Irreversible adsorption of latex particles on fibrinogen covered mica

Abstract

Physicochemical properties of bovine plasma fibrinogen (Fb) in electrolyte solutions were characterized. These comprised the diffusion coefficient (hydrodynamic radius), determined by the DLS method, electrophoretic mobility and the isoelectric point. The hydrodynamic radius of Fb was 12 nm for pH < 5. The number of uncompensated (electrokinetic) charges on the protein N c was calculated from the electrophoretic mobility data. It was found that for pH < 5.8 the electrokinetic charge was positive, independently of the ionic strength and negative for pH > 5.8. For pH = 3.5 the value of N c , was 26 for 10 −3 M. Similar electrokinetic measurements were performed for the mica substrate using the streaming potential cell. It was shown that for pH = 3.5 and 10 −3 M, the zeta potential of mica remained negative (−50 mV). This promoted an irreversible, electrostatically driven adsorption of Fb, which was confirmed in experiments carried out under diffusion-controlled transport. The surface concentration of Fb on mica was determined directly by AFM counting. By adjusting the time of adsorption, Fb monolayers of desired coverage were produced. Independently, the presence of Fb on mica was determined quantitatively by the colloid enhancement method, in which negatively charged latex particles were used, having the diameter of 800 nm. It was found that for Fb coverage below 0.05 the method was more sensitive than other indirect methods. The experimental data obtained in latex deposition experiments were adequately interpreted in terms of the random site model used previously for polyelectrolytes. It was shown that adsorption sites consisted of a cluster of Z. Adamczyk ( ) · M. Nattich · M. Wasilewska

Deposition of colloid particles on protein layers: Fibrinogen on mica

“…These effects can be properly analyzed in terms of the charge fluctuation theory previously developed to interpret particle deposition on surfaces covered by polyelectrolytes [36,37] and fibrinogen molecules [23]. In a recent work [26], this approach was exploited to interpret the influence of ionic strength on silica particle deposition rates on polyelectrolyte-covered silica surfaces.…”

“…Knowing the a parameter one can calculate the maximum coverage of latex particles on a heterogeneous surface covered by sites from the analytical dependence [23,41] modified in this work to account for the fact that H mx is a variable, rather than a constant.…”

“…The technique, referred sometimes to as the colloid enhancement (CE) [23], consists in unspecific deposition of larger colloid particles onto protein monolayers. This enables one to determine a functional relationship between the amount of adsorbed protein and the amount of adsorbed colloid, which can be assessed quantitatively via microscopic counting.…”

Zeta Potential of Beta Zeolites: Influence of Structure, Acidity, pH, Temperature and Concentration

“…Zeolites and metal-modified zeolites are widely used in industry, since they exhibit shape selectivity, their acidity can be tuned without changing the morphology and furthermore they can be easily regenerated and reused. Although, several publications can be found on zeta potential and surface charge measurements of aluminosilicates and zeolites [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ], there is still a need for systematic information on the effect of support acidity [ 9 ] or temperature on the zeta potential.…”

“…Zeta potential measurements have been reported for several types of aluminosilicates, such as mica [ 10 , 11 ], muscovite [ 12 ], montmorillonite [ 13 , 14 , 15 ], zeolite Y [ 16 ], ZSM-5 [ 6 ], beta-zeolite [ 6 , 9 ], silicalite [ 9 , 17 ], bentonite [ 18 ], chlorite [ 19 ], kaolinite [ 13 , 20 , 21 , 22 , 23 ], kaolin [ 24 ], pyrophyllite, [ 25 ] and albite [ 26 ]. Additionally, electrophoretic surface charge was reported for attapulgite [ 27 ], electrophoretic mobility for montmorillonite [ 28 ], palygorskite [ 29 ] and bentonite [ 30 ], as well as surface charge for montmorillonite [ 31 ] and natural zeolite [ 32 ].…”