Photometric glucose measurement system using glucose-sensitive hydrogel

A biosensor for measuring the concentration of a free analyte in a body fluid, comprising:

• a polymeric hydrogel filament that changes its displacement in proportion to the concentration of the free analyte;
• a photoreceptor arranged in relation to the polymer hydrogel filament so that the intensity of light received by the photoreceptor varies with the displacement of the polymer hydrogel filament;
• a source of light directing light toward the photoreceptor with the hydrogel filament positioned between the source of light and the photoreceptor to block a portion of the light from the source of light directed to the photoreceptor, the amount of light blocked depending upon the displacement of the hydrogel filament;
• and means for reporting a data signal reflective of the measured light intensity on the photoreceptor.

A biosensor for measuring the concentration of a free analyte in a body fluid, comprising:

• a polymeric hydrogel filament that changes its displacement in proportion to the concentration of the free analyte;
• a photoreceptor arranged in relation to the polymer hydrogel filament so that the intensity of light received by the photoreceptor varies with the displacement of the polymer hydrogel filament;
• a source of light directing light toward the hydrogel filiment;
• reflective material arranged on the hydrogel filament to move with displacement of the hydrogel filament and to reflect light from the source of light toward the photoreceptor, movement of the reflector changing the intensity of light reflected to the photoreceptor;
• and means for reporting a data signal reflective of the measured light intensity on the photoreceptor.

A biosensor for measuring the concentration of glucose, in a body fluid, comprising:

• a polymeric hydrogel filament that changes its displacement in proportion to the concentration of glucose;
• a photoreceptor arranged in relation to the polymer hydrogel filament so that the intensity of light received by the photoreceptor varies with the displacement of the polymer hydrogel filament;
• a battery powered telemeter for reporting a data signal reflective of the measured light intensity on the photoreceptor, receiving means positioned at a location remote to the patient for receiving the data signal;
• and computing means responsive to the data signal to compare the data signal to a calibration curve to compute a concentration of the free glucose in the body fluid and produce an output signal representing the free glucose concentration.

A biosensor for measuring the concentration of a free analyte in a body fluid, comprising:

• a polymeric hydrogel filament that chances its displacement in proportion to the concentration of the free analyte;
• a photoreceptor arranged in relation to the polymer hydrogel filament so that the intensity of light received by the photoreceptor varies with the displacement of the polymer hydrogel filament;
• means for reporting a data signal reflective of the measured light intensity on the photoreceptor;
• a reference polymeric hydrogel filament similar to the hydrogel filament but which does not change its displacement in response to the concentration of the free analyte;
• a reference photoreceptor arranged in relation to the reference polymer hydrogel filament so that the intensity of light received by the photoreceptor varies with the displacement of the reference polymer hydrogel filament;
• means for reporting a reference data signal reflective of the measured light intensity on the reference photoreceptor, and means for compensating the data signal in respones to changes in the reference data signal to compensate for any change in the data signal attributable to factors other than the analyte concentration.

A sensor for measuring the concentration of free molecules of an analyte in a fluid, comprising:

• a rigid enclosure having an open end and a closed end, the open end being covered by a semipermeable membrane adapted to be placed in the fluid;
• a hydrogel positioned within the enclosure between the semipermeable membrane and the closed end, said hydrogel changing its displacement in the enclosure depending upon analyte concentration in the fluid;
• and
• a photoreceptor positioned with respect to the enclosure so that changes in displacement of the hydrogel are accompanied by changes in light intensity detected by the photoreceptor.

A method of determining the concentration of free analyte in a fluid, comprising the steps of:

• providing a hydrogel filament having pendant charged or uncharged moieties, analyte molecules, and analyte-specific binding molecules covalently immobilized therein so that the hydrogel filament will swell to varying degrees upon exposure to varying concentrations of analyte;
• enclosing the hydrogel in a rigid structure which has at least one permeable portion for contacting the fluid, the permeable portion permitting free analyte in the fluid to diffuse into the hydrogel, the rigid structure allowing displacement of the hydrogel therein in response to the swelling of the hydrogel in response to analyte concentration in the fluid;
• positioning a photoreceptor with respect to the rigid structure so that light intensity on the photoreceptor varies with displacement of the hydrogel;
• inserting the permeable portion of the biosensor into the fluid and allowing sufficient time for free analyte molecules to diffuse to equilibrium within the hydrogel;
• sensing the light intensity on the photoreceptor and providing a data signal reflective thereof, which is also reflective of the displacement of the hydrogel;
• and
• comparing the sensed hydrogel displacement with a calibration curve to determine analyte concentration of the test fluid.