Development of a Skin Patch for Continuous Glucose Monitoring

In our current environment virtually any information, including health-related data, can be readily accessible due to the ubiquity of smart devices and health monitoring smart device accessories, such as activity, sleep, heart rate, pulse, and blood pressure tracking devices. However, currently available self-monitoring devices are restricted to extra-corporeal data, leaving many important physiological parameters such as glucose, hormone, and electrolyte level changes uncharted. Of notable interest in the area of self-monitoring is that of blood glucose levels in the pre-diabetic population. Continuous glucose monitoring (CGM) devices utilised by diabetics are invasive and cost prohibitive for general consumers and therefore uncommonly used pre-diagnosis. These devices are thus unlikely to enable the lifestyle changes and administration of the appropriate adjustments in a timely manner to pre-diabetics, which may prevent the progression to diabetes. This dissertation discusses and demonstrates the development of a minimally invasive wearable device for the continuous sensing of glucose, with Bluetooth wireless connectivity to enable data transfer to a smart device. Three major components of this device are: 1) microneedles, which serve to penetrate the skin to access the underlying dermal interstitial fluid, and to immobilise the glucose sensor; 2) fluorescent glucose sensor, which senses glucose in the dermal interstitial fluid whilst being immobilised to the microneedles; and 3) wearable fluorescence detection system, which interrogates and evaluates the light signal generated by the microneedle sensing platform. The microneedles are unique compared to the previous microneedle sensing devices, in that the sensing moiety can be chemically integrated into the microneedles to allow for continuous fluid sampling and analyte monitoring to take place simultaneously in situ. Glucose sensing is enabled by modular fluorescent sensors, consisting of glucose receptors, a reporting fluorophore, and an immobilisation site. The wearable fluorometer is 5.1 x 3.2 x 1.9 cm in dimension, is battery-powered, has an adjustable dynamic range, and exhibits fluorescence detection capability comparable to that of the gold standard microplate reader device. In vitro and in vivo assessments demonstrate that the microneedle sensing platform and the detector are able to perform their intended functions, and more importantly, can be integrated compatibly into the final envisioned system. Beyond the intended overall application of continuous glucose monitoring, each component and their fabrication methods have the potential to be utilised for the continuous monitoring of other health metrics. When these components are assembled, the end product is a wearable continuous sensing system that is easy to use, almost painless, minimally invasive, and overall, accessible in terms of convenience and cost to the general consumer