Issue 5, 2014

Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration

Abstract

Charge-driven bridging of nanoparticles by macromolecules represents a promising route for engineering functional structures, but the strong electrostatic interactions involved when using conventional polyelectrolytes impart irreversible complexation and ill-defined structures. Recently it was found that the electrostatic interaction of silica nanoparticles with small globular proteins leads to aggregate structures that can be controlled by pH. Here we study the combined influence of pH and electrolyte concentration on the bridging aggregation of silica nanoparticles with lysozyme in dilute aqueous dispersions. We find that protein binding to the silica particles is determined by pH irrespective of the ionic strength. The hetero-aggregate structures formed by the silica particles with the protein were studied by small-angle X-ray scattering (SAXS) and the structure factor data were analyzed on the basis of a short-range square-well attractive pair potential (close to the sticky-hard-sphere limit). It is found that the electrolyte concentration has a strong influence on the stickiness near pH 5, where the weakly charged silica particles are bridged by the strongly charged protein. An even stronger influence of the electrolyte is found in the vicinity of the isoelectric point of the protein (pI = 10.7) and is attributed to shielding of the repulsion between the highly charged silica particles and hydrophobic interactions between the bridging protein molecules.

Graphical abstract: Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration

Supplementary files

Article information

Article type
Paper
Submitted
11 Sep 2013
Accepted
05 Nov 2013
First published
14 Nov 2013

Soft Matter, 2014,10, 718-728

Bridging interactions of proteins with silica nanoparticles: The influence of pH, ionic strength and protein concentration

B. Bharti, J. Meissner, S. H. L. Klapp and G. H. Findenegg, Soft Matter, 2014, 10, 718 DOI: 10.1039/C3SM52401A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements