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Pancreatic cancer is currently one of the deadliest of the solid malignancies, whose incidence and death rates are increasing consistently during the past 30 years. Ribonucleotide reductase (RR) is a rate-limiting enzyme that catalyzes the formation of deoxyribonucleotides from ribonucleotides, which are essential for DNA synthesis and replication. In this study, 23 small interfering RNAs (siRNAs) against RRM2, the second subunit of RR, were designed and screened, and one of them (termed siRRM2), with high potency and good RNase-resistant capability, was selected. Transfection of siRRM2 into PANC-1, a pancreatic cell line, dramatically repressed the formation of cell colonies by inducing remarkable cell-cycle arrest at S-phase. When combining with doxorubicin (DOX), siRRM2 improved the efficacy 4 times more than applying DOX alone, suggesting a synergistic effect of siRRM2 and DOX. Moreover, the combined application of siRRM2-loaded lipid nanoparticle and DOX significantly suppressed the tumor growth on the PANC-1 xenografted murine model. The inhibition efficiency revealed by tumor weight at the endpoint of the treatment reached more than 40%. Hence, siRRM2 effectively suppressed pancreatic tumor growth alone or synergistically with DOX. This study provides a feasible target gene, a drug-viable siRNA, and a promising therapeutic potential for the treatment of pancreatic cancer., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)

Water-soluble and non-aggregating gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan. This process remarkably enhances the dispersibility of DTT-coated AuNCs in water. The resulting AuNCs, on photoexcitation at 285 nm, display strong red emission with a maximum at 650 nm and a 23% quantum yield. Fluorescence is strongly and selectively suppressed in the presence of 6-mercaptopurine (6-MP). Photoluminescence drops linearly in the 0.1-100 μM 6-MP concentration range, and the detection limit of this assay is 0.1 μM. Other features of the modified AuNCs include a decay time of 8.56 μs, a 365 nm Stokes shift, good colloidal stability, ease of chemical modification, and low toxicity. Conceivably, these NCs may find a range of applications in biological imaging and optical sensing. Graphical abstract Highly fluorescent and water-soluble gold nanoclusters (AuNCs) were obtained by modification of the AuNCs with dithiothreitol (DTT) and then coating them with carboxylated chitosan (CC). The resulting CC/DTT-AuNCs were used for sensitive and selective detection of 6-mercaptopurine.

Electrochromic materials are widely used in smart windows. An ideal future electrochromic window would be able to control visible light transmission, tune building's heat conversion of near-infrared (NIR) solar radiation, and reduce attacks by microorganisms. To date, most of the reports have primarily focused on visible-light transmission modulation using electrochromic materials. Herein, we report the fabrication of an electrochromic-photothermal film by integrating electrochromic WO 3 with plasmonic Au nanostructures and demonstrate its adjustability during optical transmission and photothermal conversion of visible and NIR lights. The localized surface plasmon resonance (LSPR) of Au nanostructures and the broadband nonradiative plasmon decay are proposed to be tunable using both the electric field and the WO 3 substrate. Further enhanced photothermal conversion is achieved in colored state, which is attributed to coupling of traditional visible-band optical switching with NIR-LSPR extinction. The resulted electrochromic-photothermal film can also effectively reduce the numbers of attacking microorganisms, thus promising for use as a sterile smart window for advanced applications.

A novel dual-emission fluorescence ratiometric probe of luminol-Tb-GMP CPNPs for highly sensitive and selective detection of ALP and As(v) has been constructed based on the stimulus responsivity of luminol. The introduction of luminol as a ligand for Tb 3+ , combined with GMP, leads to a sensor which is more robust, sensitive, and efficient.

