Search

The label-free cell-based assay is advantageous for biochemical study because of it does not require the use of experimental animals. Due to its ability to provide more dynamic information about cells under physiological conditions than classical biochemical assays, this label-free real-time cell assay based on the electric impedance principle is attracting more attention during the past decade. However, its practical utilization may be limited due to the relatively expensive cost of measurement, in which costly consumable disposable gold microchips are used for the cell analyzer. In this protocol, we have developed a general strategy to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes trypsin digestion, rinsing with ethanol and water, and a spinning step. The proposed method has been tested and shown to be effective for the regeneration and repeated usage of commercial electronic plates at least three times, which will help researchers save on the high running cost of real-time cell assays.

To tackle severe environmental pollution, a search for materials by economical and eco-friendly preparations is demanding for public health. In this study, a novel in situ method to form silver nanoparticles under mild conditions was developed using biomimetic reducing agents of polydopamine coated on the rodlike mesoporous silica of SBA-15. The synthesized SBA-15/polydopamine (PDA)/Ag nanocomposites were characterized by a combination of physicochemical and electrochemical methods. 4-Nitrophenol (4-NP) and methylene blue (MB) were used as models for the evaluation of the prepared nanocatalysts of SBA-15/PDA/Ag in which the composite exhibited enhanced catalytic performance toward degrading 4-NP in solution and MB on the membrane, respectively. Additionally, compared with that of solid core-shell SiO2/PDA/Ag, tubular SBA-15/PDA/Ag showed the prolonged inhibitory effect on microbial growth as typified by Escherichia coli (60 h), Staphylococcus aureus (36 h), and Aspergillus fumigatus (60 h), which demonstrated efficient control of silver nanoparticles release from the mesopores. The constructed dual-functional SBA-15/PDA/Ag as the long-term antimicrobial agent and the catalyst of industrial products provides an integrated nanoplatform to deal with environmental concerns.

A subset of vertices of a graph G is called a decycling set of G if its deletion results in an acyclic subgraph. The cardinality of a minimum decycling set is called the decycling number of G. This paper presents an approach to construct an acyclic subgraph of CQ_n and proves that for any integer n ≥ 2, the decycling number of CQ_n is 2^n-1 ⋅(1-c/n-1), c∊[0,1].

A facile adsorbent, a nanocomposite of Fe3 O4 and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid-phase dispersion extraction. The nanocomposite was synthesized in a one-step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and Brunauer-Emmett-Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong π-π interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05-10 μg/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95-95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe3 O4 and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment.

Based on poly sodium 4-styrenesulfonate (PSS) functionalized reduced graphene oxide (RGO) and polyamidoamine (PAMAM) dendrimer protected gold nanoparticles (AuNPs), a novel electrochemical sensing platform for sensitive detection of 4-nitrophenol and hydrazine was fabricated via electrostatic layer-by-layer (LBL) self-assembly on a gold electrode modified with a first layer of poly (diallyldimethylammonium chloride) (PDDA). The resulting nanocomposites were characterized by Raman and UV-Vis spectroscopes. Besides, electrochemical measurements were employed to investigate the electrocatalytic and sensing properties of the as-prepared modified electrode. The results indicate that the LBL assembled PSS-RGO/PAMAM-AuNPs multilayer films possess excellent electrocatalytic activities towards the reduction of 4-nitrophenol (4-NP) and the oxidation of hydrazine and also show good analytical performance for the amperometric detection of the potential poisonous substances. In addition, the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and their synergistic effect may account for the increased electrochemical activities.

Effects of hydrodynamic interactions (HI) on the crystallization of a two-dimensional suspension of colloidal particles have been investigated, by applying a multiscale simulation method combining multiparticle collision dynamics for solvent particles with standard molecular dynamics for the colloids. For a passive system, we find that HI slightly shifts the freezing point to a smaller density, while the equilibrium structure remains nearly unchanged for a given global order parameter. For an active system, however, HI can significantly shift the freezing density to a higher value and the freezing transition becomes more continuous compared to its passive counterpart. This HI-induced shift becomes more remarkable with increasing propelling force. In addition, HI may also enhance the structural heterogeneities in an active system. For both passive and active systems, it is shown that HI can accelerate the relaxation process to their final steady state.

The electrocatalytic reduction reaction of carbon dioxide can be significantly enhanced by the use of sharp tip electrode. However, the experimentally observed rate enhancement is many orders of magnitudes smaller than what one would expect from an energetic point of view. Here we demonstrate that the kinetic of this tip-enhanced reaction plays a decisive role by proposing a novel reaction-diffusion kinetic model. The experimentally observed sharp-tip enhanced reaction and the maximal producing rate of carbon monoxide under different electrode potentials are well reproduced. Moreover, the optimal performance shows a strong dependence on the interaction between CO2 and the local electric field, on the adsorption rate of CO2, but not on the reaction barrier. Two new strategies to further enhance the reaction rate have also been proposed. Our findings highlight the importance of the kinetic in modeling electrocatalytic reactions.

