Subcutaneous analyte sensor

An assembly for measuring the concentration of an analyte in a biological matrix, comprising:

• an implantable optical-sensing element comprising a body;
• a first semi-permeable membrane mounted on said body, said first semi-permeable membrane being permeable to said analyte, and impermeable to background species in said biological matrix, said first membrane and said body aligned to define a first cavity;
• a first refractive element disposed in said first cavity;
• a second membrane mounted on said body remote from said first membrane, said second membrane and said body aligned to define a second cavity;
• and a second refractive element disposed in said second cavity;
• a source for providing light into each of said first and second cavities toward said respective first and second refractive elements;
• a detector for receiving light from each of said first and second cavities;
• and
• a signal-processing and computing element optically coupled to said detector for relating said received light to a concentration of said analyte.

An implantable optical-sensing element suitable for measuring the concentration of an analyte in a biological matrix, said optical-sensing element comprising:

• a body;
• a first semi-permeable membrane mounted on said body, said first semi-permeable membrane being permeable to said analyte, and impermeable to background species in said biological matrix, said first membrane and said body aligned to define a first cavity;
• a first refractive element disposed in said first cavity;
• a second membrane mounted on said body remote from said first membrane, said second membrane and said body aligned to define a second cavity isolated from said first cavity;
• and a second refractive element disposed in said second cavity.

A method for measuring the concentration of an analyte in a biological matrix, said method comprising:

• implanting an optical-sensing element in said biological matrix, said optical-sensing element comprising a body, a semi-permeable membrane mounted to said body, said semi-permeable membrane being permeable to said analyte, but impermeable to background species in said matrix, said semi-permeable membrane and said body defining a cavity, and a refractive element disposed in said cavity;
• introducing primary light from a light-emitting source into said body of said optical-sensing element, and directing said primary light toward said refractive element;
• collecting secondary light reflected from said optical-sensing element and transmitting said secondary light to a light-detecting device;
• measuring an intensity of said secondary light, and evaluating said analyte concentration in said biological matrix by comparing said measured intensity of said secondary light with an intensity of said primary light.

A method for measuring the concentration of an analyte in a biological matrix, said method comprising

• implanting an optical-sensing element in said biological matrix, said optical-sensing element comprising a body, a first membrane mounted to said body, a second membrane mounted on said body remote from said first membrane, at least one of said membranes being permeable to said analyte, but impermeable to background species in said biological matrix, said first and second membranes and said body defining a cavity, and a refractive element disposed in said cavity;
• transmitting primary light from a light-emitting source into said cavity toward said refractive element;
• collecting secondary light reflected from refractive element, and transmitting said secondary light to a light-detecting device;
• measuring an intensity of said secondary light with said light-detecting device;
• deriving said analyte concentration in said biological matrix from said measured intensity of said secondary light by means of an evaluation algorithm and a calibration.

A method for measuring the concentration of an analyte in a biological matrix, said method comprising:

• implanting an optical-sensing element in said biological matrix, said optical-sensing element comprising:
• a body, a first semi-permeable membrane mounted on said body, a second semi-permeable membrane mounted on said body remote from said first semi-permeable membrane, said first semi-permeable membrane being permeable to said analyte, but impermeable to background species in said biological matrix, said body and said first membrane defining a first cavity, a first refractive element disposed in said first cavity, said body and said second membrane defining a second cavity isolated from said first cavity, and a second refractive element disposed in said second cavity;
• transmitting primary light from a light-emitting source to said body, and directing respective streams of said primary light into said first cavity toward said first refractive element, and into said second cavity toward said second refractive element;
• collecting light from said body resulting from reflection at said first refractive element and transmitting said light to a first channel of a light-detecting device;
• collecting light from said body resulting from reflection at said second refractive element and transmitting said light to a second channel of said light-detecting device;
• measuring the intensity of light collected from each of said first and second channels;
• computing the concentration of an analyte in said biological matrix by comparing the intensity of the transmitted light and the light collected from each of said first and second channels.

An assembly for monitoring the concentration of an analyte in a biological matrix, comprising:

• an implantable optical-sensing element, said implantable optical-sensing element comprising:
• a body;
• a membrane mounted on said body, said membrane and body defining a cavity for receiving said analyte, said membrane being substantially permeable to said analyte and substantially impermeable to background species in said biological matrix;
• and a refractive element disposed in said cavity;
• a source for providing light of a first wavelength and a second wavelength into said cavity, said refractive element having a refractive index greater than the refractive index of the analyte at the first wavelength, and less than the refractive index of the analyte at the second wavelength;
• a detector for receiving from said cavity an intensity of light at each of said first and second wavelengths at a first concentration of said analyte, and for receiving from said cavity an intensity of light at each of said first and second wavelengths at a second concentration of said analyte;
• and
• a signal-processing and computing element optically coupled to said detector for comparing said intensities of light received at said first wavelength to said intensities of light received at said second wavelength, and relating said intensities to analyte concentration.

A method for monitoring a change in the concentration of an analyte in a biological matrix of a test subject, comprising:

• implanting an optical-sensing element in said subject, said implantable optical-sensing element comprising a body;
• a membrane mounted on said body, said membrane and body defining a cavity for receiving said analyte, said membrane being substantially permeable to said analyte and substantially impermeable to background species in said biological matrix;
• and a refractive element disposed in said cavity;
• transmitting light of a first wavelength and a second wavelength into said cavity, said refractive element having a refractive index greater than the refractive index of the analyte at the first wavelength, and less than the refractive index of the analyte at the second wavelength;
• collecting from said cavity an intensity of light at each of said first and second wavelengths at a first concentration of said analyte, and an intensity of light at each of said first and second wavelengths at a second concentration of said analyte;
• and
• measuring said change in concentration of said analyte by comparing said intensities of light received at said first wavelength to said intensities of light received at said second wavelength for each of said first and second concentrations, and relating said intensities to changes in analyte concentration.