Biochar reduces antibiotic transport by altering soil hydrology and enhancing antibiotic sorption.

The performance of biochar (BC) in reducing the transport of antibiotics under field conditions has not been sufficiently explored. In repacked sloping boxes of a calcareous soil, the effects of different BC treatments on the discharge of three relatively weakly sorbing antibiotics (sulfadiazine, sulfamethazine, and florfenicol) via runoff and drainage were monitored for three natural rain events. Surface application of 1 % BC (1 %BC-SA) led to the most effective reduction in runoff discharge of the two sulfonamide antibiotics, which can be partly ascribed to the enhanced water infiltration. The construction of 5 % BC amended permeable reactive wall (5 %BC-PRW) at the lower end of soil box was more effective than the 1 %BC-SA treatment in reducing the leaching of the most weakly sorbing antibiotic (florfenicol), which can be mainly ascribed to the much higher plant available and drainable water contents in the 5 %BC-PRW soil than in the unamended soil. The results of this study highlight the importance of BC's ability to regulate flow pattern by modifying soil hydraulic properties, which can make a significant contribution to the achieved reduction in the transport of antibiotics offsite or to groundwater.

Enzyme induced molecularly imprinted polymer on SERS substrate for ultrasensitive detection of patulin.

We designed a new type of MIP-SERS substrate for specific and label-free detection of patulin (PAT), by combining molecular imprinting polymer (MIP) selectivity and SERS technology sensitivity. Initially, the solid substrate of PDMS/AAO was prepared using poly dimethylsiloxane (PDMS) concreted anodized aluminum oxide (AAO) template. Then moderate Au was sputtered on the surface of PDMS/AAO to obtain Au/PDMS/AAO SERS substrate. Based on the HRP enzyme initiated in situ polymerization on the Au/PDMS/AAO, the MIP-SERS substrate was successfully synthesized with selective polymer and high tense of SERS "hot spots". The new MIP-SERS substrate showed strong SERS enhancement effect and good selectivity for PAT. Besides, the results showed that the method owned a linear range from 5 × 10-10 to 10-6 M with the limit of detection (LOD) of 8.5 × 10-11 M (S/N = 3) for PAT. The proposed method also exhibited acceptable reproducibility (relative standard deviation, RSD = 4.7%)，good stability (Raman intensity is above 80% after two weeks) and recoveries from 96.43% to 112.83% with the average RSD of 6.3%. The substrate is easy to use without complex sample pretreatment, which makes it a potential candidate as a rapid and sensitive detection method in food samples.

[Effects of Biochar Application and Ageing on the Adsorption of Antibiotics in Purple Soil].

Effects of biochar application (at rates of 0%, 1%, and 5%) and field ageing (for 1 a) on the sorption of three antibiotics (sulfadiazine, sulfamethazine, and florfenicol) were studied by batch equilibrium tests for a calcareous purple soil of sloping cropland, which is widely distributed in hilly areas of the upper Yangtze River. A soil-water ratio of 1 g:1 mL, which was close to the actual field soil water content condition, was adopted in the experiment, and comparisons were made to the commonly used ratio of 1 g:10 mL. The results showed that adsorption isotherm data of the studied antibiotics were fitted well by the linear and Freundlich model, and the free energy (ΔGθ) ranged from -0.39 to 11.53 kJ·mol-1, thus indicating that the adsorption of the three antibiotics on the control soils and biochar amended soils was mainly physical adsorption. Application of fresh biochar was found to markedly enhance the adsorption of antibiotics, especially for sulfamethazine and florfenicol of low Kow values, while such an effect was strongly weakened after ageing. The fluorescence peak response intensity of the adsorption equilibrium solution of the aged biochar amended soil was lower than that of the fresh biochar amended soil, so the difference in adsorption performance between fresh and aged biochar amended soils may have been due to the decrease of unstable and soluble organic matter in the latter's biochar after aging.

