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Deoxyribozyme (DNAzyme) is regarded as a promising gene therapy drug. However, poor cellular uptake efficacy and low biological stability limit the utilization of DNAzyme in gene therapy. Here, we report a well-known programmable DNAzyme-based nanotweezer (DZNT) that provides a new strategy for the detection of TK1 mRNA and survivin mRNA-targeted gene silencing therapy. At the end of the DZNT arm, there are two functionalized single-stranded DNA and each consists of two parts: the segment complementary to TK1 mRNA and the split-DNAzyme segment. The hybridization with intracellular TK1 mRNA enables the imaging of TK1 mRNA. Meanwhile, the hybridization draws the split-DNAzyme close to each other and activates DNAzyme to cleave the survivin mRNA to realize gene silencing therapy. The results demonstrate that the DZNT nanocarrier has excellent cell penetration, good biocompatibility, and noncytotoxicity. DZNT can image intracellular biomolecule TK1 mRNA with a high contrast. Furthermore, the split-DNAzyme can efficiently cleave the survivin mRNA with the aid of TK1 mRNA commonly present in cancer cells, accordingly can selectively kill cancer cells, and has no harm to normal cells. Taken together, the multifunctional programmable DZNT provides a promising platform for the early diagnosis of tumors and gene therapy.

Rapid and convenient detection of protein–protein interactions (PPIs) is of great significance for understanding function of protein. For efficiently detecting PPIs, we used the changes of proteins fluorescence localization to design a novel system, fluorescence translocation co-localization (FTCL), based on nuclear localization signal (NLS) in living cells. Depending on the original state of protein localization (both in the cytoplasm, both in the nucleus, one in the nucleus and another in the cytoplasm), two target proteins can be partitioned into the cytoplasm and nucleus by adding a NLS or mutating an existing NLS. Three independent results display that the changes of protein fluorescence co-localization were observed following co-expression of the two target proteins. At the same time, we verified the accuracy of fluorescence co-localization by co-immunoprecipitation. There FTCL system provided a novel detection method for PPIs, regardless of protein localization in the nucleus or cytoplasm. More importantly, this study provides a new strategy for future protein interaction studies through organelle localization (such as mitochondria, Golgi and cytomembrane, etc.).

We have designed and synthesized a new luminescent mononuclear samarium (III) complex Sm-2h based on the [1 + 1] Schiff-base macrocycle H2L2h, derived from the cyclocondensation reaction between dialdehyde and diamine precursors, and its exact architecture is determined to be [Sm(HL2h) (NO3)2]. The sensing ability of complex Sm-2h is carefully evaluated for various common inorganic ions in solution. It is shown that complex Sm-2h is a multi-responsive fluorimetric sensor with high selectivity for F− and PO43− anions together with Zn2+ cation. The sensing process is rapid within 60 s for F− and PO43− ions and 300 s for Zn2+ ion. Further detailed responsive investigations suggest that its sensing behavior has excellent linear relationship between the fluorescence intensity (or absorption value) and ion concentration. The limit of detection (LOD) for sensing F−, PO43− and Zn2+ ions are as low as 2.61 μM (2.94 μM), 1.92 μM (1.64 μM) and 5.67 μM (3.53 μM), respectively, verified by fluorimetric (or colorimetric) titration experiments. ESI mass spectra prove that these efficient detections originate from the structure collapse of sensor Sm-2h because of the ion-induced imine bond breakage. Moreover, sensor Sm-2h shows excellent sensing performances for F−, PO43− and Zn2+ ions in real water samples, and we also have developed a convenient method to detect these three ions by use of the sensor impregnated test paper strips, providing rapid and distinguishable fluorimetric color changes. Therefore, the macrocyclic Sm(III) complex Sm-2h could be regarded as a valuable candidate for monitoring F−, PO43− and Zn2+ ions in practical applications.

Some researches have shown the associations between air pollution and hospital-based emergency department visits, while the evidence about the acute effects of air pollution on emergency ambulance dispatches for the whole population is rarely available, especially on an hourly time scale. This paper aimed to investigate the effects of hourly concentrations of ambient air pollution on hourly number of ambulance emergency call-outs (AECOs) in Shenzhen, China. AECO data were collected from Shenzhen Emergency Center from January 2013 to December 2016. A time-stratified case-crossover design with conditional Poisson regression was performed to fit the relationship between hourly air pollution and AECOs. The distributed lag model was applied to determine lag structure of the effects of air pollutants. There were a total of 502,862 AECOs during the study period. The significant detrimental effects of SO2, PM2.5, and PM10 appeared immediately with a following harvesting effect after 5 h and the effects lasted for about 96 h. The cumulative effect estimates of four pollutants over 0–96 h were 13.99% (95% CI 7.52–20.85%), 2.07% (95% CI 0.72–3.43%), 1.20% (95% CI 0.54–1.87%), and 2.46% (95% CI 1.63–3.29%), respectively. We did not observe significant effects of O3. This population-based study quantifies the adverse effects of air pollution on ambulance dispatches and provides evidence of the lag structure of the effects on an hourly time scale.

The development of inexpensive, selective and rapid-response chemosensors for detecting Cs+ in waste water is highly desirable in the nuclear power industry. Here we demonstrate an efficient Cs+ optical sensor based on the N-linked disalicylaldehyde H2Qj with excited state intramolecular proton transfer (ESIPT), and it will transform into the ligand-to-metal charge transfer (LMCT) process in the presence of Cs+, resulting in dramatically enhanced fluorescence together with a distinct change of color from light-green to green-yellow. Simultaneously, it is found that CH2Cl2 can serve as the quencher of LMCT-enhanced fluorescence, thus enabling selective CH2Cl2 detection in a turn-off fluorescence approach. Further detailed studies reveal that both Cs+ and CH2Cl2 sensing processes are rapid within 60 seconds. The corresponding limit of detection (LOD) values for sensing Cs+ and CH2Cl2 are as low as 0.37 mM and 0.37%. Moreover, it was also verified that Cs+ sensing is applicable in the range of pH = 7-11 and the reversibility of sensor H2Qj can be easily achieved by modulating pH values, and H2Qj is also assessed for its Cs+ sensing performces in real water samples. This H2Qj-Cs sensing system must provide a valuable reference for further Cs+ sensors.

RNA imaging in living animals helps decipher biology and creates new theranostics for disease treatment. Due to their low delivery efficiency and high background, however, fluorescence probes for in situ RNA imaging in living mice have not been reported. We develop a new cell-targeting fluorescent probe that enables RNA imaging in living mice via an in vivo hybridization chain reaction (HCR). The minimalistic Y-shaped design of the tripartite DNA probe improves its performance in live animal studies and serves as a modular scaffold for three DNA motifs for cell-targeting and the HCR circuit. The tripartite DNA probe allows facile synthesis with a high yield and demonstrates ultrasensitive RNA detection in vitro. The probe also exhibits selective and efficient internalization into folate (FA) receptor-overexpressed cells via a caveolar-mediated endocytosis mechanism and produces fluorescence signals dynamically correlated with intracellular target expressions. Furthermore, the probe exhibits specific delivery into tumor cells and allows high-contrast imaging of miR-21 in living mice. The tripartite DNA design may open the door for intracellular RNA imaging in living animals using DNA-minimal structures and its design strategy can help future development of DNA-based multi-functional molecular probes.

