Interactions of Hyaluronan Layers with Similarly Charged
Surfaces: The Effect of Divalent
Cations
- Publication date
- Publisher
Abstract
We
used colloidal probe atomic force microscopy to measure the
normal forces between the surface of a silica colloidal particle and
a sparse layer of hyaluronan (hyaluronic acid, HA, MW β 10<sup>6</sup> Da) covalently attached to a planar silica surface, both
across pure water and following the addition of 1 mM MgCl<sub>2</sub>. It was found that in the absence of salt the HA layer repelled
the colloidal silica surface during both approach and retraction.
The addition of the MgCl<sub>2</sub>, however, changes the net force
between the negatively charged HA layer and the opposing negatively
charged silica surface from repulsion to adhesion. This interaction
reversal is attributed to the bridging effect of the added Mg<sup>2+</sup> ions. Our results provide first direct force data to support
earlier simulation and predictions that such divalent cations could
bridge between negative charges on opposing surfaces, leading to an
overall reversal of force from repulsion to attraction