Comprehensive insights into the differences of fungal communities at taxonomic and functional levels in stony coral Acropora intermedia under a natural bleaching event.

Previous studies have reported the correlations between bacterial communities and coral bleaching, but the knowledge of fungal roles in coral bleaching is still limited. In this study, the taxonomic and functional diversities of fungi in unbleached, partly bleached and bleached stony coral Acropora intermedia were investigated through the ITS-rRNA gene next-generation sequencing. An unexpected diversity of successfully classified fungi (a total of 167 fungal genera) was revealed in this study, and the partly bleached coral samples gained the highest fungal diversity, followed by bleached and unbleached coral samples. Among these fungi, 122 genera (nearly 73.2%) were rarely found in corals in previous studies, such as Calostoma and Morchella, which gave us a more comprehensive understanding of coral-associated fungi. Positively correlated fungal genera (Calostoma, Corticium, Derxomyces, Fusicolla, Penicillium and Vishniacozyma) and negative correlated fungal genera (Blastobotrys, Exophiala and Dacryopinax) with the coral bleaching were both detected. It was found that a series of fungal genera, dominant by Apiotrichum, a source of opportunistic infections, was significantly enriched; while another fungal group majoring in Fusicolla, a probiotic fungus, was distinctly depressed in the bleached coral. It was also noteworthy that the abundance of pathogenic fungi, including Fusarium, Didymella and Trichosporon showed a rising trend; while the saprotrophic fungi, including Tricladium, Botryotrichum and Scleropezicula demostrated a declining trend as the bleaching deteriorating. The rising of pathogenic fungi and the declining of saprotrophic fungi revealed the basic rules of fungal community transitions in the coral bleaching, but the mechanism of coral-associated fungal interactions still lacks further investigation. Overall, this is an investigation focused on the differences of fungal communities at taxonomic and functional levels in stony coral A. intermedia under different bleaching statuses, which provides a better comprehension of the correlations between fungal communities and the coral bleaching.

Post-synthetic modification-driven ZIF reconstruction and functionalization for efficient SARS-CoV-2 ECL detection.

The emergence of novel pathogens, as well as their frequent variants, raises the significance of developing superior and versatile sensing materials and techniques. Herein, a post-modified zeolitic imidazolate framework (pm-ZIF) was synthesized by using ZIF-67 as a parent MOF, and zinc(II) meso-tetra (4-carboxyphenyl) porphine (ZnTCPP) as a successive exchange ligand. Due to the preservation of the tetrahedral Co-N4 units from the ZIF precursor and the introduced porphyrin luminophores, this hybrid material pm-ZIF/P(Zn) enables the linear electrochemiluminescence (ECL) signal conversion of the target DNA concentration. An efficient biosensor that can be used to quantitatively detect SARS-CoV-2 was therefore constructed. The linear range of the sensor was 10-12-10-8 M, with a limit of detection (LOD) reaching 158 pM. Compared with the traditional amplification-based methods, the duration time of our method is significantly shortened and the quantitation of the SARS-Cov-2 RdRp gene can be completed within twenty minutes at room temperature.

Diversity and Antimicrobial Activity of Intestinal Fungi from Three Species of Coral Reef Fish.

Although intestinal microbiota play crucial roles in fish digestion and health, little is known about intestinal fungi in fish. This study investigated the intestinal fungal diversity of three coral reef fish (Lates calcarifer, Trachinotus blochii, and Lutjanus argentimaculatus) from the South China Sea using a culturable method. A total of 387 isolates were recovered and identified by sequencing their internal transcribed spacer sequences, belonging to 29 known fungal species. The similarity of fungal communities in the intestines of the three fish verified that the fungal colonization might be influenced by their surrounding environments. Furthermore, the fungal communities in different intestines of some fish were significantly different, and the number of yeasts in the hindgut was less than that in fore- and mid-intestines, suggesting that the distribution of fungi in fishes' intestines may be related to the physiological functions of various intestinal segments. In addition, 51.4% of tested fungal isolates exhibited antimicrobial activity against at least one marine pathogenic microorganism. Notably, isolate Aureobasidium pullulans SCAU243 exhibited strong antifungal activity against Aspergillus versicolor, and isolate Schizophyllum commune SCAU255 displayed extensive antimicrobial activity against four marine pathogenic microorganisms. This study contributed to our understanding of intestinal fungi in coral reef fish and further increased the library of fungi available for natural bioactive product screening.