Background In cereal crop rice, auxin is known as an important class of plant hormone that regulates a plethora of plant growth and development. Glycosylation of auxin is known to be one of the important mechanisms mediating auxin homeostasis. However, the relevant auxin glucosyltransferase (GT) in rice still remains largely unknown. Results In this study, using known auxin glucosyltransferases from other species as queries, twelve putative auxin UDP-glycosyltransferase (UGT) genes were cloned from rice and the one showing highest sequence similarity, named as OsIAGT1, was expressed as recombinant protein. In vitro enzymatic analysis showed that recombinant OsIAGT1 was capable of catalyzing glucosylation of IAA, IBA and other auxin analogs, and that OsIAGT1 is quite tolerant to a broad range of reaction conditions with peak activity at 30 °С and pH 8.0. OsIAGT1 showed favorite activity towards native auxins over artificially synthesized ones. Further study indicated that expression of OsIAGT1 can be upregulated by auxin in rice, and with OsIAGT1 overexpressing lines we confirmed that OsIAGT1 is indeed able to glucosylate IAA in vivo. Consistently, ectopic expression of OsIAGT1 leads to declined endogenous IAA content, as well as upregulated auxin synthesis genes and reduced expression of auxin-responsive genes, which likely leads to the reduced plant stature and root length in OsIAGT1 overexpression lines. Conclusion Our result indicated that OsIAGT1 plays an important role in mediating auxin homeostasis by catalyzing auxin glucosylation, and by which OsIAGT1 regulates growth and development in rice.

A novel Klebsiella pneumoniae strain (BPBA052) capable of degrading 3-phenoxybenzoic acid (3-PBA) was isolated from soybean rhizosphere soil. The strain was obtained by screening after enrichment, isolation, and purification using 3-PBA as the sole carbon and energy source. It could degrade 96.37% of 3-PBA (100 mg/L) within 72 h, and its growth and 3-PBA degradation followed kinetics models of logistic growth (XBPBA052 = 0.0883 × e0.0947t / [1 − 0.0792 × (1 − 0.0883 × e0.0947t)]; μm = 0.0947 h–1, X0 = 0.0883, and Xm = 1.1145) and first-order degradation (CBPBA052 = 101.8194 × e–0.0403t, k = 0.0403, t1/2 = 17.22 h), respectively. Based on Box–Behnken response surface analysis, the optimal temperature, pH, and 3-PBA concentration for K. pneumoniae BPBA052 were 35.01 °C, 7.77, and 150 mg/L, respectively. Moreover, pyrethroid pesticides (PPs) (such as β-cypermethrin, permethrin, bifenthrin, deltamethrin, and fenvalerate) and 3-PBA metabolites (including phenol, catechol, and protocatechuate) were efficiently utilized by BPBA052. We propose a novel microbial metabolic pathway for 3-PBA, based on metabolite identification; enzyme-degrading activity; and cloning of the phenol hydroxylase, catechol 1,2-dioxygenase, and protocatechuate 3,4-dioxygenase genes. This study provides a fundamental platform for further studies to reveal the mechanism of biodegradation of 3-BPA and show K. pneumoniae BPBA052 as a potential microbial resource for bioremediation of environments polluted with 3-PBA or PPs.

DNA-based nanomachines have received increasing attention due to their great potential to mimic natural biological motors and create novel modes of motion. Here, we report a DNAzyme-based walking machine, which can operate in living cells after triggered by intracellular miRNA-21. The walking machine is constructed by assembling DNAzyme walking strands and FAM-labeled substrate strands on a single gold nanoparticle (AuNP). The DNAzyme walking strand is first silenced by a blocker strand. After cellular uptake, DNAzyme-based walker can be triggered by intracellular miRNA-21 and autonomously walk along the AuNP-based 3D track fueled by DNAzyme-catalyzed substrate cleavage. Each walking step results in the cleavage of a substrate strand and the release of a FAM-labeled DNA strand, allowing real-time monitoring of the operation of the machine. The DNAzyme-based walking machine has been successfully applied to image and monitor miRNA-21 expression levels in living cells with excellent specificity and reliability. This walking machine would hold great potential in the miRNA associated biological research and disease diagnostics.

The enzymatic amplification strategy in living cells faces challenges of highly efficient intracellular codelivery of amplification reagents including DNA polymerase. In this work, we develop biomineralized metal-organic framework nanoparticles (MOF NPs) as a carrier system for intracellular codelivery of ϕ29 DNA polymerase (ϕ29DP) and nucleic acid probes and realize a polymerization amplification reaction in living cells. A pH-sensitive biodegradable MOF NP of zeolitic imidazolate framework-8 (ZIF-8) is utilized to encapsulate ϕ29DP and adsorb nucleic acid probes. After uptake into cells, the encapsulated ϕ29DP and surface-adsorbed DNA probes are released and escaped from endolysosomes. In the presence of ϕ29DP and deoxyribonucleotide triphosphates (dNTPs), the intracellular miRNA-21 triggers a rolling circle amplification (RCA) reaction and the autonomous synthesized Mg2+-dependent DNAzyme cleaves the fluorogenic substrate, providing a readout fluorescence signal for the monitoring of miRNA-21. This is the first example of the intracellular RCA reaction in living cells. Therefore, the proposed method provides new opportunities for achieving enzymatic amplification reaction in living cells.

A novel approach to α-amino-α-cyanophosphonates has been developed. The method features a Tf2O-mediated reductive geminal cyanation/phosphonylation of secondary amides. Mild reaction conditions, high bond-forming efficiency, inexpensive readily available starting materials, and good to excellent yields with wide functional group compatibility constitute the main advantages of this method. The protocol can be run on a gram scale.

Plant systemic acquired resistance (SAR) provides an efficient broad-spectrum immune response to pathogens. SAR involves mobile signal molecules that are generated by infected tissues and transported to systemic tissues. Methyl salicylate (MeSA), a molecule that can be converted to salicylic acid (SA), is an essential signal for establishing SAR, particularly under a short period of exposure to light after pathogen infection. Thus, the control of MeSA homeostasis is important for an optimal SAR response. Here, we characterized a uridine diphosphate-glycosyltransferase, UGT71C3, in Arabidopsis (Arabidopsis thaliana), which was induced mainly in leaf tissue by pathogens including Pst DC3000/avrRpt2 (Pseudomonas syringae pv tomato strain DC3000 expressing avrRpt2). Biochemical analysis indicated that UGT71C3 exhibited strong enzymatic activity toward MeSA to form MeSA glucosides in vitro and in vivo. After primary pathogen infection by Pst DC3000/avrRpt2, ugt71c3 knockout mutants exhibited more powerful systemic resistance to secondary pathogen infection than that of wild-type plants, whereas systemic resistance in UGT71C3 overexpression lines was compromised. In agreement, after primary infection of local leaves, ugt71c3 knockout mutants accumulated significantly more systemic MeSA and SA than that in wild-type plants. whereas UGT71C3 overexpression lines accumulated less. Our results suggest that MeSA glucosylation by UGT71C3 facilitates negative regulation of the SAR response by modulating homeostasis of MeSA and SA. This study unveils further SAR regulation mechanisms and highlights the role of glucosylation of MeSA and potentially other systemic signals in negatively modulating plant systemic defense.

