A Novel Aptamer Biosensor Based on a Localized Surface Plasmon Resonance Sensing Chip for High-Sensitivity and Rapid Enrofloxacin Detection.

Enrofloxacin, a fluoroquinolone widely used in animal husbandry, presents environmental and human health hazards due to its stability and incomplete hydrolysis leading to residue accumulation. To address this concern, a highly sensitive aptamer biosensor utilizing a localized surface plasmon resonance (LSPR) sensing chip and microfluidic technology was developed for rapid enrofloxacin residue detection. AuNPs were prepared by the seed method and the AuNPs-Apt complexes were immobilized on the chip by the sulfhydryl groups modified on the end of the aptamer. The properties and morphologies of the sensing chip and AuNPs-Apt complexes were characterized by Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometer, and scanning electron microscope (SEM), respectively. The sensing chip was able to detect enrofloxacin in the range of 0.01-100 ng/mL with good linearity, and the relationship between the response of the sensing chip and the concentration was Δλ (nm) = 1.288log ConENR (ng/mL) + 5.245 (R2 = 0.99), with the limit of detection being 0.001 ng/mL. The anti-interference, repeatability, and selectivity of this sensing chip were studied in detail. Compared with other sensors, this novel aptamer biosensor based on AuNPs-Apt complexes is expected to achieve simple, stable, and economical application in the field of enrofloxacin detection.

A L-glutamine binding protein modified MNM structured optical fiber biosensor based on surface plasmon resonance sensing for detection of L-glutamine metabolism in vitro embryo culture.

A surface plasmon resonance (SPR) optical fiber sensor with multimode-coreless-multimode (MNM) structure was developed, which modified by L-glutamine-binding protein (QBP) for detection of L-glutamine (Gln). The QBP was immobilized on the surface of gold films by chemical cross-linking and exhibited a binding affinity for L-glutamine. The conformation of QBP can be changed from the "open" to the "closed", which led to a red-shift of the SPR peak when QBP bounded to L-glutamine. There was a good linear correlation between is a dependence of the SPR peak on and the concentration of L-glutamine concentration in the range 10-100 µM, with a sensitivity of 10.797nm/log10[Gln] for L-glutamine in the in vitro embryo culture (IVC) medium environment, and the limit of detection (LOD) is 1.187 µM. This QBP-modified MNM structure optical fiber SPR sensor provides a new idea for the developmental potential assessment of embryos in the process of in vitro embryo culture.

Transcriptome and Co-Expression Network Analysis Reveals the Molecular Mechanism of Rice Root Systems in Response to Low-Nitrogen Conditions.

Nitrogen is an important nutrient for plant growth and essential metabolic processes. Roots integrally obtain nutrients from soil and are closely related to the growth and development of plants. In this study, the morphological analysis of rice root tissues collected at different time points under low-nitrogen and normal nitrogen conditions demonstrated that, compared with normal nitrogen treatment, the root growth and nitrogen use efficiency (NUE) of rice under low-nitrogen treatment were significantly improved. To better understand the molecular mechanisms of the rice root system's response to low-nitrogen conditions, a comprehensive transcriptome analysis of rice seedling roots under low-nitrogen and control conditions was conducted in this study. As a result, 3171 differentially expressed genes (DEGs) were identified. Rice seedling roots enhance NUE and promote root development by regulating the genes related to nitrogen absorption and utilization, carbon metabolism, root growth and development, and phytohormones, thereby adapting to low-nitrogen conditions. A total of 25,377 genes were divided into 14 modules using weighted gene co-expression network analysis (WGCNA). Two modules were significantly associated with nitrogen absorption and utilization. A total of 8 core genes and 43 co-expression candidates related to nitrogen absorption and utilization were obtained in these two modules. Further studies on these genes will contribute to the understanding of low-nitrogen adaptation and nitrogen utilization mechanisms in rice.

Mapping of Candidate Genes in Response to Low Nitrogen in Rice Seedlings.

