A collaborative team of researchers from Khalifa University and Imperial College London has developed a new contact lens that could help people with diabetes by monitoring their glucose levels without the need for daily blood tests, while also correcting the near-sightedness common in diabetic patients.
A metabolic disease, diabetes mellitus is characterized by high blood glucose levels, and if left untreated, can lead to severe complications including blindness, kidney and heart disease, stroke, loss of limbs, and reduced life expectancy. It is a major public health problem, affecting hundreds of millions of people worldwide and representing a substantial economic burden on society.
There are two types of diabetes: Type 1 usually begins in childhood with individuals suffering from their body’s inability to produce enough insulin, while Type 2 is commonly associated with obesity and age of onset is usually in middle age. Both types of diabetes tend to run in families and hence genetic factors contribute to the disease. Among UAE citizens, the prevalence of diabetes is the second highest in the world with over 1.1 million cases of diabetes recorded in the UAE in 2017.
A collaborative team of researchers from Khalifa University and Imperial College London has developed a new contact lens that could help people with diabetes by monitoring their glucose levels without the need for daily blood tests.
Continuous monitoring of glucose levels in people with diabetes is essential to managing the disease and avoiding the complications that can be associated with poorly-managed treatment. Diabetes is predicted to become the seventh deadliest disease by 2030 and involves either a deficiency in the production of insulin or the body’s inability to use its available insulin to process glucose.
Long-term complications of diabetes develop gradually, and the less controlled a person’s blood sugar levels are, the higher the risk of complications. Eventually, diabetes complications may be disabling or even life-threatening, as excess sugar can—for example—injure the walls of the capillaries nourishing the nerves, damage the glomeruli blood vessel clusters in the kidneys, and affect the blood vessels of the retina, potentially leading to blindness.
The research team includes Dr. Haider Butt, Associate Professor of Mechanical Engineering, Dr. Mohamed Elsherif, Postdoctoral Fellow, Dr. Fahad Alam, Postdoctoral Fellow, Dr. Bader Alqattan, Visiting Researcher, and recent MSc graduate Ahmed Salih, all from Khalifa University, along with Dr. Ali Yetisen, Associate Professor of Chemical Engineering at Imperial College London. They published their research in the highly acclaimed journal, Small.
“Continuous glucose monitoring systems have emerged to obtain frequent measurements throughout the day and this could revolutionize the way diabetes is managed,” Dr. Butt explained. “However, they are currently limited by high costs and the need to be recalibrated at least twice a day as a result of signal drift. Commercial systems detect glucose concentration in the interstitial fluid, which is the fluid that fills the spaces between cells. This needs an electrochemical probe to be inserted through the skin, which is an invasive process that could be avoided by other means. Our solution uses contact lenses with integrated sensors that sample and measure tears for numerous biomarkers, including those indicative of high glucose levels.”
Tears are easily accessed and can be examined to diagnose cancer, Alzheimer’s disease, Parkinson’s disease, cystic fibrosis, systemic sclerosis and glaucoma without the need for drawing blood. Advances in electronics and microfabrication have allowed biosensors to be incorporated into contact lenses without blocking vision.
The research team’s contact lenses provide a novel way of measuring glucose levels in diabetics by integrating light diffraction sensors which are embedded in a hydrogel matrix to make the contract lenses. Hydrogels are the soft, pliable and thin materials that make up more than 90 percent of contact lenses prescribed in the United States: they are water-swollen polymeric materials that maintain a 3D structure.
Traditional glucose monitoring devices use enzyme-based sensors in which the enzymes interact with the glucose molecules, resulting in an electrical response that can be correlated to the concentration of glucose. These sensors are highly sensitive and give rapid results, but their short-term stability is affected by temperature, pH level and humidity. Enzymes are unstable by nature and sterilizing the contact lens would denature any enzymes in the sensors, rendering them useless. Additionally, hydrogen peroxide is a byproduct of the glucose-enzyme interaction, which would interfere with the sensor’s response and is not a substance desired in the eye area. Enzyme-based sensors are also difficult to embed into contact lenses and require a power supply, making their use in contact lenses impractical.
Light diffractive glucose sensors, on the other hand, use molecules that bind with parts of the glucose molecule and cause changes in the volume of the hydrogel contact lens. The lenses swell when glucose is detected, influencing the focusing efficiency. The research team used the light sensor in a smartphone to capture light reflected from the contact lenses and then used that data to determine glucose levels.
“Practically, a smartphone could be used as a portable reader for a contact lens-integrated glucose sensor,” Dr. Butt explained. “We could also install a light source in a glasses frame, which would be worn when patients need to measure their glucose concentrations. The light beam would hit the worn contact lens and the photodetector would collect data about the amount of light reflected back, sending this information to the user’s phone via Bluetooth. The smartphone application would then correlate the received signals with glucose concentrations in tears.”
Additionally, for those who need corrective eyewear in addition to glucose monitoring, a contact lens that could do both would be ideal. The research team developed their contact lenses to be bifocal, which can help produce clear vision at near and far distances. A complication of diabetes is myopia, or near-sightedness, which causes distant objects to appear blurry, while close objects appear normal. Bifocal contact lenses have been shown to help control myopia, decreasing its progression in diabetes sufferers.
The lenses can also act as an informational tool for the wearer: when glucose is detected in tears, the lenses will swell and change shape, changing the focus for the wearer. Once vision goes blurry, the user knows to check their blood glucose and top up their insulin levels.
Not only did the research team succeed in developing contact lenses that can measure glucose concentrations and correct vision, but their lenses were also shown to be reusable, with little loss of sensitivity over multiple uses.
“Our lenses can be fabricated quickly and easily and fine-tuned to any desired sensitivity for any eyesight,” Dr. Butt said. “They offer practicality in their readout methodology and could be a basis for a minimally-invasive glucose monitoring system for diabetics as well as other diseases by changing the detection methods for the various biomarkers found in tears.”
23 November 2021