Abstract

Several boronic acid (BA) derivatives, suitable for sugar sensing (see Figure), have been synthesised via a one-step nucleophilic substitution reaction from the appropriate quinoline starting materials and the benzylboronic acid derivative1. The quinoline moiety confers the fluorescent behaviour of these sensors through its associated conjugated framework. The BA moiety of the sensor is known for its strong interaction with diols and hence, the sugar sensing application1,2. On interacting with sugars (e.g. glucose, fructose and lactose) the fluorescence emission decreases with increasing sugar concentration1. The BA sensors reported previously in the literature (compounds 1, 2, 5 and 6, see Figure), have been found to be suitable for glucose sensing, in the ocular aqueous humour, in which the glucose range for a healthy person is 300-800 μM, increasing to 200-4000 μM for people with diabetes1. As a result, BA sensors have been investigated for glucose sensing when incorporated into platforms, such as smart contact lenses1,2. In this present work, novel BA sensors synthesized for the first time by us (compounds 3, 4, 7 and 8, see Figure), will be compared to BA sensor 1 in terms of their fluorescence, sensitivity to sugars and glucose sensing range.