Background: Tear glucose has been suggested previously as a potential approach for the noninvasive estimation of blood glucose. While the topic remains unresolved, an overview of previous studies suggests the importance of a tear sampling approach and warrants new technology development. A concept device is presented that meets the needs of a tear glucose biosensor.
Methods: Three approaches to chronoamperometric glucose sensing were evaluated, including glucose oxidase mediated by potassium ferricyanide or oxygen with a hydrogen peroxide catalyst, Prussian blue, and potassium ferricyanide-mediated glucose dehydrogenase. For tear sampling, calcium alginate, poly(2-hydroxyethyl methacrylate), and polyurethane foam were screened as an absorbent tear sampling material. A quantitative model based on the proposed function of concept device was created.
Results: For glucose sensing, it was found that potassium ferricyanide with glucose dehydrogenase was ideal, featuring oxygen insensitivity, long-term stability, and a lower limit of detection of 2 muM glucose. Polyurethane foam possessed all of the required characteristics for tear sampling, including reproducible sampling from a hydrogel-simulated, eye surface (4.2 +/- 0.5 microl; n = 8). It is estimated that 100 microM of glucose tear fluid would yield 135 nA (14.9% relative standard deviation).
Conclusion: A novel concept device for tear glucose sampling was presented, and the key functions of this device were tested and used to model the performance of the final device. Based on these promising initial results, the device is achievable and within reach of current technical capabilities, setting the stage for prototype development.
(c) 2010 Diabetes Technology Society.