Spatial Variation of the Charge and Sulfur Oxidation State in a Surface Gradient Affects Plasma Protein Adsorption

Abstract

A gradient of negative surface charge based on 1-D spatial variation from surface sulfhydryl to mixed sulfhydryl-sulfonate moities was prepared by controlled UV oxidation of 3-mercaptopropylsilane monolayer on fused silica. Adsorption of three human plasma proteins, albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fgn) onto such surface gradient was studied using spatially-resolved total internal reflection fluorescence (TIRF) and autoradiography. Adsorption was measured from dilute solutions equivalent to 1/100 (TIRF, autoradiography), and 1/500 and 1/1000 (autoradiography) of protein's physiological concentrations in plasma. All three proteins adsorbed more to the non-oxidized sulfhydryl region than to the oxidized, mixed sulfhydryl-sulfonate region of the gradient. In the case of HSA the adsorption contrast along the gradient was largest when the adsorption took place from more dilute protein solutions. Increasing the concentration to 1/100 of protein plasma concentration eliminated the effect of the gradient on HSA adsorption and to the lesser extent on IgG adsorption. In the case of Fgn the greatest adsorption contrast was observed at the highest concentration used. Based on adsorption kinetics, the estimated binding affinity of HSA for the sulfhydryl region what twice the affinity for the mixed sulfhydryl-sulfonate region of the gradient. For IgG and Fgn the initial adsorption was transport-limited and the initial adsorption rates approached the computed flux of the protein to the surface.

Gas phase silanization for silicon nanowire sensors and other lab‐on‐a‐chip systems

“…S1). The reaction protocol was derived from the corresponding literature [13][14][15], and comprised immersion in the isopropanolic silane solution for 24 h. Additionally, the substrates were also immersed for 1 h and 4 h during the present study to compare the performance for shorter reaction times. For the development of the gas phase reaction, a seminal report by Pavlovic et al [11] served as the starting point.…”

Coadsorption-dependent orientation of fibronectin epitopes at hydrophilic gold surfaces

“…This value, lower than the shorter dimensions (4.0 nm) of the HSA molecule in the native state, can be explained in terms of a ''squeezing'' effect induced by the AFM tip on the adsorbed molecules, as well as to a moderate unfolding process due either to the adsorption at the Au surface or to the drying step before AFM measurements. 17,57 The step height for the dry Fn adlayer adsorbed onto Au at the adsorption plateau, as shown in Fig. 3, is about 5.7 AE 0.2 nm.…”

“…[3][4][5][6][7][8] A classical topic within the vast literature dedicated to the field involves the problem of the differences in the conformation of the adsorbed protein at solid surfaces, and in particular at hydrophobic and hydrophilic surfaces, as previously shown for fibrinogen, fibronectin, bovine serum albumin (BSA), immunoglobulin G (IgG), lysozyme, and fibrinogen. 1,2,[9][10][11][12][13][14][15][16] The studies essentially involved indirect experiments, as for instance adsorption onto surfaces with a hydrophobicity gradient, 17 protein-protein exchange experiments, 18 etc., showing that, indeed, proteins and antigens may lose part of their biological activity when immobilized on a surface due to a change in conformation and/or unfavorable orientation of the molecule. It is to be stressed that the protein changes following adsorption are in general discussed in terms of ''protein orientation''.…”

Revealing deposition mechanism of colloid particles on human serum albumin monolayers

“…Because of its significance, the adsorption of albumins on various solid substrates has been studied by a variety of experimental techniques such as radioisotope labeling [15], ellipsometry [16,17], integrated optics [18,19], reflectometry [20], in situ fluorescent TIRF technique [21,22], X-ray photoelectron spectroscopy (XPS) [23][24][25] and AFM [17,26]. In Ref.…”