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Pathogenic bacterial infections in freshwater-farmed fish have high morbidity and mortality. As an effective broad spectrum antibacterial agent, silver nanoparticles (AgNPs) have great application potential in the field of aquaculture. However, due to the easy aggregation and oxidation properties of AgNPs, their practical applications are rather limited. Herein, nanocomposites of AgNPs and carbon nanodots (AgNPs@C-dots) were synthesized by using carbon nanodots as a reductant and a stabilizer. Their antibacterial activity and biosafety were systematically investigated. AgNPs@C-dots exhibit superior aggregation stability, excellent biocompatibility, and enhanced antibacterial activity compared to common AgNPs (reduced by sodium citrate).

Electrospun g-C3N5/MIL-101(Fe)/poly(acrylonitrile-co-maleic acid) nanofibers were fabricated for the highly efficient degradation of emerging pharmaceutical pollutants.

Novel graphitic carbon nitride quantum dots (g-C3N5-dots) were synthesized by an alkali-assisted hydrothermal method, having great potential applications in bioimaging and biological sensing.

Solar light-driven photoelectrocatalytic nitrogen reduction and photocatalytic degradation of pollutants based on flower-like NV-g-C3N5@VS2 heterojunctions.

Combined therapeutic strategies for bacterial infection have attracted worldwide attention owing to their faster and more effective therapy with fewer side effects compared with monotherapy. In this work, gold-platinum nanodots (AuPtNDs) are simply and quickly synthesized by a one-step method. They not only exhibit powerful peroxidase-like activity but also confer a higher affinity for hydrogen peroxide (H2O2), which is 3.4 times that of horseradish peroxidase. Under 808 nm laser irradiation, AuPtNDs also have excellent photothermal conversion efficiency (50.53%) and strong photothermal stability. Excitingly, they can combat bacterial infection through the combination of chemodynamic and photothermal therapy. In vitro antibacterial results show that the combined antibacterial strategy has a broad-spectrum antibacterial property against both Escherichia coli (Gram negative, 97.1%) and Staphylococcus aureus (Gram positive, 99.3%). Animal experiments further show that nanodots can effectively promote the healing of bacterial infection wounds. In addition, owing to good biocompatibility and low toxicity, they are hardly traceable in the main organs of mice, which indicates that they can be well excreted through metabolism. These results reveal the application potential of AuPtNDs as a simple and magic multifunctional nanoparticle in antibacterial therapy and open up new applications for clinical anti-infective therapy in the near future.

Carbon nitride materials have become one of the highly explored carbon-based nanomaterials due to their unique properties. Herein, the novel graphitic carbon nitride quantum dots (g-C

It remains an unanswered question whether the flux of K+ and H+ in lysosomes are correlated due to difficulties in simultaneously imaging these two ions. This question is of great value for understanding lysosomal acidification. Herein, we designed DNA quadruplex and triplex based luminescent nanosensors that can, respectively monitor K+ and pH in lysosomal lumen. Each sensor contained an upconversion nanoparticle luminophore and a gold nanoparticle quencher, producing green and blue luminescence signals for K+ and H+ , respectively. The sensors were tested in buffers showing dynamic ranges of 5 to 200 mM K+ and pH 5.0 to 8.2. Co-imaging using these two sensors in cells indicated that the influx of H+ was accompanied with the efflux of K+ , solving this long-standing question of the lysosomal biochemistry.

Aeromonas salmonicida (A. salmonicida) is an important opportunistic pathogen to aquatic animals that causes severe economic losses to aquaculture, which makes its rapid detection and prevention are critical. In this work, a single-stranded DNA (ssDNA) aptamer (A.s-2) with high specificity to the bacteria was selected by Systematic Evolution of Ligands by Exponential Enrichment (SELEX). The selected aptamer was confirmed with high binding ability and specificity (K

The construction of multi-modal detection methods has attracted widespread attention in the field of biosensing due to their high sensitivity and strong anti-interference ability. In this manuscript, we developed colorimetric and ratiometric fluorescence dual-signal optical methods based on cerium-based nanoparticles (Ce NPs) for the sensitive detection of vitamin C (VC). The catalysis of Ce NPs with excellent peroxidase-like activity upon the reaction of H

Due to the harsh reaction conditions, high energy consumption, and numerous carbon emissions of the traditional Haber–Bosch method, the fixation of nitrogen under environmentally friendly and milde...