We have studied spatial and temporal dynamic heterogeneity (DH) in a system of hard-sphere particles, subjected to active forces with constant amplitude and random direction determined by rotational diffusion with correlation time τ. We have used a variety of observables to characterize the DH behavior, including the deviation from standard Stokes-Einstein (SE) relation, a non-Gaussian parameter α_{2}(Δt) for the distribution of particle displacement within a certain time interval Δt, a four-point susceptibility χ_{4}(Δt,ΔL) for the correlation in dynamics between any two points in space separated by distance ΔL within some time window Δt, and a vector spatial-temporal correlation function S_{vec}(R,Δt) for vector displacements within time interval Δt of particle pairs originally separated by R. By mapping the particle motion into a continuous-time random walk with constant jump length, we can obtain the average waiting time 〈t_{x}〉∝D_{s}^{-1} and persistence time 〈t_{p}〉∝η, with D_{s} the self-diffusion coefficient and η the shear viscosity, such that the observable λ=〈t_{p}〉/〈t_{x}〉∝D_{s}η can be calculated as a function of the control parameter τ to show how it deviates from its SE value λ_{0}. Interestingly, we find λ/λ_{0} shows a nonmonotonic behavior for large volume fraction φ_{a}, wherein λ/λ_{0} undergoes a minimum at a certain intermediate value of τ, indicating that both small and large particle activity may lead to strong DH. Such a reentrance phenomenon is further demonstrated in terms of the non-Gaussian parameters α_{2}, four-point susceptibility χ_{4}, and vector spatiotemporal correlation functions S_{vec}, respectively. Detail analysis shows that it is the competition between the dual roles of particle activity, namely, activity-induced higher effective temperature and activity-induced clustering, that leads to such nontrivial nonmonotonic behaviors. In addition, we find that DH may also show a maximum level at an intermediate value of φ_{a} if τ is large enough, implying that a more crowded system may be less heterogeneous than a less crowded one for a system with high particle activity.

BiOCl-SiO2 KIT-6 composite materials with raspberry-like structures are facilely prepared under hydrothermal conditions. The mesoporous siliceous support of SiO2 KIT-6-incorporated BiOCl with enlarged yet refined surface morphology characterized by physiochemical methods exhibits an improved electrochemical performance. A sensitive electrochemical detection method of cadmium concentration using square wave anodic stripping voltammetry was developed based on BiOCl-SiO2 KIT-6 composite-modified glassy carbon electrodes, which displayed wide linear ranges of 0.5 to 10 μg/L and 10 to 300 μg/L and a detection limit of 65 ng/L. The sensitive, versatile and eco-friendly sensor was successfully applied for the determination of cadmium-spiked human blood samples.

A double-layered membrane sensing interface was fabricated for sensitive and selective detection of serotonin (5-hydroxytryptamine, 5-HT) based on reduced graphene oxide (rGO)/polyaniline (PANI) nanocomposites and molecularly imprinted polymers (MIPs) embedded with gold nanoparticles (AuNPs). rGO/PANI nanocomposites were synthesized via electro-deposition process, in which protonated anilines were first anchored on the rGO sheets through electrostatic adsorption, and then the rGO/PANI membrane was formed on the bare electrode via cyclic voltammetry method. Functionalized AuNPs (F-AuNPs) were prepared to fabricate the MIPs embedded with AuNPs (AuNPs@MIPs) membrane on the modified electrode by constant potential method in the presence of 5-HT and p-aminothiophenol. The materials prepared in this work were examined by ultraviolet-visible (UV-Vis) and Raman spectroscopy, and the as-prepared membranes were characterized by scanning electron microscope, energy dispersive spectroscopy, and electrochemical methods. In addition, the obtained sensor allowed remarkable selectivity to 5-HT against the interferences caused by ascorbic acid and other interferents. A linear dependence of peak current in differential pulse voltammograms was obtained over 0.2-10.0 μmol L −1 5-HT with the limit of detection of 11.7 nmol L −1 (S/N = 3). Furthermore, the obtained biomimetic sensor was employed to detect 5-HT in human serum samples.

Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π-π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15-100.81% with the RSD

Previous research indicated that graphene oxide (GO) can be used to deliver photosensitive anticancer drug, Hypocrellin A (HA), in photodynamic therapy (PDT). However, the anticancer activity of HA was obviously decreased after been loaded on GO. To solve this problem, a chemotherapy drug, 7-ethyl-10-hydroxycamptothecin (SN-38), was co-loaded on the HA loaded GO (HA/SN-38/GO) as a multimodal carrier for the synergistic combination of PDT and chemotherapy for cancer. In vitro results showed that the combination therapy exhibited a synergistic antiproliferative effect compared with PDT and chemotherapy alone. Therefore, HA/SN-38/GO delivery system has the potential to offer dual therapies for the synergistic combination of PDT and chemotherapy for the treatment of cancer.

