Systems and methods of voltage-gated ion channel assays

Abstract

Systems and methods are provided for optically measuring ion concentrations in biological samples. The systems and methods employ polymer-based optical ion sensors that include ion-selective ionophores and a pH sensitive chromionophore. Electrodes are providing for electrically stimulating the biological samples.

1 . A cell assay system comprising:
 a post having a distal end sized for introduction into a biological sample holder;   a plurality of electrodes, at least one of which is coupled to the post, for generating an electric field between the electrodes when introduced into the biological sample holder;   a polymer-based optical ion sensor positioned proximate the distal end of the post, wherein the optical ion sensor includes at least one ionophore for selectively binding a predetermined ion, thereby altering a pH of the optical ion sensor, and one pH-sensitive chromionophore for optically indicating the concentration the predetermined ion based on the pH of the optical ion sensor and the resulting fluorescence of the chromionophore.   
   
   
       2 . The cell assay system of  claim 1 , wherein the optical ion sensor is removably coupled to the post. 
   
   
       3 . The cell assay system of  claim 1 , wherein the optical ion sensor is coupled to the biological sample holder. 
   
   
       4 . The cell assay system of  claim 1 , wherein the optical ion sensor is suspending in a fluid in the biological sample holder. 
   
   
       5 . The cell assay system of  claim 1 , wherein the optical ion sensor is located within a cell in the biological sample holder. 
   
   
       6 . The cell assay system of  claim 1 , wherein the optical ion sensor is disposed on a transparent surface positioned in the biological sample holder. 
   
   
       7 . The cell assay system of  claim 1 , wherein the optical ion sensor is located outside of a cell when the post is introduced into the biological sample holder and a second optical ion sensor is located within a cell in the biological sample holder. 
   
   
       8 . The cell assay system of  claim 7 , wherein the second optical ion sensor includes a different ionophore than the optical ion sensor for indicating the concentration of two ions. 
   
   
       9 . The cell assay system of  claim 8 , wherein the second optical ion sensor includes a different chromionophore than the optical ion sensor. 
   
   
       10 . The cell assay system of  claim 7 , wherein the second optical ion sensor includes the same ionophore as the optical ion sensor. 
   
   
       11 . The cell assay system of  claim 1 , comprising a controllable voltage source for generating a voltage across the electrodes. 
   
   
       12 . The cell assay system of  claim 1 , wherein the controllable voltage source generates a voltage sufficient to electroporate a cell in the biological sample holder. 
   
   
       13 . The cell assay system of  claim 1 , wherein the controllable voltage source generates a voltage sufficient to activate an ion channel in a cell in the biological sample holder. 
   
   
       14 . The cell assays system of  claim 1 , wherein the post comprises an agent introduction means for introducing an agent into the biological sample holder. 
   
   
       15 . The cell assay system of  claim 14 , wherein the agent introduction means comprises a hole in the post. 
   
   
       16 . The cell assay system of  claim 14 , wherein the agent introduction means comprises a pipette. 
   
   
       17 . The cell assay system of  claim 14 , wherein the agent introduction means comprises a electromechanical agent dispenser. 
   
   
       18 . The cell assay system of  claim 17 , wherein the electromechanical agent dispenser comprises a solenoid. 
   
   
       19 . The cell assay system of  claim 1 , wherein the plurality of electrodes comprises two parallel electrodes coupled to opposing portions of the post. 
   
   
       20 . The cell assay system of  claim 1 , wherein the plurality of electrodes comprises two coaxial electrodes. 
   
   
       21 . The cell assay system of  claim 1 , wherein at least one of the plurality of electrodes couples to the biological sample holder. 
   
   
       22 . The cell assay system of  claim 1 , wherein at least one of the plurality of electrodes comprises a transparent conductor. 
   
   
       23 . The cell assay system of  claim 1 , wherein the plurality of electrodes comprises first and second pairs of parallel electrodes, wherein the first pair of electrodes is aligned perpendicular to the second pair of electrodes. 
   