MnO2 nanomaterials have aroused widespread attention because of their nanozyme activity, redox properties, good biocompatibility, and therapy-related activities. However, not many reports on self-luminescent MnO2 materials have been concerned to date, which greatly hampered their further development in various fields. In this paper, luminescent MnO2 quantum dots (MnO2 QDs) have been first prepared via a facile one-step ultrasonic method. With the assistance of bovine serum albumin (BSA) or cysteine (Cys), the synthesized MnO2 QDs (BSA-MnO2 QDs or Cys-MnO2 QDs) display strongly enhanced fluorescence (FL). The prepared BSA-MnO2 QDs with a particle size of about 1 to 2 nm show the maximum excitation and emission peaks at 320 and 410 nm with excellent salt stability, anti-photobleaching ability, and time stability. It is confirmed that BSA plays a dual function as the exfoliating agent to promote the exfoliation of bulk MnO2 nanosheets and as the capping agent to provide a friendly microenvironment for MnO2 QDs. Ag ions can destroy the microenvironment of BSA-MnO2 QDs owing to the in situ formation of Ag nanoparticles (Ag NPs) mediated by BSA on the surface of the QDs. Then, these Ag NPs can quench the FL intensity of the QDs by fluorescence resonance energy transfer. However, the FL strength of the BSA-MnO2 QDs is recovered after adding H2O2 and NaHS since they may react with Ag NPs to produce Ag+ and Ag2S, which further confirmed the role of BSA. This work not only opens up a facile and universal avenue to synthesize luminescent MnO2 QDs with enhanced FL but also provides a possible sensing platform through tuning the microenvironment of the MnO2 QDs. The MnO2 QDs with outstanding performance may show great potential as fluorescent probes in the fields of biological imaging, optical sensing, drug delivery, and therapy.

Tetrastigma hemsleyanum Diels et Gilg is a rare and wild medicinal resource. Metabolites, especially secondary metabolites, have an important influence on T. hemsleyanum adaptability and its medicinal quality. The metabolite proanthocyanidin (PA) is a polyphenol compound widely distributed in land plants, which can be used as antioxidants and anticancer agents. Here, we discovered that three types of PA accumulated in large amounts in purple leaves (PL), but not in green leaves (RG), based on widely non-targeted metabolomics. In addition, we further found that catechins and their derivatives, which are the structural units of PA, are also enriched in PL. Afterwards, we screened and obtained five key genes, DNR1/2, ANS, ANR and LAR closely related to PA biosynthesis through transcriptome analysis and found they were all highly expressed in PL compared to RG. Therefore, observed the regulatory relationship between the main compounds and genes network, and the PA metabolism regulatory pathway was complicated, which may be different to other species.

Vanadium carbide MXene (V

Nitric oxide (NO), an essential biological messenger molecule, participates in various physiological and pathological processes. The sensitive and specific detection of NO is of great significance for understanding the biological function of NO. Here, we synthesized a fluorescent probe (Rho-NO) for highly selective detection of NO both in vitro and in vivo. The high selectivity of Rho-NO is attributed to the fact that NO is easily replaced by electron donor amino group to form N-nitrosation products, causing rhodamine spiro ring open and fluorescence emit. Rho-NO showed a good linear response to NO (0-100 µM) with a low detection limit (0.06 µM). Importantly, it exhibited excellent specificity for NO detection in human serum and was also applied for imaging NO in living cells and inflammatory model of zebrafish. This work proves the potential of Rho-NO in pathological research and disease diagnosis.

