Enhancing Point-of-Care Diagnosis of African Swine Fever Virus (ASFV) DNA with the CRISPR-Cas12a-Assisted Triplex Amplified Assay.

Accurate, ultrasensitive, and point-of-care (POC) diagnosis of the African swine fever virus (ASFV) remains imperative to prevent its spread and limit the losses incurred. Herein, we propose a CRISPR-Cas12a-assisted triplex amplified colorimetric assay for ASFV DNA detection with ultrahigh sensitivity and specificity. The specific recognition of recombinase aided amplification (RAA)-amplified ASFV DNA could activate the Cas12a/crRNA/ASFV DNA complex, leading to the digestion of the linker DNA (bio-L1) on magnetic beads (MBs), thereby preventing its binding of gold nanoparticles (AuNPs) network. After magnetic separation, the release of AuNPs network comprising a substantial quantity of AuNPs could lead to a discernible alteration in color and significantly amplify the plasmonic signal, which could be read by spectrophotometers or smartphones. By combining the RAA, CRISPR/Cas12a-assisted cleavage, and AuNPs network-mediated colorimetric amplification together, the assay could detect as low as 0.1 copies/µL ASFV DNA within 1 h. The assay showed an accuracy of 100% for the detection of ASFV DNA in 16 swine tissue fluid samples, demonstrating its potential for on-site diagnosis of ASFV.

Construction of a point-of-care electrochemical biosensor for Escherichia coli 16S rRNA analysis based on MoS2 nanoprobes.

Foodborne pathogens are harmful to human health because they can contaminate food and induce diseases. To efficiently distinguish and determine foodborne bacteria, an ultrasensitive point-of-care electrochemical biosensor was designed for 16S rRNA detection by coupling a signal amplification strategy with MoS2-based nanoprobes. Gold nanoparticles and thionine co-functionalized molybdenum disulfide (MoS2) nanocomposites (MoS2-Thi-AuNPs) were used to construct nanoprobes, which can efficiently monitor the detection process and amplify the detection signal. In the presence of Escherichia coli (E. coli) 16S rRNA, a classical sandwiched DNA structure was formed on the surface of a hierarchical flower-like gold nanostructure-decorated screen-printed carbon electrode (HFGN-SPCE), generating an obvious electrochemical signal from Thi. Under optimal conditions, this designed electrochemical biosensor showed a wide dynamic range (0-1.0 × 106 fM), low detection limit (2.8 fM), high selectivity and accepted stability for E. coli 16S rRNA detection in ideal buffers. Moreover, this biosensor can efficiently determine 16S rRNA in milk samples and 10 CFU mL-1 bacterial lysate. All experimental results suggested that this biosensor has a promising application in the detection of foodborne pathogens.

Electronic Transition and Magnetic Coupling Regulation in Trimetallic Complexes Featuring a New Bridging Ligand Obtained by Oxidative Addition.

A series of trimetallic complexes [FeIII(µ-L)(py)]2MII(py)n (n = 2, MII = MnII, 1; FeII, 2; CoII, 3; ZnII, 4; n = 3, MII = CdII, 5) with a new bridging ligand L4- (deprotonated 1,2-N1,N2-bis(2-mercaptoanil) oxalimidic acid) were synthesized and fully characterized by elemental analysis, single-crystal X-ray crystallography, IR, and Mössbauer spectra. Interestingly, the bridging ligand was obtained by oxidative addition of the (gma•)3- ligand from the mononuclear precursor Fe(gma)py (gma = glyoxal-bis(2-mercaptoanil)). In the obtained complexes, the bridging ligand L4- coordinates to the terminal FeIII ions (intermediate-spin with SFe = 3/2) by the N, S atoms, and coordinate to the central metal MII ion by the four O atoms. The resonance structure of the bridging ligand can be described as the two 4π-electron delocalized systems connected by one single-bond (C1-C2), which is different from the electronic structure of the precursor Fe(gma)py. Remarkably, the magnetic coupling interaction can be regulated through the central metal. The ferromagnetic coupling constant J gradually decreases as MII changes from FeII to CoII and MnII, while the paramagnetic behaviors are presented when MII = ZnII and CdII, confirmed by the magnetic susceptibility measurements and further supported by using the PHI program. Furthermore, the bridging ligand to the terminal FeIII charge transfer (LMCT) transitions emerged in all complexes but the central FeII to terminal FeIII charge transfer (MMCT) only presented in complex 2, strongly supported by the UV/vis-NIR electronic spectra and TDDFT calculations.