Formation of highly ordered structures usually needs to overcome a high free-energy barrier that is greatly beyond the ability of thermodynamic fluctuation, such that the system would be easily trapped into a state with many defects and the annealing process of which often occurs on unreachable long time-scales. Here we report a fascinating example theoretically that active core corona particles can successfully self-assemble into a large-scaled and highly ordered stripe or trimer lattice, which is hardly achieved in a non-driven equilibrium system. Besides, such an activity-induced ordered structure shows an interesting self-healing feature of defects. In addition, there exists an optimal level of activity that most favorably enhance the formation of ordered self-assembly structures. Since core corona particles act as important units for self-assembly in real practice, we believe our study opens a new design-strategy for highly ordered materials., 8 pages, 6 figures

Sports development can lead to the emergence of external economies, which forms part of the spillover effects on regional economic growth under certain conditions. This study uses a sample of 31 provinces in China from 2008–2012 to construct a panel data model to examine the role of sports development in the regional economic growth in the C-D function. The results indicate that sports development indeed brings a good incentive effect to the economy in all areas, which suggests a spillover effect of Chinese sports development that stimulates regional economic growth, but this spillover effect reflects a greater difference between different regions. Overall, Hebei, Jiangxi, Henan, Hubei, Hunan, and Sichuan have the highest coefficient of sports investment on economy, but Jilin is relatively weak.

We study the dynamic separation process of two identical polymers confined in a cylinder, allowing both ends of the polymer chains to be free, based on a three dimensional (3D) free energy landscape combined with direct molecular dynamics (MD) simulations. The landscape suggests that the probability distribution curves of induction time (segregation time) reduced by corresponding average values would collapse into a single one under the so-called blob constraint, i.e., κ ≡ ND-1/ν is a constant, where N is the number of monomers in a chain, D is the channel diameter, and ν ≃ 3/5. Such a collapse behavior is well demonstrated by direct MD simulations and further by Brownian dynamics simulations of an effective particle on the 3D landscape. Interestingly, Brownian dynamics shows that the average induction time t¯in or segregation time t¯se decreases monotonically with κ in a power-law dependence if the diffusion coefficient D is fixed, suggesting a distinct mechanism of the induction process which is neither diffusion nor barrier-crossing, in accordance with trajectory analysis by using MD simulations. In addition, we find that both t¯in and t¯se show good power-law dependencies on the polymer length N under the blob constraint.

Pd-Pt bimetallic nanoparticles anchored on functionalized reduced graphene oxide (RGO) nanomaterials were synthesized via a one-step in situ reduction process, in which Pt and Pd ions were first attached to poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene oxide (GO) sheets, and then the encased metal ions and GO were subjected to simultaneous reduction by ethylene glycol. The as-prepared Pd3Pt1/PDDA-RGO nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electrochemical methods. In addition, an electrochemical sensor based on the graphene nanocomposites was fabricated for the simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in their ternary mixture. Three well-separated voltammetric peaks along with remarkable increasing electro-oxidation currents were obtained in differential pulse voltammetry (DPV) measurements. Under the optimized conditions, there were linear relationships between the peak currents and the concentrations in the range of 40-1200 μM for AA, 4-200 μM for DA and 4-400 μM for UA, with the limit of detection (LOD) (based on S/N=3) of 0.61, 0.04 and 0.10 μM for AA, DA and UA, respectively. This improved electrochemical performance can be attributed to the synergistic effect of metallic nanoparticles and RGO and the combination of the bimetallic nanoparticles. Furthermore, the practical electroanalytical utility of the sensor was demonstrated by the determination of AA, DA and together with UA in human urine and blood serum samples with satisfactory results.

In this work, a highly sensitive and selective biomimetic electrochemical sensor for Sildenafil in herbal sexual health products was prepared. Reduced graphene oxide (RGO), a novel highly conductive material was used to modify glassy carbon electrode (GCE) through layer-by-layer (LBL) self-assembly. The conductive molecularly imprinted films were constructed on the functional electrode surface using Sildenafil as template molecules, p-phenylenediamine (p-PD) as functional monomers. The obtained molecularly imprinted electrochemical sensor (MIES) was successfully used to detect Sildenafil in herbal sexual health products. The limit of detection (LOD) was 6.2 nmol L⁻¹. The recoveries for the spiked Sildenafil contents were in the range of 92.34-97.71% with the RSD2.31%. The selective efficiencies for Sildenafil and other structurally related analogues only slightly varied from 0.93 to 1.09.

A novel hybrid of graphene oxide (GO) and hypocrellin B (HB) was prepared using a simple noncovalent method. An efficient loading of HB on GO as high as 2 mg/mg was obtained. Mechanism analysis indicated that the π–π stacking interaction is the dominant driving force in the noncovalent interaction between HB and GO. Irradiation of HB and GO hybrid (HB–GO) results in efficient generation of singlet oxygen (1O2). In vitro studies have demonstrated the active uptake of HB–GO into the cytosol of tumor cells. Significant damage to such impregnated tumor cells was observed upon irradiation.

Polymer translocation through nanopores into a crowded environment is of ubiquitous importance in many biological processes. Here we investigate polymer translocation through a nanopore into an active bath of self-propelled particles in two-dimensional space using Langevin dynamics simulations. Interestingly, we find that the mean translocation time τ can show a bell-shape dependence on the particle activity Fa at a fixed volume fraction ϕ, indicating that the translocation process may become slower for small activity compared to the case of the passive media, and only when the particle activity becomes large enough can the translocation process be accelerated. In addition, we also find that τ can show a minimum as a function of ϕ if the particle activity is large enough, implying that an intermediate volume fraction of active particles is most favorable for the polymer translocation. Detailed analysis reveals that such nontrivial behaviors result from the two-fold effect of active bath: one that active particles tend to accumulate near the pore, providing an extra pressure hindering the translocation, and the other that they also aggregate along the polymer chain, generating an effective pulling force accelerating the translocation. Such results demonstrate that active bath plays rather subtle roles on the polymer translocation process.

