Congratulations to Fabio Marcuccio on this fantastic output from a highly successful virtual secondment with The Edwards Lab at the University of Arkansas. The paper, published in the American Chemical Society’s ACS Nanoscience journal, demonstrates a new mechanism for increasing translocation signals. It’s an important contribution to the scientific development of nanopore sensing.
Solid-state nanopores have been widely employed in the detection of biomolecules, but low signal-to-noise ratios still represent a major obstacle in the discrimination of nucleic acid and protein sequences substantially smaller than the nanopore diameter. The addition of 50% poly(ethylene) glycol (PEG) to the external solution is a simple way to enhance the detection of such biomolecules. Here, the authors demonstrate with finite-element modeling and experiments that the addition of PEG to the external solution introduces a strong imbalance in the transport properties of cations and anions, drastically affecting the current response of the nanopore. In addition, they show that the strong asymmetric current response is due to a polarity-dependent ion distribution and transport at the nanopipette tip region, leading to either ion depletion or enrichment for few tens of nanometers across its aperture. They evidence that a combination of the decreased/increased diffusion coefficients of cations/anions in the bath outside the nanopore and the interaction between a translocating molecule and the nanopore–bath interface is responsible for the increase in the translocation signals. By suggesting that tuning the diffusion coefficients of ions could enhance the sensitivity of the system, this new mechanism contributes to further developments in nanopore sensing
Phenomenal work from our fabulous Fabio!