Abstract:
The invention concerns an apparatus ( 10 ) comprising essentially a support ( 11 ) wherein is placed a measuring card ( 12 ), a perfusion device ( 13 ), a thermostat ( 14 ), a measuring box ( 15 ) and a measurement management system ( 16 ). The measuring card ( 12 ) comprises an electrode array whereof one end emerges into the chamber and the other end is placed outside said chamber. The group of cells is placed in the chamber which is connected to the perfusion device ( 13 ). The support ( 11 ) comprises a connector ( 25 ) connecting the card ( 12 ) electrodes to the measurement management system ( 16 ) via the measuring box ( 15 ).

Description:
The present invention concerns an apparatus for measuring the electrophysiological activity of a mass of cells. 
     BACKGROUND OF THE INVENTION 
     In order to measure the electrophysiological activity of a mass of cells, the cells are placed in a measurement device consisting of an electrode network. Each electrode in the network comprises a bare zone contacting the cell mass, a bare zone accessible from the outside of a container holding the cells, and an insulated zone separating the two bare zones. 
     Various devices have been developed, generally in the form of laboratory devices, to perform measurements of said electrophysiological activity. 
     These devices have several disadvantages. In particular, the structure of the container does not allow long term cells survival. Additionally, when a user wishes to measure electrophysiological cell activity, he places electrical supply points in contact with the involved electrodes in the electrode network. This contact is established manually. That means it is particularly difficult to take measurements over a specific time period or simultaneously on several electrodes. 
     When one area on the group of cells must be stimulated, the stimulation is performed manually using a stimulation electrode. This complicates the measurement and precludes taking remote measurements. Finally, this device does not provide an on line analysis of the measurement results. 
     SUMMARY OF THE INVENTION 
     The present invention proposes eliminating these disadvantages with an apparatus that is simple to manipulate, versatile, and completely capable of remote control. This apparatus also allows long term cell survival so that measurements can be taken over a long time period. 
     This goal is achieved with an apparatus such as the one described in the preamble, characterized in that it comprises a measurement card with a chamber which receives the cells for analysis and contains a network of electrodes, at least some of which contact said cell mass, comprising a connector formed of conductive tracks, with each electrode in the electrode network being connected to a conductive track on the connector and said connector being coupled with a measurement circuit which transmits electrical signals to at least one electrode on said electrode network and receives electrical signals from at least one of the electrodes. 
     According to a preferred embodiment, the electronic measurement circuit is connected to a measurement management system which controls measurement parameters and analyzes measurement signals. 
     The apparatus advantageously comprises a means for assigning at least one electrode in the electrode network an electrode measurement function, and a means for assigning at least one electrode in the electrode network an electrode stimulation function. 
     The card is preferably placed in a support and the connector is integral with said support. The support is advantageously made of metal. 
     According to an advantageous embodiment, the support cooperates with a heating means which heats the measurement card. 
     The measurement card advantageously cooperates with a perfusion device which perfuses said cell mass. 
     According to a preferred embodiment, the management system comprises a means for controlling the perfusion device and a heating means. It also comprises a remote control. 
     The apparatus advantageously comprises a viewing means which preferably consists of a camera. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention and its features will be better understood with reference to a specific embodiment of the invention and to the attached drawings, in which: 
     FIG. 1 is a view of the entire apparatus of the invention; 
     FIG. 2 is a view of a measurement card used with the apparatus of FIG. 1; 
     FIG. 3 is a cross-section of the measurement card of FIG. 2; and 
     FIG. 4 is a schematic view of a specific embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to these drawings, the apparatus  10  essentially consists of a support  11  in which a measurement card  12  is placed, along with a perfusion device  13 , a heating means  14 , an electronic measurement circuit  15 , and a measurement management system  16  which may consist of a computer  17  and a monitor  18 . 
     Support  11  essentially consists of a fixed portion  19 , in which measurement card  12  is placed, and a movable portion  20 . The measurement card essentially consists of a chamber  21  with an inlet  22  and an outlet  23 , containing the cells for analysis, a removable cover  24  which seals the chamber, and an electrode network  25 . The electrodes forming this network have a first portion  26  located inside the chamber so it can contact with certain cells in the cell mass, and a second portion  27  located outside the chamber. The movable portion  20  of the support is integral with a flexible electronic circuit formed of a network of conductive tracks, one extremity of which contacts a respective electrode on the measurement card. The other extremity of the tracks of the network of conductive tracks is placed in a connector  28  attached to the support. This support is advantageously made of metal and forms a Faraday cage around the card. The chamber may also comprise a gas injection duct  29  and a gas exhaust duct  30 . This is for introducing gas into the chamber. 
     The support has a hole  31  through its fixed portion and a hole  32  through its movable portion. These holes are aligned and arranged so that the chamber in the measurement card is placed between the two holes when the support is closed. 
     The support may be associated with a lighting and/or a viewing device  33 . Said viewing device may consist of a camera  34 , particularly a digital camera, making it possible to either observe the analyzed cells with a microscope or a magnifier, or to project an image on monitor  18  of computer  17 . 
     The support also contains a heater  14  as well as a temperature control means  35 . The heater  14  may be in the form of an electrical resistor positioned so as to heat a support zone near the cells to be analyzed. It may also consist of channels formed in the support itself for circulating hot air generated by a ventilator associated with a heating resistor. The temperature controls means  35  is connected to a thermostat  36  and may consist of a thermostatic sensor located near the cells to be analyzed. 
