Biosensor, iontophoretic sampling system and methods of use thereof

Claim 1

A sampling system for monitoring the concentration of an analyte present in a biological system, said sampling system comprising: (a) a reservoir containing an ionically conductive medium and an enzyme capable of reacting with the analyte to produce hydrogen peroxide; (b) sampling means for extracting the analyte from the biological system into the reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoir which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means is in operative contact with the reservoir; and (c) a sensor element in operative contact with the reservoir, wherein said sensor element reacts electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal, and said sensor element comprises an electrode having a geometric surface area which ranges from about 0.1 to 3 cm 2 , a background current which ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity which ranges from about 6 to 180 nA/µA of hydrogen peroxide when measured in a buffer solution at 0.6V.

Claim 11

A method for monitoring the concentration of an analyte present in a biological system, said method comprising: (a) extracting said analyte from the biological system into a reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in said reservoir; (b) contacting the analyte extracted in step (a) with an enzyme that reacts with the analyte to produce hydrogen peroxide; (c) detecting the hydrogen peroxide produced in step (b) with a sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal, wherein said sensor element comprises an electrode having a geometric surface area which ranges from about 0.1 to 3 cm 2 , a background current which ranges from about 2 to 60 nA or less when measured in a buffer solution at 0.6V, and a sensitivity which ranges from about 6 to 180 nA/µM of hydrogen peroxide when measured in a buffer solution at 0.6V; (d) measuring the signal produced in step (c); (e) correlating the measurement obtained in step (d) with the concentration of the analyte in the biological system; and (f) performing steps (a) - (d) continually, and step (e) periodically to monitor the concentration of the analyte in the biological system.

Claim 17

A method for monitoring the concentration of an analyte present in a biological system, said method comprising: (a) contacting a sampling system with the biological system, said sampling system comprising (i) first and second reservoirs where each reservoir contains an ionically conductive medium and at least the first reservoir further contains an enzyme capable of reacting with the analyte to produced hydrogen peroxide. (ii) reverse iontophoretic sampling means for extracting the analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoir which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second reservoirs, wherein each iontophoretic electrode has a geometric area ranging from about 0.3 to 1.0 cm 2 , and is capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm 2 of electrode area; and (iii) first and second sensor elements in operative contact with the first and second reservoirs, wherein each sensor element is capable of reacting electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal; (b) extracting said analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the first reservoir, wherein said extracting is carried out using the reverse iontophoretic system; (c) contacting the analyte extracted in step (b) with an enzyme that reacts with the analyte to produce hydrogen peroxide; (d) detecting the hydrogen peroxide produced in step (c) with the first sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal; (e) measuring the signal produced in step (d); (f) correlating the measurement obtained in step (e) with the concentration of the analyte in the biological system; and (g) performing steps (b)- (e) continually, and step (f) periodically to monitor the concentration of the analyte in the biological system.

Claim 20

A method for monitoring the concentration of an analyte present in a biological system, said method comprising: (a) contacting a sampling system with the biological system, said sampling system comprising (i) first and second reservoirs where each reservoir contains an ionically conductive medium and an enzyme capable of reacting with the analyte to produce hydrogen peroxide; (ii) reverse iontophoretic sampling means for extracting the analyte from the biological system into the reservoirs to obtain a sub-millimolar (sub-mM) concentration of the analyte in the reservoirs which reacts with the enzyme to produce hydrogen peroxide, wherein said sampling means comprises first and second iontophoretic electrodes in operative contact with said first and second reservoirs, wherein each iontophoretic electrode has a geometric area ranging from about 0.3 to 1.0 cm 2 , and is capable of repeated cycles of current passage in the range of about 0.01 to 1.0 mA/cm 2 of electrode area; and (iii) first and second sensor elements in operative contact with the first and second reservoirs, wherein each sensor element is capable of reacting electrochemically with the hydrogen peroxide produced in the reservoir to provide a detectable signal; (b) extracting said analyte from the biological system into the first reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the first reservoir, wherein said extracting is carried out using the reverse iontophoretic system; (c) contacting the analyte extracted in step (b) with an enzyme that reacts with the analyte to produce hydrogen peroxide; (d) detecting the hydrogen peroxide produced in step (c) with the first sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal; (e) measuring the signal produced in step (d); (f) correlating the measurement obtained in step (e) with the concentration of the analyte in the biological system; (g) extracting said analyte from the biological system into the second reservoir to obtain a sub-millimolar (sub-mM) concentration of the analyte in the second reservoir, wherein said extracting is carried out using the reverse iontophoretic system; (h) contacting the analyte extracted in step (g) with an enzyme that reacts with the analyte to produce hydrogen peroxide; (i) detecting the hydrogen peroxide produced in step (h) with the second sensor element which reacts electrochemically with the hydrogen peroxide to produce a detectable signal; (j) measuring the signal produced in step (i); (k) correlating the measurement obtained in step (j) with the concentration of the analyte in the biological system; and (l) continually performing (i) steps (b)- (e) alternating with (ii) steps (g) - (j), and periodically performing steps (f) and (k) to monitor the concentration of the analyte in the biological system.