Heavy metal spatial distribution, source analysis, and ecological risks in the central hilly area of Hainan Island, China: results from a high-density soil survey.

The presence of heavy metals in soil has gained considerable attention due to their potential risks to ecosystems and human health. In this study, a thorough soil investigation was performed in the hilly region of central Hainan, which was formerly regarded as an area with the highest ecological environmental quality. A total of 7094 soil samples were systematically collected with high density over a large area. Simultaneously, a detailed investigation was conducted on the surrounding environment of each sampling point, including environmental factors such as soil, land use and crop types. The soil samples were analysed for heavy metals, pH, organic matter, and other parameters. The soil heavy metal pollution level, ecological risk and health risk were evaluated using the geo-accumulation index and the potential ecological risk index. The findings showed that the average contents of the heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil were 1.68, 0.042, 24.2, 6.49, 0.0319, 7.06, 29.6 and 49.8 mg·kg-1 respectively. Except for Hg, the mean values of the other heavy metals were either lower than or similar to the background values of Hainan. Also, only a few localised areas showed contamination by heavy metals. The primary sources of heavy metals, identified by a positive matrix factorisation model, could be categorised into four types: natural sources related to the soil formation process from acidic intrusive rocks (such as granite); natural sources primarily influenced by atmospheric deposition; anthropogenic sources associated with agricultural activities; and natural sources related to the soil formation process from middle-mafic intrusive rocks and black shales. The correlation analysis and variance analysis findings suggested that the content of heavy metals in the soil was primarily associated with the parent rock. The study area generally had low heavy metal levels and was not significantly polluted. However, agricultural activities still affected the enrichment of heavy metals. Therefore, it is imperative to remain vigilant about the ecological risks linked to soil heavy metals while continuing land development and expanding agricultural activities in the future. These findings indicate that conducting high-density soil surveys can enhance our understanding of regional soil heavy metals and enable reliable recommendations for agricultural planning. Whether in areas with low pollution risk or potential pollution risk, it is recommended that high-density soil surveys be conducted provide scientific guidance for further agricultural development.

Impact of orthodontic-induced facial morphology changes on aesthetic evaluation: a retrospective study.

BACKGROUND: The profound influence of orthodontic treatments on facial aesthetics has been a topic of increasing interest. This study delves into the intricate interplay between orthodontic treatments, facial feature alterations, and aesthetic perceptions. METHODS: A total of 73 patients who had undergone orthodontic treatment were included in this study. Facial photographs were taken before and after treatment. Ten orthodontists provided facial aesthetic ratings (FAR) for each patient's frontal, profile, and overall views. 48 facial landmarks were manually placed by the orthodontists and normalized using Generalized Procrustes analysis (GPA). Two types of phenotypes were derived from facial landmarks. Global facial phenotypes were then extracted using principal component analysis (PCA). Additionally, 37 clinical features related to aesthetics and orthodontics were extracted. The association between facial features and changes in FAR after orthodontic treatment was determined using these two types of phenotypes. RESULTS: The FAR exhibited a high correlation among orthodontic experts, particularly in the profile view. The FAR increased after orthodontic treatment, especially in profile views. Extraction of premolars and orthognathic surgery were found to result in higher FAR change. For global facial phenotypes, the most noticeable changes in the frontal and profile views associated with FAR occurred in the lip area, characterized by inward retraction of the lips and slight chin protrusion in the profile view, as well as a decrease in lip height in the frontal view. The changes observed in the profile view were statistically more significant than those in the frontal view. These facial changes were consistent with the changes from orthodontic treatment. For clinical features, two profile features, namely pg.sm.hori and pg.n.ls, were found to be associated with FAR following orthodontic treatment. The highest FAR scores were achieved when pg.sm.hori was at 80° and pg.n.ls was at 8°. On the other hand, frontal clinical features had a subtle effect on FAR during orthodontic treatment. CONCLUSIONS: This study demonstrated that orthodontic treatment improves facial aesthetics, particularly at lip aera in the profile view. Profile clinical features, such as pg.sm.hori and pg.n.ls, are essential in orthodontic treatment which could increase facial aesthetics.