Nitrogen is not only a macronutrient essential for crop growth and development, but also one of the most critical nutrients in farmland ecosystem. Insufficient nitrogen supply will lead to crop yield reduction, while excessive application of nitrogen fertilizer will cause agricultural and eco-environment damage. Therefore, mining low-nitrogen tolerant rice genes and improving nitrogen use efficiency are of great significance to the sustainable development of agriculture. This study was conducted by Genome-wide association study on a basis of two root morphological traits (root length and root diameter) and 788,396 SNPs of a natural population of 295 rice varieties. The transcriptome of low-nitrogen tolerant variety (Longjing 31) and low-nitrogen sensitive variety (Songjing 10) were sequenced between low and high nitrogen treatments. A total of 35 QTLs containing 493 genes were mapped. 3085 differential expressed genes were identified. Among these 493 genes, 174 genes showed different haplotype patterns. There were significant phenotype differences among different haplotypes of 58 genes with haplotype differences. These 58 genes were hypothesized as candidate genes for low nitrogen tolerance related to root morphology. Finally, six genes (Os07g0471300, Os11g0230400, Os11g0229300, Os11g0229400, Os11g0618300 and Os11g0229333) which expressed differentially in Longjing 31 were defined as more valuable candidate genes for low-nitrogen tolerance. The results revealed the response characteristics of rice to low-nitrogen, and provided insights into regulatory mechanisms of rice to nitrogen deficiency.

Fe3+ in a tetrahedral position determined the electrocatalytic properties in FeMn2O4.

As an electrocatalyst for the oxygen evolution reaction (OER) for water decomposition purposes, spinel ferrite materials have gained a lot of attention from many researchers. Herein, we document a co-precipitation synthesis of antitypical spinel nanoparticles (FeMn2O4) by post-annealing at different temperatures to enable modulation of the cationic oxidation state and tuning of the conversion degree for efficient and good OER performance. The electrocatalytic activity test shows that the sample annealed at 500 °C has the most optimal catalytic activity with an overpotential of 360 mV at a current density of 10 mA cm-2 and a Tafel slope as low as 105.32 mV dec-1. The formation of FeOOH during in situ OER promotes the catalytic activity of the catalysts. More importantly, according to the results of Brunauer-Emmett-Teller normalization, we demonstrate that the activity of the catalyst is also inseparable from the internal crystal structure. This work broadens the field of research on the electrocatalysis of spinel manganese ferrites.

Surface nitriding to improve the catalytic performance of FeNi3 for the oxygen evolution reaction.

Solving the problem of the slow kinetic process of the oxygen evolution reaction by electrocatalysts has attracted extensive attention. Here, we report an enhancement of the oxygen evolution reaction (OER) electrocatalytic activity via the surface nitriding of FeNi3 nanosheets for the formation of amorphous Fe/Ni-Nx species. The optimized Fe/Ni-Nx@FeNi3 nanosheets exhibit an overpotential of 251 mV to achieve a current density of 10 mA cm-2 and an excellent durability of 210 h. The superior electrocatalytic performance is attributed to the multi-component active sites, where the Fe/Ni-Nx outer layer inhibits metal active site leaching, and the catalyst undergoes dynamic reconfiguration during the OER.

Hydrogen-etched CoS2 to produce a Co9S8@CoS2 heterostructure electrocatalyst for highly efficient oxygen evolution reaction.

There is a pressing requirement for developing high-efficiency non-noble metal electrocatalysts in oxygen evolution reactions (OER), where transition metal sulfides are considered to be promising electrocatalysts for the OER in alkaline medium. Herein, we report the outstanding OER performance of Co9S8@CoS2 heterojunctions synthesized by hydrogen etched CoS2, where the optimized heterojunction shows a low η 50 of 396 mV and a small Tafel slope of 181.61 mV dec-1. The excellent electrocatalytic performance of this heterostructure is attributed to the interface electronic effect. Importantly, the post-stage characterization results indicate that the Co9S8@CoS2 heterostructure exhibits a dynamic reconfiguration during the OER with the formation of CoOOH in situ, and thus exhibits a superior electrocatalytic performance.

Microwave permittivity, permeability, and absorption of Ni nanoplatelet composites.

The Ni nanoplatelets with an average diameter of 75 nm and an average thickness of 10 nm are coated with MnO2 by a simple solution phase chemical method. The MnO2-coated Ni nanoplatelets are dispersed in paraffin wax to form the composite samples of the magnetic filler dispersed in the nonmagnetic insulating matrix. The effect of the Ni nanoplatelet volume fraction on the complex permittivity, complex permeability, and microwave absorption of the composites has been studied in the frequency range of 0.1-10 GHz. The complex permittivity of the composites with different volume fractions of the Ni nanoplatelets is almost constant in the 0.1-10 GHz frequency range. The complex permeability of the composites shows several resonance peaks. Besides the natural resonance peak, the exchange resonance peaks are observed. The composite with 17% volume fraction of Ni nanoplatelets has excellent microwave absorption properties of a minimum reflection loss value -31 dB at 9.1 GHz for a thickness of 2 mm and a broad absorption bandwidth of 2.3-10 GHz (R < -10 dB). The Ni nanoplatelets are a possible candidate as high performance microwave absorption filler. For the Ni nanoplatelet composites, the magnetic loss is the dominant term for microwave absorption.