Extensive attention has been paid to rationally control the artificial nanoenzyme activities via suitable strategies to prepare various nanoscale functional materials. Herein, FeCo co-doped carbon sphere (FeCo@C) with intrinsic oxidase-like and peroxidase-like activity has been obtained from the carbonization of FeCo-ZIF. The unique dual-enzyme catalytic property of FeCo@C can be simply regulated and utilized for bifunctional colorimetric platforms. At pH 3.6 and catalytic reaction time of 6 min, the FeCo@C possesses strong oxidase-like activity which can catalytically oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) owing to the production of O2·− with the participation of O2 to result in typical color change of the system. Hydroquinone (HQ) as a reducing agent can induce the color fading, and therefore, a novel colorimetric biosensing platform for HQ was constructed with the linear range of 1–30 μM and detection limit of 0.8 μM. However, with the pH of 4.4 and catalytic reaction time of 3 min, the oxidase-like activity of FeCo@C was obviously weakened, and the peroxidase-like activity of FeCo@C is still high. Hence, a facile analytical method was developed to detect H2O2 based on the peroxidase-like activity of FeCo@C with the linear range of 1–240 μM and detection limit of 1 μM. Moreover, the FeCo@C has high stability and strong magnetism with the activity being kept well after several cycles of recycling, which shows great prospect in biosensing and catalysis areas.

In recent years, germanium nanoparticles (Ge NPs) have attracted considerable research attention because of its excellent electrical and optical properties. However, it is mainly applied in the field of solar cells, photodetectors and photothermal therapy. Actually, Ge NPs have the advantages of low toxicity and excellent biocompatibility, which means that they have great potential in biosensing applications. However, there are few related reports. In this paper, we discovered that Ge NPs have the intrinsic peroxidase-like catalytic activity and can significantly accelerate the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 for the first time. Compared with natural enzyme (horseradish peroxidase, HRP), Ge NPs maintain higher catalytic stability after treatment at different pH, temperature and ionic strength. Furthermore, a Ge NPs-based colorimetric platform was established for the first time to detect biomolecules with favourable sensitivity and selectivity, such as uric acid, glucose and choline. This work finds the new property of Ge NPs and extends its application in biosensing.

Carbon nitride (CN) materials are considered as promising photocatalysts due to the advantages of easy availability and visible light absorption. However, wide band gap and high recombination rates of electron-hole pairs of conventional CN materials remain the “bottleneck” of the photocatalysts. Therefore, it is necessary to develop an efficient strategy to narrow band gap of CN and accelerate its charge transfer. In addition, the introduction of nitrogen (N) vacancies is an efficient strategy to narrow band gap and reduce recombination rates of electron-hole pairs. Herein, a novel triazole ring-based graphite carbon nitride (g-C3N5) is developed by one step pathway of NaOH-assisted condensation of triazole rings for the first time. It is found that NaOH can control N vacancies and band gap of g-C3Nx. Meanwhile, the N vacancies of g-C3Nx gradually increase with the increasing concentration of NaOH in the range of 0.005–0.1 g, suppressing the recombination of photogenerated electron-hole pairs. The proposed g-C3Nx exhibits outstanding photocatalytical and photoelectrochemical performance. Therefore, the study highlights the significance of N vacancies in enhancing the photocatalytical and photoelectrochemical performance of promising g-C3N5. Keywords: g-C3N5, Controllable N vacancies, NaOH-treated condensation of triazole rings, Outstanding photocatalytical, Photoelectrochemical performance

The simple and highly sensitive detection of organophosphorus pesticides (OPs) is urgently required. Here, we have developed a sensing method for OPs based on the trypsin digestion of the template of bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs), thus leading to BSA-AuNC aggregation and quenching of their fluorescence. While the activity of trypsin was irreversibly inhibited in the presence of OPs, the fluorescence quenching efficiency of BSA-AuNCs decreased. Under the optimal conditions, the logarithm of OPs concentration was proportional to inhibition efficiency in the range of 0.1 ng mL−1 to 5 μg mL−1. The detection limit of OPs reached 0.037 ng mL−1. What's more, the sensing method was successfully utilized in the detection of OPs in real food samples. These results indicated that the OPs sensor has potential applications in the safety and monitoring of agricultural samples.

Three-dimensional graphite carbon nitride (3D-CN) has received tremendous research interest due to its unique structural features, fascinating physicochemical properties, and widespread potential a...