The gut bacterial flora associated with brown planthopper is affected by host rice varieties.

Gut microbiota plays vital roles in the development, evolution and environmental adaptation of the host insects. The brown planthopper (BPH) is one of the most destructive pests of rice, but little is known about its gut microbiota. In this study, we investigated the gut bacterial communities in two BPH populations feeding on susceptible and resistant rice varieties by high-throughput amplicon sequencing. Our results revealed that the gut bacterial communities in BPH were species diverse. A total of 29 phyla and 367 genera were captured, with Proteobacteria and Acinetobacter being the most prominent phylum and genus, respectively. Comparative analysis showed that significant differences in the profile of gut bacterial communities existed between the two BPH populations. The species richness detected in the population feeding on the resistant rice variety was significantly higher than that in the population rearing on the susceptible rice variety. Although the most dominant gut bacteria at all taxonomic levels showed no significant differences between the two BPH populations, the relative abundances of two subdominant phyla (Firmicutes and Bacteroidetes) and two subdominant classes (Bacteroidia and Clostridia) were significantly different. FAPROTAX analysis further indicated that host rice varieties might induce changes of the gut bacterial flora in BPH, as significant differences in five metabolism-related functional categories (fermentation, methylotrophy, xylanolysis, nitrate reduction and ureolysis) were detected between the two BPH populations. Our results are informative for studies which focused on the interactions between BPH and its symbiotic microbes and could also provide the basis of future BPH biological management.

Ultraintense Zero-Phonon Line from a Mn4+ Red-Emitting Phosphor for High-Quality Backlight Display Applications.

The zero-phonon line (ZPL) of Mn4+, which highly depends on its local environment, is usually much weaker than the vibrational phonon sidebands. In this work, an ultraintense ZPL emission, coming from a brand new red-emitting Rb2LiGaF6:Mn4+ (RLGFM) phosphor upon blue light excitation, is presented. The interesting spectral characteristic originates from the nonequivalent substitution of Mn4+ for Ga3+ in a rigid octahedral structure with a low symmetry, which induces neighboring cation vacancies that distort the local symmetry of the [MnF6] octahedra. Benefiting from the ultraintense ZPL emission, a wide color gamut is achieved using RLGFM and ß-SiAlON:Eu2+ as color converters. Moreover, a comprehensive investigation on the thermal quenching behavior is also conducted to provide detailed insights to explore novel Mn4+ red phosphors for high-quality backlight display applications.

The Non-Concentration-Quenching Phosphor Ca3Eu2B4O12 for WLED Application.

Commercial white LED devices usually suffer from a high color temperature and poor color rendering. Developing a new, efficient, and stable red phosphor is the key to solving this problem. In this work, a series of pure Ca3Y2-xB4O12:xEu3+ (0 < x ≤ 2) samples, including the new and fully transitional borate phosphor Ca3Eu2B4O12 (CEBO), have been successfully prepared by solid-state reaction synthesis. CEBO is isostructural with Ca3Y2B4O12 (CYBO), belonging to the orthorhombic system with space group Pnma (No. 62). Under optimal 393 nm excitation, this borate exhibits a strong red emission, peaking at 615 nm, with high color purity. Interestingly, the luminescence of CEBO is relatively higher than that of CYBO:Eu3+ phosphors. The quantum yield of this non-concentration-quenching phosphor reaches 95.6%. Furthermore, a warm pc-WLED device has been fabricated by mixing as-prepared CEBO powders and commercial BaMgAl10O17:Eu2+ and (Sr, Ba)2SiO4:Eu2+ phosphors, which exhibits a high color rendering index (Ra = 83.7) along with a color temperature of around 3883 K. The present work indicates that this new borate, with outstanding quantum efficiency and favorable thermal stability, can be used as a red phosphor for application in WLEDs.

Complete mitochodrial genome of the crab spider Ebrechtella tricuspidata (Araneae: Thomisidae): A novel tRNA rearrangement and phylogenetic implications for Araneae.

