Supplementary Information
Anintegrated current measurement system for nanopore analysis
Rui Gao1,Yi-Lun Ying1, Bing-Yong Yan2*, Yi-Tao Long1*
1 Key Laboratory for Advanced Materials & Department of Chemistry, East China University of Science and Technology, Shanghai 200237, China
2 School of Information Science and Engineering,East China University
ofScience and Technology, Shanghai 200237, China
* Correspondence author:;
EXPERIMENTAL SECTION
- Materials
α-Hemolysin and decane (≥99%) were purchased from Sigma-Aldrich (St.Louis, MO). 1,2-diphytanoly-sn-glycero-3-phosphocholine (chloroform, ≥99%) was purchased from Avanti Polar Lipids (Alabaster, AL, USA). Ultrapure water (to reach a resistivity of 18.2 MΩ·cm at 25 oC) obtained by the Milli-Q System (EMD Millipore, Billerica, MA, U.S.A.). Buffer solution (1 M KCl, 10 mM Tris-HCl, 1 mM EDTA, pH 8.0) was prepared before use. Unless otherwise noted, all other chemicals were of analytical grade.
- Methods
Biological Nanopore Experiments:1,2-diphytanoly-sn-glycero-3-phosphocholine in decane (30 mg mL-1) was applied to form a bilayer across a 150 μm orifice in a lipid bilayer chamber (Warner Instruments, Hamden, CT, USA) with buffer solution. A bilayer was deemed stable by monitoring the resistance and membranecapacitance. The solution of α-hemolysin was injected into the chamber and would assemble to form a hydrophilic channel in the bilayer. A pair of Ag/AgCl electrode was inserted into the two compartments, respectively. When theα-hemolysin self-assembly successes, the ionic current would make a step change from 0 pA to the open current.
Solid-state nanopore experiments: A low-stress Si3N4membrane, with a window area of 0.5 mm2and 100-nm thick, is deposited on a silicon chip fabricated by lithography and wet etching processes. Then the Si3N4membrane is used to fabricate a solid-state nanopore with the diameter smaller than 30 nm. The focused ion beam (FIB) operated in FEI Helios 600i is used during the fabrication. The solid-state nanopore chip is treated in (3:1) H2SO4:H2O2for 30 min and activated in a plasmacleaner (Harrick Plasma, Ithaca, NY, USA) for 1 min prior to use. The membrane chip is packaged on a polymethylmethacrylate (PMMA) electrolyte chamber with the buffer solution. The platinum electrodes are used in a solid-state nanopore experiment.
Ionic current and power spectrum measurement:The ionic current of a nanopore experiment was recorded by the integrated current measurement systemat 100 kHz sampling rate. The noise power spectral density of the biological nanopore and the solid-state nanopore experiment was calculated via Fourier transform.