Emergence of collective dynamical chirality (CDC) at mesoscopic scales plays a key role in many formation processes of chiral structures in nature, which may also provide possible routines for people to fabricate complex chiral architectures. So far, most of reported CDCs are found in systems of active objects with individual structure chirality or/and dynamical chirality, and whether CDC can arise from simple and achiral units is still an attractive mystery. Here, we report a spontaneous formation of CDC in a system of both dynamically and structurally achiral particles motivated by active motion of cells. Active moving, confinement and hydrodynamic interaction are found to be the three key factors. Detailed analysis shows that the system can support abundant collective dynamical behaviors, including rotating droplet, rotating bubble, CDC oscillation, array of collective rotation, as well as interesting transitions such as chirality transition, structure transition and state reentrance., 5 pages, 4 figures

We developed a method to regenerate arrayed gold microelectrodes equipped for a commercial label-free cell analyzer. The regeneration process includes efficient treatment of the gold surface with trypsin (0.25%, v/v) digestion, rinsing with ethanol and deionized water and spinning steps. The proposed method ensured complete regeneration and repeated usage of gold microchips up to 4 times for the real-time electric impedance measurement of anti-cancer drug cytotoxicity.

The dynamics of point-like Brownian particles in a periodic confined channel with oscillating boundaries has been studied. Directional transport (DT) behavior, characterized by net displacement along the horizontal direction, is observed even without external force which is necessary for the conventional DT where the boundaries are static. For typical parameter values, the average velocity Vt of DT reaches a maximum with the variation of the noise intensity D, being alike to the phenomenon of stochastic resonance. Interestingly, we find that Vt shows nontrivial dependences on the particle gravity G depending on the noise level. When the noise is large, Vt increases monotonically with G indicating that heavier particle moves faster, while for small noise, Vt shows a bell-shape dependence on G, suggesting that a particle with an intermediate weight may move the fastest. Such results were not observed for DT in a channel with static boundaries. To understand these findings, we have adopted an effective one-dimensional coarsening description, which facilitates us to introduce an effective entropic force along the horizontal direction. The average force is apparently nonzero due to the oscillatory boundary, hence leading to the net transport, and it shows similar dependences as Vt on the noise intensity D and particle gravity G. The dependences of the DT behavior on other parameters describing the oscillatory channel have also been investigated, showing that DT is more pronounced for larger oscillation amplitude and frequency, and asymmetric geometry within a channel period and phase difference between neighboring periods are both necessary for the occurrence of DT.

We have studied the nucleation process of a two-dimensional kinetic Ising model subject to a bias oscillating external field, focusing on how the nucleation time depends on the oscillation frequency. It is found that the nucleation time shows a clear-cut minimum with the variation of oscillation frequency, wherein the average size of the critical nuclei is the smallest, indicating that an oscillating external field with an optimal frequency can be much more favorable to the nucleation process than a constant field. We have also investigated the effect of the initial phase of the external field, which helps to illustrate the occurrence of such an interesting finding.

A novel sandwich-type molecular imprinting electrochemical sensor (MIES) with enhanced sensitivity was prepared by using reduced graphene oxide (rGO) combined with platinum nanoparticles (PtNPs). Functional monomers were chosen with the aid of Gaussian 09 software. With the formation of Pt–S bond, 6-mercaptonicotinic acid (MNA) was fabricated at the surface of PtNPs/rGO composites modified glassy carbon electrode (GCE). 17β-estradiol (E2) was assembled by forming hydrogen bond with MNA. The polymer films were formed by electropolymerization of MNA and the specific recognition cavities were formed after the removal of templates. By using the differential pulse voltammetry (DPV), the resulting sensor exhibited good linear ranges of 0.004–0.060 μM (Ip (μA) = 57.872 C (μM) + 1.6678, R = 0.9977) and 0.060–50 μM (Ip (μA) = 0.7915 C (μM) + 6.6906, R = 0.9957). The limit of detection (LOD) of E2 was 0.002 μM (S/N = 3). Moreover, the MIES was successfully used in the analysis of E2 in makeups with good recoveries (>91.9%) with lower RSDs (

Graphene/gold nanoparticle multilayer films composed of polysodium 4-styrenesulfonate (PSS) functionalized reduced graphene oxide (RGO) and polyamidoamine (PAMAM) dendrimer stabilized gold nanoparticles (AuNPs) were built up using the electrostatic layer-by-layer (LBL) self-assembly technique on a glassy carbon electrode (GCE) modified with a first layer of poly(diallyldimethylammonium chloride) (PDDA). The film assembly, the electrochemical property as well as the electrocatalytic activity toward the oxidation of dopamine were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). Electrochemical studies exhibit that the LBL assembled RGO/AuNPs films possess an excellent sensing performance for the detection of dopamine with a linear range from 1 μM to 60 μM and a limit of detection (LOD) as low as 0.02 μM based on S / N = 3. In addition, this electrochemical sensor was applied to the simultaneous detection of dopamine and uric acid by using DPV with high sensitivity and selectivity. The good analytical performance and long-term stability of the proposed sensor can be attributed to the combination of the reduced graphene oxide and gold nanoparticles in the LBL assembly films and the synergistic effect on the electrochemical oxidation of dopamine.