Mitochondrial genomes are widely used for phylogenetic and phylogeographic analyses among arthropods, but there is a lack of sufficient mitochondrial genome sequence data for spiders. Herein, we sequenced and characterized the complete mitochondrial genome of a crab spider Ebrechtella tricuspidata (Araneae: Thomisidae). The circular mitochondrial genome is 14,352 bp long, including a standard set of 37 genes and an A + T-rich region. Nucleotide composition is highly biased toward A + T nucleotides (77.3%). A novel gene order rearrangement is detected by a tRNA (trnL1) translocation. Tandem repeats are not identified in the A + T-rich region. Most of the tRNAs are greatly reduced in size and cannot be folded into typical cloverleaf-shaped secondary structures. The phylogenetic analysis confirms that the mitochondrial genome sequences are useful in resolving higher-level relationship of Araneae. Overall, our data present in this study will elevate our knowledge on the architecture and evolution of spider mitochondrial genome.

Tracking alterations of alkyl side chains of N1 species in heavy crude oil after anaerobic biodegradation with negative-ion electrospray ionization coupled with high-field Fourier transform ion cyclotron resonance mass spectrometry.

RATIONALE: Heteroatomic compounds are relatively abundant and believed to be bio-resistant in heavy crude oils. However, few studies have focused on the biodegradation of these heteroatomic compounds. METHODS: Heteroatoms, especially N1 species, in a blank crude oil and in three treated oils co-incubated with anaerobic sulfate-reducing bacteria, nitrate-reducing bacteria and fermentative consortia cultures were detected using negative-ion electrospray ionization coupled with high-field Fourier transform ion cyclotron resonance mass spectrometry. RESULTS: The relative abundance of N1 species in the three treated oils decreased, while the relative abundance of O2 species increased. Remarkably, the relative abundances of N1 species with low carbon number increased and those with higher carbon number decreased. CONCLUSIONS: These results revealed that the anaerobic biodegradations of heavy crude oil occurred. With direct evidences, the degradations of alkyl side chains of N1 species by the anaerobic microbes could be deduced.

Red Phosphor Rb2NbOF5:Mn4+ for Warm White Light-Emitting Diodes with a High Color-Rendering Index.

We successfully prepared a red-emitting phosphor Rb2NbOF5 doped with Mn4+, and investigated its crystal structure, luminescent properties, and applications in detail. Mn4+ ions in Rb2NbOF5 exhibit an intense red emission with high color purity upon a broad excitation in the blue region. The related crystal-field parameters of Mn4+ in Rb2NbOF5 have been estimated according to the luminescent spectra. More importantly, Rb2NbOF5:Mn4+ has high thermal-quenching resistance and color stability. We further fabricated a warm white light-emitting diode using the phosphor, emitting intense white light with a high color-rendering index of 90 and a low color temperature of 3418 K. The results indicate that Rb2NbOF5:Mn4+ is a potential red-emitting phosphor for white light-emitting diodes.

From Nonluminescence to Bright Blue Emission: Boron-Induced Highly Efficient Ce3+-Doped Hydroxyapatite Phosphor.

Photoluminescence quantum efficiency (QE) and thermal stability are important for phosphors used in phosphor-converted light-emitting diodes (pc-LEDs). Hydroxyapatite, Ca5(PO4)3OH, is generally not used as host for phosphors, because the OH- group in the host will lead to a high vibrational frequency around the activators and reduces the luminescent efficiency or even quenches the emission. In this work, strong blue emission at 450 nm appears after introducing boron atoms into Ce3+-doped hydroxyapatite under excitation of a UV light. Analyses suggest that B atoms enter into the host structure, which lead to the modification of crystal structure and the formation of vacancies of O and H to compensate charge mismatch. The decrease of OH- groups around Ce3+ ion on Ca (3) site is responsible for the appearance of strong blue emission. The absolute QE value of the best blue-emitting phosphor is ∼92%, and the emission intensity at 150 °C remains 81% of that at room temperature. The emission peak and International Commission on Illumination (CIE) coordinates hardly change upon increasing temperature. The results suggest that boron-modified hydroxyapatite phosphor could be a candidate for UV-LED-pumped white phosphor-converted LEDs. This strategy may provide a new insight into the exploration of phosphors' hosts and other functional materials.

