Embedded Bio-Sensor System

Abstract

Provided is a bio-sensor system which utilizes radio frequency identification technology and which includes a remote transponder in wireless communication with an implantable passively-powered on-chip transponder. The bio-sensor system is specifically adapted to provide a substantially stable and precise sensor reference voltage to a sensor assembly that is included with the on-chip transponder. The remote transponder is also configured to remotely receive data representative of a physiological parameter of the patient as well as identification data and may enable readout of one or more of the physiological parameters that are measured, processed and transmitted by the on-chip transponder upon request by the remote transponder. The precision and stability of the sensor reference voltage is enhanced by the specific circuit architecture of the glucose sensor to allow for relatively accurate measurement of the physiological parameter such as measurement of glucose concentration by a glucose sensor without the use of a microprocessor.

1 . A bio-sensor system adapted to provide a substantially stable voltage to a sensor assembly that is implantable in a patient such that physiological parameters thereof may be accurately measured, the bio-sensor system comprising: 
 a remote transponder configured to transmit a scanner signal to the sensor and to receive a data signal therefrom;    an implantable on-chip transponder in wireless communication with the remote transponder and being configured to receive the scanner signal and transmit the data signal, the on-chip transponder including: 
 a sensor being configured to generate a sensor signal representative of the physiological parameter of the patient;  
 a power receiver configured to receive the scanner signal from the remote transponder and to generate a power signal for powering the on-chip transponder;  
 an analog-to-digital (A/D) assembly connected to the power receiver and the sensor, the A/D assembly being configured to respectively receive the power signal and the sensor signal and generate a digital signal in response thereto;  
 a data processor connected to the A/D assembly and the power receiver, the data processor being configured to respectively receive, the power signal and the digital signal and generate a data signal in response thereto; and  
 an RF transmitter connected to the power receiver and the data processor and being configured to respectively receive the power signal and the data signal and to modulate, amplify, filter and transmit the data signal;  
   wherein the power receiver is configured to supply a substantially non-deviating sensor reference voltage to the sensor for accurate measurement of the physiological parameter, the remote transponder being configured to receive the data signal from the RF transmitter and to extract data representative of the physiological parameter.    
     
     
         2 . The bio-sensor system of  claim 1  wherein: 
 the sensor is a glucose sensor having an electrode assembly in fluid communication with the patient's blood and being configured to measure a glucose level thereof;    the sensor reference voltage being supplied to the electrode assembly at a substantially constant value of about positive 0.7 volts.    
     
     
         3 . The bio-sensor system of  claim 2  wherein the glucose sensor is a 2-pin glucose sensor with the electrode assembly having first and second terminals in fluid communication with the patient's blood, the glucose sensor further including: 
 a first precision resistor connected to the power receiver and configured to receive the sensor reference voltage therefrom for excitation of the glucose sensor;    a first operational amplifier connected to the first precision resistor and being configured to receive the sensor reference voltage therefrom and generate a precision sensor reference voltage in response thereto;    a voltmeter connected to the first operational amplifier and the first precision resistor and being configured to monitor the precision sensor reference voltage and establish a sensor operating point, the first operational amplifier and the voltmeter cooperating to buffer the precision sensor reference voltage and apply a substantially accurate sensor reference voltage to the first terminal;    a second operational amplifier connected to the second terminal and being configured to receive current discharging therefrom in response to the accurate sensor reference voltage applied to the first terminal; and    a tunable second precision resistor connected to the second operational amplifier and cooperating therewith to generate a sensor signal that is substantially proportional to the glucose level of the patient's blood.    
     
     
         4 . The bio-sensor system of  claim 3  wherein the glucose sensor is a 3-pin glucose sensor with the electrode assembly further including a third terminal co-located with the first and second terminals and being in fluid communication with the patient's blood, the glucose sensor further including: 
 an auxiliary control circuit connected between the third electrode and the second operational amplifier and being configured to monitor and control an amount of current discharging from the third terminal;    wherein the third terminal is configured to divert current away from the second electrode during application of the accurate sensor reference voltage applied to the first terminal such that the operational life of the glucose sensor may be increased.    
     
     
         5 . A bio-sensor system adapted to provide a substantially stable voltage to a sensor assembly that is implantable in a patient such that physiological parameters thereof may be accurately measured, the bio-sensor system comprising: 
 a remote transponder configured to transmit a scanner signal to the sensor and to receive a data signal therefrom;    an implantable on-chip transponder in wireless communication with the remote transponder and being configured to receive the scanner signal and transmit the data signal, the on-chip transponder including: 
 a sensor being configured to generate a sensor signal representative of the physiological parameter of the patient;  
 a radio frequency (RF) receiver configured to receive the scanner signal from the remote transponder and to filter, amplify and demodulate the scanner signal and generate a message signal for controlling the on-chip transponder;  
 a power receiver configured to receive the scanner signal from the remote transponder and to generate a power signal for powering the on-chip transponder;  
 an analog-to-digital (A/D) assembly connected to the power receiver, the RF receiver and the sensor, the A/D assembly being configured to respectively receive the power signal, the sensor signal and the message signal and generate a digital signal in response thereto;  
 a data processor connected to the A/D assembly, the power receiver and the RF receiver, the data processor being configured to respectively receive the power signal, the digital signal and the message signal and generate a data signal in response thereto; and  
 an RF transmitter connected to the power receiver, the data processor and the RF receiver and being configured to respectively receive the power signal, the data signal and the message signal and to modulate, amplify, filter and transmit the data signal;  
 wherein the power receiver is configured to supply a substantially non-deviating sensor reference voltage to the sensor for accurate measurement of the physiological parameter, the remote transponder being configured to receive the data signal from the RF transmitter and to extract data representative of the physiological parameter.  
   