We investigate the impact of coupling on the reliability of the logic system as well as the logical stochastic resonance (LSR) phenomenon in the coupled logic gates system. It is found that compared with single logic gate, the coupled system could yield reliable logic outputs in a much wider noise region, which means coupling can obviously improve the reliability of the logic system and thus enhance the LSR effect. Moreover, we find that the enhancement is larger for larger system size, whereas for large enough size the enhancement seems to be saturated. Finally, we also examine the effect of coupling strength, it can be observed that the noise region where reliable logic outputs can be obtained evolves non-monotonically as the coupling strength increases, displaying a resonance-like effect.

Pt and Pd–Pt nanoparticles were anchored on reduced graphene oxide (RGO) with the aid of poly(diallyldimethylammonium chloride) (PDDA), where Pt and Pd ions were first attached to PDDA-functionalized graphene oxide sheets and the encased metal ions and graphene oxide were then reduced simultaneously by ethylene glycol. As supported by transmission electron microscopy, metal nanoparticles, of small particle size even at a high metal loading, were chemically attached to PDDA–RGO. X-ray diffraction indicates that the as-prepared Pd–Pt nanoparticles have a single-phase fcc structure and are principally alloys of Pd and Pt. Among the RGO-supported Pt and Pd–Pt catalysts, Pt nanoparticles anchored on PDDA–RGO exhibit the highest activity for the oxygen reduction reaction (ORR), and the ORR activity of the Pd–Pt alloy electrocatalysts increases with Pt content. All the catalysts demonstrate an enhanced ORR durability when PDDA is present; strongly suggesting that PDDA plays a crucial role in the dispersion and stabilization of the metal nanoparticles on RGO. The ORR activities of the Pd–Pt catalysts remain enhanced even after accelerated durability testing. The formation of a Pt-rich shell, as confirmed by X-ray photoelectron spectroscopy and CO stripping voltammetry, may account for the increased activity.

In this paper, an electrochemical sensor for 17β-estradiol (E2) based on the molecular imprinting polymer (MIP) membranes had been constructed. 6-mercaptonicotinic acid (MNA) and E2 were first assembled on the surface of platinum nanoparticles-modified glassy carbon electrode (PtNPs/GCE) by the formation of Pt-S bonds and hydrogen-bonding interactions, and subsequently the polymer membranes were formed by electropolymerization. Finally, a novel molecularly imprinted sensor (MIS) was obtained after removal of E2. Experimental parameters such as deposition time, scan cycles, pH value and accumulation condition were optimized. Under optimal conditions, the MIS exhibited a large adsorption capacity and high selectivity. A good linearity was obtained in the range of 3.0×10(-8)-5.0×10(-5)molL(-1) (r=0.996) with an estimated detection limit of 1.6×10(-8)molL(-1). MIS had been successfully used to analyze E2 in water samples without complex pretreatment. Meanwhile, the average recoveries were higher than 93.9% with RSD

A bioelectrochemical platform has been constructed for the direct electron transfer and biosensing purposes of microperoxidase-11 (MP-11) immobilized on the chitosan dispersed multilayer graphene nanocomposite. The immobilized MP-11 at the modified gold electrode displays a well-defined and quasireversible redox peaks, with a formal potential of −0.38 V/SCE in a buffer solution (pH 7.0). MP-11 absorbed on the electrode surface exhibits high electrocatalytic activity toward the reduction of both oxygen and hydrogen peroxide and also shows good analytical performance for the amperometric detection of H2O2 with a linear range from 2.5 to 135 μM. These results indicate the graphene modified electrode might be used as a third generation biosensor for H2O2 detection.

Based on magnetic field directed self-assembly (MDSA) of the ternary Fe3O4@PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe3O4@PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe3O4@PANI into the graphene oxide layers via π-π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe3O4@PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N-H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe3O4@PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L(-1) (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples.

Background During the outbreak of the emergent severe acute respiratory syndrome (SARS) infection, >30% of the approximately 8000 infected persons were health care workers. The highly infectious nature of SARS coronavirus (SARS-CoV) compelled our pathologists to consider biosafety issues in the autopsy room and for tissue processing procedures. Methods A specially designed biosafety level 3 (BSL-3) autopsy laboratory was constructed and divided into a clean area, a semicontaminated area, a contaminated area, and 2 buffer zones. High-efficiency particulate air filters were placed in the air supply and exhaust systems. Laminar air flow was from the clean areas to the less clean areas. The negative pressures of the contaminated, semicontaminated, and clean areas were approximately -50 pa, -25 pa, and -5 pa, respectively. Personal protective equipment, including gas mask, impermeable protective clothing, and 3 layers of gloves worn during autopsies; the equipment was decontaminated before it was allowed to exit the facility. Strict BSL-3 practices were followed. Results When a given concentration of particulate sarin simulant was introduced into the contaminated area, it could not be detected in either the semicontaminated area or clean area, and particles >0.3 microm in size were not detected in the exhaust air. A total of 16 complete postmortem examinations for probable and suspected SARS were performed during a 2-month period. Of these, 7 reported confirmed cases of SARS. None of the 23 pathologists and technicians who participated in these autopsies was infected with SARS-CoV. Conclusions Our experience suggests that BSL-3 laboratory operating principles should be among the special requirements for performing autopsies of contaminated bodies and that they can safeguard the clinicians and the environment involved in these procedures.