A novel and efficient photochemical method has been proposed for the encapsulation of Prussian blue nanoparticles (PBNPs) inside the channels of carbon nanotubes (PB-in-CNTs) in an acidic ferrocyanide solution under UV/vis illumination, and the confinement effect of CNTs on the electrochemical properties of PBNPs is systematically explored. PB-in-CNTs show a faster electron-transfer process, an enhanced electrocatalytic activity toward the reduction of H 2 O 2 , and an increased anti-base ability compared to PBNPs loaded outside of CNTs (PB-out-CNTs). In addition, PB-in-CNTs show an increased electrochemical reversibility and an unexpected diameter-independent catalytic activity with the decrease of CNT diameters. The improved electrochemical properties of PB-in-CNTs are attributed to the modified electronic properties and dimensions of PBNPs induced by the confinement effect of CNTs. This work provides further insights into the confinement effect on the properties of nanomaterials and will inspire extensive relevant investigations in the development of novel composites or excellent catalysts.

We for the first time propose a new concept where a greater enhancement in dual potential electrochemiluminescence (ECL) of a single graphene quantum dot (GQD) emitter can be achieved through the coupling between chemical and electrochemical reactions of two different coreactants of K 2 S 2 O 8 and Na 2 SO 3 .

Objective: To explore the feasibility of intraperitoneal injection of isoproterenol (ISO) to induce cardiac remodeling in FVB/N mice., Methods: Forty-eight FVB/N mice were divided into back subcutaneous saline group (subcutaneous saline group), intraperitoneal saline group, back subcutaneous ISO group (subcutaneous ISO group), and intraperitoneal ISO group according to the route of administration of saline or ISO. ISO (30 μg/g body weight/day) was given to the subcutaneous ISO group and the intraperitoneal ISO group, twice daily with an interval of 12 hours, for 14 consecutive days. The subcutaneous saline group and the intraperitoneal saline group were injected with an equal volume of saline. The left ventricular end-diastolic posterior wall thickness was measured by echocardiography, and the ratio of heart weight to tibia length was determined. Hematoxylin-eosin staining was used to determine the myocardial fiber diameter. Picric-sirius red staining was used to determine the myocardial collagen deposition area. Quantitative real-time PCR was used to measure the mRNA expression of collagen I., Results: Compared with the subcutaneous ISO, subcutaneous saline, and intraperitoneal saline groups, the intraperitoneal ISO group had increased sizes of the cardiac cavity and the heart. Compared with the subcutaneous saline and intraperitoneal saline groups, the subcutaneous ISO group showed no significant changes in the gross morphology of the cardiac cavity and the heart. The intraperitoneal ISO group showed significant increases in the ratio of heart weight to tibia length, myocardial fiber diameter, left ventricular end-diastolic posterior wall thickness, myocardial collagen area percentage, and the mRNA expression of collagen I compared with the subcutaneous ISO, subcutaneous saline, and intraperitoneal saline groups (P<0.01). There were no significant differences in the above five indices between the subcutaneous ISO group and the subcutaneous saline and intraperitoneal saline groups (P>0.05). No significant difference in the mortality rate was found between the subcutaneous ISO and intraperitoneal ISO groups (P>0.05)., Conclusions: Intraperitoneal injection of ISO can induce cardiac hypertrophy and fibrosis in FVB/N mice.

