Methods and apparatus for nanomembrane-based nucleic acid sensing platform for portable diagnostics

Abstract

A DNA/RNA detection technology is provided. The open flow detection technique includes a substrate defining a pair of opposing microchannels, a pair of opposing electrodes in the opposing microchannels, and at least one ion exchanging nanomembrane coupled between the opposing microchannels such that the opposing microchannels are connected to each other only through the nanomembrane, wherein the nanomembrane is functionalized with a probe complementary to the macromolecule. A voltammeter is provided to measure the electrical current or potential across the nanomembrane, and detect a change in the measured electrical current or potential to quantify the presence of the macromolecule

We claim: 
     
         1 . A quantitative method for analyzing a macromolecule comprising:
 making an assay mixture containing the macromolecule;   providing a microchamber electrochemical cell comprising:
 a substrate defining a pair of opposing microchannels; 
 a pair of opposing electrodes in the opposing microchannels; 
 at least one ion exchanging nanomembrane coupled between the opposing microchannels such that the opposing microchannels are connected to each other only through the nanomembrane, wherein the nanomembrane is functionalized with a probe complementary to the macromolecule; and 
 a device for measuring at least one of measuring electrical current or potential across the nanomembrane; 
   flowing the assay mixture through the opposing microchannels of the microchamber electrochemical cell such that assay mixture contacts the nanomembrane in a manner suitable for hybridization of the assay mixture with the probe;   connecting the opposing electrodes to the device for measuring at least one of measuring electrical current or potential across the nanomembrane; and   detecting a change in the measured electrical current or potential across the nanomembrane to quantify the presence of the macromolecule.   
     
     
         2 . A method as defined in  claim 1 , wherein the nanomembrane is provided in a nanoslot. 
     
     
         3 . A method as defined in  claim 2 , wherein a depth of the nanoslot is substantially the same as a depth of the microchannel. 
     
     
         4 . A method as defined in  claim 1 , further comprising providing an AC current across the pair of opposing electrodes. 
     
     
         5 . A method as defined in  claim 1 , wherein the macromolecule is at least one of a DNA macromolecule, an RNA macromolecule, a protein macromolecule, or an organic polymer macromolecule. 
     
     
         6 . A method as defined in  claim 1 , further comprising deionizing the assay mixture proximate the nanomembrane. 
     
     
         7 . A method as defined in  claim 1 , further comprising bulk-to-membrane ion flux over the depletion region formed by the membrane at over-potentials. 
     
     
         8 . A method as defined in  claim 1 , further comprising forming a non-uniform electroosmotic flow. 
     
     
         9 . A method as defined in  claim 8 , wherein the non-uniform electroosmotic flow leads to microvorticies formed in the fluid flow. 
     
     
         10 . A method as defined in  claim 8 , wherein the non-uniform electroosmotic flow leads to a detectable enhanced ion current. 
     
     
         11 . A method as defined in  claim 1 , further comprising eliminating the overlimiting current when the surface is effectively electroneutral. 
     
     
         12 . A method as defined in  claim 11 , wherein eliminating the overlimiting current comprises providing an oppositely charged membrane from the hybridized or functionalized molecules, to invert the charge on the membrane surface 
     
     
         13 . A method as defined in  claim 1 , further comprising optimizing a frequency for each electrolyte strength. 
     
     
         14 . A method as defined in  claim 13 , wherein optimizing the frequency scales as a function of D/λ 2  where D is the molecular diffusivity of the molecule and λ is the Debye length for the given electrolyte strength. 
     
     
         15 . A microchamber electrochemical cell comprising:
 a substrate defining a pair of opposing fluid microchannels for flowing a solution of target macromolecules;   a pair of opposing electrodes in the opposing microchannels;   at least one ion exchanging nanomembrane connecting together the opposing fluid microchannels such that the opposing fluid microchannels are connected to each other only through each nanomembrane;   a device for measuring at least one of measuring electrical current or potential across the nanomembrane; and   a processor adapted to analyze the measured electrical current or potential across the nanomembrane to determine the presence of the target macromolecule.   
     
     
         16 . A microchamber as defined in  claim 15 , further comprising a nanoslot housing the nanomembrane. 
     
     
         17 . A microchamber as defined in  claim 16 , wherein a depth of the nanoslot is substantially the same as a depth of the microchannel. 
     
     
         18 . A microchamber as defined in  claim 17 , further comprising an AC current supply for supplying an AC current across the pair of opposing electrodes. 
     
     
         19 . A real-time quantitative method comprising:
 preparing an assay mixture comprising a target template;   providing a microchamber electrochemical cell comprising:
 a substrate defining a pair of opposing fluid microchannels; 
 a pair of opposing electrodes in the opposing fluid microchannels; and 
 at least one ion exchanging nanomembrane housed in a nanoslot fluidly connecting together the opposing fluid microchannels such that the opposing fluid microchannels are connected to each other only through the nanomembrane, the height porosity of the nanomembrane preventing the passage of the target template therthrough, wherein the nenomembrane is functionalized with a probe complementary to the target template; and 
 a device for measuring at least one of measuring electrical current or potential across the nanomembrane; 
   flowing the assay mixture through the opposing fluid microchannels of the microchamber electrochemical cell such that the assay mixture is in fluid communications with the nanomembrane;   coupling the opposing electrodes to the a device for measuring at least one of measuring electrical current or potential across the nanomembrane;   measuring an AC electrical current or potential across the opposing electrodes while providing an AC sinusoidal electromagnetic perturbation; and   detecting a change in the measured electrical current or potential across the nanomembrane to quantify the presence of the macomolecule.   
     
     
         20 . A method as defined in  claim 19 , wherein the nanomembrane is provided in a nanoslot. 
     
     
         21 . A method as defined in  claim 20 , wherein a depth of the nanoslot is substantially the same as a depth of the microchannel.