Iridium Complex with Specific Intercalation in the G-Quadruplex: A Phosphorescence and Electrochemiluminescence Dual-Mode Homogeneous Biosensor for Enzyme-Free and Label-Free Detection of MicroRNA.

Design and exploitation of high-property and multifunctional emitters for achieving immobilization-free, label-free, enzyme-free, and dual-mode determination of microRNA (miRNA) with high sensitivity and selectivity are particularly urgent but remain a huge challenge. Herein, for the first time, we reported an Ir3+-based N-heterocyclic complex, namely, IrPyPt, ascertained its phosphorescence and electrochemiluminescence (ECL) dual-emission behavior in homogeneous solution, and discovered its turn-up phosphorescence and signal-off ECL response to G-quadruplex DNA over other DNAs. Inspired by this, IrPyPt was pioneered as an emitter to combine nucleic acid probes (ON1 and ON2) for developing a phosphorescence and ECL dual-mode homogeneous biosensor, which was applied to label-free, enzyme-free, highly sensitive, and credible analysis of miRNA-21 used as a target analyte. miRNA-21 triggered the hybridization chain reaction of ON1 and ON2 to generate abundant G-quadruplexes, which caught IrPyPt to yield IrPyPt@G-quadruplex, in which the intramolecular rotary motion of IrPyPt was inhibited and IrPyPt was unable to diffuse to the electrode, contributing to a highly boosted phosphorescence emission and a sharply declined ECL emission. With this design, dual-mode analysis of miRNA-21 was achieved with limits of detection down to 1.40 and 0.18 pM, respectively. Furthermore, the dual-mode biosensor was triumphantly applied to determine the concentration of miRNA-21 in cancer cell lysates and thus provided a great potential alternative for miRNA-related diseases' early and accurate diagnosis.

Acidic pH and thiol-driven homogeneous cathodic electrochemiluminescence strategy for determining the residue of organophosphorus pesticide in Chinese cabbage.

Electrochemiluminescent (ECL) sensors for organophosphorus pesticides (OPs) have received considerable attention, whereas complicated electrode's immobilization, response to single hydrolysate and anodic emission correlated with ECL assays restrict their potential utilization. Herein, we developed a homogeneous dual-response cathodic ECL system for highly sensitive and reliable analysis of OP using CdTe QDs as emitters. CdTe QDs, emitting red light, were fabricated through a hydrothermal reaction and generated anodic and cathodic ECL emission upon stimulation of tripropyl amine and K2S2O8, respectively. Notably, CdTe QDs-K2S2O8 showed a simultaneous response to thiol and acidic pH, and were regarded as a ECL sensor for methidathion with limit of detection of 0.016 ng/mL based on hydrolysis of acetylthiocholine into thiocholine and CH3COOH by acetylcholinesterase (AChE) and OPs' inhibition on AChE activity. This sensor also exhibited good practicability to detect methidathion in Chinese cabbage. Overall, the sensor will supply more useful information for ensuring OPs-related food safety.

pH and Redox Dual-Response Disulfide Bond-Functionalized Red-Emitting Gold Nanoclusters for Monitoring the Contamination of Organophosphorus Pesticides in Foods.