Molybdenum disulfide nanoparticles (MoS2 NPs) hold tremendous properties in wide domain of applications. In this study, the impact of MoS2 NPs was investigated on algal physiological and metabolic properties and a two-stage strategy was acquired to enhance the commercial potential of Dunaliella salina. With 50 µg/L of MoS2 NPs exposure, cellular growth and biomass production were promoted by 1.47- and 1.33-fold than that in control, respectively. MoS2 NPs treated cells were subject to high light intensity for 7 days after 30 days of normal light cultivation, which showed that high light intensity gradually increased β-carotene content by 1.48-fold. Furthermore, analyses of primary metabolites showed that combinatorial approach significantly altered the biochemical composition of D. salina. Together, these findings demonstrated that MoS2 NPs at an optimum concentration combined with high light intensity could be a promising approach to concurrently enhance biomass and β-carotene production in microalgae.

UDP-glycosyltransferases (UGTs) play key roles in modulating plant development and responses to environmental challenges. Previous research reported that the Arabidopsis UDP-glucosyltransferase 74E2 (AtUGT74E2), which transfers glucose to indole-3-butyric acid (IBA), is involved in regulating plant architecture and stress responses. Here, we show novel and distinct roles of UGT74E2 in rice. We found that overexpression of AtUGT74E2 in rice could enhance seed germination. This effect was also observed in the presence of IBA and abscisic acid (ABA), as well as salt and drought stresses. Further investigation indicated that the overexpression lines had lower levels of free IBA and ABA compared to wild-type plants. Auxin signaling pathway gene expression such as for OsARF and OsGH3 genes, as well as ABA signaling pathway genes OsABI3 and OsABI5, was substantially downregulated in germinating seeds of UGT74E2 overexpression lines. Consistently, due to reduced IBA and ABA levels, the established seedlings were less tolerant to drought and salt stresses. The regulation of rice seed germination and stress tolerance could be attributed to IBA and ABA level alterations, as well as modulation of the auxin/ABA signaling pathways by UGT74E2. The distinct roles of UGT74E2 in rice implied that complex and different molecular regulation networks exist between Arabidopsis and rice.

Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the primary pathogens that causes severe economic losses to sericulture. Comparative transcriptomics analysis has been widely applied to explore the antiviral mechanism in resistant strains. Here, to identify genes involved in BmNPV infection, we identified differentially expressed genes (DEGs) and performed weighted gene co-expression network analysis (WGCNA) between two Bombyx mori strains: strain 871 (susceptible to BmNPV infection) and the near-isogenic strain 871C (resistant to BmNPV). Our results showed that 400 genes were associated with resistance in strain 871C, and 76 genes were related to susceptibility in strain 871. In addition, the correlation analysis of DEGs and WGCNA showed that 40 genes related to resistance were highly expressed in the resistant strain. Among them, gene BGIBMGA004291 was the most noticeable. We further identified the effect of gene BGIBMGA004291, which encoded a multiprotein bridge factor 2 (MBF2) family member (MBF2-10), on viral infection in cells. Our data suggested that MBF2-10 inhibited viral infection. Taken together, this study showed specific module trait correlations related to viral infection in strains 871 and 871C, and we identified a resistance-related gene. These findings suggested promising candidate genes with antiviral activity, aiding in the analysis of the antiviral molecular mechanisms in resistant strains.

Phenolics are a class of plant secondary metabolites that play important roles in plant growth and environmental adaptation. Glucosylation of phenolics is one of the molecular mechanisms controlling phenolics homeostasis. However, the relevant glucosyltransferases are largely unknown. In this study, a putative family 1 glucosyltransferase gene OsSGT1 was cloned from rice due to its close homology with the previously reported phenolics-related glucosyltransferases UGT84A1-A4, and the phylogenetic relationship of OsSGT1 with homologs from other species was investigated. Recombinant OsSGT1 protein showed strong activity towards phenolics to form their glucose conjugates. This is the first identified natural phenolics-related glucosyltransferase in rice. In addition, the expression patterns of OsSGT1 in different tissues of rice indicated that OsSGT1 was predominantly expressed in the old leaves and dough grains, suggesting that OsSGT1 might be involved in the maturation process of rice by regulating phenolic metabolism, and thus deepened our understanding on the roles of phenolics in rice growth and environmental adaptation.

Melanization mediated by the prophenoloxidase-activating system (proPO) is an important immune response in invertebrates. However, the role of melanization on viral infection has not been wildly revealed in Bombyx mori (B. mori), silkworm. Here, we investigated the extent of melanization of susceptible (871) and resistant (near-isogenic line 871C) B. mori strains. The result showed that the extent of melanization was significantly higher in the susceptible strain than in the resistant strain. A majority of Serpins were up-regulated in the resistant strain through iTRAQ-based quantitative proteomics, comparing with susceptible strain. Our data further identified that Serpin-5, Serpin-9 and Serpin-19 reduced PO activity, indicating that the menlanization pathway was inhibited in the resistant strain. Moreover, our results indicated that the hemolymph of 871 reduced viral infection in the presence of PTU, indicating that melanization of 871 strain hemolymph blocked viral infection. However, viral infection was significantly suppressed in the hemolymph of 871C strain regardless of the presence of PTU or not, which implied that the resistant strain inhibited viral infection independent of the melanization pathway. Taken together, our findings indicated that the melanization pathway was inhibited in resistant strain. These results expend the analysis of melanization pathway in insects and provide insights into understanding the antiviral mechanism.

In this work, we have developed a novel and highly selective signal amplification strategy based on target-assisted self-cleavage DNAzyme probes for multicolor and simultaneous imaging of miRNA-222 and miRNA-223 in living cells. The fluctuation of miRNA-222 and miRNA-223 expression levels could also be monitored.

A new strategy to construct allylamines through reductive alkenylation of secondary amides with enamines is reported. The method features the use of trifluoromethanesulfonic anhydride as an activation reagent of amides, and enamines as unconventional alkenylation reagents. In this manner, enamines serve as surrogates of alkene carbanions instead of the classical enolates equivalents. A possible mechanism involving a Hoffmann-like elimination of the amine-borane complex intermediate is proposed.