We report a novel single-molecular rupture mechanism revealed by direct sampling of the dominant pathway using a self-optimized path sampling method. Multiple dominant pathways involving multistep transitions are identified. The rupture may take place via a direct unfolding from the native state to the unfolding state, or through a two-step pathway bypassing a distinct intermediate metastable state (IMS). This scenario facilitates us to propose a three-state kinetic model, which can produce a nonlinear dependence of the rupture time on pulling forces similar to the ones reported in the literature. In particular, molecule conformations in the IMS maintain an elongation of the tail at one terminal, by which external pulling will enhance the relative stability of IMS. Consequently, even though the overall transition rate of the multistep pathway is relatively small, the molecule still has to be ruptured via the multistep pathway rather than the direct pathway. Thus, our work demonstrates an IMS trapping effect induced rupture mechanism involving an abnormal switching from a fast dominant pathway to a slow one.

We investigate the coupled dynamics of active filaments with long range hydrodynamic interactions (HI). Remarkably, we find that filaments can rotate spontaneously under the same conditions in which a single filament alone can only move in translation. Detailed analysis reveals that the emergence of coupled rotation originates from an asymmetric flow field associated with HI which breaks the symmetry of translational motion when filaments approach. The breaking is then further stabilized by HI to form self-sustained coupled rotation. Intensive simulations show that coupled rotation forms easily when one filament tends to collide with the front-half of the other. For head-to-tail approaching, we observe another interesting HI-induced coupled motion, where filaments move together in the form of one following the other. Moreover, the radius of coupled rotation increases exponentially as the rigidity of the filament increases, which suggests that HI are also important for the alignment of rigid-rod-like filaments which has been assumed to be solely a consequence of direct collisions.

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and Fas ligand (FasL) trigger apoptosis by stimulating the formation of a death inducing signaling complex at the cytoplasmic terminus of their respective receptors. Photodynamic therapy (PDT) is an approved treatment for several types of cancer as well as for age-related macular degeneration and is under investigation for different cancer, ocular, autoimmune and cardiovascular indications. The effect of low dose PDT in combination with TRAIL and FasL on Jurkat lymphoma cell apoptosis was examined. Individually, TRAIL, FasL, and PDT could induce apoptosis in these cells. However, at suboptimal levels of PDT, the number of cells undergoing apoptosis was increased when recombinant FasL and/or TRAIL were added. Additive effects of these treatments were evident for different apoptosis parameters including DNA fragmentation, caspase processing and activity and caspase substrate degradation. Overall, these results provide evidence that PDT-treated cells may be more likely to undergo apoptosis when also exposed to receptor-mediated signals delivered by factors such as TRAIL or FasL. For PDT, immune cell-mediated death receptor ligation may represent a way whereby tumor cells that have withstood the direct effects of photosensitization may be eliminated.

The nuclear factor-kappa B (NF-kappaB) gene transactivator serves in the formation of immune, inflammatory, and stress responses. In quiescent cells, NF-kappaB principally resides within the cytoplasm in association with inhibitory kappa (IkappaB) proteins. The status of IkappaB and NF-kappaB proteins was evaluated for promyelocytic leukemia HL-60 cells treated at different intensities of photodynamic therapy (PDT). The action of the potent photosensitizer, benzoporphyrin derivative monoacid ring A (verteporfin), and visible light irradiation were assessed. At a verteporfin concentration that produced the death of a high proportion of cells after light irradiation, evidence of caspase-3 and caspase-9 processing and of poly(ADP-ribose) polymerase cleavage was present within whole cell lysates. The general caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone (ZVAD.fmk) effectively blocked these apoptosis-related changes. Recent studies indicate that IkappaB proteins may be caspase substrates during apoptosis. However, the level of IkappaBbeta was unchanged for HL-60 cells undergoing PDT-induced apoptosis. IkappaBalpha levels decreased during PDT-induced apoptosis, though ZVAD.fmk did not affect this change. At a less intensive level of photosensitization, cellular IkappaBalpha levels were transiently depressed after PDT. At these times, p50 and RelA NF-kappaB species were increased within nuclear extracts, as revealed by electrophoretic mobility supershift assays. HL-60 cells transiently transfected with a kappaB-luciferase reporter construct exhibited elevated luciferase activity after PDT or treatment with tumor necrosis factor-alpha, a well-characterized NF-kappaB activator. Productive NF-kappaB activation and associated gene transcription may influence the phenotype and behavior of cells exposed to less intensive PDT regimens. However, IkappaBalpha is not subject to caspase-mediated degradation as a component of PDT-induced apoptosis. (Blood. 2000;95:256-262)