Versatile Electrochemiluminescence Assays for PEDV Antibody Based on Rolling Circle Amplification and Ru-DNA Nanotags.

The sensitive and accurate detection methods for PEDV antibody have practical significance for the prevention and treatment of PEDV. In this work, a new multiple pathways signal amplification method was proposed to construct a sensitive electrochemiluminescence (ECL) platform for the detection of PEDV antibody. Using Au NP-modified graphene nanosheet (Au-GN) as the substrate, antibody-antigen reaction as the recognition unit, rolling circle amplification (RCA) for signal enhancement, and assembled cascade Ru-DNA nanotags as signal label, the proposed platform behaved with good specificity and sensitivity. The binding system of biotin-streptavidin, RCA, and Ru(bpy)32+-doped silica nanoparticles (Ru SNPs) showed remarkable amplification efficiency, low background signal, and little nonspecific adsorption. Moreover, the proposed ECL sensor exhibited good analytical performance for PEDV antibody with a wide linear range from 0.1 pg mL-1 to 5000 pg mL-1 with a detection limit of 0.05 pg mL-1 ( S/ N = 3). The proposed strategy exhibited the advantages of excellent stability and sensitivity for determination of the PEDV antibody, which was easy to prepare and had a good application prospect.

From Electrochemistry to Electroluminescence: Development and Application in a Ratiometric Aptasensor for Aflatoxin B1.

Aflatoxin B1 (AFB1), one of the most toxic chemical carcinogens, has been widely studied. It remains challenging to develop simple, accurate, and sensitive analytical methods for the detection of AFB1 in food matrixes. In this work, on the basis of a dual-signaling strategy, a ratiometric aptasensor was designed and verified for the accurate and sensitive detection of AFB1. The electrochemical method was first used as a model to verify the specific interaction between AFB1 and the aptamer, in which ferrocene (Fc)-anchored and methylene blue (MB)-anchored DNA sequences acted as dual signals. Consequently, the specific interaction between AFB1 and its aptamer was demonstrated by the "signal-on" mode of Fc and the "signal-off" mode of MB. Due to the simple dual-signaling mode, the electrochemical sensor was further extended to the construction of an electrochemiluminoscence (ECL) aptasensor. In the ECL system, dual ECL signals were produced from CdTe/CdS/ZnS quantum dots (QDs) and luminol. Horseradish peroxidase-modified gold nanorods (HRP/Au NRs) acted as the quencher/enhancer and as such quenched the ECL signal of the QDs by ECL energy transfer and simultaneously catalyzed H2O2 to enhance the ECL of luminol. Owing to the self-calibration by the internal reference, both of the ratiometric aptasensors exhibited accurate and sensitive analytical performance for AFB1 with a good linear range from 5.0 pM to 10 nM and detection limits of 0.43 and 0.12 pM (S/N = 3), respectively. The aptasensors also exhibited good selectivity, reproducibility, and stability, revealing potential applications in food safety monitoring and environmental analysis.

Ultrasensitive detection of aflatoxin B1 by SERS aptasensor based on exonuclease-assisted recycling amplification.

Aflatoxin B1 (AFB1) is one of the most abundant and carcinogenic food-contaminating mycotoxins around the world. In this study, we proposed a surface enhanced Raman scattering (SERS) sensing strategy for the determination of AFB1. An aptamer for AFB1 partially hybridized with complementary-DNA, which was released after the recognition of AFB1 and immediately hybridized with hairpin DNA on the surface of sputtering Au film. Exonuclease III hydrolyzed the double-stranded DNA, leaving short single-stranded DNA on the Au surface and releasing complementary-DNA for next ring opening and digestion. SERS tag was captured on Au surface by DNA hybridization. Agarose gel electrophoresis and dynamic light scattering showed that SERS tag was successfully prepared. The detection principle was validated by electrochemical impedance spectroscopy and SERS at each step. High sensitivity and good selectivity for AFB1 detection were observed. The results showed that there was a good linear relation when the AFB1 concentration was from 1×10-6 to 1ng/mL, and the limit of detection (LOD) was 0.4 fg/mL. This sensor was also applied for quantifying AFB1 levels in spiked peanuts samples, the recoveries was in the range of 89-121%.