A novel ruthenium-catalyzed decarboxylative cross-coupling of carbonothioate is disclosed. This method provides straightforward access to the corresponding allyl(aryl)sulfide derivatives in generally good to excellent yields under mild conditions and features a broad substrate scope, wide group tolerance and in particular, no need to use halocarbon precursors.

The accurate determination and quantification of H2O2 and glucose are necessary for diagnosis and bioengineering. Herein, we have reported a novel method for the rapid and selective detection of H2O2 and glucose using g-C3N4–MnO2 nanocomposite. In this method, the fluorescence of graphitic-C3N4 (g-C3N4) was quenched by MnO2, which was attributed to fluorescence resonance energy transfer (FRET) between g-C3N4 nanosheets and the deposited MnO2. When H2O2 was introduced, the MnO2 was reduced to Mn2+, which led to the elimination of FRET and the recovery of the quenched fluorescence. This H2O2 detection system was also suitable for glucose detection since H2O2 is one of the main products in the oxidation reaction of glucose catalyzed by glucose oxidase. Therefore, our method has a great application prospect in diabetes research and clinical diagnosis. Additionally, the fluorescence was linear with the concentration of H2O2 in the range of 0 to 130 μM, with the detection limit of 1.5 μM, and also showed a good linear relationship with glucose in the range of 0 to 150 μM, with the detection limit of 1.5 μM. In addition to a wide linear response, the proposed sensor showed advantageous characteristics, such as easy preparation, low cost, high selectivity, rapid detection, and turn-on fluorescence response. Therefore, our proposed strategy would provide a new general strategy to develop low-cost, sensitive biological and clinical diagnostic methods.

Cytochrome c (Cyt c) and caspase-3 are the key mediators in apoptotic signaling. As is known to all, the release of Cyt c from mitochondria is a vital caspase activation pathway and defines the point of no-return in cell apoptosis. However, it has not been reported that any fluorescence imaging tools could allow simultaneous visualization of Cyt c translocation and caspase-3 activation in apoptotic cells. Here, we develop a sensitive nanosensor that holds the capability of imaging of the released Cyt c from the mitochondria and a caspase-3 activation cascade reaction in apoptotic signaling. The nanosensor is constructed by the assembly of a fluorophore (Cy5)-tagged DNA aptamer on graphene nanosheets that have been covalently immobilized with a FAM-labeled peptide. After a spatially selective delivery into the cytoplasm, the Cy5-tagged DNA aptamer assembled on the nanosensor can bind with Cyt c released from the mitochondria to the cytoplasm and dissociate from graphene, triggering a red fluorescence signal. In addition, the caspase-3 activated by the Cyt c released to the cytoplasm can cleave the FAM-labeled peptide and result in a green fluorescence output. The nanosensor exhibits rapid response, high sensitivity and selectivity for in vitro assays, and high contrast imaging of Cyt c and caspase-3 in living cells. It also provides the method for the study of the kinetic relationship between the Cyt c translocation and caspase-3 activation through simultaneous imaging of Cyt c and caspase-3. The developed nanosensor described here will be an efficient and potential platform for apoptosis research.

Triamcinolone (T) is a glucocorticoid commonly used to relieve inflammation and treat arthritis, severe allergies, and asthma; however, it is banned by the World Anti-Doping Agency in competition for athletes when administered orally, intravenously, intramuscularly, or rectally. The minimum required performance limit (MRPL) for urinary T is 30 ng/mL. However, the data about the urinary excretion of T after oral administration is limited. We investigate the elimination profile and determine whether single-dose administration of T would cause a positive doping result. Twelve healthy volunteers received a single-dose of 4-mg T rally, and urine samples were collected for 24 hours. A validated liquid chromatography-tandem mass spectrometry method was used to determine urinary T levels. Non-compartmental modeling was used to estimate the pharmacokinetic parameters. All the urinary T concentrations were much higher than the MRPL. The peak urinary T concentration was 3211.4 ± 860.3 ng/mL (mean ± SD), time to peak concentration was 1.7 ± 0.9 hours, and the estimated elimination half-life was 4.4 ± 2.8 hours. About 27.76% of the consumed dose was eliminated via urine within 24 hours of intake. After a single-dose oral administration, urinary T concentrations still exceeded the MRPL after 24 hours. This information could be useful for limiting the misuse of T. Athletes should be aware when using T in competition and acquire approval for a therapeutic use exemption prior to use. Moreover, the elimination profile of orally administered T may be crucial information for distinguishing different dosage routes.

A novel biosensor for sensitively detecting potassium ion (K+) has been developed based on fluorescent copper nanoparticles (Cu NPs). In our design, we employ a label-free single-strand DNA (ssDNA) that contains two parts. One is 3'-terminus structure-switching aptamers (SSAs) that can fold into G-quadruplex after binding with its target K+. The other is 5'-terminus poly thymine (polyT) which works as a template to construct fluorescent Cu NPs. After incubating with K+, the part SSAs go through target-induced conformational changes. Benifiting from the exceptional digestion ability of exonuclease I (Exo I), the G-quadruplexes display effective resistance to nuclease digestion, so that 5'-terminus polyT remains and the in situ formation of Cu NPs provides a turn-on fluorescent signal that is used to evaluate the concentration of K+. The recovery of the fluorescence intensity is linearly correlated with the K+ concentration in the range of 0.05 to 1 mM with a detection limit of 0.05 mM. Compared with some methods, this assay is cost-effective and facile with high specificity. Meanwhile, this excellent strategy shows a great potentiality in other sensing approaches that can study the interaction between similar SSAs and different specific targets.

The transition between sedimentary environments is compressed along land-sea boundaries in space and time. At river mouths on high standing islands, sedimentary records with high temporal resolutions formed as a result of large sediment loads and pervasive post-glacial sea level rise. Here we report on sediment core records covering the late Quaternary from the mouth of a small mountainous river in Taiwan. Results show that the study site was initially terrestrial under fluvial control. Beginning at about 10,000 yr BP (before present) the site became inundated by the rising sea and the environmental facies transitioned from a floodplain/incised river valley to a succession of marine environments, from shoreface to offshore. As the rising sea level came to a pause at 6000 yr BP, fluvial processes became dominant and sediments began to aggrade at the river mouth. After 4500 yr BP, the accumulated sediment began to prograde seaward, taking on the form of a river delta, and subtidal sand ridges appeared in the nearshore. This also introduces the deltaic development, which was limited by topography of the receiving basin. The chronology expresses the duel between sea level and fluvial processes that determined the depositional environments along the land-sea boundary at the study site.

