New-generation spacecraft water monitoring with flight-ready solid-state nanopores

Z. Xia
Goeppert LLC,
United States

Keywords: solid-state nanopore, ISS, water monitoring, aptamer


To provide a fast, simple and reliable way of identifying unwanted constituents present in the water systems aboard ISS and potentially other spacecraft (e.g., Artemis Gateway Outpost), we aim to develop a robust, portable and easy-to-use sensor system based on solid-state nanopore technology, a.k.a. SWAN. The current water monitoring capability in the ISS is only limited to electrical conductivity, total organic carbon and selected ions of iodine and silver. Any other analyte must be brought back to Earth. The maintenance of safe living conditions in ISS is important in order to support the scientific activities of the crew, and to ensure their unharmed return to Earth upon mission completion. The solid-state nanopore presents an inherent single-molecule sensor system that works on the principle of pore occlusion by the molecule which then can be registered as a change of the electrical current. Each analyte establishes its unique electrical signal upon passing through the nanopore of tailored characteristics. Here we reported the detection of mercury (Hg2+), lead (Pb2+) and silver ions (Ag+) using 2-5 nm- diameter and 20-nm thick nanopores at concentrations down to 5 nM, 0.5 nM and 5 nM, respectively, all of which are below EPA requirements and SWEGs. The detection was enabled by short DNA molecules (aptamers) as the carrier, that bind via specific interactions with metal ions. Furthermore, we continued to mature the sensor platform and successfully used it to detect diethyl phthalate (DEP), a desirable small organic analyte (~1 nm) to NASA for water monitoring purpose, without tedious sample prep and heavy use of organic solvents which are required in the typical mass spectroscopic methods on earth. This direct detection of the naked molecule is enabled by innovative ultrathin (~ 5 nm) and ultrasmall (~ 1.5 nm) nanopores. SWAN will allow the detection of low-concentration analytes in water and is thus a promising tool for a miniaturized analytical laboratory for future NASA missions, together with orthogonal analytical tools available. We observed distinct electrical translocation characteristics between these two metal ions, paving a path towards selective nanopore sensor for water monitoring purpose by identifying their “electrical fingerprints”.