title: Interactions of hyaluronan layers with similarly charged surfaces: the effect of divalent cations.
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 ≈ 10(6) Da) covalently attached to a planar silica surface, both across pure water and following the addition of 1 mM MgCl2. 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 MgCl2, 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(2+) 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.
authors.affiliation: State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, China University of Petroleum , 66 Changjiang West Road, Qingdao, Shandong 266580, P. R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
authors.forename: Simon
authors.initials: S
authors.lastname: Titmuss
authors.forename: Jacob
authors.initials: J
authors.lastname: Klein
mesh_terms: D002412:Cations / Q000737:chemistry; D003102:Colloids / Q000737:chemistry; D006820:Hyaluronic Acid / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010316:Particle Size; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D002412:Cations; D003102:Colloids; D012822:Silicon Dioxide; D006820:Hyaluronic Acid; D008274:Magnesium