Poly(ethylene glycol) Hydrogel-Encapsulated Fluorophore−Enzyme Conjugates for Direct Detection of Organophosphorus Neurotoxins

A simple approach is described for preparing poly(ethylene glycol) hydrogel materials with encapsulated seminapthofluorescein (SNAFL)−organophosphorus hydrolase enzyme conjugates. Direct determination of enzyme-catalyzed neurotoxin hydrolysis is provided by the self-referencing, pH-sensitive dye SNAFL-1, whose emission spectrum changes at λ = 550 in response to pH. Using spectrofluorimetry and paraoxon as a model organophosphate, paraoxon concentrations as low as 8 × 10-7 M could be readily detected. On the basis of the signal-to-noise ratio, a detection limit of 16 nM was determined. The materials demonstrated high stability against enzyme-denaturing, leaching, and photobleaching when stored under ambient conditions.