The complete mitogenome of a jumping spider Carrhotus xanthogramma (Araneae: Salticidae) and comparative analysis in four salticid mitogenomes.

The complete mitogenome of the jumping spider Carrhotus xanthogramma was determined and comparative analysis among four salticid mitogenomes was conducted. The circular genome is 14,563 bp in size and contains a complete set of genes that usually present in the metazoa. All of the 13 protein-coding genes begin with a typical ATN codon and stop with the canonical stop codons, except for ND4 and ND4L genes with an incomplete stop codon T. All of the tRNAs cannot be formed the fully paired acceptor stems and seven out of them cannot be folded into the typical cloverleaf-shaped secondary structures. The tRNA Glu gene translocates its position as compared to the mitogenomes of other three determined jumping spiders. The A+T content of the majority strand and the A+T-rich region are 75.1 and 80%, respectively. The phylogenetic relationships based on concatenated nucleotide and amino acid sequences of 13 protein-coding genes using Maximum Likelihood and Bayesian Inference methods indicated that mitogenome sequences were useful in resolving higher-level relationship of Araneae.

Novel Diterpenoids from the Twigs of Podocarpus nagi.

Phytochemical investigation of the twigs of Podocarpus nagi (Podocarpaceae) led to the isolation of two new abietane-type diterpenoids, named 1ß,16-dihydroxylambertic acid (1) and 3ß,16-dihydroxylambertic acid (2), along with two new ent-pimarane-type diterpenoids, named ent-2ß,15,16,18-tetrahydroxypimar-8(14)-ene (3) and ent-15-oxo-2ß,16,18-trihydroxypimar-8(14)-ene (4). Their respective structures were elucidated on the basis of spectroscopic analyses, including 1D- and 2D-NMR, IR, CD, and HR-ESI-MS. This is the first time ent-pimarane-type diterpenoids from the genus Podocarpus has been reported. All four new compounds were tested for cytotoxic activity. The MTT assay results showed that compounds 3 and 4 significantly inhibited the proliferation of human cervical cancer Hela cells, human lung cancer A549 cells, and human breast cancer MCF-7 cells at a concentration of 10 µM. Furthermore, using the lipopolysaccharide (LPS)-stimulated RAW264.7 cells, compounds 2 and 4 were found to significantly inhibit nitrogen oxide (NO) production with IC50 values of 26.5 ± 6.1 and 17.1 ± 1.5 µM, respectively.

The role of three calcineurin subunits and a related transcription factor (Crz1) in conidiation, multistress tolerance and virulence in Beauveria bassiana.

The eukaryotic calcineurin (CN) pathway comprising catalytic A (CnA) and regulatory B subunits (CnB) is crucial for many biological processes but functionally unexplored in entomopathogenic fungi. Here, we characterise three CN subunits (CnA1, CnA2 and CnB) and a downstream CN-responsive zinc finger transcription factor (Crz1) in Beauveria bassiana. CN-mediated phosphatase activity decreased by 16-38 % in all deletion mutants compared with wild type. Growth and conidiation were most defective in ΔcnB, which showed a large proportion of abnormally branched germlings but were less defective in ΔcnA1 and ΔcnA2. Conidiation defects also occurred in Δcrz1, uniquely accompanied with slower germination. Compared with wild type, the four deletion mutants became, to varying degrees, more sensitive to Ca(2+), Mn(2+), Zn(2+), Mg(2+), two oxidants, three cell wall stressors, carbendazim, heat shock and ultraviolet (UV)-B irradiation. They were also less virulent to Spodoptera litura larvae. Only ΔcnB and Δcrz1 were less tolerant to high osmolarity. The altered phenotypes of the deletion mutants were associated with lower intracellular mannitol and trehalose levels, reduced overall activity of superoxide dismutases and catalases, altered cell wall composition and down-regulation of numerous phenotype-influencing genes. Additionally, the transcription of six cascaded genes in two stress-responsive mitogen-activated protein kinase (MAPK) pathways and the phosphorylation of hallmarking Hog1 and Slt2 were largely down-regulated in all the deletion mutants under osmotic and cell wall stresses, respectively. All the changes were restored by gene complementation. Taken together, three calcineurin subunits and Crz1 play vital, but variable, roles in B. bassiana responses to environmental stresses during development and host signals during infection.

