Functionalized Hydrogel on Plasmonic Nanoantennas for Noninvasive Glucose Sensing

Plasmonic nanostructures are intensely investigated as sensors due to their high sensitivity to changes in their nearest dielectric environment. However, additional steps have to be taken to provide specificity for a particular analyte. Here, gold nanoantennas are coated with a thin layer of a boronic acid functionalized hydrogel, which reversibly swells in the presence of glucose. This process is especially sensitive to low glucose concentrations and allows for measurement of values in the physiological millimolar range. The boronic acid is highly specific to glucose, and large molecules, such as proteins, which could cause possible disturbances to the measurements, are successfully blocked from the plasmonic sensing volume by the hydrogel film. Our concept is thus suited to detect physiological glucose levels in the tear liquid under the presence of ambient proteins using functionalized plasmonic sensors on contact lenses at eyesafe wavelengths for optical readout.