摘要：
Traditional methods for detecting antibiotic and mycotoxin residues rely on large-scale instruments, which are expensive and require complex sample pretreatment processes and professional operators. Although aptamer-based electrochemical sensors have the advantages of simplicity, speed, low cost, and high sensitivity, most aptamer-based sensors lack a signal amplification strategy due to their direct use of aptamers as probes, resulting in insufficient sensitivity. To solve the sensitivity problem in the electrochemical detection process, a novel electrochemical sensing strategy was established for ultrasensitive zearalenone (ZEN) detection on the basis of exonuclease I (Exo I) and branched hybridization chain reaction (bHCR) to amplify the signal. The amplification strategy showed excellent analytical performance towards ZEN with a low detection limit at 3.1×10(-12) mol/L and a wide linear range from 10(-11) to 10(-6) mol/L. Importantly, the assay was utilized in the corn powder samples with satisfactory results, holding promising applications in food safety detection and environmental monitoring.
摘要：
Herein, an effective pyrene excimer signaled fluorescent biosensor for the determination of tetracycline based on triple-helix aptamer probe (TAP) and supramolecular inclusion of cyclodextrin was reported. The TAP was devised containing an aptamer loop, two DNA segment stems and a triplex-forming oligonucleotide (signal probe) labeled with pyrenes at 5′ and 3′ ends. The presence of target could result in its binding towards aptamer with a mighty affinity, leading to a conformation change of the TAP and whereupon the release of the signal probe. This liberty of signal probe enabled the formation of pyrene excimer, generating fluorescence signals. Further, signal amplification was fulfilled through the addition of γ-cyclodextrin which could interact with pyrene dimer, thus leading to an enhanced “on-state” of the sensing ensemble. In contrast, when the target was absent, the sensing ensemble remained “off-state” because of the long distance between two pyrene molecules. When the conditions were properly optimized, the increasing signal kept a linear dependence on target concentrations ranging from 5.0nM to 100nM, and the detection limit reached as low as 1.6nM. In this way, a newly-constructed, simple, and economically affordable protocol enjoys desirable efficiency, sensitivity, specificity in biosensing. Also, its universality as another attractive behalf in assaying diverse targets was envisioned with only the need of matched aptamer replacement.
摘要：
Based on molecular imprinting and nanotechnology, a highly specific and sensitive electrochemical aptasensor was proposed for assaying kanamycin (KAN). First, chitosan-graphene (CG) composite multilayer films and Au nanoparticles (AuNPs) were applied to modify a glassy carbon electrode (GCE) for augmented "electron antennae". Then, we constructed a KAN sensor using functional monomer of 3-aminophenylboronic acid (3-APBA) as trap. Au@Fe3O4 nanocomposites, Fe3O4 nanoparticles (Fe(3)O(4)NPs) loaded with AuNPs, were dual functionally modified with beta-cyclodextrin-ferrocene (Fc/beta-CD-SH) and KAN aptamers (APT/Fc/beta-CD-SH/Au@Fe3O4) were applied as the tracing tag. The KAN aptamer acted as the bind unit to specifically identify the KAN captured by the imprinted cavities on the MIP modified electrode surface, while the Fc/beta-CD-SH was used as a signal unit for KAN quantification. The presented assay exhibited a good linear relationship between KAN concentration (10-500 nM) and the strength of the electrochemical signal, with a detection limit of 1.87 nM and a correlation coefficient of 0.98. The selectivity, stability and reproducibility of the proposed sensor were acceptable. Furthermore, it was used successfully to detect KAN in different aqueous solution, such as in spiked milk, the proposed sensor could be applied for specifically, sensitively and rapid determination for antibiotic contamination in food, water and biological samples. (C) 2020 Elsevier B.V. All rights reserved.
摘要：
Based on a beta-cyclodextrin (beta-CD) subject-object competition model, a simple and sensitive electrochemical aptamer sensor for the determination of tetracycline (TET) was fabricated. First, the TET aptamer modified with ferrocene (Fc) as a signal molecule was captured by beta-CD loaded onto the gold electrode. Subsequently, TET was added to the detection system, causing a binding event between the target and aptamer with strong affinity during which process the aptamer configuration was changed from the original upright linear state to an agglomeration structure, resulting in its departure from the electrode surface. Consequently, an "off-signal" was turned along with the presence of the target. The results indicated that the TET concentration had a linear response to the signal ranging from 0.01 to 100 nM and the accurate detection limit could reach as low as 0.008 nM (3 delta). The fabricated TET biosensor also showed outstanding detection specificity. Moreover, the suitability of the developed method was demonstrated in the determination of TET concentrations in different samples comprising water, milk, and bacteria culture medium, achieving acceptable recoveries for spiked samples ranging from 96.0 to 104.4%. This detection system was simple, economical, time-saving but remarkably sensitive, selective, and efficient, potentially rendering services in food safety screening and medical testing.
