Real-time monitoring of sugar molecules is crucial in diabetes treatment, but current methods are invasive and expensive. Researchers from Khalifa University collaborated with an international team to investigate holey graphene, a novel low-cost material, for glucose sensors.
The World Health Organization estimates that over 382 million people worldwide have diabetes, a metabolic disorder affecting blood sugar levels. The underlying cause of diabetes varies by type, but each type can lead to excess sugar in the blood, which could cause serious health problems. For all patients, blood sugar monitoring plays a crucial role in treatment.
Researchers from Khalifa University collaborated with an international team to demonstrate the advantages of holey graphene, which is also known as perforated graphene, for glucose sensors. The sugar molecules adsorb onto a layer of holey graphene, which alters the electronic properties of the material. These changes can be measured and correspond to blood sugar monitoring data to check the blood sugar levels without invasive testing.
Dr. Muhammad Sajjad, Postdoctoral Fellow, and Dr. Nirpendra Singh, Assistant Professor, both in the Khalifa University Department of Physics, collaborated with Dr. Puspamitra Panigrahi, Hindustan Institute of Technology and Science, India, Dr. Deobrat Singh and Prof. Rajeev Ahuja, Uppsala University, Sweden, Dr. Tanveer Hussain, The University of Queensland, Australia, and Prof. J. Andreas Larsson, Lulea University of Technology, Sweden. They published their results in Applied Surface Science.
“Since the first invention of a biosensor for glucose detection, there has been tremendous demand for low-cost, portable, and reliable glucose sensors,” Dr. Singh said. “So far, most of the available devices are dependent on an expensive glucose oxidase enzyme-based recognition unit and require people to deal with the painful finger-pricking process.”
Continuous monitoring of glucose levels in people with diabetes is essential to managing the disease and avoiding the complications associated with poorly-managed treatment. There are two types of glucose monitoring sensors, enzymatic and non-enzymatic, currently available in the market.
Enzyme-based sensors use glucose dehydrogenase (GDH) or glucose oxidase (GOx), which interact with glucose molecules, resulting in an electrical response correlated to the concentration of glucose. However, these sensors are expensive to manufacture and are sensitive to environmental conditions. Non-enzymatic sensors allow glucose to be oxidized directly on the surface of the sensor, where the atoms at the surface act as the electrocatalysts, resulting in high stability with repeated use and cost-effective fabrication.
Different materials have been used to develop non-enzymatic sensors, and although each material has its own advantages and limitations, the research team focused on graphene—specifically, holey graphene.
Graphene is a unique material comprising densely packed carbon atoms arranged in a hexagonal honeycomb lattice and can be exfoliated from the graphite. It is extremely versatile and has potential applications in various fields, particularly thanks to its superior optical, electrical, thermal, and mechanical properties.
In its purest form, graphene offers myriad applications. However, in recent years, the nanoscale perforation of 2D materials has emerged as an effective strategy to enhance and widen the applications of the material beyond its pristine form.
Holey graphene is a form of graphene with nanopores in its plane. The performance of the material is affected by the pore size, density, shape, and volume. Uniform pore shape and size distribution are usually optimal as it leads to enhanced thermal, mechanical and electrical properties. These pores are perfect for adsorption, where target molecules are collected by attaching to the surface of the pores. Holey graphene has high electrical conductivity and high surface area that the research team exploited for the glucose monitoring device.
“Since the performance of an electrochemical biosensor depends on the surface area to improve charge transfer and catalytic activity, two-dimensional graphene-like nanomaterials and functionalized graphene are now the best possible materials for a new generation of highly sensitive glucose sensors,” Dr. Singh said. “The holey graphene is very sensitive even at very low concentrations of glucose.”
The team recognized the need for a cheaper, non-enzymatic, non-invasive glucose biosensor, which is sensitive enough to check glucose levels in fluids other than blood, such as tears, sweat or saliva. These fluids are easily accessed without the need for any finger pricking and can be examined to identify various biomarkers, such as those involved in cancer, Alzheimer’s disease, Parkinson’s disease, cystic fibrosis, systemic sclerosis and glaucoma, and blood sugar levels for diabetes management.
When saliva, tears, or sweat hit the surface, the sugars interact with a layer of nitrogenated holey graphene (C2N) that is only a single atom thick. Glucose, fructose and xylose are the sugar molecules found in the body and when they interact with the holey graphene layer, the electronic properties of the layer are altered. These changes are measured and interpreted as various levels of sugar in the bodily fluid tested.
This work was supported by the Swedish Research Council, the Abu Dhabi Department of Education and Knowledge, and Khalifa University of Science and Technology.
20 December 2021