We report the design, construction, and testing of a contact lens with an integrated amperometric glucose sensor, proposing the possibility of in situ human health monitoring simply by wearing a contact lens. The glucose sensor was constructed by creating microstructures on a polymer substrate, which was subsequently shaped into a contact lens. Titania sol-gel film was applied to immobilize glucose oxidase, and Nafion® was used to decrease several potential interferences (ascorbic acid, lactate, and urea) present in the tear film. The sensor exhibits a fast response (20 sec), a high sensitivity (240 µAcm −2 mM −1 ) and a good reproducibility after testing a number of sensors. It shows good linearity for the typical range of glucose concentrations in the tear film (0.1-0.6 mM), and acceptable accuracy in the presence of interfering agents. The sensor can attain a minimum detection of less than 0.01 mM glucose.

No abstract

We present an integrated functional contact lens, composed of a differential glucose sensor module, metal interconnects, sensor read-out circuit, antenna and telecommunication circuit, to monitor tear glucose levels wirelessly, continuously and non-invasively. The electrochemical differential sensor module is based on immobilization of activated and de-activated glucose oxidase. We characterized the sensor on a model polymer eye and determined that it showed good repeatability, molecular interference rejection and linearity in the range of 0–2 mM glucose, covering normal tear glucose concentrations (0.1–0.6 mM). We also report the temperature, ageing and protein-fouling sensitivity of the sensor. We report the design and implementation of a low-power (3 µW) sensor read-out and telecommunication circuit to deliver wireless power and transmit data for the sensor module. Using this small chip (0.36 mm2), we produced an integrated contact lens with sensors and demonstrated wireless operation of the system and glucose read-out over the distance of several centimeters.

No abstract

The interaction of unprotonated ammonia molecules with polypyrrole (PPy) is employed for the amperometric detection of ammonia with the use of an anodically polarized platinum electrode modified with PPy as the working electrode. The polymer was obtained by electropolymerization in potentiostatic conditions from aqueous solutions. Chloride was found to be the most suitable dopant for PPy from several dopants studied. Satisfactory dynamic characteristics of detection permit its application to the determination of ammonia in a flow injection system up to 100 pM of analyte with a detection limit of 0.6 pM. Such a detector of ammonia was also employed as the internal detector in amperometric biosensors for urea and creatinine by the immoblizdtion in a different way at the PPy surface of urease and creatinine iminohydrolase, respectively. An amperometric biosensor of very low sensitivity was obtained by urease entrapment in the PPy layer during the electropolymerization. The urea membrane biosensor was successfully applied in the determination of urea in human blood samples. On the basis of results of elemental analysis, UV and IR spectroscopy some suggestions are presented about the mechanism of the interaction between PPy and ammonia and about the anodic electrode process occurring in the amperometric detection of ammonia.