The impact of the immunomodulatory photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) and visible light on the survival and surface receptor pattern of resting and activated murine T cells was evaluated. T cells treated for 48 h with immobilized anti-CD3 monoclonal antibody upregulated expression of the interleukin-2 receptor alpha-chain (CD25), transferrin receptor (CD71), the apoptosis-regulating Fas receptor (CD95), contained a greater level of the anti-apoptotic protein Bcl-2 and accumulated significantly more BPD-MA than their unactivated counterparts. Activated T cells displayed a modestly greater susceptibility to the photodynamic induction of DNA fragmentation than resting T cells. Resting T cells treated with sub-lethal levels of BPD-MA and light did not exhibit changes in surface levels of CD3, CD4, CD8, CD28, CD45 or T cell receptor (TCR) beta-chain structures. However, levels of major histocompatibility complex (MHC) class I antigens were decreased while the density of Thy-1.2 (CD90) increased on these cells. Photodynamically treated T cells failed to express optimal CD25 levels when exposed to the mitogenic anti-CD3 antibody. Activated T cells treated with sub-lethal levels of BPD-MA and light exhibited lower CD25 levels, a temporary block in cell cycle transition, but unaltered expression of MHC Class I, CD3, CD4, CD8, CD45, CD54, CD71, CD122 (IL-2R beta-chain) or TCR beta-chain antigens 24 h afterward. Resting and activated T lymphocytes differ in susceptibility to PDT-mediated apoptosis but both types are sensitive to anti-proliferative effects the treatment exerts at sub-lethal photosensitizer levels. The marked sensitivity of activated T cells to photodynamic inactivation likely contributes to the immunomodulatory action of BPD-MA.

Treatment with the photosensitizer benzoporphyrin derivative monoacid ring A (BPD-MA, verteporfin) followed by irradiation with visible light induces apoptosis in human acute myelogenous leukaemia HL-60 cells. Photoactivation of BPD-MA induces procaspase 3 (CPP32/Yama/apopain) and procaspase 6 (Mch2) cleavage into their proteolytically active subunits in these cells. The Bcl-2 proto-oncogene product has been shown to protect cells from a number of proapoptotic stimuli. In the present study, the influence of Bcl-2 overexpression on cellular resistance to photoactivation of BPD-MA was studied. Overexpression of Bcl-2 in HL-60 cells prevented apoptosis-related events including caspase 3 and 6 activation, poly(ADP-ribose) polymerase cleavage and the formation of hypodiploid DNA produced by BPD-MA (0–200 ng ml−1) and light. However, Bcl-2 overexpression was less effective at preventing cell death that occurred after photoactivation at high levels (50–100 ng ml−1) compared with lower doses (10–25 ng ml−1) of BPD-MA. These results indicate that caspase 3 and 6 activation and their regulation by Bcl-2 may play important roles in photodynamic therapy (PDT)-induced cell killing. © 1999 Cancer Research Campaign

When given to normal male mice, the photochemotherapeutic agent Photofrin® (porfimer sodium), a complex mixture of monomeric and oligomeric non-metallic porphyrins, significantly increased relative spleen weight, spleen cell numbers, DNA replication, levels of granulocyte-macrophage and erythroid progenitors and cellular responsiveness to different recombinant (r) myeloid growth factors. In contrast, monomeric hematoporphyrin had no effect on spleen weight, cellularity, erythroid progenitor levels or spleen cell cycle status. Photofrin® significantly increased spleen cell expression of the receptor (CD71) for the iron transport protein transferrin by 72 h post-injection but did not affect levels of a receptor (CD25) for the T-cell growth factor interleukin-2 (IL-2) or spleen cell responsiveness to rIL-2. Further evidence of increased splenic erythropoietic activity in Photofrin®-treated mice was provided by double color flow cytometric studies which indicated that the treatment elevated the number of nucleated spleen cells recognized by the erythroid lineage-specific monoclonal antibody TER-119. A majority of TER-119+ cells also expressed CD71 and the heat stable antigen, a marker of developing hematopoietic cells as well as mature erythrocytes. The capacity of Photofrin® to stimulate murine hematopoietic activity appears to be a property not shared by other porphyrin photosensitizers.

Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π-π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15-100.81% with the RSD3.0%.

A novel electrochemical sensing platform based on magnetic field-induced self-assembly of Fe3O4@Polyaniline nanoparticles (Fe3O4@PANI NPs) has been for the first time fabricated for the sensitive detection of creatinine in biological fluids. The template molecule, creatinine, was self-assembled on the surface of Fe3O4@PANI NPs together with the functional monomer aniline by the formation of N-H hydrogen bonds. After pre-assembled, through the magnetic-induction of the magnetic glassy carbon electrode (MGCE), the ordered structure of molecularly imprinted polymers (MIPs) were established by the electropolymerization and assembled on the surface of MGCE with the help of magnetic fields by a simple one-step approach. The structural controllability of the MIPs film established by magnetic field-induced self-assembly was further studied. The stable and hydrophilic Fe3O4@PANI can not only provide available functionalized sites with which the template molecule creatinine can form hydrogen bond by the abundant amino groups in PANI matrix, but also afford a promoting pathway for electron transfer. The as-prepared molecularly imprinted electrochemical sensor (MIES) shows good stability and reproducibility for the determination of creatinine with the detection limit reached 0.35 nmol L(-1) (S/N=3). In addition, the highly sensitive and selective MIES has been successfully used for the clinical determination of creatinine in human plasma and urine samples. The average recoveries were 90.8-104.9% with RSD lower than 2.7%.

