Protein adsorption | EPFL Graph Search

Adsorption (not to be mistaken for absorption) is the accumulation and adhesion of molecules, atoms, ions, or larger particles to a surface, but without surface penetration occurring. The adsorption of larger biomolecules such as proteins is of high physiological relevance, and as such they adsorb with different mechanisms than their molecular or atomic analogs. Some of the major driving forces behind protein adsorption include: surface energy, intermolecular forces, hydrophobicity, and ionic or electrostatic interaction. By knowing how these factors affect protein adsorption, they can then be manipulated by machining, alloying, and other engineering techniques to select for the most optimal performance in biomedical or physiological applications. Relevance Many medical devices and products come into contact with the internal surfaces of the body, such as surgical tools and implants. When a non-native material enters the body, the first step of the immune response takes pla

Supported lipid monolayers for the investigation of specific interactions between proteins and ligands

In this work, the specific and nonspecific binding of proteins to planar surfaces was investigated. The surfaces were first modified by the spontaneous adsorption of a number of synthesized 1,2-diacyl-sn-glycero-3-phosphatidylcholine lipids with different ω-mercapto fatty acids. The influence of packing density, order, fluidity, and mobility of the head groups of these supported thiolipid monolayers on the nonspecific adsorption of proteins was systematically investigated. Nonspecific binding of fibrinogen, IgG, BSA, and rabbit serum to such surfaces was monitored on-line by surface plasmon resonance spectroscopy (SPR) and was found to be exceptionally low. Characterization of the supported thiolipid monolayers by grazing incidence infrared spectroscopy, wetting, impedance spectroscopy, calorimetry, and SPR indicates that protein adsorption is influenced by the nature of the fatty acids and suggests that besides the molecular structure of the layer-forming molecules, other supramolecular aspects such as flexibility of the immobilized lipid layer or protrusion of the lipid head groups play a role. These investigations point the way for the construction of even more highly protein repellent surfaces with potential technical applications in the medical (implants) and diagnostic fields (biosensors). To investigate specific protein-surface interactions, acetylcholine containing ligand molecules of the general molecular structure HS(CH2)15(CO)O(CH2CH2O)nCH2(CO)OCH2CH2N+(CH3)3 X- (n = 4, 6, 13) were synthesized. They allow acetylcholine, the natural agonist of the acetylcholine receptor, to be covalently immobilized on a surface. Mixed layers of thiolipids and ligand molecules were formed by self-assembly on planar gold substrates and specific interactions between the immobilized acetylcholine and the nicotinic acetylcholine receptor (nAchR) from Torpedo Californica have were investigated on-line by SPR. Though it seems that the receptor binds specifically, bound receptor could be only partially displaced from the surface by excess free ligand. However, further improvement of the sensor surfaces will surely provide in the future a powerful tool for the investigation of membrane proteins and transmembrane communication.

EPFL1997

Adsorptive Removal of Pb(II) and As(V) from Aqueous Solution by PVDF/HMO Ultrafiltration Mixed Matrix Membrane

Younes Lucas Seghrouchni

Lead and arsenic are among the designated chemicals of major concern by the World Health Organization, they affect millions of people worldwide with both acute and chronic effects on human health. In the current study, mixed matrix membranes (MMMs) were fabricated using polyvinylidene fluoride (PVDF) for the matrix and hydrous manganese dioxide nanoparticles to remove lead, Pb(II), and arsenic, As(V), form water. The objectives of the study were to fabricate membrane with HMO:PVDF ratios from 0 to 1 and to characterize their adsorption properties on the two metals and their filtration performances. The HMO nanoparticles were synthesized using manganese sulfate monohydrate and potassium permanganate. The membranes were fabricated using phase inversion, a dope solution was prepared with HMO:PVDF ratios between 0 and 1, NMP as a solvent at an NMP:PVDF ratio of 5.57 and PVP at a PVP:PVDF ratio of 0.1 to increase the permeance of the membranes. The dope solution was casted and then soaked in a water coagulation bath for phase inversion. The structure of the nanoparticles was observed using TEM, and the structure of the membranes was described using SEM. The adsorption tests assessed the adsorption capacity, the adsorption kinetic and the effect of the pH on the adsorption capacity for the two metals. The concentration in the samples was measured with ICP-OES. A FTIR analysis was performed as a proof of adsorption. The tests that were run to assess the filtration performance of the membranes were the following ones: pure water permeance test, hydrophilicity test, surface analysis using XPS, pore size with AFM and finally filtration capacity on lead and arsenic. The HMO particles that were produced had sizes in the nanometer range and were elongated, which provided them a large surface-to-volume ratio. The membranes had asymmetric structures and the membrane with large HMO ratios had the surface of their pores covered uniformly with HMO particles. The adsorption capacities of pure HMO particles were 36 [mg/g] for arsenic and 283 [mg/g] for lead. The adsorption capacity of the membranes with an HMO:PVDF ratio of 1 was 11 [mg/g] for arsenic and 146 [mg/g] for lead. The Freundlich isotherm was used to describe the adsorption capacity of the membranes for both lead and arsenic. The adsorption kinetic was described by a pseudo-second order kinetic model for arsenic and the results were not significant enough the assess the adsorption kinetic model for lead. The equilibrium was almost reached in 30 minutes for the adsorption of the two metals on pure HMO. The adsorption capacity was enhanced with increasing pH for lead adsorption and it was the opposite for arsenic adsorption. The sensitivity to the pH was higher for lead compared to arsenic and this sensitivity to the pH could be used to regenerate the membrane in case of lead adsorption. The average permeance of the membranes was around 1500 [L/m2h bar], the pore sizes were in the ultrafiltration range, between 41 [nm] and 70 [nm] and the membranes were in the hydrophilic range, with an average contact angle of 69 [°]. The HMO ratio in the membranes had a limited impact on these three parameters. The filtration capacity on arsenic was too low to remove arsenic at ppb concentrations and the results of this test on lead were not significant enough to be interpreted.

2018

Selective Adsorption of Proteins on Single-Wall Carbon Nanotubes by Using a Protective Surfactant

Anton Knyazev

The dispersion of highly hydrophobic carbon materials such as carbon nanotubes in biological media is a challenging issue. Indeed, the nonspecific adsorption of proteins occurs readily when the nanotubes are introduced in biological media; therefore, a methodology to control adsorption is in high demand. To address this issue, we developed a bifunctional linker derived from pyrene that selectively ena-bles or prevents the adsorption of proteins on single-wall carbon nanotubes (SWNTs). We demonstrated that it is possible to decrease or completely suppress the adsorption of proteins on the nanotube sidewall by using proper functionalization (either covalent or noncovalent). By subsequently activating the functional groups on the nanotube derivatives, protein adsorption can be recovered and, therefore, controlled. Our approach is simple, straightforward, and potentially suitable for other biomolecules that contain thio or amino groups available for coupling.

2011

Supported lipid monolayers for the investigation of specific interactions between proteins and ligands

EPFL1997

Adsorptive Removal of Pb(II) and As(V) from Aqueous Solution by PVDF/HMO Ultrafiltration Mixed Matrix Membrane

Younes Lucas Seghrouchni

2018