For study of the photocatalytic reaction kinetics in a confined microsystem, a photocatalysis microreactor integrated on a microfluidic device has been fabricated using an on-line UV/vis detector. The performance of the photocatalysis microreactor is evaluated by the photocatalytic degradation of Rhodamine B chosen as model target by using commercial titanium dioxide (Degussa P25, TiO 2 ) nanoparticles as a photocatalyst. Results show that the photocatalytic reaction occurs via the Langmuir-Hinshelwood mechanism and the photocatalysis kinetics in the confined microsystem (r = 0.359 min -1 ) is about 10 times larger than that in macrosystem (r = 0.033 min -1 ). In addition, the photocatalysis activity of the immobilized TiO 2 nanoparticles in the microreactor exhibits good stability under flowing conditions. The present microchip device offers an interesting platform for screening of photocatalysts and exploration of photocatalysis mechanisms and kinetics., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This report outlines a highly sensitive and facile electrochemiluminescence (ECL) sensing platform based on a novel high-quantum-yield Au-nanocluster (AuNC) probe for glutathione (GSH) detection. Owing to the prominent quenching effect of GSH on the ECL of the AuNCs, the proposed ECL nanosensor showed a wide response to GSH in the ranges of 1.0 × 10 -9 -1.0 × 10 -5 M and 1.0 × 10 -5 -1.0 × 10 -1 M and a low detection limit of 3.2 × 10 -10 M. In addition, the proposed system exhibited good selectivity for GSH in the presence of other chemical/biological interferences. Moreover, since no further functionalization of AuNC-based sensor interface was necessary, together with the stability, high sensitivity and selectivity of the proposed nanosensor, this convenient approach was able to successfully detect GSH in both of human urine samples and blood samples with excellent recoveries, which indicated its promising application under physiological conditions. Of significant importance is that this study not only helps in gaining a better understanding of the applicability of the ECL properties of AuNCs, but also provides a new avenue for the design and development of ECL sensors based on the novel high-quantum-yield AuNC-based probe and other functional-metal-based NC probes., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Construction of multifunctional photoelectrochemical energy devices is of great importance to energy saving. In this study, we have successfully prepared a mesoporous WO3 film on FTO glass via a facile dip-coating sol-gel method; the designed mesoporous WO3 film exhibited advantages including high transparency, good adhesion and high porosity. Also, multifunctional integrated energy storage and optical modulation ability are simultaneously achieved by the mesoporous WO3 film. Impressively, the mesoporous WO3 film exhibits a noticeable electrochromic energy storage performance with a large optical modulation up to 75.6% at 633 nm, accompanied by energy storage with a specific capacity of 75.3 mA h g-1. Furthermore, a full electrochromic energy storage window assembled with the mesoporous WO3 anode and PANI nanoparticle cathode is demonstrated with large optical modulation and good long-term stability. Our research provides a new route to realize the coincident utilization of optical-electrochemical energy.

Silver nanoparticles (AgNPs) have been widely used as photocatalysts and nanosensors. Observation of the spectroscopy of a single AgNP greatly helps us understand the catalytic characteristics and morphology change of the AgNP during reactions. In the present study, AgNPs physically adsorbed on indium tin oxide (ITO) conductive glass were electrochemically reduced and oxidized, and the plasmonic resonance Rayleigh scattering (PRRS) spectrum of an individual AgNP was observed under a dark-field microscopy (DFM) equipped with a spectrometer. The electrochemical oxidization of the AgNP under constant potential caused a redshift of the PRRS peak for 30±5 nm. However, electrochemical reduction of the AgNP could not make the PRRS peak completely shift back to the initial position. In situ AFM and SEM characterization confirmed that very small Ag fragments (<10 nm) formed around the AgNP core during electrochemical oxidization. Results showed that dark-field microspectroscopy could be used as a sensitive tool for estimating the morphology/structural changes of nanoparticles that can hardly be observed through the cyclic voltammograms of multiple AgNPs., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The plant Dysosma versipellis is known for its antimicrobial and anticancer properties but is a rare and vulnerable perennial herb that is endemic to China. In this study, 224 isolates were isolated from various tissues of D. versipellis, and were classified into 53 different morphotypes according to culture characteristics and were identified by sequence analyses of the internal transcribed spacer (ITS) region of the rRNA gene. Although nine strains were not assignable at the phylum level, 44 belonged to at least 29 genera of 15 orders of Ascomycota (93%), Basidiomycota (6%), and Zygomycota (1%). Subsequent assays revealed antimicrobial activities of 19% of endophytic extracts against at least one pathogenic bacterium or fungus. Antimicrobial activity was also determined using the agar diffusion method and was most prominent in extracts from four isolates. Moreover, high performance liquid chromatography (HPLC) and ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry analyses (UPLC-QTOF MS) showed the presence of podophyllotoxin in two Fusarium strains, with the highest yield of 277 μg/g in Fusarium sp. (WB5121). Taken together, the present data suggest that various endophytic fungi of D. versipellis could be exploited as sources of novel natural antimicrobial or anticancer agents.