Alkaline phosphatase (ALP) is an essential hydrolase and widely distributed in living organisms. It plays important roles in various physiological and pathological processes. Herein, a turn-on near-infrared (NIR) fluorescent probe (DXMP) was developed for sensitive detection of ALP activity both in vitro and in vivo based on the intramolecular charge transfer (ICT) mechanism. Upon incubation with ALP, DXMP exhibited a strong fluorescence increment at 640 nm, which was attributed to the fact that ALP-catalyzed cleavage of the phosphate group in DXMP induced the transformation of DXMP into DXM-OH. The probe exhibited prominent features including outstanding selectivity, high sensitivity, and excellent biocompatibility. More importantly, it has been successfully used to detect and image endogenous ALP in living cells and zebrafish.

Due to similar charges, atomic radii, and chemical properties of most metal ions, the selective sensing of these metal ions and imaging in vivo is still a challenge. A DNAzyme assemblied and near-infrared (NIR) light excited nanosensor was developed to detect and image Pb

Group IV nanodots (NDs) mainly including carbon (C), silicon (Si), germanium (Ge) have aroused much attention as one type of important nanomaterials that are widely studied in optoelectronics, semiconductors, sensors and biomedicine-related fields owing to the low cost of synthesis, good stability, excellent biocompatibility, and some attractive newly emerged properties. In this review, the synthesis, surface engineering and application in bioimaging and biotherapy of group IV NDs are summarized and discussed. The recent progress in the rational synthesis and functionalization, specific therapy-related properties, together with in vivo and in vitro bioimaging are highlighted. Their new applications in biotherapy such as photothermal therapy (PTT) and photodynamic therapy (PDT) are illustrated with respect to C, Si and Ge NDs. The current challenges and future applications of these emerging materials in bioimaging and biotherapy are presented. This review provides readers with a distinct perspective of the group IV NDs nanomaterials for synthesis and surface engineering, and newly emerging properties related to applications in biomedicine.

Germanium quantum dots (GeQDs) show unique advantages in fluorescence applications due to their large quantum confinement effect and excellent biocompatibility. However, GeQDs are confronted with difficulty in accurately controlling the fluorescence emission. This defect brings challenges to understanding the fluorescence mechanism and limits the potential applications of GeQDs. In this paper, a series of GeQDs with the average diameter of about 2.6 nm modified with different ligands were synthesized by the chemical reduction method. The fluorescence emission of GeQDs can be changed from blue to yellow-green through adjusting the surface ligands. The influence of surface ligands on the fluorescence emission of GeQDs was thoroughly investigated by experimental and theoretical calculations. Furthermore, the synthesized GeQDs exhibit good biocompatibility and photostability and can act as high-performance fluorescence probes for long-term fluorescent bioimaging. This work provides a good and deep understanding of the fluorescence mechanism of GeQDs and will facilitate diverse promising applications of GeQDs in the near future.

It remains an unanswered question whether the flux of K

The food-borne pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) causes self-limiting gastroenteritis in humans and is not easily eradicated because it often attaches to suitable surfaces to form biofilms that have high resistance to disinfectants and antimicrobials. To develop an alternative strategy for the treatment of biofilms, it is necessary to further explore the effects of flagellar motility on the development process of Salmonella biofilms. Here, we constructed flagella mutants (ΔflgE and ΔfliC) to systematically study this process. By comparing them with wild-type strains, we found that these mutants lacking flagellar motility form fewer biofilms in the early stage, and the formed mature biofilms contain more cells and extracellular polymeric substances (EPS). In addition, fewer mutant cells adhered to glass plates compared with wild-type cells even after 6 h of incubation, suggesting that flagellar motility plays a significant role in preliminary cell-surface interactions. More importantly, the motility of wild-type strain was greatly decreased when they were treated with carbonyl cyanide m-chlorophenylhydrazone, which inhibited flagellar motility and reduced biofilm formation, as in the case of the ΔflgE mutant. Overall, these findings suggest that flagellar motility plays an important role in Salmonella biofilm initiation and maturation, which can help us to counteract the mechanisms involved in biofilm formation and to develop more rational control strategies.

