Dongyun Liao,Guifang Liang,Yuyao Liu,Wenjun Yan,Yujing Guo,Wenting Liang,Chuan Dong,Lifang Fan
In this work, an efficient and novel photoelectrochemical (PEC) aptasensor for 2,3′,5,5′-tetrachlorobiphenyl (PCB72) was constructed based on [email protected] [email protected] quantum dots ( [email protected] QDs)-decorated TiO 2 nanotubes (TiO 2 NTs). [email protected] QDs were prepared by the combination of CdTe and CdS with a proper lattice mismatch. Due to their large band offsets, [email protected] QDs can reduce undesirable carrier recombination, significantly improving their charge separation efficiency. Then the synthesized [email protected] QDs were modified on TiO 2 NTs ( [email protected] QDs/TiO 2 NTs) through electrostatic adsorption method. The as-prepared composites exhibit a wide visible light absorption range, good PEC activity and high photoelectric conversion efficiency. Also, the PEC aptasensor prepared via the immobilization of anti-PCB72 aptamer on the composites exhibits outstanding analytical performance with high sensitivity and specificity for PCB72 under visible-light irradiation, achieving a detection limit as low as 0.03 ng/L. It was also applied to detect PCB72 in four different real environmental samples with satisfactory results.
The article describes a multiplex aptamer based voltammetric assay for the food pollutants chloramphenicol (CAP) and polychlorinated biphenyl-72 (PCB72). The method is based on the displacement of a nanotracer (an aptamer-labeled magnetic dendritic probe) by the analytes which cause the release of the corresponding encoded nanotracers. Thiolated aptamers of CAP and PCB72 were first self-assembled on magnetic gold nanoparticles (Fe 3 O 4 @Au) as capture probes to concentrate the target analytes CAP and PCB72, respectively. Next, their hybridized complementary strands (cDNA1 or cDNA2) and a dendritic polymerase were linked to quantum dots (CdS or PbS) to form the respective nanotracers. Finally, encoded composite magnetic probes were obtained through hybridization reaction between aptamers and cDNAs. Once CAP and PCB72 are recognized by the composite probes, the nanotracers are released into the supernatant where they can be detected simultaneously by voltammetry of the metal ion markers Cd(II) and Pb(II) at −0.81 and −0.57 V (vs. Ag/AgCl), respectively. The concentration measured for Cd(II) and Pb(II) are directly proportional to the concentrations of CAP and PCB72, respectively, in the range from 0.001 to 100 ng mL −1 . The detection limits for CAP and PCB72 are 0.33 and 0.35 pg mL −1 , respectively (at an S/N ratio of 3), which is 2 to 3 orders of magnitude lower than the routinely performed and commercially available ELISA. The method is perceived to possess large potential in that it may be applied to other antibiotics by using the appropriate aptamers.
After chloramphenicol and polychlorinated biphenyl-72 are captured by the respective magnetic aptamer probes, the metal signal tags Pb(II) and Cd(II) are released from respective quantum dots to the supernatant where they are simultaneously detected by differential pulse stripping voltammetry.
Polychlorinated biphenyl (PCB) detection in the environment is significant for both environmental protection and human health. Herein, a highly sensitive aptamer sensor has been established by employing a 2,3′,5,5′-tetrachlorobiphenyl (PCB72) targeting aptamer as a highly specific recognition element and a gold/silver (Au@Ag) nanocomposite as the surface-enhanced Raman spectroscopy (SERS) substrate for detecting environmental PCB72. The Au@Ag nanoparticles (NPs) exhibit a strong SERS enhancement and provide an efficient substrate for immobilizing the PCB72 aptamer and Raman signal labelled molecule, 4-mercaptobenzoic acid (4-MBA). The targeted PCB72 could competitively bind with the PCB72 aptamer, resulting in a few aptamers sticking to the Au@Ag NPs and the “hot spot” strengthening effect of the substrate. Under optimal conditions, this aptamer sensor exhibits great performance with high sensitivity, excellent selectivity and stability for the monitoring of PCB72, which shows an excellent linear correlation ranging from 1 to 1000 pg mL−1 with a limit of detection of 0.3 pg mL−1. Furthermore, this aptamer assay exhibits high specificity and selectivity for PCB72 with the detection error of less than 0.27 for other PCBs and 0.21 for other interfering species, even if the coexisting interferents are 100-fold concentration in the system. Additionally, the recognition mechanism of the binding of aptamers to PCB72 is analyzed via UV-vis spectroscopy and molecular docking simulations, which suggest that PCB72 could insert into the aptamers. Furthermore, this method is successfully utilized for PCB72 detection in real water samples with a simple pre-treatment. In general, this work provides a new and effective method using an environmental aptamer sensor for rapid and sensitive PCB72 detection.
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