VEGF loaded nanofiber membranes inhibit chronic cerebral hypoperfusion-induced cognitive dysfunction by promoting HIF-1a/VEGF mediated angiogenesis.

We investigated the potential effects and mechanisms of vascular endothelial growth factor (VEGF)-nanofiber membranes (NFMs) treatment in a rat model of chronic cerebral hypoperfusion (CCH). VEGF-NFMs treatment promoted angiogenesis in surgical temporal cortex and hippocampus, alleviating decreased CBF in these two cerebral regions. VEGF-NFMs application improved reduced NAA/Cr ratio, preventing neuronal loss. VEGF-NFMs sticking decreased the number of TUNEL-positive cells in surgical temporal cortex, ameliorated impaired synaptic plasticity, and inhibited the release of pro-inflammatory cytokines and the activation of microglia and astrocytes in surgical temporal cortex and hippocampus. Furthermore, BDNF-TrkB/PI3K/AKT, BDNF-TrkB/ERK and HIF-1a/VEGF/ERK pathways were involved in the treatment of VEGF-NFMs against CCH-induced neuronal injury. These results showed the neuroprotective effects of VEGF-NFMs sticking may initiate from neurovascular repairing followed by inhibition of neuronal apoptosis and neuronal and synaptic damage, eventually leading to the suppression of cognitive dysfunction, which provided theoretical foundation for further clinical transformation of VEGF-NFMs.

Reverse genetic study reveals the molecular targets of chordotonal organ TRPV channel modulators.

Insecticides have been widely used for the control of insect pests that have a significant impact on agriculture and human health. A better understanding of insecticide targets is needed for effective insecticide design and resistance management. Pymetrozine, afidopyropen and flonicamid are reported to target on proteins that located on insect chordotonal organs, resulting in the disruption of insect coordination and the inhibition of feeding. In this study, we systematically examined the susceptibility of six Drosophila melanogaster mutants (five transient receptor potential channels and one mechanoreceptor) to three commercially used insecticides, in order to identify the receptor subunits critical to the insect's response to insecticides. Our results showed that iav1, nan36aand wtrw1 mutants exhibited significantly reduced susceptibility to pymetrozine and afidopyropen, but not to flonicamid. The number of eggs produced by the three mutant females were significantly less than that of the w1118 strain. Meanwhile, the longevity of all male mutants and females of nan36a and wtrw1 mutants was significantly shorter than that of the w1118 strain as the control. However, we observed no gravitaxis defects in wtrw1 mutants and the anti-gravitaxis of wtrw1 mutants was abolished by pymetrozine. Behavioral assays using thermogenetic tools further confirmed the bioassay results and supported the idea that Nan as a TRPV subfamily member located in Drosophila chordotonal neurons, acting as a target of pymetrozine, which interferes with Drosophila and causes motor deficits with gravitaxis defects. Taken together, this study elucidates the interactions of pymetrozine and afidopyropen with TRPV channels, Nan and Iav, and TRPA channel, Wtrw. Our research provides another evidence that pymetrozine and afidopyropen might target on nan, iav and wtrw channels and provides insights into the development of sustainable pest management strategies.

Synthesis of Graphene Oxide-Coupled CoNi Bimetallic MOF Nanocomposites for the Simultaneous Analysis of Catechol and Hydroquinone.