Luminescent copper nanoclusters (CuNCs) constitute a very active research topic due to their unique properties and lower cost than gold and silver NCs. In this study, we report a new, facile, and rapid top-down etching method for synthesizing luminescent CuNCs, using Cu nanoparticles (CuNPs) as the precursor and ammonia (NH3) as the etchant. The etching mechanism is systematically investigated and the optical and structural properties of the obtained CuNCs are carefully studied. The NH3-triggered etching process is very fast and the newly generated CuNCs can emit strong green fluorescence with a high quantum yield. Moreover, by coupling the urease-catalyzed hydrolysis of urea with the NH3-induced etching of CuNPs, we developed a novel fluorescence turn-on assay for urea. The linear range for urea detection is from 0.25 to 5 mM, and the limit of detection is 0.01 mM. This novel sensing approach, with good sensitivity and excellent selectivity, is then successfully utilized to detect urea in human serum samples, demonstrating its great potential in clinical diagnosis. In addition, the proposed coupling method can be extended to monitor other analytes that influence the size-focusing etching process, allowing metal NCs to be used to construct diverse chemosensors and biosensors.

Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single-molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au-Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency. On the basis of the experimental results and digital simulation, it was concluded that a concentration difference arose at the asymmetric bimetallic interface according to different heterogeneous electron-transfer rate constants at Au and Pt. The fluid slip around the Janus particle enhanced local redox reactions and protected the particle surface from passivation., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A versatile and sensitive platform for label-free bioanalysis has been proposed on the basis of attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) using Au/ZnSe as the enhancement substrate that allows a wide spectral range down to 700 cm -1 . Au nanoparticles are stably deposited on the surface of a ZnSe prism due to the formation of Au-Se bonds via electroless deposition, and the enhancement factor of the resultant Au/ZnSe substrate is about 2 times larger than that of the commonly used Au/Si substrate. As a demonstration, the Au/ZnSe-based SEIRAS has been applied to obtain abundant structural information in the fingerprint region and quantitative analysis of various biomolecular interactions such as DNA hybridization and immunoreaction without any labeling process.

Naringin, as a component universal existing in the peel of some fruits or medicinal plants, was usually selected as the material to synthesise bioactive derivates since it was easy to gain with low cost. In present investigation, eight new acacetin-7-O-methyl ether Mannich base derivatives (1-8) were synthesised from naringin. The bioactivity evaluation revealed that most of them exhibited moderate or potent acetylcholinesterase (AChE) inhibitory activity. Among them, compound 7 (IC 50 for AChE = 0.82 ± 0.08 μmol•L -1 , IC 50 for BuChE = 46.30 ± 3.26 μmol•L -1 ) showed a potent activity and high selectivity compared with the positive control Rivastigmine (IC 50 for AChE = 10.54 ± 0.86 μmol•L -1 , IC 50 for BuChE = 0.26 ± 0.08 μmol•L -1 ). The kinetic study suggested that compound 7 bind to AChE with mix-type inhibitory profile. Molecular docking study revealed that compound 7 could combine both catalytic active site (CAS) and peripheral active site (PAS) of AChE with four points (Trp84, Trp279, Tyr70 and Phe330), while it could bind with BuChE via only His 20.

The development of simple yet powerful methods for monitoring enzyme activity is of great significance. Herein, a facile, convenient, cost-effective, and continuous fluorescent method for the detection of arginase and its inhibitor has been reported based on a host-guest interaction-controlled and enzymatic hydrolysis-controlled luminescent nanoswitch. The fluorescence intensity of 6-aza-2-thiothymine-stabilized gold nanoparticle (ATT-AuNP) is enhanced by l-arginine, owing to the formation of a supramolecular host-guest assembly between the guanidine group of l-arginine and ATT molecules capped on the AuNP surface. However, hydrolysis of l-arginine, catalyzed by arginase, leads to a decrease in the fluorescence intensity of l-arginine/ATT-AuNPs hybrids. Upon incorporation of the arginase inhibitor l-norvaline, the fluorescence of the ATT-AuNP-based detecting system is restored. The linear range of arginase activity determination is from 0.0625 to 1.15 U/mL and the limit of detection is 0.056 U/mL. The half-maximal inhibition value IC 50 of l-norvaline is determined to be 5.6 mM. The practicability of this luminescent nanoswitch is validated by assaying the arginase activity in rat liver and monitoring the response of rat liver arginase to pharmacological agent. Compared to the existing fluorescent method of arginase activity assay, the approach demonstrated here does not involve any complicated technical manipulation, thereby greatly simplifying the detection steps. We propose that this AuNP-based luminescent nanoswitch would find wide applications in the field of life sciences and medicine.

