Adsorption Kinetics Of Albumin Research Articles

Statics and Kinetics of Albumin Adsorption by Natural Zeolite

Statics and Kinetics of Albumin Adsorption by Natural Zeolite

Effect of the electrochemical characteristics of titanium on the adsorption kinetics of albumin.

An electrochemical quartz crystal microbalance (EQCM) was used to examine the electrochemical behaviour of pure titanium in phosphate buffered saline (PBS) and PBS-containing bovine serum albumin (BSA) solutions, and the associated adsorption characteristics of BSA under cathodic and anodic applied potentials. It was found that the electrochemical behaviours of bulk titanium substrate and titanium-coated QCM sensors are slightly different in PBS buffer solution, which is attributed to the difference in their surface roughness. The oxide film formed on the surface of the QCM sensor during potentiostatic tests was found to affect its electrochemical behaviour, while cathodic cleaning is not sufficient to have it removed. Lastly, the excessive amount of electrons on the titanium surface upon application of a cathodic potential could result in the desorption of BSA due to electrostatic repulsion and protein dehydration. In contrast, application of anodic potential charges the titanium surface positively and can facilitate protein adsorption when the surface is not saturated with protein.

Recombinant albumin adsorption on mica studied by AFM and streaming potential measurements

Recombinant human serum albumin (rHSA) in monomeric state is widely used in pharmaceutical industry as a drug excipient and for preparing coatings for medical devices. In this work the adsorption process of rHSA on model mica surface at pH 3.5 was studied using the atomic force microscopy (AFM) and in situ streaming potential measurements. The kinetics of albumin adsorption was determined by a direct enumeration of single molecules over various substrate areas. These results were consistent with streaming potential measurements carried out for the parallel-plate channel flow and with theoretical predictions derived from the random sequential adsorption (RSA) model. Desorption kinetics of albumin under flow conditions was also evaluated via the streaming potential measurements. In this way, the amount of irreversibly bound albumin was quantitatively evaluated to be 0.64 and 1.2mgm−2 for ionic strength of 0.01 and 0.15M, respectively. This agrees with previous results obtained for HSA and theoretical calculations derived from the RSA model. Additionally, it was demonstrated that there existed a fraction of reversibly bound albumin that can be fully eluted within a few hours. The binding energy of these fraction of molecules was −18kT that is consistent with the electrostatic controlled adsorption mechanism of albumin at this pH. It was concluded that the rHSA monolayers of well-defined coverage can find applications for quantitatively analyzing ligand binding and for performing efficient biomaterials and immunological tests.

Das Zetapotential informiert über die Proteinadsorption

The zeta potential supports the research on new biomaterials and provides information on the adsorption of proteins and other biomolecules on material surfaces. For macroscopic solids the zeta potential is determined from the measurements of the streaming potential. Applications of the zeta potential for the surface analysis of S-layers and the adsorption kinetics of albumin are demonstrated.

Study of albumin adsorption on ion beam irradiated polymer surfaces

The process of adsorption of human serum albumin has been studied for poly-hydroxy-methylsiloxane and poly-ethylene-terephtalate surfaces modified by 5 keV Ar+ irradiation. The adsorption kinetics of albumin has been investigated as a function of the modifications induced by irradiation of the two polymer surfaces. Fluorescence spectroscopy, X-ray photoelectron spectroscopy and contact angle technique, respectively, have been used to determine the adsorption kinetics and to characterize the chemical composition and the surface free energy of the irradiated surfaces. Two basic classes of adsorption kinetics were found in connection with two different adsorption mechanisms. The irradiation-induced effects have been seen to be able to change the type of the adsorption process from one class to the other one as a function of the total surface free energy modification.

Chromatographic study of the adsorption kinetics of albumin on monoclonal and polyclonal immunoadsorbents

High-performance liquid chromatography (HPLC) has been used to study the adsorption kinetics of proteins on immunoadsorbents. The adsorption rate constant of human serum albumin (HSA) on monoclonal and polyclonal anti-HSA antibodies immobilized on a silica HPLC support was determined by saturating the column with repeated pulse injections. Studies on polyclonal immunodsorbents of different capacities enable evaluation of the contribution of transport to the binding sites.

Effect of the Electrode Roughness on the Kinetics of Albumin Adsorption at a Rotating Disk Electrode Investigated by Double‐Layer Capacitance Measurements

The roughness effect on the kinetics of the adsorption of bovine serum albumin on a platinum or glassy carbon RDE is investigated by analyzing the roughness dependence on adjustable parameters involved in the equation of the calculated curve which fits the experimental curve. This experimental variation satisfies a two‐exponential law, which is consistent with a two‐step irreversible mechanism: . Thus, the adsorption kinetics can be quantified by the time‐constants of the two steps, and the adsorbed states are characterized by the double‐layer capacitance values of the interface covered with a monolayer of each adsorbate. Whatever the material investigated, a change of the electrode roughness, at constant potential, markedly affects the kinetics of both steps. In addition, the roughness conditions the adsorption mechanism, i.e., the structure of the two adsorbates. Two distinct mechanisms are indeed determined, the one occurring on smooth interfaces, and the other on rough interfaces, the former being slower and leading to stronger interactions between the electrode and the protein layer. Moreover, the role of roughness per se, investigated at constant electrical charge, corroborates that the kinetics are generally faster and the interactions weaker on rough interfaces.