Herein, a three-dimensional flower-like cobalt-nickel bimetallic metal-organic framework (CoNi-MOF) coupled with two-dimensional graphene oxide (GO) nanocomposites was successfully synthesized for the selective and simultaneous electrochemical determination of catechol (CC) and hydroquinone (HQ). The three-dimensional flower-like structure of the CoNi-MOF/GO nanocomposite has a multilayer structure and a large surface area, which greatly improves its electrocatalytic activity towards CC and HQ. Differential pulse voltammetry (DPV) results showed that the peak-to-peak separation of CC (0.223 V) and HQ (0.120 V) was 103 mV at a CoNi-MOF/GO modified glassy carbon electrode (CoNi-MOF/GO/GCE), suggesting that the proposed modified electrode can selectively and simultaneously determine them. Under optimal conditions, the CoNi-MOF/GO/GCE showed an excellent analytical performance for the simultaneous determination of CC and HQ, including a wide linear range (0.1-100 µM), low detection limit (0.04 µM for HQ and 0.03 µM for CC) and high anti-interference ability. As expected, the developed modified electrode has been used to analyze CC and HQ in river water, with acceptable results.

Fecal microbiota transplantation and replenishment of short-chain fatty acids protect against chronic cerebral hypoperfusion-induced colonic dysfunction by regulating gut microbiota, differentiation of Th17 cells, and mitochondrial energy metabolism.

BACKGROUND: Little is known about the association between gut microbiota and intestinal injury under a state of chronic cerebral hypoperfusion (CCH). Here, the effects of gut microbiota and short-chain fatty acids (SCFAs), as important metabolic products, on intestinal function and potential mechanisms after CCH were investigated. METHODS: Rats were subjected to bilateral common carotid artery occlusion (BCCAo) to induce CCH. The gut microbiota and metabolites of SCFAs were assessed by 16S rRNA sequencing and targeted metabolomics, respectively. Transcriptomic analysis of colon tissues was also conducted. Subsequently, potential molecular pathways and differentially expressed genes were verified by western blot, immunoprecipitation, and immunofluorescence analyses. Furthermore, the integrity of the colonic barrier was evaluated by hematoxylin and eosin and mucin 2 staining and expression levels of tight junction proteins. Besides, colonic inflammation was further assessed by flow cytometry and expression levels of inflammatory cytokines. In addition, colonic mitochondrial dysfunction was analyzed via membrane potential, reactive oxygen species, electron transport chain (ETC) activities, adenosine triphosphate content, and mitochondrial ultrastructure. RESULTS: CCH modified gut microbial composition and microbial metabolism of SCFAs, which may be associated with inhibition of mitochondrial ETC activities and oxidative phosphorylation, leading to dysregulation of mitochondrial energy metabolism. Furthermore, CCH induced differentiation of pathogenic Th17 cells, promoted the formation of complexes of interferon regulatory factor 4 and signal transducer and activator of transcription 3 (STAT3), and increased the phosphorylation of STAT3. This was associated with an impairment of colonic barrier function and chronic colonic inflammation. In contrast, FMT and SCFA replenishment ameliorated CCH-induced gut microbial dysbiosis by increasing the intestinal content of Ruminococcus_sp_N15_MGS_57 and modulating microbial metabolism of SCFAs by increasing acetic acid contents associated with an improvment of the balance between Tregs and Th17 cells, mitochondrial ETC activities, and oxidative phosphorylation to prevent colonic inflammation and dysregulation of mitochondrial energy metabolism. CONCLUSION: These findings indicate that FMT and SCFA replenishment present a promising therapeutic strategy against colonic dysfunction under a state of chronic cerebral ischemia.

Gold-Nanoparticle-Mediated Assembly of High-Order DNA Nano-Architectures.

