Structural attributes affecting peptide entrapment in PEO brush layers

Abstract

A more quantitative understanding of peptide loading and release from polyethylene oxide (PEO) brush layers will provide direction for development of new strategies for drug storage and delivery. In this work we recorded selected effects of peptide structure and amphiphilicity on adsorption into PEO brush layers based on covalently stabilized Pluronic®F 108. Optical waveguide lightmode spectroscopy and circular dichroism measurements were used to characterize the adsorption of poly-L-glutamic acid, poly-L-lysine, and the cationic amphiphilic peptide WLBU2, to the brush layers. The structure of WLBU2 as well as that of the similarly-sized homopolymers was controlled between disordered and more ordered (helical) forms by varying solution conditions. Adsorption kinetic patterns were interpreted with reference to a simple model for protein adsorption, in order to evaluate rate constants for peptide adsorption and desorption from loosely and tightly bound states. While more ordered peptide structure apparently promoted faster adsorption and elution rates, resistance to elution while in the PEO layer was dependent on peptide amphiphilicity. The results presented here are compelling evidence of the potential to create anti-fouling surface coatings capable of storing and delivering therapeutics.

Sequential and competitive adsorption of peptides at pendant PEO layers

“…The concentration of each peptide solution was prepared at 50 μM in all peptide sequential and competitive adsorption experiments, in order to ensure an amount of peptide sufficient for monolayer coverage of the surface area presented by a 1 mg/mL suspension of F108-coated nanoparticles [16, 17]. Figure 1 shows the percentage of the first peptide displaced by the second after the sequential adsorption of two peptides.…”

“…Self-assembled PEO brush layers were formed by suspension of hydrophobic silica nanoparticles (R816, Degussa, 190 m 2 /g, 10-12 nm) in Pluronic® F108 (BASF) in HPLC water for 10 h on a rotator [1, 2, 16]. The complete surface coverage of F108 is about 3.3 mg/m 2 [16, 17].…”

“…The complete surface coverage of F108 is about 3.3 mg/m 2 [16, 17]. A 5× excess of F108 over this amount was used to ensure good coverage of the nanoparticles.…”

“…200 μL of TCVS was evaporated at 20°C into a stream of dry nitrogen carrier gas, which was directed over the waveguide and silicon wafers surfaces for 4 h. The silanized waveguides and silicon wafers were then immersed in a solution of 5% w/v Pluronic® F108 in water, and were rotated in solution overnight. After incubation, samples were γ-irradiated to 0.3 Mrad to covalently attach the F108 to the surface [16, 19]. The irradiated sensors were rinsed with HPLC water, dried with nitrogen, and stored in the dark under nitrogen until used.…”

Building a working understanding of protein adsorption with model systems and serendipity

“…Peptide conformation in each case was controlled between disordered and ˛-helical forms by varying the concentration of perchlorate ion. Through experimentation with CD, OWLS, and quartz crystal microbalance with dissipation monitoring (QCM-D), we have shown rather convincingly that an initially more ordered (˛-helical) structure will promote peptide adsorption into the PEO layer, and that upon entry, a partially helical peptide will undergo a cooperative increase in helicity [77,78]. And in all of our work to date, peptide retention within the PEO layer was strongly correlated with peptide amphiphilicity, with that effect modulated by the distribution of polar and non-polar residues on the peptide [79].…”