Sequential and competitive adsorption of peptides at pendant PEO layers

Abstract

Earlier work provided direction for development of responsive drug delivery systems based on modulation of the structure, amphiphilicity, and surface density of bioactive peptides entrapped within pendant polyethylene oxide (PEO) brush layers. In this work, we describe the sequential and competitive adsorption behavior of such peptides at pendant PEO layers. Three cationic peptides were used for this purpose: the arginine-rich, amphiphilic peptide WLBU2, a peptide chemically identical to WLBU2 but of scrambled sequence (S-WLBU2), and the nonamphiphilic peptide poly-L-arginine (PLR). Optical waveguide lightmode spectroscopy (OWLS) was used to quantify the rate and extent of peptide adsorption and elution at surfaces coated with PEO. UV spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to quantify the extent of peptide exchange during the course of sequential and competitive adsorption. Circular dichroism (CD) was used to evaluate conformational changes after adsorption of peptide mixtures at PEO-coated silica nanoparticles. Results indicated that amphiphilic peptides are able to displace adsorbed, non-amphiphilic peptides in PEO layers, while non-amphiphilic peptides were not able to displace more amphiphilic peptides. In addition, peptides of greater amphiphilicity dominated the adsorption at the PEO layer from mixtures with less amphiphilic or non-amphiphilic peptides.

Molecular Structure and Conformation of Biodegradable Water-Soluble Polymers Control Adsorption and Transport in Model Soil Mineral Systems

“…This coverage likely led to electrostatic and steric repulsion between the adsorbed and dissolved (B)­WSPs, thereby slowing down further adsorption and giving rise to the “excluded-area effect” (see Figure g for a schematic depiction). Uncharged (B)­WSPs may experience strong attractive intermolecular forces due to H-bonding (DEX) and possibly also the hydrophobic effect (PLL, pH 9). − It is conceivable that DEX molecules that were adsorbed in the initial kinetic phase (i.e., phase 1, fast adsorption) had two effects: they sterically impaired adsorption of additional DEX molecules to the sorbent surface, while at the same time, they may have enabled slow additional adsorption of DEX molecules by allowing for H-bonding with the already adsorbed DEX molecules (i.e., kinetic phase 2, slow adsorption). The continuous adsorption of DEX may result in adlayer architectures in which DEX–DEX H-bonding plays a large role besides DEX-IOCS H-bonding.…”