Constructing high-order DNA nano-architectures in large sizes is of critical significance for the application of DNA nanotechnology. Robust and flexible design strategies together with easy protocols to construct high-order large-size DNA nano-architectures remain highly desirable. In this work, the authors report a simple and versatile one-pot strategy to fabricate DNA architectures with the assistance of spherical gold nanoparticles modified with thiolated oligonucleotide strands (SH-DNA-AuNPs), which serve as "power strips" to connect various DNA nanostructures carrying complementary ssDNA strands as "plugs". By modulating the plug numbers and positions on each DNA nanostructure and the ratios between DNA nanostructures and AuNPs, the desired architectures are formed via the stochastic co-assembly of different modules. This SH-DNA-AuNP-mediated plug-in assembly (SAMPA) strategy offers new opportunities to drive macroscopic self-assembly to meet the demand of the fabrication of well-defined nanomaterials and nanodevices.

Effects of cis/trans-Configuration and Ligand Substitution of the Cyanidometal Bridge on Metal to Metal Charge Transfer Properties in Mixed Valence Complexes.

To investigate the effects of cis/trans-configuration of the cyanidometal bridge and the electron donating ability of the auxiliary ligand on the cyanidometal bridge on metal to metal charge transfer (MMCT) in cyanidometal-bridged mixed valence compounds, two groups of trinuclear cyanidometal-bridged compounds cis/trans-[Cp(dppe)Fe(µ-NC)Ru(4,4'-dmbpy)2 (µ-CN)Fe(dppe)Cp][PF6 ]n (n=2 (cis/trans-1[PF6 ]2 ), 3 (cis/trans-1[PF6 ]3 ), 4 (cis/trans-1[PF6 ]4 )) and cis/trans-[Cp(dppe)Fe(µ-NC)Ru(bpy)2 (µ-CN)Fe(dppe)Cp][PF6 ]3 (cis/trans-2[PF6 ]3 ) were synthesized and fully characterized. The experimental results indicate that for these one- and two-electron oxidation mixed valence compounds, the trans-configuration compounds are more beneficial for MMCT than the cis-configuration compounds, and increasing the electron donating ability of the auxiliary ligand on the cyanidometal bridge is also conductive to MMCT. Moreover, compounds cis/trans-1[PF6 ]n (n=3, 4) and cis/trans-2[PF6 ]3 belong to localized compounds by analyzing the experimental characterization results, supported by the TDDFT calculations.

Construction of a Molybdenum Disulfide-Based Colorimetric Sensor for Label-Free Infectious Disease Analysis Coupled with a Catalyzed Hairpin Assembly Reaction.

The simple and accurate determination of pathogenic infectious diseases is very beneficial to public health prevention and control. For this purpose, we designed a colorimetric sensor for label-free avian influenza A (H7N9) virus gene sequence detection based on gold@platinum core-shell bimetallic-nanoparticle-decorated molybdenum disulfide (MoS2-Au@Pt) nanocomposites. MoS2-Au@Pt nanocomposites were used as nanoenzymes to catalyze 3,3',5,5'-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) because of their intrinsic peroxidase-mimicking activity. Coupled with different affinities of MoS2-Au@Pt nanocomposites toward single-stranded (ss) and double-stranded (ds) DNA and the target-triggered catalyzed hairpin assembly (CHA) reaction, the proposed sensor can qualitatively and quantitatively determine H7N9 by the naked eye. Experimental results showed that this sensor can detect H7N9 in buffer and real samples because of its high sensitivity, selectivity, and repeatability.

Explainable machine learning approach to predict extubation in critically ill ventilated patients: a retrospective study in central Taiwan.

