Aptamer-Based Fluorescence Assay for Detection of Isocarbophos and Profenofos

A fluorescence method for detection of isocarbophos and profenofos was established based on the specific recognition of aptamer. The aptamer (F-ssDNA) recognizing isocarbophos and profenofos was labeled with FAM at 5'-end, and when it bound to complementary DNA chain (Q-ssDNA) labeled with DABCYL at 3'-end, the double stranded structure would be formed and the fluorescence signal would become very weak due to the effect of fluorescent resonance energy transfer. However, the complementary DNA would dissociate from the double-stranded structure when the aptamer recognized the added target molecules, and the fluorescence signal would thus be recovered and become stronger. Based on this principle, isocarbophos and profenofos could be quantitatively detected. The optimized experimental conditions were as follows: 25 nM F-ssDNA and 50 nM Q-ssDNA-2 were incubated for 20 min at 25 degrees C, then the equal volume pesticides were added and incubated for 60 min before the fluorescence intensity of the system was determined. Under the optimal conditions, the change of the fluorescence intensity of the system (Delta I) showed a linear relationship with the isocarbophos or profenofos concentration in the range of 50-500 mu M. The detection limit (LOD, 3 sigma) was 11.4 mu M for isocarbophos with the relative standard deviation (RSD) of 5.8% (n = 10). The detection limit was 14.0 mu M for profenofos with RSD of 4.9% (n = 10). The recovery ranged from 85.8% to 95.3% when the method was applied to measure isocarbophos and profenofos in real water samples.