   
       24 . The cell assay system of  claim 1 , comprising a light sensor for measuring the fluorescence of the optical ion sensors. 
   
   
       25 . The cell assay system of  claim 24 , comprising a computing device for measuring the output of the light sensor. 
   
   
       26 . The cell assay system of  claim 25 , wherein the computing device comprises a voltage control module for causing varying voltages to be generated across the electrodes. 
   
   
       27 . The cell assay system of  claim 25 , wherein the computing device comprises an analysis module for comparing the output of the light sensor at the various voltages. 
   
   
       28 . The cell assay system of  claim 25 , wherein the computing device comprises an agent introduction control module for controlling the introduction of an agent into the biological sample holder. 
   
   
       29 . The cell assay system of  claim 28 , wherein the computer comprises an analysis module for comparing the output of the light sensor before an introduction of the agent into the biological sample holder to the output of the light sensor after the introduction of the agent into the biological sample holder. 
   
   
       30 . The cell assay system of  claim 1 , comprising an excitation light source for exciting the optical ion sensor. 
   
   
       31 . A cell assay system, comprising:
 an array of posts having distal ends spaced and sized for introduction into an array of biological sample holders;   a plurality of electrode sets, wherein at least one electrode of each electrode set is coupled to a respective post, and each electrode set is configured to generate an electric field when introduced into a corresponding biological sample holder in the array of biological sample holders;   a plurality of polymer-based optical ion sensors positioned proximate the distal end of the respective posts in the array of posts, wherein the optical ion sensors include at least one ionophore for selectively binding a predetermined ion, thereby altering a pH of the optical ion sensor, and one pH-sensitive chromionophore for optically indicating the concentration of the predetermined ion based on the pH of the optical ion sensor and the resulting fluorescence of the chromionophore.   
   
   
       32 . The cell assay system of  claim 31 , wherein at least two of the optical ion sensors in the plurality of ion sensors include different ionophores to indicate the concentration of multiple predetermined ions corresponding to the different ionophores. 
   
   
       33 . The cell assay system of  claim 32 , wherein the at least two different optical ion sensors are proximate a single post in the array of posts. 
   
   
       34 . The cell assay system of  claim 32 , wherein the at least two different optical ion sensors are proximate different posts in the array of posts. 
   
   
       35 . The cell assay system of  claim 31 , wherein the array of biological sample holders comprises one of a 6-well, 12-well, 24-well, 48-well, 96-well, 384-well, and a 1534-well plate. 
   
   
       36 . The cell assay system of  claim 31 , comprising a computing device including an agent introduction control module for controlling the introduction of an agent into at least one of the biological sample holders. 
   
   
       37 . The cell assay system of  claim 36 , wherein the agent introduction control module controls the introduction of a plurality of agents into respective ones of the biological sample holders in the array of biological sample holders. 
   
   
       38 . The cell assay system of  claim 37 , wherein the computing device comprises an analysis module for comparing the fluorescence of the plurality of optical ion sensors before an introduction of at least one agent into at least one of the respective biological sample holders to the fluorescence of the corresponding plurality of optical ion sensors after the introduction of the at least one agent into the respective biological sample holders. 
   
   
       39 . The cell assay system of  claim 31 , comprising a robotics module for robotically introducing the array of posts into the array of biological sample holders. 
   
   
       40 . The cell assay system of  claim 39 , wherein the robotics module is configured to introduce the array of posts into a plurality of arrays of biological sample holders in sequence. 
   
   
       41 . A method of conducting a biological assay comprising:
 introducing a polymer-based optical ion sensor into a biological sample holder, wherein the optical ion sensor includes at least one ionophore for selectively binding a predetermined ion, thereby altering a pH of the optical ion sensor, and one pH-sensitive chromionophore for optically indicating the concentration of the predetermined ion based on the pH of the optical ion sensor and the resulting fluorescence of the chromionophore;   generating an electric field across a cell in the biological sample holder;   measuring an output of a light sensor monitoring the a fluorescence of the optical ion sensor in response to the generation of the electric field.   
   
