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 neur otoxin hydrolysis is provided by the self-referencing, pH-sensitive dye SNA FL-1, whose emission spectrum changes at lambda = 550 in response to pH. Us ing spectrofluorimetry and paraoxon as a model organophosphate, paraoxon co ncentrations as low as 8 x 10(-7) M could be readily detected. On the basis of the signal-to-noise ratio, a detection limit of 16 nM was determined. T he materials demonstrated high stability against enzyme-denaturing, leachin g, and photobleaching when stored under ambient conditions.