Recombinant Albumin Monolayers on Latex Particles

Abstract

The adsorption of recombinant human serum albumin (rHSA) on negatively charged polystyrene latex micro-particles was studied at pH 3.5 and the NaCl concentration range of 10(-3) to 0.15 M. The electrophoretic mobility of latex monotonically increased with the albumin concentration in the suspension. The coverage of adsorbed albumin was quantitatively determined using the depletion method, where the residual protein concentration was determined by electrokinetic measurements and AFM imaging. It was shown that albumin adsorption was irreversible. Its maximum coverage on latex varied between 0.7 mg m(-2) for 10(-3) M NaCl to 1.3 mg m(-2) for 0.15 M NaCl. The latter value matches the maximum coverage previously determined for human serum albumin on mica using the streaming potential method. The increase in the maximum coverage was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. These facts confirm that albumin adsorption at pH 3.5 is governed by electrostatic interactions and proceeds analogously to colloid particle deposition. The stability of albumin monolayers was measured in additional experiments where changes in the latex electrophoretic mobility and the concentration of free albumin in solutions were monitored over prolonged time periods. Based on these experimental data, a robust procedure of preparing albumin monolayers on latex particles of well-controlled coverage and molecule distribution was proposed.

Mechanism of immunoglobulin G adsorption on polystyrene microspheres

“…This suggests that IgG adsorption on latex particles proceeds according to the adsorption mechanism, characterized by a significant contribution of head-on orientations. This behavior was previously observed for fibrinogen [26,27] and rHSA adsorption at latex particles [28].…”

“…3. In each case,the zeta potential increases with the IgG coverage and As previously done for fibrinogen [26,27] and rHSA [28], the experimental datapresented in Fig. 3 were interpreted in terms of the mean-field Gouy-Chapman model and the three-dimensional (3D) model.According to the GC model,the net charge density of the latex covered by IgG can be calculated from the formula [31,37,38] σ= σ 0 + q e (Av/M w ) Γ…”

“…The IgG deposition on particleswas carried out according to the procedurebefore used for recombinant albumin(rHSA) [28] and fibrinogen [26,27]: …”

“…(6) is valid for spherical particles in the low zeta potentials limit. On the other hand, in the limit of thin double layers where κd H < 1, the charge can be calculated from the following equation valid for arbitrary shape of particles [28,37] e q  3…”

“…It should be mentioned that this method has been before used to determine adsorption mechanism of fibrinogen [26,27] and albumin [28] on latex particles.…”