Next gen sequencing – Nanopores

Since the advent of dideoxy sequencing method by Sanger, important biological data has accumulated explosively. Several automations  to this method, has made sequencing routine work in molecular biology research. But several new sequencing technologies do emerge in aim of reducing cost and time further. One such technology is Nanopore sequencing technology.

Nanopore is simply a hole and the internal diameter is in the order of 1 nanometer ranges. When two chambers containing different electrolyte concentrations are separated by a nanopore containing membrane a potential difference is formed between the two chambers. If this voltage is disrupted (say for example by blocking the pore), the resulting ionic current can be measured using standard techniques. Thus it was independently proposed by two researchers from University of California and University of Harvard, that the modulation of this current could also be done by electrophoretically driving a strand of DNA or RNA through a nanopore of appropriate diameter. If the internal diameter of the nanopore is approximately equal to a nucleotide of a ssDNA molecule, two important properties could be achieved.
1. The unraveling of coiled DNA upon mobilizing through the nanopore
2. Translocation of a single nucleotide in the nucleic acid molecule through the pore in sequential order

Due to the partial blockage of current through the nanopore upon nucleotide translocation, there is a relative reduction of ionic current compared to the current through the nanopore when it is empty. Thus each nucleotide in the nucleic acid molecule produced a unique current modulation upon passage through the nanopore. However several problems persist given the extraordinary ability of nanopores for sensing single molecules.

Solving all drawbacks, Oxford Nanopore technologies has introduced the world’s first miniaturized 900$ sequencing machine. It may be possible to sequence a whole human genome in just hours, which took 13 years less than a decade ago.


1. – The potential and challenges of nanopore sequencing