Gecko-Inspired Nanotentacle Surface-Enhanced Raman Spectroscopy Substrate for Sampling and Reliable Detection of Pesticide Residues in Fruits and Vegetables.

Rapid sampling and multicomponent detection are crucial for monitoring of pesticide residues analysis. Here, a gecko-inspired nanotentacle surface-enhanced Raman spectroscopy (G-SERS) platform is proposed for the first time for the simultaneous detection of three kinds of pesticides via a simple and intuitive "press and peeled-off" approach. The G-SERS platform obtained from seeding deposition of silver nanoparticles (Ag NPs) on 3D PDMS nanotentacle array is flexible and free-standing. Compared with other substrates, this G-SERS substrate can simultaneously provide outstanding SERS activity (enhancement factor = 1.2 × 107), superior reproducibility (RSD = 5.8%) and countless flexible nanoscale "tentacles" (∼6.7 × 108/cm2). Moreover, the high density of "tentacles" can freely approach the microarea and enable efficient target collection, which were confirmed by SEM and HPLC. By direct sampling from cucumber, apple, and grape surfaces, thiram (TMTD), methyl parathion (MPT), malachite green (MG), and their multiple components have been rapidly and reliably determined. For example, under the optimal conditions, a sensitivity of 1.6 ng/cm2 (S/N = 3) for TMTD was obtained on apple peels with a correlation coefficient (R) of 0.99. Therefore, the G-SERS substrate could offer a great practical potential for on-spot identification of various pesticide residues on real samples.

Ultrasensitive SERS detection of Bacillus thuringiensis special gene based on Au@Ag NRs and magnetic beads.

Highly sensitive and selective detection of specific DNA sequences is of great importance in clinical diagnosis, environmental and food monitoring, but it still remains challenges to develop a facile method for real sample detection in aqueous solution. Here, a simple and recyclable surface enhanced Raman scattering (SERS) sensor was constructed for Bacillus thuringiensis (Bt) special gene fragment detection by Fe3O4 magnetic beads (MBs) and Au-Ag core-shell nanorods (Au@Ag NRs). A hairpin DNA with sulfhydryl and biotin was attached to Au@Ag NRs as indicator, and MBs with streptavidin (SA) were acted as the capture probe. On the basis of the biotin-SA specific interaction, target sequences were first hybridized with the hairpin DNA and exposed the biotin. Subsequently, the Au@Ag NRs were captured by the streptavidin modified MBs, which reduced the suspended NRs and led to the change of Raman intensity. Under the optimal conditions, the SERS intensity revealed a good linearity with Bt transgene fragment ranging from 0.1pM to 1nM with a detection limit of 0.14pM (S/N=3). To demonstrate the specificity of the strategy, the single-base mismatch in DNA was discussed in the SERS assay. The results showed that the sensitivity and accuracy of the proposed method was acceptable in DNA detection, revealing a great potential in special gene detection.

Enzymatic biosensor of horseradish peroxidase immobilized on Au-Pt nanotube/Au-graphene for the simultaneous determination of antioxidants.

A new electrochemical method has been proposed for the simultaneous determination of butylated hydroxyanisole (BHA) and propyl gallate (PG) in food matrices based on enzymatic biosensors. Spiny Au-Pt nanotubes (SAP NTs) was first synthesized and demonstrated to exhibit intrinsic peroxidase and catalase-like activity. The structure of SAP NTs provides large surface area and favorable medium for electron transfer, on which HRP were immobilized and acted as enzymatic biosensor for the simultaneous detection of BHA and PG. The results revealed that BHA and PG both have well-defined oxidation waves with peak potentials of 624 and 655 mV, respectively. Under the optimal conditions, the method behaved satisfactory analytical performance towards BHA and PG with a wide linear range of 0.3-50 mg L(-1) and 0.1-100 mg L(-1), as well as a detection limit of 0.046 mg L(-1) and 0.024 mg L(-1) (3σ/slope), respectively. Besides, the proposed method exhibits good sensitivity, stability and reproducibility, providing an alternative to fabricate electrode and construct sensitive biosensors.