     
     
         6 . The bio-sensor system of  claim 5  wherein: 
 the sensor is a glucose sensor having an electrode assembly in fluid communication with the patient's blood and being configured to measure a glucose level thereof;    the sensor reference voltage being supplied to the electrode assembly at a substantially constant value of about positive 0.7 volts.    
     
     
         7 . The bio-sensor system of  claim 6  wherein the glucose sensor is a 2-pin glucose sensor with the electrode assembly having first and second terminals in fluid communication with the patient's blood, the glucose sensor further including: 
 a first precision resistor connected to the power receiver and configured to receive the sensor reference voltage therefrom for excitation of the glucose sensor;    a first operational amplifier connected to the first precision resistor and being configured to receive the sensor reference voltage therefrom and generate a precision sensor reference voltage in response thereto;    a voltmeter connected to the first operational amplifier and the first precision resistor and being configured to monitor the precision sensor reference voltage and establish a sensor operating point, the first operational amplifier and the voltmeter cooperating to buffer the precision sensor reference voltage and apply a substantially accurate sensor reference voltage to the first terminal;    a second operational amplifier connected to the second terminal and being configured to receive current discharging therefrom in response to the accurate sensor reference voltage applied to the first terminal; and    a tunable second precision resistor connected to the second operational amplifier and cooperating therewith to generate a sensor signal that is substantially proportional to the glucose level of the patient's blood.    
     
     
         8 . The bio-sensor system of  claim 7  wherein the glucose sensor is a 3-pin glucose sensor with the electrode assembly further including a third terminal co-located with the first and second terminals and being in fluid communication with the patient's blood, the glucose sensor further including: 
 an auxiliary control circuit connected between the third electrode and the second operational amplifier and being configured to monitor and control an amount of current discharging from the third terminal;    wherein the third terminal is configured to divert current away from the second electrode during application of the accurate sensor reference voltage applied to the first terminal such that the operational life of the glucose sensor may be increased.    
     
     
         9 . The bio-sensor system of  claim 5  further including a plurality of sensors, each one of the sensors being operative to sense a distinct physiological parameter of the patient and generate a sensor signal representative thereof.  
     
     
         10 . The bio-sensor system of  claim 9  wherein the RF receiver is configured to coordinate requests for data from one or more of the sensors for subsequent transmission of the data to the remote transponder.  
     
     
         11 . The bio-sensor system of  claim 10  wherein the wherein the data processor is configured to assign a preset identification code to the digital signal for identifying the sensor from which the sensor signal originates.  
     
     
         12 . A method of remotely monitoring physiological parameters using a bio-sensor system comprising a remote transponder and an on-chip transponder having a sensor implantable in a patient, the method comprising the steps of: 
 a. remotely generating and wirelessly transmitting a scanner signal with the remote transponder, the scanner signal containing radio signal power and a telemetry data request;    b. receiving the scanner signal at the on-chip transponder and filtering, amplifying and demodulating the scanner signal to generate a message signal in response thereto;    c. collecting the radio signal power from the scanner signal and generating a power signal in response thereto;    d. sensing at least one physiological parameter of the patient at the sensor and generating an analog sensor signal in response thereto;    e. receiving the power signal, the analog sensor signal and the message signal at an analog-to-digital (A/D) assembly and generating a digital signal representative of the analog sensor signal;    f. receiving the power signal, the message signal and the digital signal at a data processor and preparing the digital signal for modulation and generating a data signal representative of the digital signal;    g. receiving the power signal, the message signal and the data signal at an RF transmitter and modulating, amplifying, filtering and wirelessly transmitting the data signal; and    h. receiving the data signal at the remote transponder and extracting data representative of the physiological parameter of the patient.    
     
     
         13 . The method of  claim 12  wherein the sensor is a 2-pin glucose sensor having an electrode assembly with first and second terminals in fluid communication with the patient's blood for sensing a glucose level of the patient, step (d) further comprising the steps of: 
 tuning the power signal with a first precision resistor to generate a sensor reference voltage of about positive 0.7 volts for excitation of the glucose sensor;    receiving the sensor reference voltage at a first operational amplifier and generating a precision sensor reference voltage;    monitoring the precision sensor reference voltage with a voltmeter connected to the first operational amplifier and the first precision resistor to establish a sensor operating point;    buffering the precision sensor reference voltage with the first operational amplifier in cooperation with the voltmeter to generate a substantially accurate sensor reference voltage;    applying the substantially accurate sensor reference voltage to the first terminal to cause current to discharge from the second terminal in response to a reaction with the patient's blood at the first and second terminals;    receiving the discharging current at a second operational amplifier, the current being proportional to the glucose level of the patient's blood; and    tuning a second precision resistor connected to the second operational amplifier to form a voltage divider with the glucose sensor;    measuring the discharging current with the second precision resistor in cooperation with the second operational amplifier; and    generating the sensor signal that is substantially proportional to the glucose level.    
     
     
         14 . The method of  claim 13  wherein the sensor is a 3-pin glucose sensor additionally including a third terminal co-located with the first and second terminals and being in fluid communication with the patient's blood, step (d) further comprising the steps of: 
 diverting a portion of the current away from the second terminal by discharging current at the third terminal during application of the substantially accurate sensor reference voltage to the first terminal;    receiving the discharging current at an auxiliary control circuit connected between the third electrode and the second operational amplifier; and    monitoring and controlling an amount of current discharging from the third terminal in order to stabilize the substantially accurate sensor reference voltage applied to the first terminal and increase the operational life of the glucose sensor