US4340458A — Glucose sensor

Claim 1

Independent Claim 138 words

Apparatus implantable in a living body for sensing the concentration of glucose in biological fluids, comprising an electrode for catalytically promoting electrochemical oxidation of glucose, a voltage source, means for applying a varying voltage from said source to said electrode to cause a current flow therethrough, means for integrating current at the electrode with respect to time, and control means automatically operative without manual intervention to cause said voltage to sweep over a range in a first direction from a first limit to a second limit and in the reverse direction back toward said first limit, and to selectively activate said means for integrating during a period including at least a portion of said voltage sweep in both directions selected to produce a total charge sensitive to glucose concentration and relatively insensitive to other components in the fluid.

Claim 2

Dependent Claim 138 words

Apparatus implantable in a living body for sensing the concentration of glucose in biological fluids, comprising an electrode for catalytically promoting electrochemical oxidation of glucose, a voltage source, means for applying a varying voltage from said source to said electrode to cause a current flow therethrough, means for integrating current at the electrode with respect to time, and control means automatically operative without manual intervention to cause said voltage to sweep over a range in a first direction from a first limit to a second limit and in the reverse direction back toward said first limit, and to selectively activate said means for integrating during a period including at least a portion of said voltage sweep in both directions selected to produce a total charge sensitive to glucose concentration and relatively insensitive to other components in the fluid.

Claim 3

Dependent Claim 86 words

The apparatus of claim 1 in which said portion is selected so that the charge responsive to glucose concentration has predominantly the same algebraic sign throughout said period, and so that the charge responsive to interfering components of said fluid has a positive sign in one segment of said period and a negative sign in another segment of said period, whereby the glucose-responsive charge, and thus sensitivity to glucose, is reinforced, and the charge responsive to interfering substances at least partially cancels, thus reducing such interference.

Claim 4

Dependent Claim 56 words

The apparatus of claim 1 or 2 in which the lower limit of such voltage sweep is between -1.0 and -0.6 volts and the upper limit is between 0.7 and 1.1 volts, said sweep including an anodic sweep from said lower to said upper limit and a cathodic sweep from said upper to said lower limit.

Claim 5

Dependent Claim 35 words

The apparatus of claim 1 or 2 in which said voltage sweep includes dwell periods at said upper and lower limits, and the rate of voltage change during said anodic and cathodic sweeps is constant.

Claim 6

Dependent Claim 19 words

The apparatus of claim 1 or 2 in which said integration takes place continuously during one complete voltage sweep.

Claim 7

Dependent Claim 34 words

The apparatus of claim 1 or 2 in which said period includes the anodic sweep between -0.45 volts and said upper limit, the dwell at said upper limit, and the entire cathodic voltage sweep.

Claim 8

Dependent Claim 28 words

The apparatus of claim 1 or 2 in which the rate of voltage change during said cathodic voltage sweep is more rapid than during said anodic voltage sweep.

Claim 9

Dependent Claim 35 words

The apparatus of claim 1 or 2 in which said varying of said applied voltage ceases during holding periods between said limits, said holding periods being at potentials at which glucose undergoes an electrochemical reaction.

Claim 10

Dependent Claim 41 words

The apparatus of claim 1 or 2 in which said period is selected so that the charge attributable to any specific interfering component of the fluid cancels, whereby changes in concentration of that specific component do not affect the charge measured.

Claim 11

Dependent Claim 32 words

The apparatus of claim 1 or 2 in which said apparatus includes normalizing means for forming the ratio of said total charge to the total absolute value of charge during said period.

Claim 12

Dependent Claim 29 words

Apparatus according to claim 10 wherein said voltage variation includes an anodic sweep and a cathodic sweep, said rate of voltage variation being between 0.5 volts/min and 4 volts/min.

Claim 13

Dependent Claim 24 words

Apparatus according to claim 11 in which the rate of voltage change during said cathodic sweep is more rapid than during said anodic sweep.

Claim 14

Dependent Claim 141 words

Apparatus for sensing the concentration of glucose in biological fluids comprising an electrode for catalytically promoting electrochemical oxidation of glucose, a voltage source, means for applying a varying voltage from the source to said electrode to cause a current to flow therethrough, means for measuring current at said electrode, and control means automatically operative without manual intervention to cause said voltage to sweep over a range in a first direction from a first limit to a second limit and in the reverse direction back toward said first limit, and to selectively activate said means for measuring at at least one isolated point, between 0.2 volts and 0.6 volts during the anodic variation of the voltage sweep, selected to be sensitive to changes in levels of glucose concentration in said fluid but relatively insensitive to levels of other constituents of said fluid.

Claim 15

Dependent Claim 141 words

Apparatus for sensing the concentration of glucose in biological fluids comprising an electrode for catalytically promoting electrochemical oxidation of glucose, a voltage source, means for applying a varying voltage from the source to said electrode to cause a current to flow therethrough, means for measuring current at said electrode, and control means automatically operative without manual intervention to cause said voltage to sweep over a range in a first direction from a first limit to a second limit and in the reverse direction back toward said first limit, and to selectively activate said means for measuring at at least one isolated point, between 0.2 volts and 0.6 volts during the anodic variation of the voltage sweep, selected to be sensitive to changes in levels of glucose concentration in said fluid but relatively insensitive to levels of other constituents of said fluid.

Claim 16

Dependent Claim 30 words

Apparatus of claim 13 in which said lower limit of said voltage variation is between -1.0 and -0.6 volts and the said upper limit is between 0.7 and 1.1 volts.

Claim 17

Dependent Claim 26 words

Apparatus of claim 13 in which the rate of change of said voltage variation is constant between said limits, and includes dwell periods at each limit.

Claim 18

Dependent Claim 15 words

Apparatus according to claim 15 in which said dwell periods are greater than 2 seconds.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1985-07-19	1986-01-18	1986-07-20	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1989-07-19	1990-01-18	1990-07-20	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1993-07-19	1994-01-18	1994-07-20	$7700.00	Window Closed / Lapsed

Glucose sensor

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