Test system

• US 20070000777A1
• Filed: 06/01/2006
• Published: 01/04/2007
• Est. Priority Date: 06/03/2005
• Status: Active Grant

• Current Assignee: ARKRAY, Inc
• Original Assignee: Arkray Factory Ltd. (ARKRAY, Inc)
• Inventors: Chambers, Paul, Ho, Wah, Rippeth, John
• Granted Patent: US 7,695,600 B2
• Time in Patent Office: Days
• US Class Current: 204/403.140
• CPC Class Codes: C12Q 1/001 Enzyme electrodes

Abstract

A test system for measuring analyte concentration in a fluid sample includes:

• • (i) a capillary-fill biosensor (20) having a working electrode (24), a reference electrode (22) and a separate counter electrode (23), arranged such that a fluid sample which flows evenly along the capillary flow path will substantially completely cover the reference electrode (22) before the fluid sample makes contact with any part of the counter electrode (23); and
  • (ii) a test meter (42) for receiving the biosensor (20), the meter (42) including:
  • first signal circuitry (31) for producing a first signal when an electrical circuit is detected between the reference electrode (22) and the working electrode (24);
  • second signal circuitry (33) for producing a second signal when an electrical circuit is detected between the counter electrode (23) and at least one of the reference electrode (22) and the working electrode (24);
  • a timer (35) for determining the time interval between production of said first signal and said second signal; and
  • a processor (32) for triggering an error condition if said time interval exceeds a preset value or if said second signal is not produced within a preset time after said first signal is produced.

Claims

1. A test system comprising:

(i) a capillary-fill biosensor for indicating electrochemically the catalytic activity of an enzyme in the presence of a fluid sample containing an analyte acted upon by said enzyme;

the biosensor having a fluid inlet, a fluid outlet, and a capillary flow path connecting the fluid inlet and the fluid outlet;

the biosensor further including a working electrode, a reference electrode and a counter electrode located within the capillary flow path;

the working electrode including a catalytically-active quantity of said enzyme;

wherein the reference electrode is separate from the counter electrode, and the reference and counter electrodes are arranged such that a fluid sample which flows evenly along the capillary flow path from said fluid inlet will substantially completely cover the reference electrode before the fluid sample makes contact with any part of the counter electrode; and

(ii) a test meter for receiving said biosensor, the meter comprising;

contacts for making electrical contact with each electrode on said biosensor;

circuitry for performing an electrochemical measurement on said biosensor to produce a measured electrochemical value;

circuitry for determining an analyte concentration value for a specified biological fluid from said measured electrochemical value; and

circuitry for indicating a determined analyte concentration value;

the meter further comprising;

first signal circuitry for producing a first signal when an electrical circuit is detected between the reference electrode and the working electrode;

second signal circuitry for producing a second signal when an electrical circuit is detected between the counter electrode and at least one of the reference electrode and the working electrode;

a timer for determining the time interval between production of said first signal and said second signal; and

a processor for triggering an error condition if said time interval exceeds a preset value or if said second signal is not produced within a preset time after said first signal is produced.

2. A system according to claim 1, further comprising:

a switch for releasably connecting the reference electrode and the counter electrode, the switch being closed before an electrical circuit has been detected between the reference electrode and the working electrode; and

circuitry for opening the switch when an electrical circuit has been detected between the reference electrode and the working electrode.

3. A system according to claim 2, wherein said circuitry for opening the switch is a potentiostat circuit which makes a feedback loop when an electrical circuit has been made between the working electrode and the counter electrode.

4. A system according to claim 2, wherein the reference electrode will go open circuit when the switch is opened.

5. A system according to claim 1, wherein the biosensor comprises:

a first substrate;

a second substrate overlying at least a part of the first substrate;

the working electrode, the counter electrode, and the reference electrode each being provided on either one of the substrates;

conductive tracks connected to said working, counter and reference electrodes for making electrical connections with a test meter apparatus;

a spacer layer having a channel therein and disposed between the first substrate and the second substrate, the spacer layer channel co-operating with adjacent surfaces to define the capillary flow path which extends from an edge of at least one of said substrates to said electrodes.

6. A system according to claim 1, wherein each of said electrodes is non-mediated and includes a base layer comprising particles of a platinum-group metal or platinum-group metal oxide bonded together by a resin.

7. A system according to claim 6, wherein each of said electrodes further includes a top layer comprising a buffer on the base layer, and a catalytically-active quantity of an oxidoreductase enzyme in at least one of the top layer and the base layer.

8. A system according to claim 1, wherein the counter electrode is downstream of the working electrode in the capillary flow path.

9. A system according claim 1, wherein the working electrode is positioned such that a fluid sample which flows evenly along the capillary flow path from said edge will make contact with the reference electrode no later than it will make contact with the working electrode.