Luminescent properties of Ca3SiO4Cl2 co-doped with Ce(3+) and Eu(2+) for near-ultraviolet light-emitting diodes.

Ca3SiO4Cl2 co-doped with Ce(3+),Eu(2+) was prepared by high temperature reaction. The structure, luminescent properties and the energy transfer process of Ca3SiO4Cl2:Ce(3+),Eu(2+) were investigated. Eu(2+) ions can give enhanced green emission through Ce(3+) → Eu(2+) energy transfer in these phosphors. The green phosphor Ca2.9775SiO4Cl2:0.0045Ce(3+),0.018Eu(2+) showed intense green emission with broader excitation in the near-ultraviolet light range. A green light-emitting diode (LED) based on this phosphor was made, and bright green light from this green LED could be observed by the naked eye under 20 mA current excitation. Hence it is considered to be a good candidate for the green component of a three-band white LED.

Luminescent properties and energy transfer in the green phosphors LaBSiO5:Tb3+, Ce3+.

LaBSiO5 phosphors doped with Ce(3+) and Tb(3+) were synthesized using the conventional solid-state method at 1100 °C. The phase purity and luminescent properties of these phosphors are investigated. LaBSiO5:Tb(3+) phosphors show intense green emission, and LaBSiO5 phosphors doped with Ce(3+) show blue-violet emission under UV light excitation. LaBSiO5 phosphors co-doped with Ce(3+) and Tb(3+) exhibit blue-violet and green emission under excitation by UV light. The blue-violet emission is due to the 5d-4f transition of Ce(3+) and the green emission is ascribed to the (5) D4 → (7) F5 transition of Tb(3+). The spectral overlap between the excitation band of Tb(3+) and the emission band of Ce(3+) supports the occurrence of energy transfer from Ce(3+) to Tb(3+), and the energy transfer process was investigated.

Bbssk1, a response regulator required for conidiation, multi-stress tolerance, and virulence of Beauveria bassiana.

Ssk1-type response regulator proteins are the core elements of histidine-to-aspartate systems that mediate fungal stress tolerance, a determinant to the biocontrol potential of fungal entomopathogens. We characterized the functions of Beauveria bassiana Ssk1 (Bbssk1) by analyzing multi-phenotypic changes in ΔBbssk1 and differentially expressed genes in the digital gene expression (DGE) libraries of ΔBbssk1 and wild-type constructed under osmotic stress. The Bbssk1 disruption caused 25 % reductions in conidial yield and virulence to Spodoptera litura larvae and significant defects in tolerances to two osmotic salts (81-84 %), H2O2 oxidation (23 %), two fungicides (21-58 %), three cell wall biosynthesis inhibitors (25-36 %), and three metal ions (~8 %) during colony growth, respectively, but little changes in cell sensitivity to menadione oxidation and in conidial thermotolerance and UV-B resistance. RNA-seq analysis with the DGE libraries revealed differential expressions of 1,003 genes in the ΔBbssk1 genome. Of those, many associated with conidiation, stress response, xenobiotic transport, cell wall integrity, and protein/carbohydrate metabolism were remarkably down-regulated, including the genes involved in mitogen-activated protein kinase (MAPK) signal pathway that downstream of Bbssk1. Our results indicate that Bbssk1 regulates positively the expressions of the MAPK cascade in the pathway of B. bassiana and many more downstream genes associated with conidiation, multi-stress tolerance, and virulence.

Hybrid nanospheres of silica covalently containing yellow-emitting cationic iridium(III) complex: preparation and application in white light-emitting diodes.

