Figure 1

Plasmonic cuvette: plasmonic interferometry coupled to dye chemistry. (A) The Amplex–red/Glucose–oxidase/Glucose (AR/GOx/Glucose) assay consumes glucose and produces resorufin, a red-fluorescent molecule, in a 1:1 stoichiometric ratio via enzymatic reactions; measurement of steady-state resorufin concentration leads to determination of glucose concentration initially present in solution; (B) Reaction 1: oxidation of β-D-glucose to D-gluconolactone by O2 to produce H2 O2, catalyzed by GOx; (C) Reaction 2: oxidation of Amplex red (colorless) into resorufin (red), catalyzed by HRP; (D) Reaction 3: side reaction with low yield that further oxidizes resorufin to an optically inactive product; (E) the effective rate constants for the three reactions (K1, K2 and K3) were determined by time-dependent kinetic studies of resorufin absorption; (F) absorption cross-section (σ) and extinction coefficient (ε) of resorufin as a function of wavelength, needed to extract resorufin (and therefore glucose) concentration from absorption measurements; (G) schematic of a plasmonic interferometer; (H) sample data from the plasmonic cuvette: spectral absorption is correlated with resorufin concentration.

© De Gruyter