Search

It is known that gold nanoparticles (AuNPs) possess peroxidase-like activity. They can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine by HO which leads to a color change from red to blue. It is shown here that the peroxidase-like activity of AuNPs can be inhibited by passivating its surface passivation with a ssDNA aptamer against sulfadimethoxine. If, however, the target molecule (sulfadimethoxine) is present, the aptamer is desorbed from the AuNPs surface, and this results in the reactivation of the catalytic property of the AuNPs. The color change of the solution (from purple to blue) is related to the analyte concentration, and this can be judged visually or by UV-visible absorptiometry at 650 nm. The assay, under optimized conditions, has a detection limit of 10 ng·mL of sulfadimethoxine, and the calibration plot is linear over a rather wide concentration range (0.01-1000 μg·mL). The assay can be performed within <15 min, is sensitive, and therefore is well suited for fast screening in food analysis. Conceivably, it can be extended to many other small analytes for which aptamers are available. [ABSTRACT FROM AUTHOR]

A class-specific molecular imprinted polymer (MIP) is described for simultaneous recognition of prometryn and simetryn prior to their determination via a fingerprint signal (at 974 cm−1 and 1074 cm−1) in the surface enhanced Raman scattering (SERS) spectra that were acquired in the presence of gold nanoparticles. The imprinted nanoparticles were applied to the analysis of rice and wheat samples spiked with both herbicides. The method has fairly good recoveries (72.7-90.9%) with a relative standard deviation of 1.7-7.8%, and a 20 μg·kg−1 limit of detection. The imprint factors (compared to non-imprinted polymers) are 5.3 for prometryn and 4.2 for simetryn (both at 10 μg·mL−1 of the initial solution).A MIP-SERS method was developed for simultaneous detection of triazine herbicides (prometryn and simetryn) in food samples. [ABSTRACT FROM AUTHOR]