Protein adsorption on and swelling of polyelectrolyte brushes: A simultaneous ellipsometry-quartz crystal microbalance study

Abstract

With a coupled spectroscopic ellipsometry-quartz crystal microbalance with dissipation (QCM-D) experimental setup, quantitative information can be obtained about the amount of buffer components (water molecules and ions) coupled to a poly(acrylic acid) (PAA) brush surface in swelling and protein adsorption processes. PAA Guiselin brushes with more than one anchoring point per single polymer chain were prepared. For the swollen brushes a high amount of buffer was found to be coupled to the brush-solution interface in addition to the content of buffer inside the brush layer. Upon adsorption of bovine serum albumin the further incorporation of buffer molecules into the protein-brush layer was monitored at overall electrostatic attractive conditions [below the protein isolectric poimt (IEP)] and electrostatic repulsive conditions (above the protein IEP), and the shear viscosity of the combined polymer-protein layer was evaluated from QCM-D data. For adsorption at the "wrong side" of the IEP an incorporation of excess buffer molecules was observed, indicating an adjustment of charges in the combined polymer-protein layer. Desorption of protein at pH 7.6 led to a very high stretching of the polymer-protein layer with additional incorporation of high amounts of buffer, reflecting the increase of negative charges on the protein molecules at this elevated pH.

Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit

“…Organic layers of few-nm thickness are important for chemical and biological detection, 1 tissue scaffolding, 2 detergent, 3 and surface property tuning 4 applications. Both qualitative and quantitative understanding of organic adsorbate attachment to solid surfaces is of high contemporary interest, especially if performed within liquid ambient.…”

Dynamic analysis of DNA nanoparticle immobilization to model biomaterial substrates using combinatorial spectroscopic ellipsometry and quartz crystal microbalance with dissipation

“…While both SE and QCM-D are commonly used separately, only recently have these devices and techniques been combined to form a hybrid measurement platform known as combinatorial in situ SE/QCM-D, which is used to characterize the adsorption processes of a diverse array of organic molecules and thin films [14][15][16][17][18][19]. By combining both measurement systems, new physical parameters of thin films can be elucidated, such as the porosity of a thin film or the amount of entrapped and associated solvent in real time.…”

Combined QCM-D/GE as a tool to characterize stimuli-responsive swelling of and protein adsorption on polymer brushes grafted onto 3D-nanostructures

“…They appear in an ellipsoidal shape with a major axis of 14 nm and a minor axis of 4 nm [52]. Protein adsorption to PAA brushes on STFs On flat samples, BSA has been shown to adsorb on PAA Guiselin brushes both under electrostatic attractive and moderately repulsive conditions [14]. In this study, adsorption under electrostatic attractive conditions at pH 5 was investigated, since a higher driving force for the proteins to diffuse into the polymer layer inside the intercolumnar space is to be expected.…”

“…Applying polymer brushes, functional coatings with switchable properties, such as wetting properties [6,7], adsorption behavior [8][9][10], ion gating [11], or electrochemical properties [12] have been fabricated. A comprehensive characterization of the responsive behavior and further functionalization is possible using a combined setup of quartz crystal microbalance with dissipation monitoring (QCM-D) together with spectroscopic ellipsometry [13][14][15].…”