Nanochannel/nanopre based analysis methods have attracted increasing interest in recent years due to their exquisite ability to reveal changes in molecular volume. In this work, a highly asymmetric nanochannel-ionchannel hybrid coupled with an electrochemical technique was developed for copper ion (Cu 2+ ) detection. Polyglutamic acid (PGA) was modified in a nanochannel array of porous anodic alumina (PAA). When different concentrations of Cu 2+ were introduced into the nanochannel-ionchannel hybrid in a neutral environment, a Cu 2+ -PGA chelation reaction occurs, resulting in varied current-potential (I-V) properties of the nanochannel-ionchannel hybrid. When PAA was immersed in a low pH solution, the Cu 2+ -PGA complex dissociated. On the basis of the change in ionic current, a label-free assay for Cu 2+ was achieved along with the ability to regenerate and reuse the constructed platform. Because of the unique mass transfer property of the nanochannel-ionchannel hybrid combined with the highly amplified ionic current magnitude of the nanochannel array, significantly increased assay sensitivity was achieved, as expected. To evaluate the applicability of the present methodology for detecting Cu 2+ in a real sample, the Cu 2+ content in real blood samples was analyzed. The results demonstrate that the present method shows excellent selectivity with high sensitivity toward Cu 2+ detection in real blood samples.

Self-assembled monolayer (SAM) has been extensively applied as ideal interface layer for construction of biosensors. Its chain length and end functional groups determine the physical and chemical properties of the modified surfaces, which will affect the performance of constructed biosensors. Herein, we studied the influence of chain length of n-alkanethiols SAMs on the immunoreaction kinetics employing attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). Antibody (rabbit immunoglobulin) is assembled on carboxyl terminated SAMs of n-alkanethiols with different chain lengths (n = 3, 6, 11, 16). The whole fabrication steps of the immunoassay can be monitored in situ by the ATR-SEIRAS. From the time-dependent SEIRA spectra, the interfacial immunoreaction kinetics between the immobilized antibody and antigen (goat anti-rabbit immunoglobulin) can be evaluated. We found that the immunoreaction became faster with increasing the chain length of SAMs. This chain length dependent kinetics might be attributed to different orientations of the assembled antibody caused by different packing densities of SAMs. The present research offers a sensing platform to evaluate immunoassay kinetics and provides fundamentals for construction of immunoassay with high performance., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A novel microfluidic method for measuring liquid interfacial tension using monodisperse microbubbles generated in situ has been proposed. Instead of bulky gas supply used in traditional microfluidic devices, microbubbles are efficiently generated via water electrolysis in the devices. Since the bubble formation frequency is related to the interfacial tension of liquids used, thus, precisely measuring the interfacial tension of liquids in microfluidics can be achieved. In addition, it is found that during the microbubble formation, the electrochemical potential fluctuates regularly at controlled electrolysis current, and the fluctuating period depends on the microbubble generation rate. Therefore, the change in electrochemical potential can be directly used to monitor the bubble formation process, which avoids the use of an external optical detection system. As demonstration, the interfacial tension of isopentanol solutions with different concentrations was measured, and the results show good agreement with the ones obtained using the maximum bubble pressure method, confirming the accuracy of the present method. The proposed strategy offers a simple, low cost and accurate solution to measure the liquid interfacial tension confined in microfluidic channels. The present platform is easily constructed and facilely manipulated in common laboratories, which is expected to be widely used in microfluidic-based research and application fields., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Electrochemical biosensors based on enzymatic reaction have been applied to a wide range of fields. As the trend continues to grow, these biosensors are approaching the limit imposed by physics and chemistry. To further improve the performance of biosensors, the interplay of mass transport and enzymatic reaction kinetics, especially in enzyme cascade systems, should be considered in the design of biosensors. Herein, we propose a simple approach to studying the influence of mass transport and enzyme molecule motion on the kinetics of enzyme cascade reactions. β-Galactosidase (β-Gal) and glucose oxidase (GOx) of the enzyme cascade reaction are precisely immobilized onto the disk and ring electrodes, respectively, of a rotating ring-disk electrode (RRDE) via covalent attachment. At a low rotating speed (<600 rpm), convective transport promotes the enzyme cascade reaction. When the rotating speed is higher than 600 rpm, the cascade reaction becomes kinetically controlled. Further increase of the rotating speed results in a slow decline in reaction rate, possibly due to the production inhibition effect. In addition, the effect of conformation change of the enzyme at higher centrifugal forces on enzyme activity should be considered. This study would shine light on the effect of convective force on regulation of kinetics of enzyme cascade reaction, offering an ideal platform for studying other enzyme cascade reactions and providing fundamentals to design high-performance biosensors, biofuel cells, and bioelectronics.

