Single-Channel Measurements of Conductance through Sub-Nanometer Carbon Nanotube Porins

Abstract

Carbon nanotubes (CNTs) have narrow hydrophobic inner pores, highly reminiscent of protein channels, that enable fast transport of water and ions. Their rigid structure and chemical robustness allow for diverse ex vivo applications. We have recently reported biomimetic membrane channels cased on carbon nanotubes—carbon nanotube porins (CNTPs). We have shown that CNTPs self-insert into lipid membranes and form stable pores. In this study, we used electrophysiological single-channel measurements to quantify ion conductance and selectivity of 0.8 nm diameter CNTPs. We report the conductance of single CNTP channels, as well as the scaling of the conductance with the ion concentration. We also used the reversal potential measurements to characterize the selectivity of the ion transport and found that CNTPs are highly selective to cations over anions. We will discuss the mechanism of this selectivity, and demonstrate ways to control it. These findings are important and relevant for developing CNTPs into a potential candidate nanopore for water treatment applications. Our studies on intrinsic characterization of CNTP transport properties will also enable researchers to consider this new material for a variety of biophysical applications.