Ion transport through ion bio-channels confined inside nanopores: a combined theoretical and experimental project – TRANSION

Partner 1 aims at making micro-devices with 2 micro reservoirs separated by a wall including a single or several CNTS. different methods for CNT growth on Si substrat are used. Besides, micro-lithography in clean room is used to build the micro-device. CNT are characterised by Raman and ionic conductivity of the microdevice is measured using Patch-Clamp technique.
Partner 2 makes single or multi nanopore polymeric or inorganic (SiN). Nanopores are obtained with ion or electron beams and etching techniques. Membrane conductivity is also measured via the Patch-Clamp technique. IBC confinement in nanopore is followed by fluorescence spectroscopie.
Partner 3 develops analytical models based on transport and electro transport equations.
Partner 4 investigates our nanopore/IBC systems via all atom numerical simulation using supercomputer. Molecular dynamics and Monte Carlo technics are used.

P1 Fabrication of the µ-devices has been optimised in order to improve structural stability/durability of the system and the clogging of the CNT. The first results concerning the ionic conductivity are expected before the end of this year.
P2, P3 and P4. single nanopore membranes have been made. Atomic Layer Deposition has been used to control the diameter and the surface chemistry of the nanopore. Ionic conductivity showed very interesting resulting which can be fitted by the analytical model developed by P3 as a function of the ionic concentration. When gA is inserted at high concentration, it was shown that transport of H+ was blocked while K+ was not. An atomistic mechanism was proposed based on P4 simulation.

last work opens up new perspectives in term of research. Nanopores with more complex geometry (conical instrad of cylindrical) and with specific grafting treatment will be developped. Analytical models refinment could lead to the development of original non-linear models.

1. “Enhanced Potassium selectivity in Bioinspired Solid Nanopore membrane” F. Picaud, S. Kraszewski, Ch. Ramseyer, S. Balme, Ph. Déjardin, J.M. Janot & F. Henn , PhysicalChemistry ChemicalPhysics, 2013, 15 (45), 19601 – 19607
2. “Controlling potassium selectivity and proton blocking in a hybrid biological/solid-state polymer nanoporous membrane” Balme, S ; Picaud, F; Kraszewski, S; Dejardin, P; Janot, JM; Lepoitevin, M; Capomanes, J ; Ramseyer, C & Henn, F, Nanoscale 5(2013)3961-3968
3. Abou-Chaaya, A.; Lepoitevin, M.; Cabello-Aguillar, S.; Balme, S.; Bechelany, M.; Kraszewski, S.; Picaud, F.; Cambedouzou, J.; Balanzat, E.; Janot, J. M.; Thami, T.; Miele, P.; Dejardin, P., Enhanced Ionic Transport Mechanism by Gramicidin A Confined Inside Nanopores Tuned by Atomic Layer Deposition. J Phys Chem C 2013, 117 (29), 15306-15315.
4. Thiele, D.; Kraszewski, S.; Balme, S.; Picaud, F.; Janot, J.-M.; Déjardin, P., Structure and ionic selectivity of a hybrid polyene/artificial polymer solid state membrane. Soft Matter 2013, 9, 684-691.
5. Balme, S.; Thiele, D.; Kraszewski, S.; Picaud, F.; Janot, J. M.; Dejardin, P., Ionic selectivity of nystatin A1 confined in nanoporous track-etched polymer membrane. IET Nanobiotechnology 2014, 8 (3), 138 - 142.

Our project aims at confining Ion Bio-Channel (IBC) in two different solid-state nanopores and at investigating their functional properties in terms of ionic permeability and selectivity. In other words, our goal is to build hybrid artificial/biological nanoporous systems exhibiting exceptional ion transport properties. Our project combines two subjects:
(1) Synthesis of new artificial membranes
Recent advances in membrane science allow the use of membranes in many fields such as food and agriculture, potable water production, industrial water treatment, biotechnology,..etc. Among the newly developed technologies, nanofiltration for liquids is one of the most promising. In that domain, one of the scientific and technical challenges is to develop nanoporous membranes with both ion permeability and selectivity higher than those of the existing systems. New materials for nanofiltration membranes are thus clearly needed.
(2) Ion Bio-Channel
Ionic bio-channels (IBC) insure the in- and out-exchange of ions (Na+, K+, ..) across living cells. Their properties in terms of ionic transport are exceptional since they exhibit fast ionic conductivity, i.e. permeability, and, at the same time, high ionic selectivity. Unfortunately, the transfer of their unique properties to artificial systems with mechanical strength high enough to ensure their practical use in various applications has neither been realized, nor even proposed, yet.
Here, by coupling these two subjects, we propose to investigate at the nanoscopic levels completely new and potentially rich hybrid biological/solid-state nanoporous systems with both high ionic permeability and selectivity made of IBC confined inside cylindrical solid-state nanopores.
The IBC considered in this project will be gramicidin-A (gA), amphotericin-B (AmB) and nystatin (NYST). The investigated two solid-state nanoporous systems are: (i) a 5µm thick track-etched polymer film with cylindrical nanopores (CNP) whose diameter (phi) is about 10 nm or less and (ii) a microfluidic device incorporating an ultra-long, i.e. a few hundreds of µm, individual single wall carbon nanotube (SWCNT) (phi=1-3 nm).
In order to solve some of the scientific and methodological challenges associated with this project, a trans-disciplinary, i.e. biophysics/physics/chemistry, and trans-methodology (i.e. experiment/molecular simulation/analytical model) research consortium is proposed.