Most of the fluorescence sensors require choline oxidase or quenchers to detect organophosphorus pesticides (OPs) based on a single hydrolysate and suffer from high cost, complex procedures, weak stability, and low sensitivity. Here, we proposed a brand-new fluorescence strategy for highly sensitive detection of OPs based on both hydrolysate-response disulfide bond-functionalized gold nanoclusters (S-S-AuNCs) without additional substances. S-S-AuNCs were synthesized via a facile one-step redox reaction and emitted bright red light with ultrasmall size and high water dispersion. Interestingly, S-S-AuNCs displayed a unique response to thiol compounds and low pH values and were thus pioneered as a high-efficiency sensor for OPs based on acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylthiocholine into thiocholine and CH3COOH and OP inhibition of AChE activity. Further, S-S-AuNCs were employed to monitor the residue, distribution, and metabolization of methidathion in pakchoi with acceptable results. We believe that this work supplies a simpler and more highly sensitive approach for OP assay than the known ones and opens a new avenue to development of multistimulus-responsive and high-performance fluorescence substances.

Inorganic Recognizer-Assisted Homogeneous Electrochemiluminescence Determination of Organophosphorus Pesticides via Target-Controlled Emitter Release.

Given the relevance of organophosphorus pesticides (OPs) with food safety, it is highly urgent to develop sensitive and reliable sensors for OPs. However, most of the OP sensors are developed based on colorimetric and fluorescent techniques, which are limited to severe interference of color and fluorescence from pigments and organic acids in agricultural crops. Herein, we develop an inorganic recognizer-based homogeneous electrochemiluminescence (ECL) sensor for the highly sensitive and credible determination of OPs based on manganese dioxide and tris(2,2'-bipyridine)ruthenium [Ru(bpy)3]2+. Through electrostatic interaction, manganese dioxide nanoflakes-[Ru(bpy)3]2+ nanocomposites (MnNFs-Ru) are formed and exhibit a weak ECL signal due to the confinement of [Ru(bpy)3]2+ in MnNFs-Ru. Interestingly, MnNFs-Ru are capable of recognizing thiols due to the analyte-initiated reduction of MnNFs into Mn2+ and release of [Ru(bpy)3]2+ from MnNFs-Ru into solution. Further, MnNFs-Ru are employed for the homogeneous ECL determination of OPs, where acetylcholinesterase (AChE) catalyzes the hydrolysis of acetylthiocholine (ATCh) into thiocholine, which in turn decomposes MnNFs of MnNFs-Ru into Mn2+, and OPs inhibit AChE activity. This study widens the application of inorganic recognizers from colorimetry/fluorescence to homogeneous ECL and effectively avoids the interference of color and fluorescence, opening up a new path to the development of high-performance OP sensors and supplying a promising tool for guaranteed OP-related food safety.

pH-Response Quantum Dots with Orange-Red Emission for Monitoring the Residue, Distribution, and Variation of an Organophosphorus Pesticide in an Agricultural Crop.

Development of simple, sensitive, and reliable fluorescence sensors for monitoring the residue, distribution, and variation of organophosphorus pesticides (OPs) in agricultural crops is highly urgent but remains challenging, which is ascribed to deprivation of an ideal fluorophore and ingenious detection strategy. Herein, we report the fabrication of cadmium telluride quantum dots (CdTe QDs) with bright emission, good water dispersion, and long emission wavelength for OP screening based on the unique response of CdTe QDs to pH and the inhibition of OPs on acetylcholinesterase (AChE) activity. AChE catalyzed hydrolysis of acetylcholine (ACh) into CH3COOH, which protonated CdTe QDs to decline the fluorescence, whereas target OP impeded AChE from catalyzing hydrolysis of ACh into CH3COOH, making little influence in fluorescence of CdTe QDs. On the basis of the change in fluorescence, sensitive detection of OP was acquired, with the limit of detection at 0.027 ng/mL, which was comparable or lower than that of most known OP sensors. Furthermore, the CdTe-QD-based sensor was successfully applied for precisely monitoring the residue, distribution, and variation of methidathion in Chinese cabbage and cultivated soil. Therefore, the proposed sensor was anticipated to supply a promising alternative for food safety guarantee and was an valuable application for OP screening.

