Paper-Based Colorimetric Biosensor for Tear Glucose Measurements

This paper describes a paper-based colorimetric biosensor for measuring glucose concentration levels in human tear samples. Colorimetric biosensors were wax printed on paper platforms and modified with chitosan previously prepared in acetic acid. The proposed device was explored to measure the glucose levels in human tear samples using 3,3',5,5'-tetramethylbenzydine (TMB) as the chromogenic reagent. The paper-based colorimetric biosensor exhibited a linear behavior for the glucose concentration range between 0.1 and 1.0 mM. The achieved analytical sensitivity and limit of detection (LOD) were 84 AU/mM and 50 mu M, respectively. Moreover, the device provided analytical reliability and no statistical difference when compared to the data recorded with a commercial glucometer. The proof-of-concept of our device was successfully demonstrated by measuring the glucose levels in six tear samples from nondiabetic subjects. In general, the results showed that the colorimetric biosensor has noticeable potential to be used as a powerful tool for tear glucose monitoring, since this fluid offers lower potential interferences, non-invasive sample collection and is pain-free. Furthermore, the proposed device could facilitate the treatment of diabetic patients who need constant control of glucose levels and cannot tolerate multiple finger sticks per day.