Analysis and physical significancy of the kinetic parameters associated with albumin adsorption onto glassy carbon obtained by electrochemical impedance measurements

The kinetics of albumin adsorption onto a glassy carbon rotating disk electrode in a phosphate buffer, is reported from the time variations of the double-layer capacitance C d, of the charge transfer resistance R t and of the Tafel coefficient of the electrochemical reaction b; these three electrical quantities are determined by electrochemical impedance and faradaic current I measurements. The variations of C d, 1/ R t, b  ( R t I) −1 and I can be written under the form: α 0 + α 1 e − t/τ1 + α 2 e − t/τ2 , where α 0, α 1, α 2, τ 1, τ 2 characterize a given electrical quantity. We demonstrate that this type of variation validates a two-step adsorption mechanism already proposed, starting from simply taking into account C d( t). We analyze and discuss comprehensively various possibilities of interpreting the shifts between the time-constants associated with thevarious quantities as well as the correlations between these constants and those associated with physical adsorption phenomena.

Analysis and physical significancy of the kinetic parameters associated with albumin adsorption onto glassy carbon obtained by electrochemical impedance measurements

The kinetics of albumin adsorption onto a glassy carbon rotating disk electrode in a phosphate buffer, is reported from the time variations of the double-layer capacitance C d, of the charge transfer resistance R t and of the Tafel coefficient of the electrochemical reaction b: these three electrical quantities are determined by electrochemical impedance and faradaic current I measurements. The variations of C d, 1/ R t, b  ( R t I) −1 and I can be written under the form: α 0 + α 1 e − t/τ 1 + α 2 e − t/τ 2 , where α 0, α 1, α 2, τ 1, τ 2 characterize a given electrical quantity. We demonstrate that this type of variation validates a two-step adsorption mechanism already proposed, starting from simply taking into account C d( t). We analyze and discuss comprehensively various possibilities of interpreting the shifts between the time-constants associated with the various quantities as well as the correlations between these constants and those associated with physical adsorption phenomena.

Effect of the ionic strength of the supporting electrolyte on the kinetics of albumin adsorption at a glassy carbon rotating disk electrode

The effect of the ionic strength of the supporting electrolyte (phosphate buffer, pH = 7.4, xM + 10 −2 x M Fe(CN) 6K 4, 25°C, 10 −2 ⩽ x ⩽ 1) on the kinetics of the adsorption of bovine serum albumin at a glassy carbon rotating disk electrode ( rde) was investigated. The kinetics were determined by analysing the double-layer capacitance C d( t) variation during adsorption. The experimental variation obeys the following relationship: C d( t) = a 0 + Σ i a i exp(− t/τ i ) the number i of detectable exponential functions depending on ionic strength. The time-constants τ i are related to the kinetic parameters of the successive irreversible steps of the mechanism, and a 0, a i to the double layer capacitance for the various states of the interface (bare or entirely covered by the adsorbed protein in state i). All the calculated parameters depend on the ionic strength. The various effects are explained by three modifications induced by the ionic strength change, ie (i) a change of the electrical charge of the interface, (ii) a change of the electrical charge of the protein and (iii) a change of the diffuse double-layer thickness.

Kinetics of albumin and fibrinogen adsorption onto a rotating disk electrode: Effect of temperature, concentration and material

In a previous paper, the kinetics of albumin adsorption onto a platinum rotating disk electrode polarized at 75 mV/SCE were reported as measured by the variations of the double layer capacitance C d. The adsorption was found to consist of two steps. In the present work, a better characterization of these steps was attempted through a study of the concentration and temperature dependence of the adsorption of albumin and fibrinogen onto platinum and of fibrinogen onto carbon. As expected from the model, each of the two steps of the adsorption process displayed a specific reaction order and activation energy. The reaction orders of the first and second steps were found to be, respectively, 0.36 and 0 for albumin onto platinum, 0.44 and 0 for fibrinogen onto platinum, and 0.81 and 0.61 for fibrinogen onto carbon. In the case of albumin adsorption onto platinum, activation energies of 14.6 and 10.9 kJ mol −1 were calculated for the first and second step, respectively. The area of close contact between the adsorbed protein and the electrode was found to be significantly larger on carbon than platinum. Concerning albumin adsorption onto platinum, the bulk concentration dependence of the variation of C d suggests that proteins adsorb in a different conformation depending on their concentration in solution.

Adsorption kinetics of human plasma albumin on negatively charged hydroxyapatites. Surface charge effects

The influence of potential determining Ca 2+ or H 2PO − 4 ions (p.d.i.) on the adsorption kinetics of albumin on human enamel beads (HEB) or synthetic hydroxyapatite powder (HAP) was studied by the continuous recording of the excess interfacial protein concentration. Assuming a Langmuir model, adsorption ( k a), and desorption ( k d) rate constants and affinity constants K were calculated. Depending on the superficial charges, one or three ( k a, k d) pairs were necessary to fit the kinetic data over the whole adsorption range. An adsorption mechanism is proposed for the uptake of the negatively charged albumin molecules on apatite surfaces, as a function of their superficial charge increase.