Due to the harsh reaction conditions, high energy consumption, and numerous carbon emissions of the traditional Haber-Bosch method, the fixation of nitrogen under environmentally friendly and milder conditions is of great importance. Recently, photoelectrochemical (PEC) strategies have attracted extensive attention, where the catalysts with the advantages of cost-effectiveness and improved efficiency are critical for the nitrogen reduction reaction (NRR). Herein, we synthesized nitrogen vacancies that contained g-C

MnO

A sensitive and selective method for the determination of the antibiotic chloramphenicol (CAP) is described, which is based on double signal amplification and GO as an efficient fluorescence quencher. The nucleic acid probe is composed of three well-defined regions, viz. the signal probe I, the signal probe II, and the capture probe. The capture probe will bind to CAP specifically and the signal probes produce a significant fluorescence signal. One end of the signal probes is labeled with the fluorophore 6-carboxyfluorescein (FAM). The labeled probes can be adsorbed on graphene oxide (GO) via π-stacking interactions, upon which the green fluorescence of FAM (measured at excitation/emission wavelengths of 490/514 nm) is quenched. On addition of CAP, the aptamer/CAP complexes are formed, and this leads to the restoration of fluorescence due to the removal of the probes from GO. The double signal probes, together with GO as quencher, improve the fluorescence signal significantly and lower the detection limit. Under optimized conditions, the assay works in the 20- to 200-ppb CAP concentration range and has a 0.3-ppb detection limit. It is also successfully applied to the determination of CAP in spiked swine urine samples. The recoveries from spiked swine urine samples are between 97.73 and 108.56%, and the repeatability (expressed as the RSD) is between 4.66 and 8.90%. Graphical abstract The constructed DNA probes form a stable structure and bind to chloramphenicol specifically. One end of signal probes was labeled with the fluorophore 6-carboxyfluorescein (FAM). The detection sensitivity of chloramphenicol was significantly enhanced by using double signal amplification, which was superior to the traditional methods. The quantities of CAP can be achieved by fluorescence increment.

The authors describe a dual-signal colorimetric and ratiometric fluorescent probe for uric acid (UA). It is based on cascade catalysis and an inner filter effect. The method involves uricase-catalyzed oxidation of UA and iodide-catalyzed oxidation of the colorless peroxidase substrate o-phenylenediamine (OPD) to form yellow 2,3-diaminophenazine (oxOPD). This can be visually observed or monitored by measuring absorbance at 417 nm. Furthermore, oxOPD quenches the fluorescence of silicon nanoparticles (SiNPs) (with peaks at 450 and 565 nm) via an inner filter effect. The change in the ratio of emissions peaking 565 and 450 (at excitation wavelength of 380 nm) increases linearly in the 0.01-0.8 mM UA concentration range). The lower detection limits are 8.4 and 0.75 μM when using the colorimetric and ratiometric fluorometric method, respectively. The assay was successfully applied to the quantitation of UA in spiked serum samples. Graphical abstractA dual-signal colorimetric and ratiometric fluor ometric assay was developed for uric acid (UA). The fluorometric assay is based on the inner filter effect between fluorescent silicon nanoparticles and 2,3-diaminophenazine. It involves uricase-catalyzed oxidation of UA, and iodide-catalyzed oxidation of o-phenylenediamine.

To gain better insight into the regulatory networks of anthocyanin biosynthesis, an integrated analysis of the metabolome and transcriptome in purple and green leaves of Tetrastigma hemsleyanum was conducted. Transcript and metabolite profiles were archived by RNA-sequencing data analysis and LC-ESI-MS/MS, respectively. There were 209 metabolites and 4211 transcripts that were differentially expressed between purple and green leaves. Correlation tests of anthocyanin contents and transcriptional changes showed 141 significant correlations (Pearson correlation coefficient >0.8) between 16 compounds and 14 transcripts involved in the anthocyanin biosynthesis pathway. Some novel genes and metabolites were discovered as potential candidate targets for the improvement of anthocyanin content and superior cultivars.