Solute-phase electrochemical aptamer sensors for improved longevity and sensitivity

Abstract

A device and method for detecting the presence of, or measuring the concentration or amount of, at least one analyte in a sample fluid. The device 100 includes at least one electrode 150, a sensor fluid 18, a plurality of aptamers freely diffusing in the sensor fluid, and a plurality of redox tags associated with at least a subset of aptamers of the plurality of aptamers. The sensor fluid is capable of having a sample fluid 14 introduced thereinto, and the detection or measurement of any analyte may occur through a change in electron transfer from at least one redox tag of the plurality of redox tags.

What is claimed is: 
     
         1 . A device for detecting the presence of, or measuring the concentration or amount of, at least one analyte in a sample fluid, the device comprising:
 at least one electrode;   a sensor fluid;   a plurality of aptamers freely diffusing in the sensor fluid; and   a plurality of redox tags associated with at least a subset of aptamers of the plurality of aptamers;   wherein the sensor fluid is capable of fluidic connection with a sample fluid introduced thereinto; and   wherein the detection or measurement of any analyte may occur through a change in electron transfer from at least one redox tag of the plurality of redox tags.   
     
     
         2 . The device of  claim 1 , wherein the device is a continuous sensing device. 
     
     
         3 . The device of  claim 1 , wherein the device is a single-use device. 
     
     
         4 . The device of  claim 1 , further comprising a passivating layer on the at least one electrode. 
     
     
         5 . The device of  claim 4 , wherein the passivating layer includes exogenous molecules. 
     
     
         6 . The device of  claim 4 , wherein the passivating layer includes molecules that are endogenous to the sample fluid. 
     
     
         7 . The device of  claim 6 , wherein a source of the endogenous molecules is the sample fluid. 
     
     
         8 . The device of  claim 6 , wherein a source of the endogenous molecules is the sensor fluid. 
     
     
         9 . The device of  claim 1 , further comprising at least one membrane, wherein the membrane separates the sample fluid and the sensor fluid and the membrane retains at least a portion of the aptamers in the sensor fluid. 
     
     
         10 . The device of  claim 9 , wherein the at least one membrane has a molecular weight cutoff that is chosen from less than 300 Da, less than 1000 Da, less than 3 kDa, less than 10 kDa, less than 30 kDa, less than 100 kDa, and less than 300 kDa. 
     
     
         11 . The device of  claim 9 , wherein the change in electron transfer is chosen from greater than 5%, greater than 10%, greater than 20%, greater than 50%, greater than 100%, and greater than 200%. 
     
     
         12 . The device of  claim 1 , wherein the measurement of change in electron transfer is performed using voltammetry. 
     
     
         13 . The device of  claim 1 , wherein the plurality of aptamers comprise a plurality of signaling aptamers and a plurality of anchor aptamers. 
     
     
         14 . The device of  claim 13 , wherein the plurality of redox tags are bound to the signaling aptamers, but are not bound to the anchor aptamers. 
     
     
         15 . The device of  claim 14 , wherein the plurality of anchor aptamers are adapted to bind the analyte, and wherein each signaling aptamer of a majority of the plurality of signaling aptamers is bound to a respective anchor aptamer when a majority of anchor aptamers are not bound to any analyte. 
     
     
         16 . The device of  claim 14 , wherein the plurality of anchor aptamers are adapted to bind the analyte, and wherein a subset of signaling aptamers dissociates from the anchor aptamers when at least a subset of anchor aptamers bind to any analyte. 
     
     
         17 . The device of  claim 13 , wherein the concentration of signaling aptamer is less than the concentration of anchor aptamer. 
     
     
         18 . The device of  claim 13 , wherein the plurality of anchor aptamers are immobilized to a first material. 
     
     
         19 . The device of  claim 18 , wherein the first material is not freely diffusing in fluid. 
     
     
         20 . The device of  claim 1 , wherein the plurality of redox tags comprises two or more redox tags per each aptamer of the plurality of aptamers, wherein the distance between the two or more redox tags alters depending on the presence of analyte. 
     
     
         21 . The device of  claim 20 , wherein the two or more redox tags are comprised of identical molecules. 
     
     
         22 . The device of  claim 20 , wherein the two or more redox tags are comprised of different molecules. 
     
     
         23 . The device of  claim 1 , wherein the electrode is coated with at least one membrane. 
     
