| dc.description.abstract | Diabetes mellitus, marked by elevated blood glucose levels, has been a leading contributor to global morbidity and mortality. The prolonged elevated blood glucose levels can lead to secondary complications such as renal disorders, heart disease, blindness, and stroke. Maintaining healthy glucose levels is crucial to prevent or delay diabetic complications. This can be ensured by regularly monitoring blood glucose levels and making necessary adjustments to diet and medication. Although traditional finger prick tests provide a reliable way to self-monitor blood glucose, their effectiveness depends on the frequency of tests. Multiple finger pricks in a day can be painful and inconvenient, especially for pediatric patients. Moreover, critically high or low glucose levels occurring in between finger prick tests and nocturnal hypoglycemia can often go undetected. This brings about a need for a continuous glucose monitoring (CGM) systems that can measure real-time glucose levels, enabling effective management of diabetes.
An electrochemical enzymatic glucose sensor has been developed that utilizes metal electrodes and a redox-active mediator molecule to facilitate electron transfer between enzyme and electrodes. Initial experiments were carried out on commercial screen-printed electrodes, subsequently transitioning to microfabricated metal electrodes for long-term stability. Metal electrodes were fabricated on silicon and flexible polyethylene terephthalate (PET) substrates, achieving a sensing probe length of 1 mm to target dermal interstitial fluid. The fabricated electrodes were characterized using standard redox molecule to determine their suitability in electrochemical sensing applications. A test setup was developed to ensure a controlled and continuous analyte flow during glucose sensing experiments.
Further, we have investigated ferrocene derivatives as potential mediators enabling glucose detection at lower potential. We developed and optimized simple immobilization strategies to minimize the leaching of enzyme and mediator into the test solution, enabling continuous in vivo glucose monitoring. The enzyme concentration, mediator concentration, enzyme : mediator ratio and detection potential were optimized to enhance the sensor performance. The developed sensor exhibited linearity up to 400 mg/dL glucose with minimal susceptibility to common interference molecules such as ascorbic acid, urea, uric acid, creatinine, dopamine, acetaminophen, and human serum albumin.
The sensor demonstrated higher sensitivity and lower detection potential than most of the reported CGM systems. The sensor reliably monitored glucose in vitro for up to 7 days, underscoring the robustness of the immobilized chemistry. The sensor with platinum as a pseudo-reference electrode eliminated the need for conventional silver/silver chloride electrodes that could cause toxicity due to silver ion leaching during in vivo applications. The shelf-life studies showed consistent performance between sensors stored for 48 hours and those stored for 1 month. Finally, the sensors were sterilized through X-ray irradiation and evaluated in vivo using a mouse model. The in vivo studies demonstrated the sensor’s capability to continuously monitor interstitial glucose levels, which correlated well with blood glucose readings. Hence, the simplified microfabrication process, coupled with a simple immobilization strategy, eliminated the necessity for complex synthesis procedures, thereby providing a scalable and cost-effective method for developing an indigenous CGM system.
In the final part of the study, we investigated the potential of doped nanostructures as alternatives to ferrocene derivative meditators. Nanostructures are known to improve the overall performance of biosensors by providing a high surface area and biocompatible microenvironment for enzyme immobilization. We have studied the redox activity of doped nanostructures and evaluated their performance as mediators in continuous electrochemical glucose monitoring. We have optimized the choice of solvents and dopants, dopant concentration, and enzyme : nanostructure ratios to enhance the sensor performance. The enzymatic sensor with doped nanostructures showed stable response for up to 7 days in vitro with minimal impact from common interferents.
In summary, a proof-of-concept CGM sensor has been developed and designed for dermal interstitial fluid. The study prioritized simple, scalable and cost-effective approach to enhance the accessibility and usability of CGM technology among wider range of patients. The developed sensor with robust response for 7 days in vitro, minimal impact from interferents, and reliable in vivo glucose sensing has laid a promising foundation for the development of an indigenous CGM system. | en_US |