10. A test system comprising:

(i) a capillary-fill biosensor having a working electrode, a reference electrode and a counter electrode located within a capillary flow path between a fluid inlet and a fluid outlet;

wherein the reference electrode is separate from the counter electrode, and the reference and counter electrodes are arranged such that a fluid sample which flows evenly along the capillary flow path from said fluid inlet will substantially completely cover the reference electrode before the fluid sample makes contact with any part of the counter electrode; and

(ii) a test meter for receiving said biosensor, said test meter including;

circuitry for producing a first signal when an electrical circuit is detected between the reference electrode and the working electrode;

circuitry for producing a second signal when an electrical circuit is detected between the counter electrode and at least one of the reference electrode and the working electrode;

a timer for determining the time interval between production of said first signal and said second signal; and

a processor for triggering an error condition if said time interval exceeds a preset value or if said second signal is not produced within a preset time after said first signal is produced.

11. A test system comprising:

(i) a capillary-fill biosensor for indicating electrochemically the catalytic activity of an enzyme in the presence of a fluid sample containing an analyte acted upon by said enzyme;

the biosensor having a working electrode, a reference electrode and a counter electrode located within a capillary flow path between a fluid inlet and a fluid outlet;

the working electrode including a catalytically-active quantity of said enzyme;

wherein the reference electrode is separate from the counter electrode, and the reference and counter electrodes are arranged such that a fluid sample which flows evenly along the capillary flow path from said fluid inlet will substantially completely cover the reference electrode before the fluid sample makes contact with any part of the counter electrode; and

(ii) a test meter for receiving said biosensor, the meter comprising;

means for making electrical contact with each electrode on said biosensor;

circuitry for performing an electrochemical measurement on said biosensor to produce a measured electrochemical value;

means for determining an analyte concentration value for a specified biological fluid from said measured electrochemical value; and

means for indicating a determined analyte concentration value;

the meter further comprising;

first signal means for producing a first signal when an electrical circuit is detected between the reference electrode and the working electrode;

second signal means for producing a second signal when an electrical circuit is detected between the counter electrode and at least one of the reference electrode and the working electrode;

timing means for determining the time interval between production of said first signal and said second signal; and

processing means for triggering an error condition if said time interval exceeds a preset value or if said second signal is not produced within a preset time after said first signal is produced.

12. A test meter for use with a biosensor, the meter comprising:

a first electrode contact for making an electrical connection with a working electrode on the biosensor;

a second electrode contact for making electrical contact with a reference electrode on the biosensor;

a third electrode contact for making an electrical connection with a counter electrode on the biosensor;

a processor for receiving an input signal from said electrode contacts;

a data store containing data relating to a specified biological fluid and accessible by said processor;

circuitry for measuring an electrical property of a fluid sample applied to a biosensor when the biosensor is inserted in the meter;

wherein the processor is arranged in operation to access the data store and to output an output signal representative of analyte concentration derived from the input signal and data contained in the accessed data store;

an output device for visually or audibly outputting information dependent on said output signal;

first signal circuitry for producing a first signal when an electrical circuit is detected between said first electrode contact and said second electrode contact;

second signal circuitry for producing a second signal when an electrical circuit is detected between said third electrode contact and at least one of said first electrode contact and said second electrode contact;

a timer for determining the time interval between production of said first signal and said second signal; and

circuitry for triggering an error condition if said time interval exceeds a preset value or if said second signal is not produced within a preset time after said first signal is produced.

13. A test meter according to claim 12, further comprising:

a switch for releasably connecting the second electrode contact and the third electrode contact, the switch being closed before an electrical circuit has been detected; and

switch-opening circuitry for opening the switch when an electrical circuit has been detected.

14. A test meter according to claim 13, wherein said switch-opening circuitry is a potentiostat circuit which makes a feedback loop when an electrical circuit has been made between the first electrode contact and the third electrode contact.

15. A test meter according to claim 13, wherein the second electrode contact will go open circuit when the switch is opened.

16. A test meter for use with a biosensor, the meter comprising:

a first electrode contact for making an electrical connection with a working electrode on the biosensor;

a second electrode contact for making electrical contact with a reference electrode on the biosensor;

a third electrode contact for making an electrical connection with a counter electrode on the biosensor;

a processor for receiving an input signal from said electrode contacts;

storage means containing data relating to a specified biological fluid and accessible by said processor;

means for measuring an electrical property of a fluid sample applied to a biosensor when the biosensor is inserted in the meter;

wherein the processor is arranged in operation to access the storage means and to output an output signal representative of analyte concentration derived from the input signal and data contained in the accessed storage means;

means for visually or audibly outputting information dependent on said output signal;

a switch for releasably connecting the second electrode contact and the third electrode contact, the switch being closed before a first electrical circuit has been detected;

potentiostat circuitry for opening the switch when said first electrical circuit has been detected, which will cause the second electrode contact to go open circuit;

said circuitry being adapted to make a feedback loop when a second electrical circuit has been made between the first electrode contact and the third electrode contact;

timing means for determining the time interval between detection of said first electrical circuit and detection of said second electrical circuit; and

means for triggering an error condition if said time interval exceeds a preset value or if said second electrical circuit is not detected within a preset time after said first electrical circuit.