作者机构：
[Hu, Xinjiang; Zhao, Yunlin; Xu, Zhenggang; He, Tianpei; Wu, Yaohui; Wu, YH; Zhao, YL; Liu, Wen; Wang, Yonghong; Chen, Xiaoyong] Cent South Univ Forestry & Technol, Coll Life Sci & Technol, Changsha 410004, Peoples R China.;[Ning, Ge] Hunan Univ Chinese Med, Int Educ Inst, Changsha 410208, Peoples R China.;[Chen, Xiaoyong] Governors State Univ, Coll Arts & Sci, University Pk, PA 60484 USA.
通讯机构：
[Wu, YH; Zhao, YL] C;Cent South Univ Forestry & Technol, Coll Life Sci & Technol, Changsha 410004, Peoples R China.
摘要：
Norfloxacin (NOF) is an environmentally harmful and ubiquitous aquatic pollutant with extensive production and application. In this study, a novel composition named carbon-based composite photocatalytic material of zinc oxide and zinc sulphide (ZnO/ZnS@BC) was successfully obtained by the impregnation-roasting method to remove NOF under UV-light. Scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and energy dispersive spectrometer characterised the composition. ZnO/ZnS was successfully decorated on the surface of biochar (BC). The pH, the ZnSO(4)/PS ratio, and ions and quenchers, were investigated. High removal efficiency was obtained with a pH of 7 and a ZnSO(4)/PS ratio of 1:1, and the removal ratio of NOF reached 95% within three hours; the adsorption and degradation ratios reached 46% and 49%, respectively. Fe(2+) promoted the degradation of NOF, whereas other ions inhibited it, with NO(3)(-) showing the strongest inhibitory effect. Three reactive species (tert-butanol, quinone, and ammonium oxala) were identified in the catalytic system. The decreasing order of the contribution of each reactive species was: O(2)(-) > ·OH(-) > h(+). Additionally, a recycling experiment demonstrated the stability of the catalyst; the catalytic degradation ratio of NOF reached 78% after five successive runs. Therefore, ZnO/ZnS@BC possessed strong adsorption capacity and high ultraviolet photocatalysis ability.
作者机构：
[Liu, Gaoqiang; Chen, Zhifen; He, Tianpei; Wu, Yaohui; Jiang, Chenyang; Wang, Yonghong; Chen, Xiaoyong] Cent South Univ Forestry & Technol, Hunan Prov Key Lab Forestry Biotechnol, Changsha, Peoples R China.;[Zhao, Yunlin; Xu, Zhenggang; Wu, Yaohui] Cent South Univ Forestry & Technol, Hunan Res Ctr Engn Technol Utilizat Environm & Re, Changsha, Peoples R China.;[Xu, Zhenggang] Hunan City Univ, Hunan Urban & Rural Ecol Planning & Restorat Engn, Yiyang, Hunan, Peoples R China.;[Ning, Ge] Hunan Univ Chinese Med, Int Educ Inst, Changsha, Peoples R China.
通讯机构：
[Wu, Yaohui] C;Cent South Univ Forestry & Technol, Hunan Prov Key Lab Forestry Biotechnol, Changsha, Peoples R China.;Cent South Univ Forestry & Technol, Hunan Res Ctr Engn Technol Utilizat Environm & Re, Changsha, Peoples R China.
摘要：
In the present work, a series of magnetically separable Fe3O4/g-C3N4/MoO(3)nanocomposite catalysts were prepared. The as-prepared catalysts were characterized by XRD, EDX, TEM, FT-IR, UV-Vis DRS, TGA, PL, BET and VSM. The photocatalytic activity of photocatalytic materials was evaluated by catalytic degradation of tetracycline solution under visible light irradiation. Furthermore, the influences of weight percent of MoO(3)and scavengers of the reactive species on the degradation activity were investigated. The results showed that the Fe3O4/g-C3N4/MoO3(30%) nanocomposites exhibited highest removal ability for TC, 94% TC was removed during the treatment. Photocatalytic activity of Fe3O4/g-C3N4/MoO3(30%) was about 6.9, 5, and 19.9-fold higher than those of the MoO3, g-C3N4, and Fe3O4/g-C(3)N(4)samples, respectively. The excellent photocatalytic performance was mainly attributed to the Z-scheme structure formed between MoO(3)and g-C3N4, which enhanced the efficient separation of the electron-hole and sufficient utilization charge carriers for generating active radials. The highly improved activity was also partially beneficial from the increase in adsorption of the photocatalysts in visible range due to the combinaion of Fe3O4. Superoxide ions (center dot O-2(-)) was the primary reactive species for the photocatalytic degradation of TC, as degradation rate were decreased to 6% in solution containing benzoquinone (BQ). Data indicate that the novel Fe3O4/g-C3N4/MoO(3)was favorable for the degradation of high concentrations of tetracycline in water.
