Stability and fusion of lipid layers on polyelectrolyte multilayer supports studied by colloidal force spectroscopy

Abstract

The interaction between lipid layers supported by polyelectrolyte multilayer cushions has been studied by means of colloidal force spectroscopy. In a typical experiment, a colloidal probe engineered with a layer-by-layer film and a lipid bilayer on top is approached to a planar surface coated in a symmetrical way. Kinks of a few nanometres in width appear when lipid layers are pressed together--reflecting either fusion processes between lipid layers or membranes, or the penetration of polymer blobs into or through the lipid layers. Retracting curves show a stepwise shape, which results from lipid tether formation or from polymer stretching, the latter suggesting that polyelectrolyte multilayers make contact as a result of penetration or lipid fusion.

Novel Engineered Ion Channel Provides Controllable Ion Permeability for Polyelectrolyte Microcapsules Coated with a Lipid Membrane

“…The flickery bis-gA opening (patch-clamp electrophysiology) indicated the possibility for simultaneous ionic conduction across multiple bilayers in the lipid-coated microspheres, which is a feature that can be exploited in the utilization of the system in a physiologically responsive drug release microcapsule. The existence of multiple bilayers, especially for the case of PClipids, was suggested in the colloidal force spectroscopy studies from Kohler et al [31] Those colloidal force spectroscopy studies also suggested the possibility of incomplete lipid-covering over polyelectrolytes, especially with PC/cholesterol mixed bilayers as we have utilized in the present report. However, our diffusion experiments with lipid-coated microcapsules indicated that the lipid coating provided a good insulating seal.…”

“…An additional and intriguing aspect of variations in the kinetics of the gating of incorporated membrane-spanning bis-gA ion channels is the possibility to gain further insight into the mechanisms underlying instability in the lipid coating of polyelectrolyte supports. Measuring the kinetics of channel open/ close activity could be a valuable addition to techniques such as colloidal force spectroscopy [31] in enhancing an understanding of the mechanisms of interaction between lipid bilayers and polyelectrolyte supports. Notwithstanding, the microcapsule system that we report provides a platform for the development of a sealed microcontainer for drug delivery or smart sensing that can navigate in the physiological environment and be controlled with physiologically relevant stimuli.…”

“…However, our diffusion experiments with lipid-coated microcapsules indicated that the lipid coating provided a good insulating seal. When considered in the context of those colloidal spectroscopy studies, [31] the flickery behavior of the membrane-spanning bis-gA channels recorded with patch-clamp electrophysiology and our observations that the lipid coating effectively insulated the polyelectrolyte microcapsules lends support to the existence of multiple bilayers distributed in patches over the microcapsules. It is also intriguing to consider that observations of the kinetics of opening of incorporated membrane-spanning ion channels, combined with techniques such as colloidal force spectroscopy, can provide additional insights into the stability of lipid coatings on a polyelectrolyte support.…”

“…The open/close kinetics of membranespanning ion channels may assist in answering questions about how the polyelectrolyte support modifies the structure and dynamics of lipid layers compared to free membranes. [31] www.afm-journal.de …”

Lipid layers on polyelectrolyte multilayer supports

“…Furthermore, lipid layers can be formed on polyelectrolyte multilayer coated colloidal particles. [25][26][27] This brings a considerable advantage over the use of flat macroscopic surfaces because powerful particle-based experimental techniques such as flow cytometry (FACS) can be applied.…”