Abstract

Diabetes is a severe metabolic, autoimmune disease that affects the cardiovascular, peripheral nervous system and kidneys, also known to have fatal side effects1. These effects include blindness, heart or kidney failures that arise from hyper- or hypoglycemia1. Monitoring the disease marker, glucose, has proven to prolong life expectancy in many cases, however non-invasive continuous monitoring systems are limited2. ‘Finger-pricking’ is the most common method, however invasive and non-continuous2. Flaws in this method include measurements taken only at the time of sampling, meaning that episodes of hypo- or hyperglycemia can be missed1-2. Invasively drawing blood is an inconvenience to diabetics too and compliance for these monitoring methods is challenging for the elderly and children1. Currently, over 380 million people worldwide suffer with diabetes and by 2030, it is expected that this number will rise by 54%3. This highlights the necessity for non-invasive continuous monitoring systems to improve management of this life-threatening condition. Boronic acids (BAs) are well known for their strong, reversible interactions with diol-containing compounds, like glucose1. The incorporation of a fluorescent moiety into the structural framework of a BA derivative, allows for interactions with glucose to be continuously monitored by creating an optical response for glucose sensing, due to a decrease in fluorescence intensity of the BA derivative on increased glucose concentrations1. In this context, we have successfully synthesised a novel fluorescent BA derivative o-COOHBA, and characterised its response towards glucose. It was shown that in a buffer solution of physiological pH, the fluorescence intensity of o-COOHBA is decreased on increased glucose concentrations in the range from 0-50mM. This range is of particular interest as it corresponds to glucose concentrations in aqueous humour, from 50μM – 5mM in diabetic patients, which is directly related to the blood-glucose levels of ~3-40mM for diabetics1. In addition, immobilisation of o-COOHBA on to polydimethylsiloxane lens-type surfaces was also demonstrated. The final goal of this immobilisation approach is to create a colorimetric contact-lens for real-time glucose monitoring in the ocular fluid, which will allow diabetics to personally monitor their glucose levels non-invasively in a continuous manner.