Modification of a Supported Lipid Bilayer by Polyelectrolyte Adsorption

Abstract

Addition of a weak polyelectrolyte, poly(methacrylic acid) (PMA), to a supported phospholipid bilayer made from 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) depresses the melting temperature and alters the morphology of the bilayer in the gel phase. Ellipsometry measurements show that PMA adsorption lowers the phase transition temperature by 2.4 degrees C. Atomic force microscopy (AFM) showed no visible contrast in the fluid phase (above the melting temperature) but a rich morphology in the gel phase. In the gel phase, adsorption leads to formation of significantly less mobile phospholipid islands and other defects. One consequence of this lower mobility is a decrease in the implied cooperativity number of the phase transition, N, when polymer is added. Additionally, AFM images of the gel-phase bilayer show a highly defected structure that anneals significantly more slowly than in the absence of adsorbed polymer. Tentatively, we suggest that PMA preferentially decorates island and defect edges of the DMPC bilayer.

Oligonucleotide Adsorption Affects Phase Transition but Not Interdigitation of diC14-Amidine Bilayers

“…38,39 As discussed in the previous section, polyelectrolyte adsorption can decrease phase transition cooperativity due to the formation of domains. 40,41 This effect might be further enhanced considering that, at the saturating ODN concentration used here ( Figure 2B), there are negatively charged unbound phosphate groups at the bilayer surface, strongly attached to the membrane by adsorbed ODN moieties. The electrostatic repulsion between these negative overhangs could be responsible for the early start of the bilayer gel−fluid transition as well as contribute to the substantial decrease in its cooperativity.…”

Molecular Motion at Soft and Hard Interfaces: From Phospholipid Bilayers to Polymers and Lubricants

“…The adsorption and biology communities have focused on the extreme limits-the polymer side of the interface in the adsorption community, and the practical consequences, especially when membranes are disrupted, in the biology community. In fact, recent studies of surface equilibration dynamics at supported phospholipid bilayers www.annualreviews.org • Soft and Hard Interfaces ANRV308-PC58-13 ARI 28 October 2006 16:29 find patterns of dynamic physical behavior that differ remarkably from what is characteristic of adsorption onto frozen surfaces (51,(55)(56)(57)(58)(59). This has bearing not only from biological and biophysical standpoints (60), but also for formulating many cosmetics and pharmaceutical products (61).…”

Physico-chemical Studies on the Interaction of Dendrimers with Lipid Bilayers. 1. Effect of Dendrimer Generation and Liposome Surface Charge

“…This class of dendrimers can cause bilayer disruption easily and their activities are generation dependent 21,24 . Biocompatibilities of PAMAM dendrimers have encouraged several research groups to study their effect on lipid bilayers 27 31 .…”