BACKGROUND: Weaning from mechanical ventilation (MV) is an essential issue in critically ill patients, and we used an explainable machine learning (ML) approach to establish an extubation prediction model. METHODS: We enrolled patients who were admitted to intensive care units during 2015-2019 at Taichung Veterans General Hospital, a referral hospital in central Taiwan. We used five ML models, including extreme gradient boosting (XGBoost), categorical boosting (CatBoost), light gradient boosting machine (LightGBM), random forest (RF) and logistic regression (LR), to establish the extubation prediction model, and the feature window as well as prediction window was 48 h and 24 h, respectively. We further employed feature importance, Shapley additive explanations (SHAP) plot, partial dependence plot (PDP) and local interpretable model-agnostic explanations (LIME) for interpretation of the model at the domain, feature, and individual levels. RESULTS: We enrolled 5,940 patients and found the accuracy was comparable among XGBoost, LightGBM, CatBoost and RF, with the area under the receiver operating characteristic curve using XGBoost to predict extubation was 0.921. The calibration and decision curve analysis showed well applicability of models. We also used the SHAP summary plot and PDP plot to demonstrate discriminative points of six key features in predicting extubation. Moreover, we employed LIME and SHAP force plots to show predicted probabilities of extubation and the rationale of the prediction at the individual level. CONCLUSIONS: We developed an extubation prediction model with high accuracy and visualised explanations aligned with clinical workflow, and the model may serve as an autonomous screen tool for timely weaning.

Explainable machine learning to predict long-term mortality in critically ill ventilated patients: a retrospective study in central Taiwan.

BACKGROUND: Machine learning (ML) model is increasingly used to predict short-term outcome in critically ill patients, but the study for long-term outcome is sparse. We used explainable ML approach to establish 30-day, 90-day and 1-year mortality prediction model in critically ill ventilated patients. METHODS: We retrospectively included patients who were admitted to intensive care units during 2015-2018 at a tertiary hospital in central Taiwan and linked with the Taiwanese nationwide death registration data. Three ML models, including extreme gradient boosting (XGBoost), random forest (RF) and logistic regression (LR), were used to establish mortality prediction model. Furthermore, we used feature importance, Shapley Additive exPlanations (SHAP) plot, partial dependence plot (PDP), and local interpretable model-agnostic explanations (LIME) to explain the established model. RESULTS: We enrolled 6994 patients and found the accuracy was similar among the three ML models, and the area under the curve value of using XGBoost to predict 30-day, 90-day and 1-year mortality were 0.858, 0.839 and 0.816, respectively. The calibration curve and decision curve analysis further demonstrated accuracy and applicability of models. SHAP summary plot and PDP plot illustrated the discriminative point of APACHE (acute physiology and chronic health exam) II score, haemoglobin and albumin to predict 1-year mortality. The application of LIME and SHAP force plots quantified the probability of 1-year mortality and algorithm of key features at individual patient level. CONCLUSIONS: We used an explainable ML approach, mainly XGBoost, SHAP and LIME plots to establish an explainable 1-year mortality prediction ML model in critically ill ventilated patients.

A New Cationic Fluorescent Probe for HSO3- Based on Bisulfite Induced Aggregation Self-Assembly.

In comparison with the numerous studies that have centered on developing molecular frameworks for the functionalization of fluorescent materials, less research has addressed the influence of the side chains, despite such appendages contributing significantly to the properties and applications of fluorescent materials. In this work, a new series of cationic fluorescent probes with AIE characteristics have been developed, which exhibit unique sensitivity for charge-diffusion anions, namely HSO3-, via the interactions of ions and the cooperation of the controllable hydrophobicity. The impact of the alkyl chain length attached at the cationic probes suggested that the fluorescent intensity and sensitivity of the probes could be partially enhanced by adjusting their aggregation tendency through the action of the hydrophobic effect under aqueous conditions. DLS and SEM images indicated that different particle sizes and new morphologies of the probes were formed in the anion-recognition-triggered self-assembly process, which could be attributed to the composite effect of electrostatic actions, Van der Waals forces and π-π stacking.

Modular DNA Circuits for Point-of-Care Colorimetric Assay of Infectious Pathogens.

