Nanostructured Contact Lens Changes Colors to Warn Diabetics of Insulin Need

A glucose biosensor integrated with a disposable nanostructured contact lens provides a safe, convenient and non-expensive glucose sensing device. The biosensor sensing device provides an efficient and non-invasive solution for monitoring blood glucose according to University of Western Ontario (London, CA) Department of Chemical and Biochemical Engineering Assistant Professor Jin Zhang and researcher Gerald Hodge William in U.S. Patent Application 20100113901

Contact lens with an integrated biosensor provides continuous, non-invasive monitoring of physiological glucose by employing biocompatible nanostructure-laden lens materials.

These patent pending contact lenses can be worn by diabetics who can colorimetrically see changes in their contact lens color or other fluorescence-based properties, giving an indication of tear and blood glucose levels. 

Physiologically compatible porous nanostructures are selected from the group consisting of silica nanoparticles, nanotubes, nanofilms, and bio-polymer nanostructures including alginate, chitosan nanoparticles (NP), nanofibers, 2-D and 3-D foams with highly nanoporous structures. 

There are three major reasons that make porous nanostructures ideal materials as optical probes. Firstly, most nanostructures exhibit stable optical signals, porous nanostructures, acting as nanocontainners, can keep the organic dye/proteins stable because most of organic dye and proteins decompose or in-active easily. In addition, due to large surface area and porous structure, nanostructures can act as an analyte, e.g. glucose, glucose oxidase (GOx), reservoir which is helpful for uniform immobilization and high loading of analyte, glucose, GOx, for glucose sensing. Thirdly, the large surface areas of nanostructures may lead to higher selectivity for glucose sensing. 

In addition, the porous nanostructures are able to keep multiple dyes and materials to the same sensing medium, allowing synergistic sensing schemes for the detection of more types of analytes, based on ion correlation or enzyme reaction. 

Detection of the color change of the portion of the contact lens containing the biosensor for glucose can be visually detected when the concentration of glucose is larger than 3 mM. The device can achieve sensitivities in the range of greater than 0 to 1800 mg/dL of glucose The best reported Con-A/dextran systems for sensing glucose based on competitive binding and resonance energy transfer (RET) had the sensitivity in the range of about.10^-4 ratio units/(mg/dL) and shows increasing fluorescence with increasing glucose concentration. The fluorescence intensity is displayed digitally on a hand-held photofluorometer and may also be sent by telemetry to an insulin pump. 

The goal of the Multifunctional Nanocomposites Lab (MNL) led by Dr. Zhang at Western is to develop multifunctional nanomaterials used for the advanced biomedical devices and food packaging. We are working with different types of materials, including biopolymers, inorganic, and organic molecules. To achieve the goal, the Zhang group is dedicated to the study on the interface of hybrid nanomaterials, and the interaction between nanomaterials andbiological system.

Currently, the research activities of the Zhang group focus on developing advanced nanomaterials with enhanced chemical, magnetic, and optical properties. Three research directions in the Zhang group include (1) multifunctional nanocomposites-processing & properties, (2) targeted drug delivery, and (3) protein and chemical sensor.