A novel fluorescence sensing platform for ultrasensitive detection of S1 nuclease activity has been constructed based on MnO2 nanosheets and FAM labeled single-stranded DNA (FAM-ssDNA). In this system, MnO2 nanosheets were found to have different adsorbent ability toward ssDNA and mono- or oligonucleotide fragments. FAM-ssDNA could adsorb on MnO2 nanosheets and resulted in significant fluorescence quenching through fluorescence resonance energy transfer (FRET), while mono- or oligonucleotide fragments could not adsorb on MnO2 nanosheets and still retained strong fluorescence emission. With the addition of S1 nuclease, FAM-ssDNA was cleaved into mono- or oligonucleotide fragments, which were not able to adsorb on MnO2 nanosheets and the fluorescence signal was never quenched. The different fluorescence intensity allowed for examination of S1 nuclease activity. The developed method can detect S1 nuclease activity in the range of 0 - 20 U mL-1 with a detection limit of 0.05 U mL-1. Benefits of the system include less time-consuming processes and more simple design compared to other endonuclease assays. Satisfactory performance for S1 nuclease in complex samples has been successfully demonstrated with the system. The developed assay could potentially provide a new platform in bioimaging and clinical diagnosis.

A new p-TsOH-promoted dehydroxylated [3+2] cyclization strategy has been established, allowing a flexible, practical and regiospecific approach to 23 examples of 1,5,6,7-tetrahydro-4H-indol-4-ones from low-cost and readily accessible β-hydroxy ketones and cyclic enaminones. Notably features of this work include broad functional group compatibility, mild reaction conditions and good reaction yields.

Herein, we report our strategy to develop the efficient chemosensor and real-time monitoring technique for cyanuric chloride (TCT) detection. A luminescent macrocyclic mononuclear Sm(III) complex Sm-2k bearing with two dynamic imine bonds has been constructed via the template synthesis between dialdehyde H2Qk and matched diamine 1,2-bis(2-aminoethoxy)ethane. Sensing experiments reveal that complex Sm-2k exhibits the turn-off fluorescent and colorimetric response for TCT in CH3OH. It is especially encouraging that this optical sensing process is not only rapid within 60 s but also high-efficient in the presence of TCT analogues as well as sensitive with the low limit of detection (LOD, 1.74 μM) and wide linear sensing range. Mechanism studies demonstrate that TCT sensing is mainly based on the imine bond transformation of probe Sm-2k, which is due to the increased acidity induced by TCT. Meanwhile, a smartphone-based analytical method was developed to make complex Sm-2k accessible for the real-time TCT detection by RGB value outputs. It is believed that this work can shed some constructive lights on design of chemosensors and convenient detection technique for highly reactive analytes.

The three-dimensional (3D) DNA nanostructure has been got much attention due to its excellent biocompatibility, enhanced structural stability, highly programmable and perfect cell-delivery performance. Here, a novel 3D DNA tetrahedron amplifier (DTA) has been developed for rapid and efficient mRNA imaging in living cells using target catalyzing spatial-confinement hairpin DNA assembly cascade reaction inside the DNA nanostructure. The DTA was constructed by assembling a DNA tetrahedron with four DNA strands at first, and then by assembling two metastable DNA hairpins H1 (Cy5) and H2 (Cy3) at specific locations of the DNA tetrahedron. In the presence of target mRNA, the catalyzed hairpin assembly (CHA) reaction on the DTA could be triggered and a H1-H2 duplexes nanostructure could be formed, which would obtain a significant fluorescence resonance energy transfer (FRET) signal, and release the target mRNA could trigger next H1-H2 duplexes formation. Due to the 3D DNA tetrahedral spatial-confinement effect, the circular reaction of DTA could achieve rapid and efficient amplification detection of target mRNA in living cells. Moreover, the DTA show excellent structural stability and non-cytotoxicity. This strategy presents a versatile method for the ultrasensitive detection of biomarkers in living system and gains a deeper development of the DNA nanostructures in biomedical functions.

Metabolic engineering has been hailed as a promising tool to impart oil productivity in fast-growing microalgae, thereby generating industry-suitable strains. However, complex regulatory networks in lipogenesis hampered the success to unify the abundance of metabolic carbon precursors and reducing equivalents towards lipogenesis. To obviate the biological bottlenecks, we attempted to rewire the pyruvate pathway, which could enhance the supply of NADPH by heterologously overexpressing a malic enzyme from the oleaginous diatom Phaeodactylum tricornutum (PtME) in fast-growing microalga Tetradesmus obliquus (previously known as Scenedesmus obliquus). PtME overexpression did not impair physiological properties and upheld lipogenesis by facilitating the adequate provision of CO2 and NADPH, respectively, through malate decarboxylation. The malate-pyruvate pathway played a role in elevating lipid content by 2.4-fold via coupling the carbon precursors and reducing equivalents. The malic enzyme activity increased by 9.9-fold, thereby elevated lipogenic NADPH. Together, these data exemplify the crucial role of PtME in pyruvate cycle for amalgamating the provision of metabolic carbon precursors and NADPH towards lipid accumulation and lay a strong foundation for metabolic engineering in algal industrialization.

The development of convenient and efficient fluorescence techniques is of great significance for selective detection and precise determination of biotoxic N2H4 in human health and environmental sciences. By the pre-organization-assisted template synthesis, disclosed here is a luminescent Sm(III) macrocycle-based probe Sm-2m bearing dynamic imine bonds as recognition moieties which provides the selective and ratiometric turn-off fluorescence sensing for N2H4 over various amine species based on the N2H4-induced structure transformation. This fluorescent sensing process finished within 20 min shows the low limit of detection (0.18 μM, 7.2 ppb) and wide linear sensing range (0–60.0 μM). Furthermore, probe Sm-2m is also be used to quantitatively determine N2H4 in vapor gas and water samples through fluorescence color changes, which are evaluated by the Sm-2m-impregnated test paper strips and RGB value outputs. Finally, our proposed smartphone-based analytical method gives satisfactory N2H4 detection results. It is thus believed that this work can shed some lights on development of optical probes and detection techniques for N2H4, even other hazardous chemicals.

Copper triflate catalyzed oxidative C–H functionalization of glycine derivatives with allyltributyltin has been established using oxygen or tert-butyl hydroperoxide as oxidant. Various glycine esters and glycine amides were suitable substrates for this oxidative allylation reaction and afforded the desired homoallylic amines in moderate to good yields.

As an important biological small molecule, ascorbic acid (AA) plays a key role in many bioprocesses. Here, we developed a novel method to evaluate AA based on the redox reaction between CoOOH and AA. In our work, a nanosystem was constructed with fluorescent polydopamine (PDA) nanoparticles and CoOOH nanosheets, which were used as signal indicators and an oxidant respectively. This is the first time that fluorescent PDA nanoparticles were synthesized through oxidation by CoOOH nanosheets. In the absence of AA, dopamine was oxidized to quinone derivatives and further spontaneously polymerized into fluorescent PDA nanoparticles which had strong fluorescence signals. When there was AA in the reaction system, CoOOH nanosheets would be reduced to Co2+, which would prevent the synthesis of fluorescent PDA nanoparticles due to the absence of oxidant CoOOH, resulting in weak fluorescence. We hence used the fluorescence intensity of the PDA nanoparticles to detect AA concentration. The fluorescence of this sensing platform was linear with the concentration of AA in the range of 0–500 μM with a detection limit of 4.8 μM. In addition, the sensor was simple, fast, label-free, and low cost, and may be used to detect other small molecules based on the redox reaction.