Highly sensitive enzyme-free immunosorbent assay for porcine circovirus type 2 antibody using Au-Pt/SiO2 nanocomposites as labels.

Improving the performance of conventional enzyme-linked immunosorbent assay (ELISA) is of great importance to meet the demand of early clinical diagnosis of various diseases. Herein, we report a feasible enzyme-free immunosorbent assay (EFISA) system using antibody conjugated Au-Pt/SiO2 nanocomposites (APS NCs) as labels. In this system, Au-Pt/SiO2 nanospheres (APS NPs) were first synthesized by wet chemical method and exhibited intrinsic peroxidase and catalase-like activity with excellent water-solubility. Then APS NCs were utilized as labels to replace HRP conjugated antibody, and Fe3O4 magnetic beads (MBs) to entrap the analyte. To discuss the performance of EFISA system, Human IgG was served as a model analyte, and porcine circovirus type 2 (PCV2) serums as real samples. The system boosted the detection limit of HIgG to 75pgmL(-1) with a RSD below 5%, a 264-fold improvement as compared with conventional ELISA. This is the first time that APS NCs have been used and successfully optimized for the sensitive dilution detection of PCV2 antibody (5:10(7)) in ELISA. Besides, APS NCs have advantages related to low cost, easy preparation, good stability and tunable catalytic activity, which make them a potent enzyme mimetic candidate and may find potential applications in bioassays and clinical diagnostics.

Platinum Dendritic-Flowers Prepared by Tellurium Nanowires Exhibit High Electrocatalytic Activity for Glycerol Oxidation.

Dentritic Pt-based nanomaterials with enriched edge and corner atoms have recently attracted considerable attention as electrocatalysts. Meanwhile, Pt(111) facets are generally considered more active for the glycerol oxidation reaction (GOR). Thus, it is significant to construct the rational design and synthesis of dentritic Pt whose surface is mostly enclosed by {111} facets. Reported herein is a unique Pt-branched structure enriched by a large amount of valency unsaturated atoms prepared by the aggravation of the galvanic replacement strategy. The synthesis is developed to generate highly crystallized Pt nanoflowers using Te nanowires as a template. Furthermore, the electrochemical results show that Pt nanoflower is an excellent catalyst with higher mass activity and better structure stability than commercial Pt/C (20% Pt) for glycerol electro-oxidation. Besides, the template-broken approach could provide a novel potential way to synthesize Pt-based or other noble metals/alloys for their advanced functional applications.

Modification of montmorillonite surfaces using a novel class of cationic gemini surfactants.

A novel class of cationic gemini surfactants were prepared and used as modifiers for sodium montmorillonite (MMT-Na). The modified montmorillonites were characterized by X-ray diffraction (XRD), thermal analysis (TG), Fourier transform infrared spectroscopy (FTIR), dispersibility measurement, and scanning electron microscopy (SEM). The results show that the surfactants have been intercalated into the montmorillonite layers successfully. XRD measurements indicate that the gemini surfactant is more effective at expanding the interlayer space of the MMT than the corresponding single chain surfactant. Moreover, the high efficiency can be obtained by lengthening the hydrophobic chains of gemini surfactants. Thermal analysis shows that there are four different molecular environments for gemini surfactants in the modified montmorillonite. The dispersibility measurement and SEM results indicate that the modified montmorillonite are more hydrophobic and prone to agglomerate in water than MMT-Na. These modified materials have the potential for removal of environment pollutants such as pesticides, phenol, etc. or being used as antimicrobial materials.