Accurate, specific, and inexpensive detection of multiple infectious pathogens simultaneously is a significant goal for human health and safety. Herein we present a rationally designed modular DNA circuit for point-of-care (POC) detection of a variety of infectious pathogens based on nucleic acid isothermal amplification technology and DNAzyme-mediated colorimetric readout. A modular DNA circuit was constructed with a fixed module and a flexible module and was rationally designed according to genetic targets. On this basis, the platform could detect multiple genetic targets corresponding to infectious pathogens simultaneously. Signal amplification properties of the DNA circuit and the peroxidase-like DNAzyme enable the detection limits to reach the picomolar level. By urea treatment and magnetic separation, the fixed module can be reused at least five times, which makes this assay more economical and environmentally friendly. The detection of genetic infectious pathogens should be accomplished in 2 h with naked-eye observation and may provide an efficient tool for POC analysis of multiple infectious pathogens, especially in resource-poor areas.

Encoding DNA Frameworks for Amplified Multiplexed Imaging of Intracellular microRNAs.

Real-time imaging of multiple low-abundance microRNAs (miRNAs) simultaneously in living cells with high sensitivity is of vital importance for accurate cancer clinical diagnosis and prognosis studies. Maintaining stability of nanoprobes resistant to enzyme degradation and enabling effective signal amplification is highly needed for in vivo imaging studies. Herein, a rationally designed one-pot assembled multicolor tetrahedral DNA frameworks (TDFs) by encoding multicomponent nucleic acid enzymes (MNAzymes) was developed for signal-amplified multiple miRNAs imaging in living cells with high sensitivity and selectivity. TDFs could enter cells via self-delivery with good biocompatibility and stability. Two kinds of MNAzymes specific for miRNA-21 and miRNA-155 with fluorescein labeling were encoded in the structure of TDFs respectively through one-step thermal annealing. In the intracellular environment, the TDFs could be specifically bound with its specific miRNA target and form an active DNAzyme structure. The cleavage of the active site would trigger the release of target miRNA and circular fluorescence signal amplification, which enabled accurate diagnosis on miRNA identifications of different cell lines with high sensitivity. Meanwhile, with the specific AS1411 aptamer targeting for nucleolin overexpressed on the surface of the carcinoma cells, this well-designed TDFs nanoprobe exhibited good discrimination between cancer cells and normal cells. The strategy provides an efficient tool for understanding the biological function of miRNAs in cancer pathogenesis and therapeutic applications.

Influence of Fine Ligand Substitution Modification of the Isocyanidometal Bridge on Metal-to-Metal Charge Transfer Properties in Class II-III Mixed Valence Complexes.

The synthesis and characterization of Class II-III mixed valence complexes have been an interesting topic due to their special intermediate behaviour between localized and delocalized mixed valence complexes. To investigate the influence of the isocyanidometal bridge on metal-to-metal charge transfer (MMCT) properties, a family of new isocyanidometal-bridged complexes and their one-electron oxidation products cis-[Cp(dppe)Fe-CN-Ru(L)2 -NC-Fe(dppe)Cp][PF6 ]n (n=2, 3) (Cp=1,3-cyclopentadiene, dppe=1,2-bis(diphenylphosphino)ethane, L=2,2'-bipyridine (bpy, 1[PF6 ]n ), 5,5'-dimethyl-2,2'-bipyridyl (5,5'-dmbpy, 2[PF6 ]n ) and 4,4'-dimethyl-2,2'-bipyridyl (4,4'-dmbpy, 3[PF6 ]n )) have been synthesized and fully characterized. The experimental results suggest that all the one-electron oxidation products may belong to Class II-III mixed valence complexes, supported by TDDFT calculations. With the change of the substituents of the bipyridyl ligand on the Ru centre from H, 5,5'-dimethyl to 4,4'-dimethyl, the energy of MMCT for the one-electron oxidation complexes changes in the order: 13+ <23+ <33+ , and that for the two-electron oxidation complexes decreases in the order 14+ >34+ >24+ . The potential splitting (ΔE1/2 (2)) between the two terminal Fe centres for N[PF6 ]2 are the largest potential splitting for the cyanido-bridged complexes reported so far. This work shows that the smaller potential difference between the bridging and the terminal metal centres would result in the more delocalized mixed valence complex.

A label-free electrochemical sensor for ultrasensitive microRNA-21 analysis based on the poly(l-cysteine)/MoS2 sensing interface.

