Analyte sensors employing multiple enzymes and methods associated therewith
Methods and analyte sensors including at least a first working electrode having a first active area thereon, and performing a dip coating operation to deposit a bilayer membrane upon the first working electrode and the first active area. The bilayer may include an inner layer having a first membrane polymer and an outer layer having a second membrane polymer, the first membrane polymer and the second membrane polymer differing from one another. The dip coating operation may comprise one or more first dips in a first membrane formulation to form the inner layer of the bilayer membrane and one or more second dips in a second membrane formulation to form the outer layer of the bilayer membrane upon the inner layer.
1 . An analyte sensor for detecting glucose and ketones in vivo, the sensor comprising:
at least a first working electrode and a second working electrode;
a ketones-responsive active area disposed upon a surface of the first working electrode;
a glucose-responsive active area disposed upon a surface of the second working electrode;
a mass transport limiting membrane overcoating the ketones-responsive active area and the glucose-responsive active area;
wherein:
(i) one or more of an area, a size, or an areal ratio of the glucose-responsive area and the ketones-responsive active area vary with respect to one another;
(ii) the mass transport limiting membrane has a thickness over the ketones-responsive active area that differs from a thickness of the mass transport limiting membrane over the glucose-responsive active area; or
(iii) both (i) and (ii);
wherein (i), (ii), and (iii) provide independent variation of analyte sensitivity at each working electrode, and
wherein the sensor is configured to be partially inserted into a user's skin such that a distal portion of the sensor is in contact with an interstitial fluid to detect glucose and ketones in vivo.
2 . The analyte sensor of claim 1 , wherein the ketones-responsive active area comprises a first polymer and an enzyme system comprising nicotinamide adenine dinucleotide (NAD) and at least two enzymes that facilitate detection of ketones.
3 . The analyte sensor of claim 2 , wherein the glucose-responsive active area comprises a second polymer and a glucose-responsive enzyme.
4 . The analyte sensor of claim 3 , wherein the glucose-responsive enzyme comprises glucose oxidase.
5 . The analyte sensor of claim 3 , wherein the glucose-responsive area comprises a second electron transfer agent.
6 . The analyte sensor of claim 2 , wherein the enzyme system comprises β-hydroxybutyrate dehydrogenase and diaphorase.
7 . The analyte sensor of claim 2 , wherein the ketones-responsive area comprises a first electron transfer agent.
8 . The analyte of sensor of claim 1 , wherein the thickness of the mass transport limiting membrane over the ketones-responsive active area differs from the thickness of the mass transport limiting membrane over the glucose-responsive active area.
9 . The analyte sensor of claim 8 , wherein the mass transport limiting membrane comprises a multi-component membrane portion disposed upon the ketone-responsive active area.
10 . The analyte sensor of claim 9 , wherein the mass transport limiting membrane disposed upon the ketone-responsive active area is a bilayer membrane.
11 . The analyte sensor of claim 9 , wherein the multi-component membrane comprises polyvinylpyridine and polyvinylpyridine-co-styrene.
12 . The analyte sensor of claim 8 , wherein the mass transport limiting membrane comprises a first portion overcoating the ketones-responsive active area and a second portion overcoating the glucose-responsive active area; and wherein the first portion is thicker than the second portion of the membrane.
13 . The analyte sensor of claim 1 , wherein the size of the glucose-responsive active area and the ketones-responsive active area vary with respect to one another.
14 . The analyte sensor of claim 13 , wherein the ketones-responsive and glucose-responsive active areas each comprises at least one sensing spot, and the ketones-responsive and glucose-responsive active areas each range in size from about 0.01 mm 2 to about 1 mm 2 .
15 . The analyte sensor of claim 1 , wherein the first working electrode is configured to generate a first signal indicative of β-hydroxybutyrate concentration, and wherein the second working electrode is configured to generate a second signal indicative of glucose concentration.
16 . The analyte sensor of claim 15 , wherein the first signal and second signal are measured simultaneously via first channel and second channels, respectively.
17 . A sensor control device, comprising:
(i) the sensor of claim 15 ; and
(ii) sensor electronics configured to determine a β-hydroxybutyrate concentration and glucose concentration based on the first and second signals using a calibration curve for each analyte.
18 . An analyte sensing system for detecting glucose and ketones in vivo comprising the sensor control device of claim 17 .
19 . The analyte sensing system of claim 18 , further comprising a reader device to display the β-hydroxybutyrate concentration and glucose concentration.
20 . The analyte sensor of claim 1 , wherein the mass transport limiting membrane comprises a first membrane disposed over the ketones-responsive active area and a second membrane disposed over the first membrane and the glucose-responsive active area.
21 . The analyte sensor of claim 20 , wherein the first membrane comprises a first membrane polymer and the second membrane comprises a second membrane polymer that differs from the first membrane polymer.
22 . The analyte sensor of claim 21 , wherein the first membrane polymer comprises a crosslinked polyvinylpyridine homopolymer or copolymer.
23 . The analyte sensor of claim 22 , wherein the second membrane polymer comprises a crosslinked polyvinylpyridine-co-styrene polymer.