micelles is Strongly Shape-Dependent

Abstract

We describe a genetically encoded micelle for targeted delivery consisting of a diblock polypeptide with segments derived from repetitive protein motifs inspired by Drosophila melanogaster Rec-1 resilin and human tropoelastin with a C-terminal fusion of an integrin-targeting fibronectin type III domain. By systematically varying the weight fraction of the hydrophilic elastin-like polypeptide (ELP) block and molecular weight of the diblock polypeptide, we designed micelles of different morphologies that modulate the binding avidity of the human wild-type 10th fibronectin domain (Fn3) as a function of shape. We show that wormlike micelles that present the Fn3 domain have a 1000-fold greater avidity for the αvβ3 receptor compared to the monomer ligand and an avidity that is greater than a clinically relevant antibody that is driven by their multivalency. The amplified avidity of these micelles leads to significantly increased cellular internalization, a feature that may have utility for the intracellular delivery of drugs that are loaded into the core of these micelles.

Recent trends in protein and peptide-based biomaterials for advanced drug delivery

“…The hydrophobic / self-assembling block impacts the molecular architecture of the self-assembled peptide-based delivery system. For example, increased resilin content in the self-assembling block in an elastin-resilin fusion peptide shifts the self-assembled morphology from spherical micelles to elongated “worm-like” micelles, and can increase the avidity of a micelle with exposed peptide ligands that bind the α v β 3 integrin receptor by 1000-fold compared to a monomeric ligand [ 55 ]. Lipids and hydrophobic peptides like resilin are used not only to drive self-assembly but also to entrap hydrophobic drugs.…”

“…Dzuricky and coworkers expanded upon this work to observe how nanoparticle morphology impacted cell uptake [ 55 ]. A fibronectin type-III (Fn3) -binding domain that binds the α v β 3 integrin was fused to the C-terminus of an RLP-ELP diblock copolymer.…”

“…While a spherical RLP-ELP micelle that presented a Fn3 domain showed a respectable 10-fold increase in affinity for the α v β 3 integrin compared to the monovalent RLPELP-Fn3 unimer, the worm-like RLP-ELP-Fn3 nanoparticles showed a remarkable 1000-fold increase in affinity for the integrin ( Fig. 21 ) [ 55 ]. The combination of morphology and high avidity yielded a picomolar K D , a remarkable achievement considering that a therapeutic antibody against the same integrin exhibits a K D of only 20 nM.…”

“…The combination of morphology and high avidity yielded a picomolar K D , a remarkable achievement considering that a therapeutic antibody against the same integrin exhibits a K D of only 20 nM. Consequently, the worm-like RLP-ELP-Fn3 was more readily taken up by cells than the antibody [ 55 ]. These studies demonstrate that RLP-ELP nanoparticles can be harnessed for robust, specific cellular targeting and uptake of therapeutic agents.…”

“…Multivalency increased the affinity of the nanoparticles for its target by decreasing the off-rate. Adapted from [ 55 ]. …”