Arylboronic acids: A diabetic eye on glucose sensing

Tight control of blood glucose is the most important goal in the treatment of diabetes mellitus. This limits the long term consequences, which include damage to the heart, eyes, kidneys, nerves and other organs, among others, caused by malign glycation of vital protein structures. Proper clinical glucose control is difficult, since many factors influence the glucose concentration. Handy blood glucose monitors have been available for over a decade and have improved the general control and prognosis of the patients. Such meters however require invasive events and are thus inconvenient to the patient. Approaches towards semi-invasive and non-invasive methods have been made, but despite a lot of effort, no practical solutions, which provide proper comfort, have been reported so far. Arylboronic acids potentially have applications as optical or electrochemical reporters that can replace the commonly applied semi-invasive and non-invasive techniques relying on glucose-binding proteins, such as concanavalin A or enzymes such as glucose oxidase, glucose dehydrogenase, and hexokinases/glucokinases. Arylboronic acids are capable of providing immediate information of glucose concentrations, due to the fast and reversible formation of esters with 1,2-cis-diols or 1,3-diols of the glucose molecule. Arylboronic acids potentially offer non-invasive continuous blood glucose monitoring, in some cases without the need for reference measurements. The information can be provided by attachment of the boronic acid moiety to a proper reporting unit, which undergoes a significant change in fluorescence emission/lifetime, a significant colorshift or a significant shift in the redox potential.This review will focus on the important properties of boronic acids which eventually will make them suitable as key elements in future non-invasive continuous glucose sensors. We will further emphasize the developments made in boronic acid based polymers, imprinted polymers, and surface immobilized boronic acids as such materials may enhance key properties, such as selectivity, sensitivity and binding strength of arylboronic acids significantly.