Chemically-Tuned Solid-State Nanopores for Single-Molecule Biophyics

Abstract

Solid-state nanopores (SSNs) are nanofluidic conduits fabricated through synthetic materials such as silicon nitride, silicon dioxide, graphene, etc. Intrapore variations, temporal fluctuations in open-pore current and analyte sticking are legacy limitations associated with SSNs which have challenged its footprint in single molecule science. We report a modification to the Controlled Dielectric Breakdown (CDB) method of nanopore fabrication on silicon nitride (SiNx) membranes where a blend of electrolyte and sodium hypochlorite is used as the conducting solution. These chemically tuned SSNs are devoid of the fundamental challenges associated with SSNs. The change in surface chemistry, with ∼3 orders of magnitude weaker Ka compared to conventional CDB nanopores, is thought to be inextricably linked with the Ohmic nature, extremely stable open-pore current during analyte translocation (hours), minimum analyte sticking with self-correction of current signal (if analyte sticking causes current deviation) and higher analyte responsiveness. The transport phenomena through these chemically modified nanopores are successfully tested by translocating 1 kb dsDNA and the human serum transferrin (hSTf) protein, with the highlight being the yield of an excess of 200 thousand DNA translocation events. Moreover, a comprehensive noise analysis done for the low frequency regime of this new class of SSNs revealed interesting characteristics which are distinct from the conventionally fabricated SSNs.