Apparatuses and methods for determining analyte charge

Abstract

The present disclosure provides a sensor including a pore and an applied electric field that is capable of detecting analytes such as nucleic acids. In accordance with various embodiments, the sensor comprises a fluidic chamber having electrically opposing portions with a membrane between, the membrane providing a pore suitable for the passage of an electrolyte between the electrically opposing portions of the fluidic chamber, and having at least one charged analyte tethered in proximity to the pore, a first circuit configured to apply an electric field capable of passing the electrolyte through the pore and pulling the at least one charged analyte into the pore, and a second circuit configured to measure a signal indicative of the charge of the at least one charged analyte. Also provided are methods for using the sensor, for example, to sequence a nucleic acid molecule.

What is claimed is: 
     
         1 . A method for detecting a charged analyte, comprising:
 (a) providing a fluidic chamber comprising electrically opposing portions and a membrane between the electrically opposing portions, wherein one of the electrically opposing portions includes an electrolyte, wherein the membrane comprises a pore suitable for (i) flow of the electrolyte between the electrically opposing portions of the fluidic chamber, and (ii) flow of at least one charged analyte tethered in proximity to the pore into the pore;   (b) applying an electric field to direct the electrolyte through the pore and direct the at least one charged analyte into the pore; and   (c) measuring a signal indicative of a charge or change in charge of the at least one charged analyte upon the at least one charged analyte being directed into the pore.   
     
     
         2 . The method of  claim 1 , wherein in response to the electric field applied in (b), the at least one charged analyte is directed to a position in proximity to a periphery of the pore. 
     
     
         3 . The method of  claim 1 , wherein the membrane is a solid state membrane, and wherein the pore is formed in the solid state membrane. 
     
     
         4 . The method of  claim 1 , wherein the at least one charged analyte is tethered substantially concurrently with directing the at least one charged analyte into the pore. 
     
     
         5 . The method of  claim 1 , wherein the electrically opposing portions include a first portion and a second portion separated by the membrane, which electrically opposing portions interact with the at least one charged analyte to tether the at least one charged analyte in proximity to the pore. 
     
     
         6 . The method of  claim 1 , wherein the signal is measured using a sensing electrode that is located at a distance of at least 2-times a Debye length associated with the at least one charged analyte. 
     
     
         7 . The method of  claim 1 , wherein the signal is measured using a sensing electrode embedded in the membrane. 
     
     
         8 . The method of  claim 1 , wherein a diameter of the pore and a diameter of the charged analyte are each at most 10 nanometers. 
     
     
         9 . The method of  claim 1 , wherein the electric field has a strength sufficient to suppress electrical-charge shielding within the pore. 
     
     
         10 . The method of  claim 1 , wherein (1) the at least one charged analyte or (2) the membrane and a wall of the pore are surrounded by an electrical double layer (EDL), and wherein the electric field de-screens the EDL. 
     
     
         11 . The method of  claim 1 , wherein the at least one charged analyte is a nucleic acid molecule. 
     
     
         12 . The method of  claim 1 , wherein the electric field generates a non-equilibrium transport condition with respect to the electrolyte. 
     
     
         13 . A system for detecting a charged analyte, comprising:
 a fluidic chamber comprising electrically opposing portions and a membrane between the electrically opposing portions, wherein the membrane comprises a pore suitable for (i) flow of an electrolyte between the electrically opposing portions of the fluidic chamber and (ii) flow of at least one charged analyte tethered in proximity to the pore into the pore;   a first circuit configured to apply an electric field capable of directing the electrolyte through the pore and directing the at least one charged analyte into the pore; and   a second circuit configured to measure a signal indicative of a charge or change in charge of the at least one charged analyte upon the at least one charged analyte being directed into the pore.   
     
     
         14 . The system of  claim 13 , wherein the electrically opposing portions include a first portion and a second portion separated by the membrane, and wherein the electrically opposing portions of the fluidic chamber are configured to interact with the at least one charged analyte to tether the at least one charged analyte in proximity to the pore. 
     
     
         15 . The system of  claim 13 , wherein the second circuit comprises a sensing electrode for measuring the signal, wherein the sensing electrode is located at a distance of at least 2-times a Debye length associated with the at least one charged analyte. 
     
     
         16 . The system of  claim 13 , wherein a diameter of the pore is at most 10 nanometers. 
     
     
         17 . The system of  claim 13 , wherein the electric field has a strength sufficient to suppress electrical-charge shielding within the pore. 
     
     
         18 . The system of  claim 13 , wherein the second circuit comprises an electrode embedded in the membrane in proximity to the pore. 
     
     
         19 . The system of  claim 13 , further comprising an amplifier capable of amplifying the signal, wherein the amplifier is within 5000 μm from the pore. 
     
     
         20 . The system of  claim 13 , wherein the membrane is a solid state membrane, and wherein the pore is formed in the solid state membrane.