Abstract: A sensor for fluorescence measurement comprising: a light source arranged for emitting light to a sample region, wherein the light source intensity is modulatable; an indicator system located at the sample region, said indicator system comprising: a receptor for an analyte; and a fluorophore associated with said receptor, wherein the fluorophore has a fluorescence lifetime that changes in response to the presence of analyte at the receptor; a single photon avalanche diode arranged to receive fluorescence light emitted from said sample region in response to the light incident on the sample region from the light source, and to generate an output signal; a driver arranged to modulate the light source intensity at a first frequency; a bias voltage source arranged to apply a bias voltage to the single photon avalanche diode, wherein the bias voltage is modulated at a second frequency, different from the first frequency, and wherein the bias voltage is above the breakdown voltage of the single photon avalanche diod

Abstract: A glucose sensor for intravascular measurement of glucose concentration wherein the sensor is arranged to measure glucose concentration by monitoring the lifetime of the fluorophore, the sensor comprising:—an indicator system comprising a receptor for selectively binding to glucose and a fluorophore associated with said receptor, wherein the fluorophore has a life-time of less than 100 ns;—a light source;—an optical fibre arranged to direct light from the light source onto the indicator system; —a detector arranged to receive fluorescent light emitted from the indicator system; and—a signal processor arranged to determine information related to a fluorescence lifetime of the fluorophore based on at least the output signal of the detector.

Abstract: A glucose sensor for measurement of glucose in subcutaneous tissue, the sensor comprising: a probe for subcutaneous insertion, the probe containing an indicator system comprising a receptor for selectively binding to glucose and a fluorophore associated with said receptor, wherein the fluorophore has a fluorescence lifetime of less than 100 ns; a detector head which is optically connected to the probe and which is for location outside the body; a light source; and a detector arranged to receive fluorescent light emitted from the indicator system, wherein the light source and detector are optionally located within the detector head; wherein the sensor is arranged to measure glucose concentration in subcutaneous tissue by monitoring the fluorescence lifetime of the fluorophore.