A new series of tertiary amine derivatives of chlorochalcone (4a∼4l) were designed, synthesized and evaluated for the effect on acetylcholinesterase (AChE) and buthylcholinesterase (BuChE). The results indicated that all compounds revealed moderate or potent inhibitory activity against AChE, and some possessed high selectivity for AChE over BuChE. The structure-activity investigation showed that the substituted position of chlorine significantly influenced the activity and selectivity. The alteration of tertiary amine group also leads to obvious change in bioactivity. Among them, IC 50 of compound 4l against AChE was 0.17 ± 0.06 µmol/L, and the selectivity was 667.2 fold for AChE over BuChE. Molecular docking and enzyme kinetic study on compound 4l suggested that it simultaneously binds to the catalytic active site (CAS) and peripheral anionic site (PAS) of AChE. Further study showed that the pyrazoline derivatives synthesized from chlorochalcones had weaker activity and lower selectivity in inhibiting AChE compared to that of chlorochalcone derivatives.

It is desirable but challenging to assemble various biomimetic properties into a functional catalytic cascade system. In this work, cupric oxide nanoparticles were investigated as oxidase mimics for the aerobic oxidation of cysteine to cystine with the generation of hydrogen peroxide. Coupling this property with the peroxidase-like activity of CuO nanoparticles, we constructed a self-organized cascade reaction system based on a single-component nanozyme, which includes the oxidation of cysteine to yield cystine and hydrogen peroxide and the hydrogen peroxide-mediated oxidation of terephthalic acid to produce a fluorescence change. Based on this artificial enzymatic cascade reaction system, a fluorometric assay method with a low detection limit of 6.6nM was established for cysteine determination. This platform was then applied for the detection of cysteine in pharmaceutical products and human plasma, which yielded satisfactory results. Our investigations open up a new route and holds promise for the development and applications of multifunctional nanomaterials as enzyme mimics., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Metal-organic frameworks (MOFs) have been successfully used as efficient quenchers for fluorescent DNA detection. However, the surface charge property of MOFs can inevitably affect their fluorescence quenching behavior. Herein, nanoscale MOFs (NMOFs), including MOF nanosheets and nanoparticles, have been employed to investigate the relationship between the fluorescence quenching and surface properties of NMOFs. We find that the positively and negatively charged NMOFs exhibited totally opposite fluorescence quenching properties toward negatively charged FAM-labeled double-stranded DNA (dsDNA). On the contrast, they show negligible influence on the sensing of positively charged TAMRA-labeled dsDNA. This study provides a new insight of the fluorescence quenching property of NMOFs and offers a new concept for construction of ratiometric fluorescence DNA biosensors.

