Human Fibrinogen Monolayers on Latex Particles: Role of Ionic Strength

Abstract

The adsorption of human serum fibrinogen on polystyrene latex particles was studied using the microelectrophoretic and concentration depletion methods. Measurements were carried out for pH 3.5 and an ionic strength range of 10(-3) to 0.15 M NaCl. The electrophoretic mobility of latex was determined as a function of the amount of adsorbed fibrinogen (surface concentration). A monotonic increase in the electrophoretic mobility (zeta potential) of the latex was observed, indicating a significant adsorption of fibrinogen on latex for all ionic strengths. No changes in the latex mobility were observed for prolonged time periods, suggesting the irreversibility of fibrinogen adsorption. The maximum coverage of fibrinogen on latex particles was precisely determined using the depletion method. The residual protein concentration after making contact with latex particles was determined by electrokinetic measurements and AFM imaging where the surface coverage of fibrinogen on mica was quantitatively determined. The maximum fibrinogen coverage increased monotonically with ionic strength from 1.8 mg m(-2) for 10(-3) M NaCl to 3.6 mg m(-2) for 0.15 M NaCl. The increase in the maximum coverage was interpreted in terms of the reduced electrostatic repulsion among adsorbed fibrinogen molecules. The experimental data agree with theoretical simulations made by assuming a 3D unoriented adsorption of fibrinogen. The stability of fibrinogen monolayers on latex was also determined in ionic strength cycling experiments. It was revealed that cyclic variations in NaCl concentration between 10(-3) and 0.15 M induced no changes in the latex electrophoretic mobility, suggesting that there were no irreversible molecule orientation changes in the monolayers. On the basis of these experimental data, a robust procedure of preparing fibrinogen monolayers on latex particles of well-controlled coverage was proposed.

KfrA plasmid protein monolayers on latex particles-electrokinetic measurements

“…2 ). The analogous increase in the maximum coverage on latex particles with NaCl concentration was previously reported for fibrinogen [ 19 ].…”

“…The stock suspension of the latex, having solid content of 8.1%, was diluted to 240 mg L −1 (0.024%) prior to the KfrA adsorption. The residual concentration of the protein after adsorption on latex was determined via the concentration depletion procedure previously used for fibrinogen adsorption studies [ 19 ]. Briefly, the method was as follows: the latex particle suspensions, after the KfrA adsorption step, were transferred to the diffusion cell.…”

“…These procedures were successfully used in Ref. [ 19 ] to determine the maximum coverage of fibrinogen on latex.…”

The clinical relevance of altered fibrinogen packaging in the presence of 17β-estradiol and progesterone

“…It contain three pairs of polypeptide chains (Aα, Bβ and γ polypeptides) which are curved into a central E-region with two distal D-regions [43,44] (see Figure 8). Fibrinogen orientation is influenced by fibrinogen concentration [45,46] as well as the surface charge [47]. At high fibrinogen concentrations and negatively charged surfaces the molecules tend to stand on the surface in an end-on fashion rather than in a side-on manner [45][46][47] (see Figure 9).…”

“…Fibrinogen orientation is influenced by fibrinogen concentration [45,46] as well as the surface charge [47]. At high fibrinogen concentrations and negatively charged surfaces the molecules tend to stand on the surface in an end-on fashion rather than in a side-on manner [45][46][47] (see Figure 9). Hydrophobicity has a direct correlation to the degree of conformational alterations [48,49].…”