Effects of symmetric and asymmetric salt conditions on a selective solid-state nanopore assay

Conventional solid-state nanopore measurements sense all translocating entities, necessitating meticulous analysis to differentiate target biomolecules. To address this, we have established a selective assay with the platform that has shown utility in quantifying several nucleic acid biomarkers. However, limited detection efficiency and intrinsic noise have so far limited assay resolution to 10 nM. Improvements in this value require manipulation of translocation dynamics. Here, we report the effects of NaCl conditions on assay performance. We first investigate symmetric conditions, finding sensitivity increases with salt concentration but selectivity is maximized at 1.0 M NaCl. We then probe asymmetric conditions, showing a remarkable impact on assay sensitivity and selectivity when measurement buffer NaCl concentration in the reservoir with the translocating molecules is low and the opposite reservoir is increased. Using optimum conditions, we demonstrate detection of target biomolecules down to a concentration of 100 pM which is an improvement of 2 orders of magnitude over past results.