Rapid structural analysis of nanomaterials in aqueous solutions

Abstract

Rapid structural analysis of nanoscale matter in a liquid environment represents innovative technologies that reveal the identities and functions of biologically important molecules. However, there is currently no method with high spatio-temporal resolution that can scan individual particles in solutions to gain structural information. Here we report the development of a nanopore platform realizing quantitative structural analysis for suspended nanomaterials in solutions with a high z-axis and xy-plane spatial resolution of 35.8 ± 1.1 and 12 nm, respectively. We used a low thickness-to-diameter aspect ratio pore architecture for achieving cross sectional areas of analyte (i.e. tomograms). Combining this with multiphysics simulation methods to translate ionic current data into tomograms, we demonstrated rapid structural analysis of single polystyrene (Pst) beads and single dumbbell-like Pst beads in aqueous solutions.

Pore Structures for High-Throughput Nanopore Devices

“…Here, a phosphorus-doped Si wafer with 5 S/m and 137-mmol/L-PBS buffer were employed as a Si membrane and buffer solution, respectively, and an electrophoretic field of 100 mV was applied to the pore, utilizing two Ag/AgCl electrodes. The ionic current was detected at 1 MHz by employing a home-built current amplifier backed by a digitizer (NI-5922, National Instruments, Austin, TX, USA) and stored in a RAID hard drive (HDD-8265, National Instruments, Austin, TX, USA) under LabVIEW control [ 7 ]. Thereafter, 1 MHz ionic current–time data were finally compressed to 100 kHz and normalized at 0 A to compare the peak-to-peak noise level between the two ionic current data.…”

“…The chambers are filled with an electrolyte solution, and analytes dispersed in the cis chamber translocate to the trans chamber via a nanopore by electrophoresis ( Figure 1 a). Nanopore devices provide size and/or shape information for single analytes passing through a nanopore by probing temporal changes in the ionic current because an analyte excludes ions inside a nanopore during the translocation and causes an ionic current blockade with amplitudes proportional to its feature size [ 7 , 8 ]. Nanopore structures thus enable label-free sensing of single biomolecules and bioparticles by estimating the size and/or shape of the analytes passing through a nanopore from the pulsed ionic current blockades.…”

“…Properties of nanopore devices are often discussed with a simple equivalent circuit consisting of the R pore and the R acc in a series ( Figure 1 b). In this instance, each resistance can be described by where α is the resistivity of the buffer solution, h is the thickness of a nanopore, and D c is the diameter of a nanopore [ 7 , 14 ]. As R pore and R acc are in a series, a higher R pore compared to R acc causes more drastic potential drop inside a nanopore.…”

Analysis Method of the Ion Current-Time Waveform Obtained from Low Aspect Ratio Solid-state Nanopores

“…Multiphysics simulation has been used to reproduce the ion current-time waveform of low aspect ratio nanopores. [41][42][43][44][45] The results of streptococci with a connected form of cocci are illustrated in Fig. 6.…”

“…[38][39][40] The ion current-time waveform obtained with a low aspect ratio nanopore provides more information than that of a high aspect ratio pore, such as the volume, surface structure, surface charge, and flow dynamics of the analyte. [41][42][43][44][45] The analysis of these can complementary be made by the development of multiphysics simulation techniques with finite element methods. 46,47 In order to extract these four types of information from the waveform, it is necessary to analyze the vector quantities representing the waveform, not the scalar quantities of Ip or td.…”