Blood Protein Exclusion from Polymer Brushes

Abstract

We report interactions between adsorbed copolymers of poly(ethylene glycol) (PEG) in the presence of two abundant blood proteins, serum albumin and an immunoglobulin G, up to physiological blood concentrations. We directly and nonintrusively measure interactions between PEG triblock copolymers (PEG−PPO−PEG) adsorbed to hydrophobic colloids and surfaces using Total Internal Reflection Microscopy, which provides kT-and nanometer-scale resolution of interaction potentials (energy vs separation). In the absence of protein, adsorbed PEG copolymer repulsion is consistent with dimensions and architectures of PEG brushes on both colloids and surfaces. In the presence of proteins, we observe concentration dependent depletion attraction and no change to brush repulsion, indicating protein exclusion from PEG brushes. Because positive and negative protein adsorption are mutually exclusive, our observations of concentration dependent depletion attraction with no change to brush repulsion unambiguously indicate the absence of protein coronas at physiological protein concentrations. These findings demonstrate a direct sensitive approach to determine interactions between proteins and particle/surface coatings important to diverse biotechnology applications.

Polyelectrolyte-Doped Block Copolymer-Stabilized Nanocarriers for Continuous Tunable Surface Charge

“…Analysis of cationic PS particles shows the serum protein corona denatures on the particle surface and the denatured protein-PS complex drives nonphagocytotic receptor-mediated endocytosis of the cationic PS lattices. 6 Hydrophilic polymer stabilizers tend to adsorb less protein 15,16,65 than PS lattices with little denaturation 66,67 of the corona proteins, yet the hydrophilic polymer-stabilized NCs here show similar cell-type uptake trends as the hydrophobic PS lattices. This suggests that hydrophobic interactions are not significant in the evolution of the protein corona and its specificity for certain cell types.…”

“…Three critical attributes for NCs are size, surface stabilizer composition, , and surface charge. − Stable, circulating NCs have optimal hydrodynamic diameters between 20 and 150 nm to avoid size-based clearance mechanisms. − Surface composition and charge mediate the interaction between a circulating NC and the surrounding biological environment. NC surfaces are often engineered to minimize protein corona formation that can adversely impact stability, circulation times, , or cellular uptake. , Dense, brush-regime PEG coatings resist protein adsorption − and produce mucodiffusive , NCs with long in vivo circulation times. ,, …”

Analysing Sources of Error in Total Internal Reflection Microscopy (TIRM) Experiments and Data Analysis

“…Consequently, TIRM has been used in a plethora of studies over the last three decades to study a wide range of interaction types [30], including screened Coulomb interactions [29], van der Waals attraction [31], depletion interaction due to various depletants [32][33][34][35][36], steric repulsion [37], or fluctuation interaction [38,39]. More recently, biophysically relevant issues have also been investigated, such as the non-specific interaction between protein-functionalized [40] or DNA-coated particles [41] or the exclusion of blood proteins from polymer brushes [42]. For a long time, it was not possible to investigate non-spherical particles with TIRM, due to the lack of a theoretical framework.…”