Two-Dimensional MnO2 Nanozyme-Mediated Homogeneous Electrochemical Detection of Organophosphate Pesticides without the Interference of H2O2 and Color.

Traditional peroxidase-like nanozyme-based sensors suffer from self-decomposition and high toxicity of H2O2, as well as the interference of color from nanozymes themselves and testing samples. In this work, we adopt nanozymes (two-dimension (2D) MnO2 sheets, manganese dioxide nanosheets (MnNS)) with oxidase-like and peroxidase-like properties as advanced catalysts to develop a novel homogeneous electrochemical sensor for organophosphate pesticides (OPs) using dissolved O2 as a coreactant without the interference of H2O2 and color. Owing to the large surface area and unique catalytic activity of MnNS, a large amount of tetramethylbenzidine (TMB) is catalyzed oxidation, leading to a significantly declined differential pulse voltammetry (DPV) current. Obviously, MnNS display an excellent response to thiocholine, deriving from the catalyzing hydrolysis of acetylthiocholine (ATCh) by acetylcholinesterase (AChE), which switches a homogeneous electrochemical OP detection process based on the depressing AChE activity with a limit of detection (LOD) of 0.025 ng mL-1. The as-proposed strategy on using nanozymes with oxidase-like and peroxidase-like properties to develop a homogeneous electrochemical sensor will provide a new pathway for improving the performance of nanozyme-based sensors, and the established MnNS-based homogeneous electrochemical sensor will find more applications for OP residue determination in food samples.

Label-free homogeneous electrochemical detection of MicroRNA based on target-induced anti-shielding against the catalytic activity of two-dimension nanozyme.

In traditional homogeneous electrochemical sensing system, methylene blue was stricken with nonspecific intercalation and weak stability, inevitably distorting the diagnosis results. Given the unique catalytic activity of oxidase- and peroxidase-like nanozymes, it is interesting to develop a nanozyme-based homogeneous electrochemical biosensor. Whereas, the preparation of nanozymes with dual enzyme-like activities and two dimensional (2D) morphology is a great challenge. Herein, a soft template-directed wet chemical approach was proposed for preparation of 2D MnO2 nanoflakes, in which the morphology can be easily tuned by the template dosage. Interestingly, not only the oxidase-like activity was discovered, but 2D MnO2 nanoflakes also display a significant peroxidase-like activity. Noticeably, 2D MnO2 nanoflakes exhibit superior response to single stranded deoxyribonucleic acid (ssDNA) over double stranded DNA in the aspect of binding and catalytic activity, which triggers a highly sensitive homogeneous electrochemical detection of microRNA. This study about finding nanozymes with dual enzyme-like activities and ssDNA with inhibiting effect will set up a new avenue to extend the application range of nanozymes and throws a new light on the development of higher-performance electrochemical biosensors.

Quaternary Ammonium Salt-Functionalized Tetraphenylethene Derivative Boosts Electrochemiluminescence for Highly Sensitive Aqueous-Phase Biosensing.

Aggregation induced emission active compounds (AIEgens) have appeared as a new kind of electrochemiluminescence (ECL) emitters due to their bright emission in the aggregated state but lack functional groups. Herein, we report a quaternary ammonium salt groups-functionalized AIEgen (QAU-1) and discover that coating QAU-1 on the indium tin oxide (ITO) surface (QAU/ITO) enabled QAU-1 to display significant cathodic ECL emission compared with that of QAU-1 in the dissolved state. Inspired by this, we applied QAU-1 as emitters to develop a novel ECL biosensor (Fc-DNA/QAU/ITO) through electrostatic attraction between QAU/ITO and a ferrocene-labeled ssDNA (Fc-DNA), and the developed biosensor was employed to detect bleomycin (BLM) with high sensitivity based on the target-initiated specific cleavage and subsequent removal of Fc molecules from the electrode. We envision this work will open up a new avenue to development of high-performance ECL biosensors, which will display a significant potential application in the field of analysis.