Nanofluidic Ion and Molecule Transport in Boron Nitride Nanotube Porins

Biological membrane channels, which exhibit excellent efficiency and selectivity in ion and molecule transport, have sparked considerable interest in the development of their synthetic analogues. Numerous artificial nanochannels that can be integrated into lipid membranes have been designed and synthesized over the past decade, e.g., the remarkable one-dimensional carbon nanotube porins that exhibit exceptional nanofluidic transport properties. However, there is still a need to diversify the nanotube porin family to include nanochannels made of different materials that provide access to different geometries, surface properties, and electronic structure.<br/><br/>Here, we present the fabrication and nanofluidic transport studies of boron nitride nanotube (BNNT) porins. With the combination of liposome transport measurement and Cryo-EM imaging, we show that BNNT porins can insert into lipid membranes to form functional channels. Ion transport studies, which used the droplet interface bilayer setup, reveal distinct ion conductivity profiles and scaling behaviors at high ion concentrations. The ion transport also exhibits an inverted U-curve dependency on pH with the highest conductance at the neutral pH value. Reversal potential measurements suggest that BNNT porins have a high cation/anion selectivity. We attribute these observations to the strong ion interactions and pronounced surface adsorptions in the highly charged and extremely confined nanotubes. Furthermore, we present evidence of the ability of these BNNT porins to transport DNA molecules. Our findings position BNNT porins as a promising biomimetic platform for the investigation of nanofluidic transport and the development of membranes and biosensors.