Biomimetic Membranes with Aqueous Nano Chanels but without Proteins: Impedance of Impregnated Cellulose Ester Filters

Abstract

Earlier we have shown that many important properties of ionic aqueous channels in biological membranes can be imitated using simple biomimetic membranes. These membranes are composed of mixed cellulose ester-based filters, impregnated with isopropyl myristate or other esters of fatty acids, and can be used for high-throughput drug screening. If the membrane separates two aqueous solutions, combination of relatively hydrophilic polymer support with immobilized carboxylic groups results in the formation of thin aqueous layers covering inner surface of the pores, while the pore volume is filled by lipid-like substances. Because of these aqueous layers biomimetic membranes even without proteins have a cation/anion ion selectivity and specific (per unit of thickness) electrical properties, which are similar to typical properties of biological membranes. Here we describe frequency-dependent impedance of the isopropyl myristate-impregnated biomimetic membranes in the 4-electrode arrangement and present the results as Bode and Nyquist diagrams. When the membranes are placed in deionized water, it is possible to observe three different dispersion processes in the frequency range 0.1 Hz to 30 kHz. Only one dispersion is observed in 5 mM KH(2)PO(4) solution. It is suggested that these three dispersion features are determined by (a) conductivity in aqueous structures/channels, formed near the internal walls of the filter pores at high frequencies, (b) dielectric properties of the whole membrane at medium frequencies, determined by polymer support, aqueous layers and impregnating oil, and, finally, (c) by the processes in hydrated liquid crystal structures formed in pores by impregnating oil in contact with water at low frequencies.

Nonlinear dynamics of ion concentration polarization in porous media: The leaky membrane model

“…Relaxing these assumptions and deriving suitable modifications of the model provide challenging avenues for research. For example, charge regulation in a multicomponent electrolyte due to specific adsorption of ions is a classical source of nonlinearity, which in leaky membrane can lead to OLC by “current‐induced membrane discharge.” The LMM with charge regulation could have relevance for electrokinetic remediation in soils, as well as ion transport in biological cells and membranes . The dynamics of charged colloids in leaky membranes may also lead to interesting nonlinear dynamics, generalizing shock waves in capillary electrophoresis .…”

“…Assuming fast adsorption kinetics, the LMM then closely resembles Amundson's classical models of exchange beds of the form (1), except that the LMM also accounts for the electrokinetic coupling between ion adsorption via the macroscopic charge balance (4). The LMM with charge regulation could also be applied to biological membranes, for example, in nerve cells, or biomimetic membranes with distinct surface and bulk transport phases . In these situations, polymeric ion‐exchange membranes, or electroactive gels, it could also be important to account for the deformation of the solid matrix in response to electrochemical transport, but here we focus on rigid porous media, such as the glass frit in Figure .…”

Interactions of Surfactants with Biomimetic Membranes. 1. Ionic Surfactants

“…A potentiostat/galvanostat Autolab PG‐Stat (Metrohm‐Autolab, Utrecht, Netherlands) with a frequency response analyzer was used to conduct electrochemical measurements, though all of them, except for frequency effects, could be done with a simple multimeter. Both the membrane and experimental details were described elsewhere (Kocherginsky et al, 1987; Kocherginsky et al, 1996; Kocherginsky and Lvovich, 2010).…”

Aquaporin, forward osmosis and biomimetic membranes

“…It is much easier and cheaper to make biomimetic membranes, which are based on simple nitrocellulose filters impregnated with esters of fatty acids (Kocherginsky et al 1984(Kocherginsky et al , 1987(Kocherginsky et al , 1996Kocherginsky and Lvovich 2010). The pore volume in this case is filled with oils, but still water enters the filters and covers internal surface of pores.…”