Although the corresponding carbon-metal interactions can be very different, a similar nonlinear growth behavior of graphene has been observed for different metal substrates. To understand this interesting experimental observation, a multiscale ``standing-on-the-front'' kinetic Monte Carlo study is performed. An extraordinary robust geometry effect is identified, which solely determines the growth kinetics and makes the details of carbon-metal interaction not relevant at all. Based on such a geometry-determined mechanism, the epitaxial growth behavior of graphene can be easily predicted in many cases. As an example, the orientation-sensitive growth kinetics of graphene on an Ir(111) surface has been studied. Our results demonstrate that the lattice mismatch pattern at the atomic level plays an important role in macroscopic epitaxial growth.

In this work, a highly sensitive and selective biomimetic electrochemical sensor for the amperometric detection of trace dopamine (DA) in human serums was achieved by gold nanoparticles (AuNPs) doped molecularly imprinted polymers (MIPs). Functionalized AuNPs (F-AuNPs), a novel functional monomer bearing aniline moieties on the surface of the AuNPs, were prepared via a direct synthesis method and then used to fabricate the conductive MIPs film on the modified electrode by electropolymerization method in the presence of DA and p-aminobenzenethiol (p-ATP). The obtained electrochemical sensor based on the conductive film of AuNPs doped MIPs (AuNPs@MIPs) could effectively minimize the interferences caused by ascorbic acid (AA) and uric acid (UA). The linear range for amperometric detection of DA was from 0.02 μmol L −1 to 0.54 μmol L −1 with the detection limit of 7.8 nmol L −1 (S/ N =3). Furthermore, the AuNPs@MIPs modified electrode (AuNPs@MIES) was successfully employed to detect trace DA in different human serums.

Rare events such as nucleation processes are of ubiquitous importance in real systems. The most popular method for nonequilibrium systems, forward flux sampling (FFS), samples rare events by using interfaces to partition the whole transition process into sequence of steps along an order parameter connecting the initial and final states. FFS usually suffers from two main difficulties: low computational efficiency due to bad interface locations and even being not applicable when trapping into unknown intermediate metastable states. In the present work, we propose an approach to overcome these difficulties, by self-adaptively locating the interfaces on the fly in an optimized manner. Contrary to the conventional FFS which set the interfaces with euqal distance of the order parameter, our approach determines the interfaces with equal transition probability which is shown to satisfy the optimization condition. This is done by firstly running long local trajectories starting from the current interface $\l_i$ to get the conditional probability distribution $P_c$, and then determining $\l_{i+1}$ by equalling $P_c$ to a give value $p_0$. With these optimized interfaces, FFS can be run in a much efficient way. In addition, our approach can conveniently find the intermediate metastable states by monitoring some special long trajectories that nither end at the initial state nor reach the next interface, the number of which will increase sharply from zero if such metastable states are encountered. We apply our approach to a model two-state system and a two-dimensional lattice gas Ising model. Our approach is shown to be much more efficient than the conventional FFS method without losing accuracy, and it can also well reproduce the two-step nucleation scenario of the Ising model with easy identification of the intermidiate metastable state., Comment: 6 pages, 6 figures

— This study compared the ability of highly purified resting and activated DBA/2 mouse peritoneal macrophages to survive treatment with the photosensitizer benzoporphyrin derivative (BPD, verteporfin) and light. Culture of macrophages with recombinant murine interferon-γ (rIFN-γ, 100 U/mL) for 72 h imparted a phenotypic and functional activation by dramatically increasing cell surface expression of major histocompatibility complex Class II (Ia) molecules and the formation of nitric oxide. The rIFN-γ-activated macrophages were significantly (P < 0.05) more sensitive (lethal dose to cause a 50% reduction in cell survival, LD50= 14.4 ± 1.1 ng/mL) to photodynamic killing with BPD and light (10 J/cm2) than cells (LD50= 18.2 ± 2.0 ng/mL) cultured in medium alone. In contrast, macrophages treated with different concentrations of bacterial lipopolysaccharide (LPS) were as resistant or more resistant to photodynamic killing than cells cultured in medium alone. No cytotoxic effect of BPD was detected in cultures containing the drug but protected from light. Comparable amounts of BPD were taken up in vitro by unactivated and rIFN-γ-activated macrophages, as detected by flow cytometric analysis. However, cells cultured with LPS (10 μg/mL) took up more BPD than macrophages cultured in medium alone or with rIFN-γ. The DBA/2 P815 mastocytoma cells took up greater amounts of the drug and were subsequently more vulnerable to treatment with BPD and light (LD50= 6.9 ng/mL) than macrophages cultured under any condition. The explanation for the increased vulnerability of rIFN-γ-activated macrophages and the greater resistance of LPS-activated macrophages, relative to medium-cultured macrophages, to photodynamic killing with BPD is uncertain. However, the increased susceptibility of macrophages, activated with the immunomodulatory cytokine IFN-γ, to treatment with BPD and light might indicate how photodynamic therapy could interfere with the development of experimental autoimmune disease, conditions in which activated macrophages are known to be involved.