Changes in Protein Adsorption on Self-Assembled Monolayers with Monolayer Order:  Comparison of Human Serum Albumin and Human Gamma Globulin

Abstract

The role that alkyl chain packing density in a self-assembled monolayer (SAM) plays in the adsorption of protein to the SAM surface was investigated using in situ neutron reflectivity (NR) and total internal reflection fluorescence (TIRF) measurements of the adsorption behavior of human serum albumin (HSA) and human immunoglobulin G (HGG). The proteins differ particularly in the fact that HSA has specific binding pockets for alkyl chains while HGG does not. NR results show that HSA adsorbs from a 1.0 mg/mL solution as a single layer on the SAMs, with the protein interpenetrating into a less densely packed SAM, but not into a more densely packed SAM. Likewise, the kinetics of the HSA adsorption to the SAMs varies markedly with the alkyl chain packing. In contrast, both the structure of the adsorbed layer and adsorption kinetics vary little with the alkyl chain packing density in the case of HGG adsorbing from solution. HGG also does not penetrate into loosely packed SAMs. NR results reveal that the HGG adsorbs as two layers, with the layer closest to the SAM being more tightly packed. When HSA and HGG compete for adsorption sites on a SAM, HGG effectively displaces HSA from a tightly packed SAM, but does not compete effectively with HSA adsorbed tenaciously onto a loosely packed SAM.

Protein adsorption on mixtures of hydroxyl‐ and methyl‐terminated alkanethiols self‐assembled monolayers

“…This could be related to the more highly ordered monolayer of the pure C15CH3 SAM compared with the loosely packed layers created by the mixture of thiols with different terminal groups and different chain lengths. In a recently work, Petrash et al 52 described that HSA adsorption to a hydrophobic SAM varies with the packing density of the alkyl SAMs. HSA was not displaced by immunoglobulin G when adsorbed onto a loosely packed SAM.…”

Temperature-dependent intermolecular force measurement of poly(N-isopropylacrylamide) grafted surface with protein

“…According to Kidoaki et al, the absence of adhesion at 25 and 40 • C is due to the hydrophilic nature of the albumin molecule. However, about half of the amino acids in the BSA molecule contain nonpolar residues [32], and it is known that albumin molecules are the main carriers of fatty acids in the human body and have hydrophobic pockets within their structure [38].…”

Synovial Fluid Lubrication: The Effect of Protein Interactions on Adsorbed and Lubricating Films

“…Adsorption of the proteins albumin and gamma-globulin, both independently and together have been investigated under static conditions using techniques such as quartz crystal microbalance (QCM) [15,16], fluorescence imaging [17], ellipsometry [18,19] and surface plasmon resonance spectroscopy [20]. These studies show that competition between the proteins for adsorption sites can affect the mass, thickness and viscoelastic properties of the adsorbed layers.…”

“…Note many of the studies [15][16][17][18][19][21][22][23][24] have been carried out at relatively low protein concentrations, typically 0.01 -1 mg ml -1…”