   
       42 . The method of  claim 41 , comprising varying the electric field. 
   
   
       43 . The method of  claim 41 , comprising introducing an agent into the biological sample holder. 
   
   
       44 . The method of  claim 43 , comprising detecting a change in the output of the light sensor in response to the introduction of the agent. 
   
   
       45 . The method of  claim 44 , comprising determining that the agent is toxic. 
   
   
       46 . The method of  claim 44 , comprising detecting a nerve toxin. 
   
   
       47 . The method of  claim 44 , comprising detecting a heart toxin. 
   
   
       48 . The method of  claim 44 , comprising determining that the agent is a candidate for treating a condition. 
   
   
       49 . The method of  claim 44 , comprising comparing the change in the output of the light sensor to the change of output of the light sensor caused by a plurality of known agents. 
   
   
       50 . The method of  claim 49 , comprising identifying the agent. 
   
   
       51 . The method of  claim 41 , wherein the optical ion sensor is coupled to a post, and wherein introducing the optical ion sensor into the biological sample holder comprises positioning the post in the biological sample holder. 
   
   
       52 . The method of  claim 51 , wherein the electric field is generated at least in part by an electrode coupled to the post. 
   
   
       53 . The method of  claim 41 , wherein the optical ion sensor comprises an optical ion sensor particle, and wherein introducing the optical ion sensor into the biological sample holder comprises dispensing the optical ion sensor particle into a fluid in the biological sample holder. 
   
   
       54 . The method of  claim 53 , comprising introducing the optical ion sensor into a cell located in the biological sample holder. 
   
   
       55 . The method of  claim 54 , comprising electroporating the cell, thereby allowing the optical ion sensor to enter the cell. 
   
   
       56 . The method of  claim 54 , comprising applying a compound to the optical ion sensor to breach a vesicle formed by the cell around the optical ion sensor. 
   
   
       57 . The method of  claim 41 , wherein the electric field is generated, at least in part, by an electrode coupled to a post positioned in the biological sample holder. 
   
   
       58 . The method of  claim 41 , wherein introducing the optical ion sensor into the biological sample holder comprises inserting the optical ion sensor into a cavity formed in the post. 
   
   
       59 . The method of  claim 41 , comprising forming a cell monolayer on the interior of the biological sample holder. 
   
   
       60 . The method of  claim 41 , wherein introducing the optical ion sensor into a biological sample holder comprises introducing a first optical ion sensor into a cell in the biological sample holder and introducing a second optical ion sensor into the biological sample holder outside of the cell. 
   
   
       61 . A method of conducting a biological assay comprising:
 providing an array of biological sample holders;   introducing an array of polymer-based optical ion sensors into biological sample holders in the array of biological sample holders, wherein the optical ion sensors include at least one ionophore for selectively binding a predetermined ion, thereby altering a pH of the optical ion sensor, and one pH-sensitive chromionophore for optically indicating the concentration of an ion corresponding to the ionophore based on the pH of the optical ion sensor and the resulting fluorescence of the chromionophore;   generating electric fields across cells in the biological sample holders in the array of biological sample holders;   measuring an output of a light sensor monitoring the a fluorescence of the array of optical ion sensors in response to the electric fields.   
   
   
       62 . The method of  claim 61 , comprising introducing a first agent into one of the biological sample holders in the array of biological sample holders. 
   
   
       63 . The method of  claim 62 , comprising introducing a second agent into a second of the biological sample holders in the array of biological sample holders. 
   
   
       64 . The method of  claim 63 , detecting a change in the output of the light sensor resulting from the introduction of the first and second agents. 
   
   
       65 . The method of  claim 61 , comprising, providing a second array of biological sample holders and robotically introducing the array of optical ion sensors into the second array of biological sample holders.