The use of plastics has rapidly progressed during recent years in food packaging, which can be attributed to technological innovations in the synthesis of plastics and lower costs. However, the massive accumulation of plastic waste is often accompanied with their excessive consumption because of their poor degradability. Consequently, interest in the native materials is growing. It is noted that zein is a corn protein, has good compatibility and has been widely applied in the food industry. However, microbial contamination is a huge detriment to its long-term applications. This study aims to identify a method, which can provide antibacterial activity to a zein thin film. Monodispersed and spindle-like ZnO crystals made of nanocrystals were synthesized and added into zein thin films. EDX mapping confirmed the homogeneous distribution of ZnO in films. The antibacterial activities have been approved and showed great stability. In summary, the potential of zein thin films incorporating ZnO crystals as a functional packaging film has been demonstrated.

A receptor binding class of d-amino acid-containing peptides (DAACPs) is formed in animals from an enzymatically mediated post-translational modification of ribosomally translated all-l-amino acid peptides. Although this modification can be required for biological actions, detecting it is challenging because DAACPs have the same mass as their all-l-amino acid counterparts. We developed a suite of mass spectrometry (MS) protocols for the nontargeted discovery of DAACPs and validated their effectiveness using neurons from Aplysia californica. The approach involves the following three steps, with each confirming and refining the hits found in the prior step. The first step is screening for peptides resistant to digestion by aminopeptidase M. The second verifies the presence of a chiral amino acid via acid hydrolysis in deuterium chloride, labeling with Marfey's reagent, and liquid chromatography-mass spectrometry to determine the chirality of each amino acid. The third involves synthesizing the putative DAACPs and comparing them to the endogenous standards. Advantages of the method, the d-amino acid-containing neuropeptide discovery funnel, are that it is capable of detecting the d-form of any common chiral amino acid, and the first two steps do not require peptide standards. Using these protocols, we report that two peptides from the Aplysia achatin-like neuropeptide precursor exist as GdYFD and SdYADSKDEESNAALSDFA. Interestingly, GdYFD was bioactive in the Aplysia feeding and locomotor circuits but SdYADSKDEESNAALSDFA was not. The discovery funnel provides an effective means to characterize DAACPs in the nervous systems of animals in a nontargeted manner.

Exploiting photocatalysts with characteristics of cost effectiveness, environmental friendliness, visible light response, high reactivity and good durability is a great challenge for solar H 2 generation. Here, we synthesis of MoS 2 -graphene composite as a highly-efficient cocatalyst to enhance the photocatalytic activity of ZnIn 2 S 4 under visible light irradiation. Through the optimizing of each composition proportion, the hierarchical MoS 2 -graphene/ZnIn 2 S 4 photocatalyst shows the highest H 2 evolution rate of 4169 μmol h −1 g −1 under visible light irradiation in presence of Na 2 S and Na 2 SO 3 as sacrificial reagents when the content of MoS 2 -graphene is 1.2 wt% and the weight ratio of MoS 2 to graphene is 10:1, which is almost 22.8 times higher than that of pure ZnIn 2 S 4 . More importantly, the ternary MoS 2 -graphene/ZnIn 2 S 4 composite exhibits much higher photocatalytic activity than Pt-loaded ZnIn 2 S 4 photocatalyst, suggesting that the MoS 2 -graphene composite can act as a more efficient cocatalyst than the commonly used Pt metal. The superior catalytic activity of MoS 2 -graphene cocatalyst can be assigned to the positive synergistic effect between MoS 2 and graphene, which act as a hydrogen evolution reaction catalyst and an electron transport bridge, respectively. The effective charge transfer from ZnIn 2 S 4 to MoS 2 through graphene is demonstrated by the significant enhancement of photocurrent responses in MoS 2 -graphene/ZnIn 2 S 4 composite photoelectrodes.

A new rhodamine-based derivative bearing pyrrole unit, R1 was synthesized as a dual-mode Cu2+-selective sensor via the rhodamine ring-opening approach and ratiometric displacement. A colorimetric and “off-on” signal for Cu2+ through rhodamine ring opening in R1 and ratiometric fluorescent signal output when Cu2+ displaces the bound Cd2+ in the R1-Cd2+ complex can be observed. The application of fluorescent R1 to biological imaging was also demonstrated.

Exploiting photocatalysts respond to visible light is of huge challenge for photocatalytic H2 production. Here, we synthesize a new composite material consisting of few-layer MoS2 nanosheets grown on CuInS2 surface as an efficient photocatalyst for solar H2 generation. The photocatalytic results demonstrate that the 3 wt % MoS2 /CuInS2 photocatalyst exhibits the highest H2 generation rate of 316 μmol h(-1) g(-1) under visible light irradiation, which is almost 28 times higher than that of CuInS2 . Importantly, the MoS2 /CuInS2 photocatalyst shows a much higher photocatalytic activity than that of Pt-loaded CuInS2 photocatalyst. The enhanced photocatalytic activities of MoS2 /CuInS2 photocatalysts can be attributed to the improved charge separation at the interface of MoS2 and CuInS2, which is demonstrated by the significant enhancement of photocurrent responses in MoS2 /CuInS2 photoelectrodes. This work presents a noble-metal-free photocatalyst that responds to visible light for solar H2 generation.

Four new cyclometalated bo-based iridium(III) complexes with different N^O ancillary ligands, [Ir(bo)2pic] (1), [Ir(bo)2prz] (2), [Ir(bo)2bop] (3) and [Ir(bo)2btp] (4) (bo = 2-phenylbenzo[d]oxazole, pic = picolinate, prz = pyrazinate, bop = 2-benzoxazol-2-yl phenol, btp = 2-benzothiazol-2-yl phenol), have been synthesized and investigated by optical spectroscopy, electrochemistry as well as density functional theory (DFT). The crystal structures of 1, 2 and 4 have been determined, which show that each adopts the distorted octahedral coordination geometry. They exhibit intense green to orange phosphorescence (λmax = 531–598 nm) with quantum yields of 0.19–0.94 and lifetimes of 0.078–0.468 μs in solution at 298 K. The broad range color tuning of complexes 1–4 is dependent on the ancillary ligand structure. The cyclic voltammetry has been measured, showing a quasireversible, metal-centered oxidation with potentials at 1.00–1.49 V. The frontier molecular orbital diagrams and the lowest-energy electronic transitions of 1–4 have been calculated with density functional theory (DFT) and time-dependent DFT (TD-DFT).

