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 sensor for detecting a charged analyte, the sensor comprising:
 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 upon at least one charged analyte being pulled into the pore.   
     
     
         2 . The sensor of  claim 1 , wherein the at least one charged analyte is tethered, in proximity to the pore, concurrently with the pulling of the at least one charged analyte into the pore. 
     
     
         3 . The sensor of  claim 1 , wherein the electrically opposing portions include a top portion and a bottom portion separated by the membrane, and the at least one charged analyte is tethered in proximity to the pore caused by interaction between the at least one charged analyte and the electrically opposing portions of the fluidic chamber. 
     
     
         4 . The sensor of  claim 1 , wherein the second circuit comprises a sensing electrode for measuring the signal, wherein the sensing electrode is located at a distance away from the at least one charged analyte. 
     
     
         5 . The sensor of  claim 2 , wherein the distance is at least 2-times a Debye length associated with the at least one charged analyte. 
     
     
         6 . The sensor of  claim 2 , wherein the Debye length is calculated using the Debye-Hückel equation: Λ D ˜√{square root over (∈kT/C 0 )}, wherein  D =Debye length, =electric constant, k=Boltzman constant, T=temperature, and C 0 =ionic concentration. 
     
     
         7 . The sensor of  claim 1 , wherein the pore has a diameter that is sized for the charged analyte, wherein both the diameter of the pore and the diameter of the charged analyte are on the order of more than several nanometers. 
     
     
         8 . The sensor of  claim 1 , wherein the electric field has a strength in terms of million of Volts per meter (V/m) sufficient to suppress electrical-charge shielding within a geometry defined by a portion of the membrane defining the pore. 
     
     
         9 . The sensor of  claim 1 , wherein the at least one charged analyte has an electrical double layer (EDL) surrounding it and the electric field is capable of de-screening the EDL. 
     
     
         10 . The sensor of  claim 1 , wherein the membrane and walls of the pore have an EDL surrounding them and the electric field is capable of de-screening the EDL. 
     
     
         11 . The sensor of  claim 1 , wherein the electric field is capable of generating a non-equilibrium transport condition. 
     
     
         12 . The sensor of  claim 1 , wherein the membrane is electrically insulating. 
     
     
         13 . The sensor of  claim 1 , wherein the first circuit comprises a first electrode in one of the electrically opposing portions of the fluidic chamber and a second electrode in another of the electrically opposing portions of the fluidic chamber. 
     
     
         14 . The sensor of  claim 1 , wherein the second circuit comprises an electrode embedded in the membrane in proximity to the pore. 
     
     
         15 . The sensor of  claim 1 , wherein the signal is linearly proportional to the charge of the at least one charged analyte. 
     
     
         16 . The sensor of  claim 1 , wherein the at least one charged analyte is a nucleic acid molecule. 
     
     
         17 . The sensor of  claim 1 , wherein the at least one charged analyte is tethered in proximity to the pore by a molecular structure. 
     
     
         18 . The sensor of  claim 1 , wherein the diameter of the pore corresponds to the at least one charged analyte to pass through the pore. 
     
     
         19 . A method for detecting a charged analyte, the method comprising:
 providing a fluidic chamber having electrically opposing portions with a membrane between, one of the electrically opposing portions having an electrolyte, the membrane providing a pore suitable for the passage of the electrolyte between the electrically opposing portions of the fluidic chamber, and having at least one charged analyte tethered in proximity to the pore;   applying an electric field to pass the electrolyte through the pore and pull the at least one charged analyte into the pore; and   measuring a signal indicative of the charge of the at least one charged analyte upon the at least one charged analyte being pulled into the pore.   
     
     
         20 . The method of  claim 19 , wherein in response to the applied electric field, the at least one charged analyte is pulled to a position in proximity to a periphery of the pore. 
     
     
         21 . A kit for detecting a charged analyte, the kit comprising:
 at least one charged analyte; and   a sensor including:
 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 the 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 upon at least one charged analyte being pulled into the pore. 
   
     
     
         22 . The kit of  claim 21 , wherein the second circuit comprises an amplifier capable of amplifying the signal. 
     
     
         23 . The kit of  claim 22 , wherein the amplifier is within about 5000 μm from the pore. 
     
     
         24 . The kit of  claim 21 , wherein the at least one charged analyte is tethered in proximity to the pore by, and sufficiently near the pore for, immobilization caused by interaction between the at least one charged analyte and the electrically opposing portions of the fluidic chamber.