A fluorometric assay is described for the determination of the herbicide atrazine. The assay is based on the use of tyrosinase and fluorescent nitrogen-doped graphene quantum dots (N-GQDs). The N-GQDs were synthesized via one-pot hydrothermal reaction starting from citric acid and ammonia. Their fluorescence excitation and emission maxima are at 355 and 435 nm, and the quantum yield is 18%. Tyrosinase catalyzes the oxidation of dopamine to form dopaquinone which reduces the fluorescence of the N-GQDs through a dynamic quenching process. On addition of atrazine, the catalytic activity of tyrosinase is inhibited. This leads to less formation of dopaquinone and less reduction of fluorescence. The assay has a linear response in the 2.5–100 ng·mL −1 atrazine concentration range, and the detection limit is 1.2 ng·mL −1 . The assay was applied to the determination of atrazine in spiked environmental water samples.
Schematic presentation of the fluorometric assay of atrazine detection based on tyrosinase-induced fluorescence (FL) quenching effect on the nitrogen-doped graphene quantum dots (N-GQDs) and inhibitory effect of atrazine on tyrosinase.
Minling Li,Dechan Lu,Ruiyun You,Huiying Shen,Lanjin Zhu,Qingqiang Lin,Yudong Lu
Tyrosinase (TYR) is a key rate-limiting enzyme of melanin and a biomarker for melanoma diagnosis. Therefore, detection of TYR in biological samples is essential for the clinical diagnosis of melanoma. A novel portable surface-enhanced Raman scattering (SERS) sensor is proposed to detect TYR activity. It is based on dopamine (DA)-functionalized Au nanorod (Au NR) arrays as the capture substrate and 4-mercaptophenylboronic acid (4-MPBA)-modified silver nanoparticles (Ag NPs) as the SERS probe. In this case, the Au NR arrays are modified with 3,3′-dithiodipropionic acid di(N-succinimide ester) (DSP) to capture DA. In the presence of TYR, DA is oxidized to dopaquinone (DQ), which resulted in a decrease in the concentration of SERS probes further adsorbed onto the arrays. The activity of TYR is detected by changes in the intensity of the phenylboronic acid signal. Furthermore, this detection system has a wide linear detection range and high sensitivity that can effortlessly evaluate a linear range of 0.0001–100 U/mL of TYR activity. More significantly, the presented SERS sensor can perform well on both the determination of TYR activity in serum and the assessment of TYR inhibitors, which offers new opportunities for diagnosis of melanoma and other TYR-related diseases under complex biological conditions.
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