A yellow-emitting cationic iridium(III) complex [(dfppy)2Ir(TBD)]PF6 (TBD: N4,N4'-bis(3-(triethoxysilyl)propyl)-[2,2'-bipyridine]-4,4'-dicarboxamide; dfppy: 2-(2,4-difluorophenyl)pyridine) containing hydrolysable alkoxysilanes was synthesized. Then, a series of silica-based hybrid nanospheres with diameters of around 400 nm was prepared via the hydrolysis of this complex together with tetraethyl orthosilicate (TEOS, a silica source). When the amount of the complex used was 5.0 wt%, hybrid nanospheres showed the best photoluminescence (PL) properties, relative to the PL quantum yield of pure solid [(dfppy)2Ir(TBD)]PF6 (12.7%), that of hybrid nanospheres increased to 26.2%. Moreover, the thermal decomposition temperature (Td) of pure solid [(dfppy)2Ir(TBD)]PF6 was 331 °C, the Td of the complex in hybrid nanospheres increased to 447 °C. However, the yellow light emission was almost unchanged and was still located at 500-750 nm with a maximum wavelength (λem,max) of 577 nm. Under the excitation of blue-emitting chips (λem,max ≈ 455 nm), cold/neutral/warm white light-emitting diodes (WLEDs) with good luminous quality can all be fabricated using these hybrid nanospheres as phosphors in epoxy resin at different blending concentrations. Compared with two or three iridium(III) complexes being contained in silica-based particles as phosphors as described in literatures, in this study, silica-based hybrid nanospheres covalently containing only one yellow-emitting cationic iridium(III) complex as phosphors provide a more effective and simpler method for preparation high-performance WLEDs.

Defense Responses of Different Rice Varieties Affect Growth Performance and Food Utilization of Cnaphalocrocis medinalis Larvae.

Rice leaf folder, Cnaphalocrocis medinalis (Guenée), is one of the most serious pests on rice. At present, chemical control is the main method for controlling this pest. However, the indiscriminate use of chemical insecticides has non-target effects and may cause environmental pollution. Besides, leaf curling behavior by C. medinalis may indirectly reduce the efficacy of chemical spray. Therefore, it is crucial to cultivate efficient rice varieties resistant to this pest. Previous studies have found that three different rice varieties, Zhongzao39 (ZZ39), Xiushui134 (XS134), and Yongyou1540 (YY1540), had varying degrees of infestation by C. medinalis. However, it is currently unclear whether the reason for this difference is related to the difference in defense ability of the three rice varieties against the infestation of C. medinalis. To explore this issue, the current study investigated the effects of three rice varieties on the growth performance and food utilization capability of the 4th instar C. medinalis. Further, it elucidated the differences in defense responses among different rice varieties based on the differences in leaf physiological and biochemical indicators and their impact on population occurrence. The results showed that the larval survival rate was the lowest, and the development period was significantly prolonged after feeding on YY1540. This was not related to the differences in leaf wax, pigments, and nutritional components among the three rice varieties nor to the feeding preferences of the larvae. The rate of superoxide anion production, hydrogen peroxide content, and the activity of three protective enzymes were negatively correlated with larval survival rate, and they all showed the highest in YY1540 leaves. Compared to other tested varieties, although the larvae feeding on YY1540 had higher conversion efficiency of ingested food and lower relative consumption rate, their relative growth was faster, indicating stronger food utilization capability. However, they had a lower accumulation of protein. This suggests that different rice varieties had different levels of oxidative stress after infestation by C. medinalis. The defense response of YY1540 was more intense, which was not conducive to the development of the larvae population. These results will provide new insights into the interaction mechanism between different rice varieties and C. medinalis and provide a theoretical basis for cultivating rice varieties resistant to this pest.

Catalases play differentiated roles in the adaptation of a fungal entomopathogen to environmental stresses.

