Resolving Nitrogen Bases in Single Stranded DNA with Hexagonal Boron Nitride/ ALD TiO₂ Nanopores
Oviedo Robles, Juan Pablo
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Recent advances in the synthesis and quality of 2D materials within the last decade, such as graphene and MoS₂, have led to a new generation of solid state nanopore DNA sequencing devices with improved sub-nanometer spatial resolution. Among these, hexagonal boron nitride nanopores stand out, due to their excellent chemical stability and atomic layer thickness for identifying molecular features, such as nitrogen bases, by means of ionic current blockage patterns. By minimizing their suspended area to reduce 1/f noise, increasing their hydrophilicity through ALD titanium oxide coatings and UV-ozone treatments, and using viscosity gradients to decelerate DNA translocations across them, the spatiotemporal resolving power of hexagonal boron nitride nanopores has been successfully optimized down to the single nucleotide regime. Using these devices, it is shown that ssDNA translocations become sub-divided into concatenated saw-tooth pulse trains or “sub-translocations” of nitrogen bases, a pattern which can be described in terms of their characteristic blocked currents, dwell times, and sub-translocation slopes. These features provide critical information about a ssDNA analyte, such as its total number of nucleotides, their sub-translocation speed, and, under optimal conditions, can be matched to their corresponding nitrogen bases on a one-to-one basis. This research opens thus the tantalizing prospect of solid state nanopore sequencing enabled purely by the identification of ionic current patterns.