Hydrophobic Cholesteryl Moieties Trigger Substrate Cell–Membrane Interaction of Elastin–Mimetic Protein Coatings in Vitro

Abstract

A cellular coating based on hydrophobic interactions of an elastin-like recombinamer (ELR) with the cell membrane is presented. It is well-documented that biophysical properties such as net charge, hydrophobicity, and protein-driven cell–ligand (integrin binding) interactions influence the interaction of polymers, proteins or peptides with model membranes and biological cells. Most studies to enhance membrane–substrate interactions have focused on the introduction of positively charged groups to foster electrostatic interactions with the negatively charged membrane. Herein, we present an antagonistic approach based on ELRs with varying amounts of hydrophobic cholesteryl groups (ELR CTA s). The ability of the membranes to stabilize cholesteryl groups is hypothesized to assist the coordination of hydrophobic ELRs with the membrane. The main objective was to generate a defined cellular coating of a recombinant protein that allows for total sequence control and less host, or batch-to-batch, variation as a substitute for the existing coatings like alginate, polyelectrolytes, collagens, and fibronectin. We used an in vitro cell-binding assay to quantify cell–substrate interactions, showing enhanced cellular recognition and matrix distribution with an increasing number of cholesteryl groups incorporated. These novel materials and the versatile nature of their protein sequence have great potential as cellular markers, drug carriers, or hydrophobic cell-binding domains.

Solution behavior and encapsulation properties of fatty acid–elastin-like polypeptide conjugates

“…In the first one, recombinantly expressed ELPs were purified and chemically modified on specific amino acids selected as guest residues of the ELP sequence. Following this approach, cholesterol was grafted on lysine residues 18 and oleic acid on methionine residues. 19 In both cases, the grafting of lipid chains to the ELP backbone yielded brush-like lipoproteins that can self-assemble into micelles with ELP–cholesterol, 18 or polymersomes with ELP–oleic acid.…”

“…Following this approach, cholesterol was grafted on lysine residues 18 and oleic acid on methionine residues. 19 In both cases, the grafting of lipid chains to the ELP backbone yielded brush-like lipoproteins that can self-assemble into micelles with ELP–cholesterol, 18 or polymersomes with ELP–oleic acid. 19 However, these materials are highly hydrophobic owing to the number of lipid molecules grafted per ELP, and therefore difficult to handle in biological media.…”