The catalase family of Beauveria bassiana (fungal entomopathogen) consists of catA (spore-specific), catB (secreted), catP (peroxisomal), catC (cytoplasmic) and catD (secreted peroxidase/catalase), which were distinguished in phylogeny and structure and functionally characterized by constructing single-gene disrupted and rescued mutants for enzymatic and multi-phenotypic analyses. Total catalase activity decreased 89% and 56% in ΔcatB and ΔcatP, corresponding to the losses of upper and lower active bands gel-profiled for all catalases respectively, but only 9-12% in other knockout mutants. Compared with wild type and complement mutants sharing similar enzymatic and phenotypic parameters, all knockout mutants showed significant (9-56%) decreases in the antioxidant capability of their conidia (active ingredients of mycoinsecticides), followed by remarkable phenotypic defects associated with the fungal biocontrol potential. These defects included mainly the losses of 40% thermotolerance (45°C) in ΔcatA, 46-48% UV-B resistance in ΔcatA and ΔcatD, and 33-47% virulence to Spodoptera litura larvae in ΔcatA, ΔcatP and ΔcatD respectively. Moreover, the drastic transcript upregulation of some other catalase genes observed in the normal culture of each knockout mutant revealed functionally complimentary effects among some of the catalase genes, particularly between catB and catC whose knockout mutants displayed little or minor phenotypic changes. However, the five catalase genes functioned redundantly in mediating the fungal tolerance to either hyperosmotic or fungicidal stress. The differentiated roles of five catalases in regulating the B. bassiana virulence and tolerances to oxidative stress, high temperature and UV-B irradiation provide new insights into fungal adaptation to stressful environment and host invasion.

Sensitive fluorescent detection of phosmet and chlortetracycline in animal-derived food samples based on a water-stable Cd(II) chain-based zwitterionic metal-organic framework.

The residues of pesticides and antibiotics have always been a major concern in agriculture and food safety. In order to provide a new method for the rapid detection of organophosphorus pesticides and antibiotics, a novel Cd(II) chain-based zwitterionic metal-organic framework MOF 1 with high sensitivity fluorescence sensing performance was successfully synthesized. A series of researches showed that the water- and pH-stable bifunctional MOF 1 has a great ability to detect phosmet (PSM) and chlortetracycline (CTC) in water through fluorescence quenching effect, with high detection sensitivity, low detection limits (0.0124 µM and 0.0131 µM), short response time (40 s) and reusability. Practical application results revealed that MOF 1 could detect PSM and CTC in milk, beef, chicken and egg samples, with satisfactory recoveries (95.2%-103.7%). As a novel fluorescence probe, MOF 1, is known the first case that can detect PSM in animal-derived samples, and the first dual-function material capable of detecting PSM and CTC. Mechanism studies displayed that competitive absorption and photoinduced electron transfer clearly authenticate the high quenching performance of the material.

A Droplet Digital PCR-Based Approach for Quantitative Analysis of the Adulteration of Atlantic Salmon with Rainbow Trout.

Low-cost fish species are often used to adulterate or substitute for Atlantic salmon products, posing a serious threat to market order and public health. Hence, reliable techniques are urgently needed to detect Atlantic salmon adulteration. In this study, a precise method for identifying and quantifying adulterated Atlantic salmon with rainbow trout based on droplet digital PCR (ddPCR) testing was developed. Species-specific primers and probes were designed targeting the single-copy nuclear gene myoglobin of two salmonids. A quantitative formula for calculating the mass fraction of adulterated Atlantic salmon with rainbow trout was established based on a one-step conversion strategy, in which the DNA copy number ratios were directly transformed to meat mass fractions by introducing a fixed constant (the transfer coefficient). The dynamic range of the established ddPCR method was from 1% to 90%, with a limit of detection (LOD) of 0.2% and a limit of quantification (LOQ) of 0.8% for rainbow trout in Atlantic salmon, respectively. The quantification method demonstrated an acceptable level of repeatability and reproducibility, as the values of the relative standard deviation (RSD) for the tested meat mixtures with the known fractions were all less than 5%. Thermal and freezing treatments, as well as adding food additives within the recommended dosage limits, had no significant effect on the quantification accuracy. The method was successfully applied to detect rainbow trout adulteration in commercial raw and processed Atlantic salmon products. In comparison to real-time quantitative PCR (qPCR) testing, the established ddPCR method exhibited a higher level of stability and accuracy. Overall, the ddPCR-based quantitative method exhibited high levels of accuracy, stability, sensitivity, and practicability, suitable for applications in the routine surveillance and quality assurance of salmon products.