Human Serum Albumin Self-Assembly on Weak Polyelectrolyte Multilayer Films Structurally Modified by pH Changes

Abstract

Adsorption of proteins onto film surfaces built up layer by layer from oppositely charged polyelectrolytes is a complex phenomenon, governed by electrostatic forces, hydrogen bonds, and hydrophobic interactions. The amounts of the interacting charges, however, both in polyelectrolytes and in proteins adsorbed on such films are a function of the pH of the solution. In addition, the number and the accessibility of free charges in proteins depend on the secondary structure of the protein. The subtle interplay of all these factors determines the adsorption of the proteins onto the polyelectrolyte film surfaces. We investigated the effect of these parameters for polyelectrolyte films built up from weak "protein-like" polyelectrolytes (i.e., polypeptides), poly(L-lysine) (PLL), and poly(glutamic acid) (PGA) and for the adsorption of human serum albumin (HSA) onto these films in the pH range 3.0-10.5. It was found that the buildup of the polyelectrolyte films is not a simple function of the pure charges of the individual polyelectrolytes, as estimated from their respective pKa values. The adsorption of HSA onto (PLL/PGA)n films depended strongly on the polyelectrolyte terminating the film. For PLL-terminated polyelectrolyte films, at low pH, repulsion, as expected, is limiting the adsorption of HSA (having net positive charge below pH 4.6) since PLL is also positively charged here. At high pH values, an unexpected HSA uptake was found on the PGA-ending films, even when both PGA and HSA were negatively charged. It is suggested that the higher surface rugosity and the decrease of the alpha-helix content at basic pH values (making accessible certain charged groups of the protein for interactions with the polyelectrolyte film) could explain this behavior.

Polyelectrolyte Multilayers on Silica Surfaces: Effect of Ionic Strength and Sodium Salt Type

“…In the literature, [14][15][16] several studies of protein adsorption on previously formed polyelectrolyte multilayers could be found. Müller and coworkers [14] examined the sorption of HSA on poly(ethyleneimine)/poly(acrylic acid) multilayers using ATR FTIR spectroscopy, while Gergelly et al [15] analysed adsorption of the same protein on poly(L-lysine)/ poly(glutamic acid) multilayer by Optical Waveguide LightMode Spectroscopy (OWLS) and AFM. The secondary structure of lysozyme and bovine serum albumin (BSA) adsorbed onto PAH/PSS multilayers was investigated by Schaaf and co-workers.…”

Bioenabled Surface‐Mediated Growth of Titania Nanoparticles

“…Earlier work has demonstrated that the interactions of proteins with polymeric surfaces strongly depend on the charge states of both a protein and a surface. [35,36] Accordingly, the highly polycationic rSilC molecules (pI ¼ 11.8) are expected to adsorb and remain strongly tethered to the negatively charged PSS surface (pK a ¼ 1) [37] at acidic and neutral pH. The presence of tethered rSilC was confirmed by in-situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, which revealed two characteristic bands in the amide I (1600-1700 cm…”

Artificial and Natural Membranes

“…These films can be functionalised with widely varying features, ranging from antifungal activity (Etienne et al, 2005) to antiinflammatory properties (Schultz et al, 2005) to electro-optical devices (Eckle and Decher, 2001). By varying the electrolytes and/or the build-up conditions, the properties of the films -such as thickness (Shiratori and Rubner, 2000), cell adhesion , and protein adsorption (Gergely et al, 2004) -can be largely modified (Figure 3, panels a and b). The build-up of the polyelectrolyte film began with poly(ethyleneimine) (PEI).…”

“…It seems that the forces which keep the DPPC bilayer together, in order to optimise the bilayer structure, can compress the extruding parts of the PGA/PLL films (Pilbat et al, 2007). Depending on the components used, polyelectrolyte films may exhibit linear or exponential growth regimes Gergely et al, 2004). Exponential growth requires the free diffusion of at least one of the film components in the interior of the film .…”