     When a cell sample is put in place for measurement, it is located in chamber  21  of the card. Removable cover  24  is closed, movable support portion  20  is removed to allow card  12  to be placed in the support, then movable support portion  20  is replaced, closing the support. 
     The chamber inlet  22  and outlet  23  are respectively connected to a flexible inlet tube and a flexible exhaust tube. The inlet tube is connected to perfusion device  13 . Said perfusion device is used first, to deliver liquid nutrient to the cells located in the card and second, to administer a product for testing to the cells. 
     Said perfusion device is formed of a support  37  containing one or more syringes  38  and actuators  39  which independently activate the syringe pistons. Piston movement is controlled by measurement management system  16  so that the desired product is delivered at any given instant or over any given time period, in a certain quantity or at a certain rate. 
     Depending upon the measurements to be performed or the nature of the cells or of the products to be tested, a gas may be introduced through gas injection duct  29 . It is also possible to generate gas flow into the chamber by introducing gas through duct  29  and exhausting it through gas exhaust duct  30 . 
     Thermostat  36  defines a given temperature or temperature evolution over time. It is also controlled by measurement management system  16  and acts on the heater. 
     The electronic measurement circuit  15  is an interface between measurement management system  16  and measurement card  12 . This circuit amplifies and multiplexes the electrical signals being displaced in both directions between the card and the measurement management system. 
     Said electronic measurement circuit comprises a means for amplifying the electrical signals circulating between the card and the management system. It also comprises a means for modifying the amplification factor, as well as the multiplex order. These modifications can be made using measurement management system  16 , that is, without any mechanical action on the electronic measurement circuit. It should be noted that the circuit may also be made in the form of an electronic card integrated into measurement management system  16 . 
     The measurement control system  16  comprises processor  17 , which uses measurement software specifically designed for the application desired. Specifically, the software controls the operation of perfusion device  13 , heater  14 , and electronic measurement circuit  15 . It also assigns different functions to the electrodes. More specifically, in a concrete embodiment, two electrodes are chosen as stimulation electrodes. An electrical signal is thus sent from the electronic measurement circuit to these electrodes. Other electrodes, for example, eight of the forty total electrodes forming the circuit, are used as measurement electrodes. An electrical signal originating from the card is thus received by the electronic circuit. The choice of electrodes depends upon the organization of the tissue. 
     It is also possible to reserve one or more electrodes as bio-sensors in order to detect the presence and/or concentration of a given product. 
     In order to be able to see the organization of the tissues and make a judicious choice of electrodes, it is important to provide a viewing means, either a direct view through a transparent portion or a camera  34  which can project of an image on screen  18 . 
     The management system provides simple definition of all parameters relative to the measurements performed. During electrical stimulation, the length, period, and amplitude of the impulses can be specifically defined. Stimulation can also be accomplished using an external device to program the different parameters. 
     The data for effecting measurements, as well as the results of these measurements, can be stored in a storage unit placed in measurement management system  16 . This allows the data to be stored and analyzed later. 
     The embodiment shown in FIG. 4 represents the “monoblock” version of apparatus  10  of the invention. 
     This apparatus comprises a chassis  40  within which are located support  11  receiving measurement card  12 , perfusion device  13 , heater  14 , thermostat  36 , electronic measurement circuit  15 , measurement management device  16 , and viewing means  33 . 
     Support  11  has a drawer  41  which opens for placement of measurement card  12  and access to perfusion device  13 . When drawer  41  is closed, measurement card  12  is located opposite camera  34 . 
     In the embodiment shown, perfusion device  13  comprises peristaltic pumps  42 . 
     The monoblock embodiment is advantageous primarily because it is very compact. 
     The present invention offers a certain number of advantages over existing systems. In particular, the apparatus is very simple to manipulate. Placing the cart in the support actually assures the electrical connection of all the electrodes in the network. The choice of electrodes used is made simply using management system  16 . The images from the viewing camera are displayed on screen  18 . For this reason it is possible, by using the appropriate computer program, to individually assign a function to each electrode using a pointer on the screen. 
     In the same way, it is possible to program functions for each electrode. These functions might vary over a period of time according to a predefined program. 
     In addition, it is possible to control all the operations of the apparatus, such as temperature, temperature variations, activating each of the syringe plungers or peristaltic pumps, with computer  17 . 
     All the parameters are introduced through this management system, which also can be remote-controlled using a modem. 
     Additionally, thanks to the viewing device, the choice of electrodes as a function of tissue organization, as well as surveillance of cell survival, can all be done from a distance. 
     Since the measurement card is closed by a cover and placed in a support, the cells are insulated from the exterior environment and therefore the measurements can be performed in a non-sterile environment. 
     The support is advantageously made of metal. Thus, it serves as a Faraday cage, eliminating the necessity of adding another Faraday cage. 
     The present invention is not limited to the embodiment described, but extends to any modification or variation obvious to a person skilled in the art. 
     In particular, other functions such analysis of certain particular measurement parameters, may be integrated into the software in management system  16 . 
     The entire apparatus can also be adapted to specific cases where measurements are taken—for example, if viewing from a particular perspective is not necessary, or if the apparatus is always used for the same type of measurement requiring specific conditions. 
     It is also possible to place the measurement card in a microscope support. An electrical cord extends to connect the measurement card with support  11 , allowing the card to be used outside its support. 
     The number and disposition of the electrodes can also be modified according to analysis requirements.