The label-free detection of nucleic acids has attracted interest of scientists due to the fact that it is simple, fast and efficient. Herein, l-cysteine was electropolymerized on the molybdenum disulfide (MoS2) surface to form a stable and electroactive poly(l-cysteine)-functionalized molybdenum disulfide (Pl-Cys/MoS2) sensing interface. Taking microRNA-21 (miRNA-21) as an analytical model, a label-free electrochemical sensor was designed according to the properties of the Pl-Cys/MoS2 sensing interface. Experimental data exhibited that the designed electrochemical sensor exhibited excellent sensitivity, selectivity and stability towards miRNA-21 detection in buffer and real samples. This study offers a methodology to construct a label-free sensing interface by combining MoS2 nanosheets and electroactive molecules.

Programming Surface-Enhanced Raman Scattering of DNA Origami-templated Metamolecules.

DNA origami holds an unprecedented capability on assembling metallic nanoparticles into designer plasmonic metamolecules of emerging properties, including surface-enhanced Raman scattering (SERS). SERS metamolecules were produced by positioning nanoparticles in close proximity to each other on a DNA origami template for Raman enhancement. In earlier reports, SERS metamolecules were generally assembled into clusters containing small number of nanoparticles (2, 3, or 4) and thus had limited programmability over SERS. Herein, we expanded the structural complexity of SERS metamolecules by increasing the number of nanoparticles and by arranging them into sophisticated configurations. DNA origami hexagon tile was used as the assembling template to fabricate clusters consisting of 6, 7, 12, 18, and 30+ metallic nanoparticles. Programmable SERS was realized via controlling the size, number, or spatial arrangement of nanoparticles. We believe this method offers a general platform for fabricating sophisticated nanodevices with programmable SERS that may be applied to a variety of fields including plasmonics, nanophotonics, and sensing.

DNA Origami-Based Nanoprinting for the Assembly of Plasmonic Nanostructures with Single-Molecule Surface-Enhanced Raman Scattering.

Metallic nanocube ensembles exhibit tunable localized surface plasmon resonance to induce the light manipulation at the subwavelength scale. Nevertheless, precisely control anisotropic metallic nanocube ensembles with relative spatial directionality remains a challenge. Here, we report a DNA origami based nanoprinting (DOBNP) strategy to transfer the essential DNA strands with predefined sequences and positions to the surface of the gold nanocubes (AuNCs). These DNA strands ensured the specific linkages between AuNCs and gold nanoparticles (AuNPs) that generating the stereo-controlled AuNC-AuNP nanostructures (AANs) with controlled geometry and composition. By anchoring the single dye molecule in hot spot regions, the dramatic enhanced electromagnetic field aroused stronger surface enhanced Raman scattering (SERS) signal amplification. Our approach opens the opportunity for the fabrication of stereo-controlled metal nanostructures for designing highly sensitive photonic devices.

The Electron Transfer Process in Mixed Valence Compounds with a Low-lying Energy Bridge in Different Oxidation States.

Mixed-valence compounds with the iso-cyanidometal-ligand bridge in different oxidation states are used as models for the investigation of the electron-transfer process. We synthesized a series of trimetallic isocyanidometal-bridged compounds with [Fe-CN-Ru-NC-Fe]n+ (n=2-4), in which the one-electron oxidation product (N3+ ) and two-electron oxidation product (N4+ ) compounds possess an isocyanidometal bridge whose energy is, respectively lower and slightly higher than the terminal metal centers energies. For the N3+ compounds, the bridge state (FeII -RuIII -FeII ) and mixed-valence states (FeIII -RuII -FeII or FeII -RuII -FeIII ) could be simultaneously observed on the IR timescale. For the N4+ compounds, as the donor becomes stronger the electron transfer bridge excited state (FeIII -RuII -FeIII ) becomes more and more stable, and even becomes ground state due to the strong electronic coupling between Fe and Ru.