Ionic diffusion through a bio-inspired membrane

1. Introduction One of the scientific challenges in nanofiltration is to develop nanofilters with both high ion permeability and selectivity, which are often considered as antagonist features. Today, the number of solid state membranes that are readily useable is limited and their performances, i.e. ion permeability and selectivity, are restricted. New materials for nanofiltration are thus clearly requested. On the other hand, it is well known that biological ion-channels insure ionic (Na + , K + …) exchange of living cells and that their properties in terms of ionic permeability and selectivity are extremely high. Unfortunately, the transfer of these properties to artificial setup whose the mechanical strength is high enough to be useful in many different types of applications has not been achieved yet. So, the idea of combining nanoporous solid-state materials with biological ion channel appears as a scientific and technical challenge that could open new perspectives in nanofiltration. Recently [1], we report the first extremely encouraging results on insertion of the ion channel gramicidin A (gA) inside a nanoporous track-etched membrane. These primary results have demonstrated the feasibility for hybrid bio-inspired membrane made of a biological ion channel and a nanoporous polymer material. The next goal of our project is the enhancement of the hybrid membrane performances in term of ionic selectivity via optimization of the gA confinement inside the nanopores. In this paper, we report the results obtained when the experimental conditions used for the protein insertion are changed : solvent (water/methanol mixture) used for the insertion and temperature. Experimental results on ion diffusion and selectivity through the membrane are interpreted thanks to data obtained from molecular simulation. .