Patent ID: 8679308

Claim:
A sensor to detect an analyte in a physiological fluid, comprising: a sensor having a surface a membrane, in contact with the sensor surface, the membrane comprising: an outer layer; a plurality of alternating layers of conversion layers comprising an enzyme capable of converting an analyte in a physiological fluid sample into a charged species and polyelectrolyte layers, the polyelectrolyte layers acting as matrices to host the conversion layers, wherein the polyelectrolyte comprises repeating units having an electrolyte group which dissociates in the physiological fluid, making the polyelectrolyte layer negatively charged, wherein the polyelectrolyte layers have a pKa value that differs by two pH units or more than the operating pH of the sensor; and wherein the conversion layers and the polyelectrolyte layers are selected to control the exclusion of a negatively charged physiological buffer species found in the physiological fluid sample, thereby enhancing the rate or sensitivity of the conversion of the analyte into a charged species, and wherein the outer layer of the membrane is negatively charged; and a transducer adapted to detect the presence or amount of the charged species, thereby detecting the presence or amount of the analyte in a physiological fluid sample.