Adsorption of proteins on spherical polyelectrolyte brushes in aqueous solution

Abstract

We consider the adsorption of bovine serum albumin (BSA) on spherical polyelectrolyte brushes (SPB). The SPB consist of asolid polystyrene core of 100 nm diameter onto which linear polyelectrolyte chains [poly(acrylic acid), (PAA)] are grafted. The adsorption of BSA is studied at a pH of 6.1 at different concentrations of added salt and buffer. We observe strong adsorption of BSA onto the SPB despite the effect that the particles as weil as the dissolved BSA are charged negatively. The adsorption of BSA is strongest at low salt concentration and decreases drastically with increasing amounts of added salt. Virtually no adsorption takes place at salt concentration of 0.1 M. Moreover, the adsorbed protein can be washed out again by raising the ionic strength from low to high values. A major driving force for the adsorption is located at a lower pH within the brush at low ionic strength. Thus, the isoelectric point of the protein may be approached or even reached. In this case strong interaction between the SPB and the protein results. Moreover, the negative charge of the polyelectrolyte interacts with the patches of positive charges on the protein. In this way the protein becomes a multivalent counterion within the brush and monovalent counterions will be released. All results demonstrate that the SPB present a new elass of colloidal carrier partieIes whose interaction with proteins can be tuned in a well-defined fashion.

Salt-induced protein resistance of polyelectrolyte brushes studied using fluorescence correlation spectroscopy and neutron reflectometry

“…23 . The Si wafers that served as solid support for planar PAA brushes were purchased from Siliciumbearbeitung Andrea Holm (Tann, Germany).…”

“…It has been found that the SPB particles bind huge w Presented at the annual meeting of the Deutsche Bunsen-Gesellschaft fu¨r Physikalische Chemie, Dresden, Germany, May 20-22, 2004. amounts of BSA under electrostatic repulsion at low ionic strength. 23 Moreover, BSA that is irreversibly adsorbed at low ionic strength can be desorbed from the SPB particles by rinsing with a 500 mM sodium chloride solution. This observation is rather unexpected, since the elevated ionic strength is shielding the direct electrostatic repulsion between BSA and the SPB particles.…”

“…18,21,22 In a recent study, the binding of bovine serum albumin (BSA) to spherical polyelectrolyte brush (SPB) particles was characterized. 23 The particles consist of a solid core of poly(styrene) (PS) onto which long linear poly(acrylic acid) (PAA) chains are grafted. 24,25 The adsorbed amount of protein was measured ex situ, i.e., in the absence of non-adsorbed protein.…”

pH-responsive aqueous/LC interfaces using SGLCP-b-polyacrylic acid block copolymers

“…[27][28][29][30] In order to test the sensing capability of the TEM grid cell for detecting proteins, small amounts of the lysozyme protein were dissolved in the aqueous phase at pH ¼ 12. Fig.…”

Elaboration of targeted nanodelivery systems based on colloidal polyelectrolyte complexes (PEC) of chitosan (CH)-dextran sulphate (DS)

“…Such high loading capacity can be explained by the diffusion of IgAs through the chitosan shell. This diffusion process can be understood by considering the protein as a multivalent counter-ion interacting with the ammonium groups of the shell, as suggested by Ballauff et al for spherical polyelectrolyte brushes [40] . The concomitant release of monovalent counter-ions induces an entropic gain that counter-balances the repulsive electrostatic interactions and steric hindrance.…”