Strip-type Sensor for Blood Glucose Measurement through Tear Fluid

Abstract

A strip-type sensor with sensing paper treated with cerium oxide nanoparticles (CNPs) and glucose oxidase (GOX) was designed to detect glucose levels in tears. The strip-type sensor was produced by 3D printing. It is put against the inferior palpebral conjunctiva (IPC) to collect tears without irritating the eyes. When GOX reacts with the glucose in the collected tears, hydrogen peroxide (H2O2) is generated, and this H2O2 reacts with the CNP. The H2O2 causes the Ce3+ on the surface of the CNP to turn into Ce4+, and the color of the CNP becomes yellow. Therefore, the higher the concentration of glucose, the higher the amount of H2O2 produced and the more yellow the CNP becomes. The concentration of glucose in the tears can be measured with an optical vision system that measures the degree of yellowing of the CNP on the sensing paper. After the sensing paper turns yellow, a RGB detection was performed through a colorimetric analysis algorithm. In the in vitro experiments, the sensing paper was loaded into the strip-type sensor. The normalized b value and glucose concentration showed a linear correlation. A tear glucose index was created from these results. The strip-type sensor was also tested in an in vivo rabbit model and the correlation between blood glucose and tear glucose was confirmed, thus suggesting that strip-type sensors are useful as a self-diagnostic sensor.