Thin hydrogel films based on lectin-saccharide biospecific interaction for label-free optical glucose sensing

Concanavalin A (Con A) has been widely used as glucose recognition element in glucose sensors, however, these sensors typically detect glucose by fluorescence, and suffer from laborious labeling processes. Here a new labelfree optical Con A-based glucose sensor was designed. The sensor uses Con A-containing thin hydrogel films as sensing material and Fabry-Perot cavity simultaneously, which were fabricated by layer-by-layer assembly of Con A and dextran, using lectin-saccharide biospecific interaction as driving force. These films display FabryPerot fringes on their reflection spectra, from which optical path length of the films can be calculated. The films swell upon addition of glucose, which causes a shift of Fabry-Perot fringes on the reflection spectra of the film, from which the glucose concentration can be reported. The glucose-induced swelling is reversible, and the increase in optical path length increases linearly with glucose concentration over a wide range of glucose concentration. The sensor works well at physiological temperature, pH and ionic strength. Other sugars, which may present in blood, do not interfere with glucose detection, because of their very low concentrations in the blood. Particularly, unlike other hydrogel-based sensors, this sensor responds quite fast, because the hydrogel films are very thin. The new sensor may have potential for real time, continuous glucose monitoring.