Effect of CNT Length on Channel Formation in Lipid Bilayers

Artificial channels that transport substances across cell membranes are being actively studied for analytical techniques, drug delivery, and other applications. One example is carbon nanotubes (CNTs), tubular carbon materials with diameters in the nanometer range, whose hollow structure allows ions and small molecules to pass through easily. When single-walled CNTs are cut to lengths of several to several tens of nanometers (ultrashort CNTs, US-CNTs) and coated with phospholipids, they can spontaneously insert into cell membranes and artificial lipid bilayers. Furthermore, US-CNTs have attracted attention as artificial ion channels whose mechanical and chemical properties can be modified to control their permeability. The principle of US-CNTs forming channels in lipid bilayers has been investigated by molecular dynamics simulations, although this has seldom been examined experimentally. In this work, we estimated the channel-forming ability of US-CNTs by measuring the channel current signals of CNTs with different length distributions. The channel current signal pattern was found to differ depending on the length distribution, suggesting that length affects the ability of CNTs to form channels in membranes.