In this technology, a contact lens sensor containing cerium oxide nanoparticles is developed to quantitatively detect glucose levels in tears. Due to the presence of the nanoparticles, a chemical reaction occurs and induces a colour change from colourless to yellow. The intensity of the colour change is then analysed by an image processing algorithm to determine the glucose levels present in the sample. This technology could potentially be applied for the non-invasive monitoring and early diagnosis of diabetes in patients, based on tear samples.
The contact lens sensor is made up of a 2-hydroxyethyl methacrylate (HEMA)-based contact lens photopolymerized with a complex of cerium oxide nanoparticles (CNP), polyethylene glycol (PEG) and glucose oxidase (GOX). Using PEG as a spacer, GOX was immobilized on the surface of the modified CNPs. The structure of the modified CNPs was confirmed by X-ray photoelectron spectroscopy, X-ray powder diffraction and high-resolution transmission electron microscopy.
The new sensor has similar mechanical properties as HEMA contact lens. Preliminary testing in bench and preclinical studies showed that the sensor had good physical properties, stability and had no toxicity. The correlation between the colour intensity is also linearly proportionate to the concentration of glucose levels. An app analyses the image captured of the sensor and displays the results of the glucose concentration. This sensor can be worn like conventional contact lens with a transparent centre allowing for normal vision. Fabrication is also easy with conventional ‘molds’.