Background Although road traffic casualty (RTC) is preventable, it remains the eighth leading cause of death globally, especially in developing countries. Previous studies suggested the association between RTC and monthly or daily weather conditions, while the acute effects of weather conditions on an hourly timescale remains unknown. This study aims to quantify hourly effects of precipitation and temperature on RTC. Methods Using ambulance records on RTC during 2010–2016 for the whole population in Shenzhen, China, we conducted a time-stratified case-crossover design which can inherently control for hour of the day, day of the week, seasonality, time trends and potential time-invariant confounders. Conditional quasi-Poisson regression with distributed lag nonlinear model was used to determine the effects of hourly precipitation and temperature on RTC. Results Light and heavy precipitation increased RTC in current and following 2 h by 8.09% (95% CI: 4.20–12.12%) and 11.62% (95% CI: 5.93–17.62%), respectively. A J-shaped temperature-RTC curve revealed that each 1 °C increment above 17 °C were associated with a 0.87% (0.52–1.22%) increase in RTC. High temperature accounted for 6.44% (95% CI: 3.95–8.91%) of all RTC, with a high fraction of 10.64% (95% CI: 4.33–15.96%) during warm season and 8.30% (95% CI: 4.26–12.66%) in traffic peak hours. Precipitation contributed to 0.68% (95% CI: 0.44–0.92%) of RTC within 3 h. The middle-aged and female suffered more from precipitation-associated RTC, and the younger suffered more from high temperature-associated RTC. Conclusions High temperature increased substantially hourly RTC. Precipitation was also a risk factor of RTC and the adverse effect lasted for 3 h. The findings would be helpful to guide the development of targeted intervention to accelerate progress in road traffic safety.

The rapid and sensitive detection of water has attracted wide interests in the chemical and energy industry for its harmful influences, which encourage researchers to explore kinds of materials for sensing water. Herein, we report the sensing performance of a Schiff-base macrocyclic Sm(III) complex Sm-2g as the turn-off fluorescent and colorimetric probe for water detection in organic solvents (DMF, methanol and acetone) and liquid fuels (bioethanol and avgas). It is especially encouraging that the probe Sm-2g exhibits a rapid and sensitive response for water, and it could be easily distinguished by the distinct fluorescence quenching and absorption shift. Electrospray ionization mass spectra prove that this efficient detection is achieved based on the transformation from complex Sm-2g to corresponding dialdehyde precursor, originating from the imine bond cleavage after the addition of water. Furthermore, the Sm-2g impregnated paper strip also provides a convenient way to detect water by its rapid and distinguishable fluorescent color changes in organic media. Therefore, the luminescent Sm(III) complex Sm-2g shows promise as a valuable candidate for the detection of water.

Background Verticillium wilt (VW), also known as “cotton cancer,” is one of the most destructive diseases in global cotton production that seriously impacts fiber yield and quality. Despite numerous attempts, little significant progress has been made in improving the VW resistance of upland cotton. The development of chromosome segment substitution lines (CSSLs) from Gossypium hirsutum × G. barbadense has emerged as a means of simultaneously developing new cotton varieties with high-yield, superior fiber, and resistance to VW. Results In this study, VW-resistant investigations were first conducted in an artificial greenhouse, a natural field, and diseased nursery conditions, resulting in the identification of one stably VW-resistant CSSL, MBI8255, and one VW-susceptible G. hirsutum, CCRI36, which were subsequently subjected to biochemical tests and transcriptome sequencing during V991 infection (0, 1, and 2 days after inoculation). Eighteen root samples with three replications were collected to perform multiple comparisons of enzyme activity and biochemical substance contents. The findings indicated that VW resistance was positively correlated with peroxidase and polyphenol oxidase activity, but negatively correlated with malondialdehyde content. Additionally, RNA sequencing was used for the same root samples, resulting in a total of 77,412 genes, of which 23,180 differentially expressed genes were identified from multiple comparisons between samples. After Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis on the expression profiles identified using Short Time-series Expression Miner, we found that the metabolic process in the biological process, as well as the pathways of phenylpropanoid biosynthesis and plant hormone signal transduction, participated significantly in the response to VW. Gene functional annotation and expression quantity analysis indicated the important roles of the phenylpropanoid metabolic pathway and oxidation-reduction process in response to VW, which also provided plenty of candidate genes related to plant resistance. Conclusions This study concentrates on the preliminary response to V991 infection by comparing the VW-resistant CSSL and its VW-susceptible recurrent parent. Not only do our findings facilitate the culturing of new resistant varieties with high yield and superior performance, but they also broaden our understanding of the mechanisms of cotton resistance to VW. Electronic supplementary material The online version of this article (10.1186/s12870-018-1619-4) contains supplementary material, which is available to authorized users.

This study revealed that the Arabidopsis UGT75B1 plays an important role in modulating ABA activity by glycosylation when confronting stress environments. The cellular ABA content and activity can be tightly controlled in several ways, one of which is glycosylation by family 1 UDP-glycosyltransferases (UGTs). Previous analysis has shown UGT75B1 activity towards ABA in vitro. However, the biological role of UGT75B1 remains to be elucidated. Here, we characterized the function of UGT75B1 in abiotic stress responses via ABA glycosylation. GUS assay and qRT-PCR indicated that UGT75B1 is significantly upregulated by adverse conditions, such as osmotic stress, salinity and ABA. Overexpression of UGT75B1 in Arabidopsis leads to higher seed germination rates and seedling greening rates upon exposure to salt and osmotic stresses. In contrast, the big UGT75B1 overexpression plants are more sensitive under salt and osmotic stresses. Additionally, the UGT75B1 overexpression plants showed larger stomatal aperture and more water loss under drought condition, which can be explained by lower ABA levels examined in UGT75B1 OE plants in response to water deficit conditions. Consistently, UGT75B1 ectopic expression leads to downregulation of many ABA-responsive genes under stress conditions, including ABI3, ABI5 newly germinated seedlings and RD29A, KIN1, AIL1 in big plants. In summary, our results revealed that the Arabidopsis UGT75B1 plays an important role in coping with abiotic stresses via glycosylation of ABA.

Multiple drug resistance is a persistent obstacle for efficient chemotherapy of cancer. Herein, we report a novel drug delivery platform. A zeolitic imidazole framework-8 (ZIF-8) film with a few nanometer thickness was in situ synthesized on the surface of carboxylated mesoporous silica (MSN-COOH) nanoparticles (NPs) for pore blocking and efficient loading of small interfering RNAs to fabricate a pH-responsive drug delivery system. The ZIF-8 film could convert the charge of MSN-COOH from negative to positive for efficient loading of siRNA via electrostatic interactions and protect siRNA from nuclease degradation. The positively charged ZIF-8 film facilitates cellular uptake and endo-lysosome escape of the NPs. In addition, the ultrathin ZIF-8 film can decompose in the acidic endo-lysosome and trigger the intracellular release of siRNAs and chemotherapeutic drugs, leading to a significantly enhanced chemotherapeutic efficacy for multidrug-resistant cancer cells including MCF-7/ADR and SKOV-3/ADR cells as demonstrated by the confocal laser scanning microscopy image, cell viability assay, Annexin VPI staining, and flow cytometry. This approach provides a promising strategy for pH-triggered, stimuli-responsive delivery of nucleic acid drugs and chemotherapeutic agents with remarkably enhanced chemotherapeutic efficacy.

