Ultrasensitive and selective detection of isocarbophos pesticide based on target and random ssDNA triggered aggregation of hemin in polar organic solutions

This paper reports a new assay platform that performed in polar organic solutions for ultrasensitive and highly selective detection of isocarbophos pesticide. The sensing system just contains hemin molecules and random ssDNAs. Free hemin molecules have a strong absorption peak at Soret band in polar organic solvents, and they can assemble into few small particles with random ssDNAs via their special pi-pi stacking interaction. However, the subsequent addition of isocarbophos into above sensing system can aggregate hemin molecules to form many larger particles, which result in a great decrease in absorbance value of sensing solution. UV/Vis absorption spectra and scanning probe microscope (SPM) were used to characterize hemin aggregation. Additionally, the effects of some parameters like type of solvents, hemin amount and random ssDNAs on the sensing platform were also investigated. The present assay platform has a detection limit as low as 0.2 mu g/L, a dynamic range of 0.5-500 mu g/L, and high selectivity over other competitive pesticides. Moreover, the assay platform also displays excellent stability and accuracy in the detection of spiked real samples, suggesting that such sensing platform will play an important role in biological and environmental detection. (C) 2016 Elsevier B.V. All rights reserved.