     
         24 . The device of  claim 1 , wherein the concentration of the plurality of aptamers is chosen from less than 500 nM, less than 5 μM, and less than 50 μM. 
     
     
         25 . The device of  claim 1 , where each aptamer of the plurality of aptamers has a molecular weight chosen from at least 1 kDa, at least 10 kDa, and at least 100 kDa. 
     
     
         26 . The device of  claim 1 , wherein the change in electron transfer is associated with a condition chosen from a change in folding pattern of the aptamer, a changing in binding between two or more aptamers, a change in distance between the redox tag and the electrode, a change in rate of diffusion for the redox tag to the electrode, a change in electrochemical behavior of the redox tag, a change in hydrodynamic radius of the aptamer, a change in diffusion coefficient of the aptamer, a change in redox potential of the redox tag, a change in redox current magnitude of the redox tag, and a change in electron transfer rate. 
     
     
         27 . The device of  claim 1 , wherein the device is factory-calibrated. 
     
     
         28 . The device of  claim 1 , wherein the device is calibration-free. 
     
     
         29 . The device of  claim 1 , wherein the device contains two or more types of aptamers for measurement of two or more analytes. 
     
     
         30 . The device of  claim 29 , wherein distinguishing between measurement of two or more analytes is accomplished via use of one or more of frequency, potential, and time. 
     
     
         31 . The device of  claim 1 , wherein the at least one electrode further comprises a plurality of electrodes, wherein each electrode of the plurality of electrodes is are used at a different time than each of the other electrodes of the plurality of electrodes. 
     
     
         32 . The device of  claim 1 , wherein the measurement of change in electron transfer is amperometry. 
     
     
         33 . The device of  claim 1 , wherein the in electron transfer is due to a change in diffusion coefficient for the aptamers. 
     
     
         34 . The device of  claim 1 , wherein the at least one electrode is paired with at least a second electrode and the distance between the electrodes is chosen from less than 50 μm, less than 10 μm, less than 2 μm, and less than 0.4 μm. 
     
     
         35 . The device of  claim 1 , wherein the measurement of change in electron transfer is chronoamperometry or chronocoulometry. 
     
     
         36 . The device of  claim 35 , wherein the chronoamperometric or chronocoulometric measurement is performed and has a data measurement window within the measurement curve that is after charging currents have dissipated to less than 10% of the current value provided by electron transfer from the aptamers. 
     
     
         37 . The device of  claim 36 , wherein the chronoamperometric or chronocoulometric measurement has a slope and a change in slope and the slope or change in slope is the measurement of analyte through a change in electron transfer. 
     
     
         38 . A method for detecting the presence of, or measuring the concentration or amount of, at least one analyte in a sample fluid, the method comprising:
 bringing a sample fluid into contact with at least one aptamer of a plurality of aptamers that are freely diffusing in a sensor fluid, wherein a plurality of redox tags are associated with at least a subset of aptamers of the plurality of aptamers; and   detecting or measuring a change in electron transfer from at least one redox tag of the plurality of redox tags.   
     
     
         39 . The method of  claim 38 , wherein bringing the sample fluid into contact with at least one aptamer further comprises introducing solutes in the sample fluid into the sensor fluid. 
     
     
         40 . The method of  claim 38 , wherein the change in electron transfer results from a condition chosen from a change in folding pattern of the aptamer, a changing in binding between two or more aptamers, a change in distance between the redox tag and the electrode, a change in rate of diffusion for the redox tag to the electrode, a change in electrochemical behavior of the redox tag, a change in hydrodynamic radius of the aptamer, a change in diffusion coefficient of the aptamer, a change in redox potential of the redox tag, a change in redox current magnitude of the redox tag, and a change in electron transfer rate. 
     
     
         41 . The method of  claim 38 , wherein detecting or measuring a change in electron transfer from at least one redox tag comprises the use of an electrical measurement technique. 
     
     
         42 . The method of  claim 41 , wherein the electrical measurement technique is chosen from voltammetry, square wave voltammetry, amperometry, chronoamperometry, coulometry, and chronocoulometry. 
     
     
         43 . The method of  claim 42 , wherein the electrical measurement technique is square wave voltammetry. 
     
     
         44 . The method of  claim 38 , wherein detecting or measuring a change in electron transfer further comprises taking only one measurement. 
     
     
         45 . The method of  claim 38 , wherein detecting or measuring a change in electron transfer further comprises taking multiple separate measurements over a defined time period.