Efficient delivery and endo-lysosomal release of active proteins in living cells remain a challenge in protein-based theranostics. We report a novel protein delivery platform using protein-encapsulating biomineralized metal-organic framework (MOF) nanoparticles (NPs). This platform introduces an adapted biomimetic mineralization method for facile synthesis of MOF NPs with high protein encapsulation efficiency and a new polymer coating strategy to confer the NPs with long-term stability. In vitro results show that protein-encapsulating MOF NPs have the advantages of preserving protein activity for months and protecting proteins from enzyme-mediated degradation. Live cell studies reveal that MOF NPs enable rapid cellular uptake, efficient release and escape of proteins from endo-lysosomes, and preservation of protein activity in living cells. Moreover, the developed platform is demonstrated to enable easy encapsulation of multiple proteins in single MOF NPs for efficient protein co-delivery. To our knowledge, it is the first time that protein-encapsulating MOF NPs have been developed as a generally applicable strategy for intracellular delivery of native active proteins. The developed protein-encapsulating biomineralized MOF NPs can provide a valuable platform for protein-based theranostic applications.

Tetrapods-like titanium nitride–reduced graphene oxide (TiN–rGO) nanohybrids were synthesized by ultraviolet (UV) irradiation method for the first time. With the aid of UV light, the photogenerated electrons in TiN were transfered into GO which was then reduced to form rGO, so the TiN–rGO nanohybrids were obtained. The TiN–rGO nanohybrids were characterized by UV–vis spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that GO could be effectively converted to rGO, and TiN–rGO nanohybrids were successfully prepared. In addition, the application of TiN–rGO nanohybrids were investigated by modified electrode, it demonstrated good performance in sensing of chloramphenicol (CAP) because of the synergic effect between tetrapods-like TiN and rGO. This idea appeared to be a very effective and simple strategy to prepare excellent TiN–rGO nanohybrid materials with promising potential in wider analytical applications including electrochemical analysis, biosensors, fuel cells and supercapacitors

Phosphorylation of nucleic acids with 5'-OH termini catalyzed by polynucleotide kinase (PNK) is an inevitable process and has been implicated in many important cellular events. Here, we found for the first time that there was a significant difference in the adsorbent ability of cobalt oxyhydroxide (CoOOH) nanoflakes between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA), which resulted in the fluorescent dye-labeled dsDNA still retaining strong fluorescence emission, while the fluorescence signal of ssDNA was significantly quenched by CoOOH nanoflakes. Based on this discovery, we developed a CoOOH nanoflake-based nanoprobe for the fluorescence sensing of T4 PNK activity and its inhibition by combining it with λ exonuclease cleavage reaction. In the presence of T4 PNK, dye-labeled dsDNA was phosphorylated and then cleaved by λ exonuclease to generate ssDNA, which could adsorb on the CoOOH nanoflakes and whose fluorescence was quenched by CoOOH nanoflakes. Due to the high quenching property of CoOOH nanoflakes as an efficient energy acceptor, a sensitive and selective sensing approach with satisfactory performance for T4 PNK sensing in a complex biological matrix has been successfully constructed and applied to the screening of inhibitors. The developed approach may potentially provide a new platform for further research, clinical diagnosis, and drug discovery of nucleotide kinase related diseases.

An aptasensor based on a fluorophore-labelled aptamer and cobalt oxyhydroxide (CoOOH) nanosheets was developed for determining the concentration of thrombin. We first found that the CoOOH nanosheets had the ability to distinguish a G-quadruplex from single-stranded DNA (ssDNA) due to the different abilities of the nanosheet to absorb these two DNA forms. The absorption of 6-carboxyfluorescein (6-FAM) labelled aptamer (ssDNA) on the surface of the CoOOH nanosheets resulted in the quenching of the fluorescence of the FAM through fluorescence resonance energy transfer (FRET) between the FAM and the CoOOH nanosheets. However, the binding of the aptamer to its target resulted in the formation of an antiparallel G-quadruplex complex, for which the CoOOH nanosheets had weak affinity, resulting in a recovery of fluorescence. We applied this strategy to the detection of thrombin. The intensity of the fluorescence recovery was found to be linear with the logarithm of the thrombin concentration in the range of 0.5 to 100 nM, and the limit of detection (LOD) was determined to be 0.5 nM. Because of the high selectivity of the aptamer and strong quenching ability of the CoOOH nanosheets, similar aptasensors but with different specific aptamers may potentially serve as platforms to detect a wide range of analytes, and may hence have promising applications in clinical diagnosis.

Polydopamine (PDA) nanoparticles, as a kind of popular polymer material, have attracted a great deal of attention from various areas including materials science, biomedicine, energy, environmental science and so on owing to their striking physicochemical properties. Herein, we reported for the first time the synthesis of intrinsic fluorescent PDA nanoparticles using MnO2 as an oxidant. In the presence of MnO2, dopamine was quickly oxidized into its quinone derivative, and autopolymerized into fluorescent PDA nanoparticles. Using fluorescent PDA nanoparticles as a fluorescence signal indicator, we further established a cost-effective sensor for rapid, sensitive and selective sensing of reduced glutathione (GSH) based on the redox reaction between MnO2 and GSH, and the key role of MnO2 in the formation of fluorescent PDA nanoparticles. GSH has the capability of reducing MnO2 into Mn(2+), which inhibited the formation of the fluorescent PDA nanoparticles. Thus, the concentration of GSH was directly related to the decreased fluorescence signal intensity of the PDA nanoparticles. The sensor showed good sensing performance for GSH detection with high sensitivity and desirable selectivity over other potential interfering species. Additionally, the sensor exhibited excellent practical applications for GSH detection in human whole blood samples, which presents potential applications in biological detection and clinical diagnosis.

MicroRNAs (miRNAs) play important roles in cell differentiation, proliferation, and apoptosis and have been recognized as valuable biomarkers for clinical disease diagnosis. Here, we adopt for the first time zeolitic imidazolate framework-8 (ZIF-8) as a nanocarrier to efficiently deliver a nucleic acid probe to living cells and develop a novel ratiometric fluorescence strategy based on DNAzyme for miRNA-21 imaging. A Cy5-labeled 8-17 DNAzyme strand and a Cy3-labeled substrate strand containing a segment complementary to the target miRNA-21 first form a duplex probe, and fluorescence resonance energy transfer (FRET) takes place. After adsorption on the ZIF-8 surface and cellular uptake, the probe/ZIF-8 nanocomplex degrades in acidic endosome and releases duplex probes and Zn2+, and the latter can act as an effective cofactor for 8-17 DNAzyme. The intracellular miRNA-21 hybridizes with the complementary segment of the substrate strand and results in dissociation from the DNAzyme–substrate duplex probe after...