Water-splitting devices for hydrogen generation through electrolysis (hydrogen evolution reaction, HER) hold great promise for clean energy. However, their practical application relies on the development of inexpensive and efficient catalysts to replace precious platinum catalysts. We previously reported that HER can be largely enhanced through finely tuning the energy level of molybdenum sulfide (MoS 2 ) by hot electron injection from plasmonic gold nanoparticles. Under this inspiration, herein, we propose a strategy to improve the HER performance of MoS 2 by engineering its energy level via direct transition-metal doping. We find that zinc-doped MoS 2 (Zn-MoS 2 ) exhibits superior electrochemical activity toward HER as evidenced by the positively shifted onset potential to -0.13 V vs RHE. A turnover of 15.44 s -1 at 300 mV overpotential is achieved, which by far exceeds the activity of MoS 2 catalysts reported. The large enhancement can be attributed to the synergistic effect of electronic effect (energy level matching) and morphological effect (rich active sites) via thermodynamic and kinetic acceleration, respectively. This design opens up further opportunities for improving electrocatalysts by incorporating promoters, which broadens the understanding toward the optimization of electrocatalytic activity of these unique materials.

With the growing demands of the early, accurate, and sensitive diagnosis for cancers, the development of new diagnostic technologies becomes increasingly important. In this study, we proposed a strategy for efficient capture and sensitive detection of circulating tumor cells (CTCs) using an array nanochannel-ion channel hybrid coupled with an electrochemical detection technique. The aptamer probe was immobilized on the ion channel surface to couple with the protein overexpressed on the CTCs membrane. Through this special molecular recognition, CTCs can be selectively captured. The trapped CTCs cover the ion channel entrance efficiently, which will dramatically block the ionic flow through channels, resulting in a varied mass-transfer property of the nanochannel-ion channel hybrid. On the basis of the changed mass-transfer properties, the captured CTCs can be sensitively detected using the electrochemical linear sweep voltammetry technique. Furthermore, due to the amplified response of array channels compared to that of a single channel, the detection sensitivity can be enhanced greatly. The results showed that acute leukemia CCRF-CEM (a type of CTC) concentration as low as 100 cells mL -1 can be successfully captured and detected. The present method provides a simple, sensitive, and label-free technique for CTCs capture, detection, and release, which would hold great potential in the early clinical diagnosis and treatment of cancers.

An electrochemical sensor using ultralight and porous copper-nitrogen-doped graphene (CuNRGO) nanocomposite as the electrocatalyst has been constructed to simultaneously determine DNA bases such as guanine (G) and cytosine (C), adenine (A), and thymine (T). The nanocomposite is synthesized by thermally annealing an ice-templated structure of graphene oxide (GO) and Cu(phen) 2 . Because of the unique structure and the presence of Cu 2+ -N active sites, the CuNRGO exhibits outstanding electrocatalytic activity toward the oxidation of free DNA bases. After optimizing the experimental conditions, the CuNRGO-based electrochemical sensor shows good linear responses for the G, A, T, and C bases in the concentration ranges of 0.132-6.62 μM, 0.37-5.18 μM, 198.2-5551 μM, and 270.0-1575 μM, respectively. The results demonstrate that CuNRGO is a promising electrocatalyst for electrochemical sensing devices.

The effective capture and release of circulating tumor cells (CTCs) is of significant importance in cancer prognose and treatment. Here we report a highly efficient method to capture and release human leukemic lymphoblasts (CCRF-CEM) using aptamers modified gold nanowire arrays (AuNWs). The gold nanowires, showing tunable morphologies from relatively random pillar deposit to relatively uniform arrays, were fabricated by electrochemical deposition using anodic aluminum oxide (AAO) as template. Upon simply being modified with aptamers by Au-S chemistry, the AuNWs exhibit higher specificity to target cells. Also compared to flat gold substrate, the AuNWs with nanostructure can capture target cells with much higher capture yield. Moreover, the captured CCRF-CEM cells can be released from AuNWs efficiently with little damage through an electrochemical desorption process. We predict that our strategy has great potential in providing a simple and economical platform for CTCs isolation, cancer diagnosis, and therapy.

We herein report the intrinsic alkaline peroxidase-like activity exhibited by CuO nanoparticles when 3-(4-hydroxyphenyl)propionic acid was employed as a substrate. Based on this observation, a fluorometric assay method with a low detection limit of 0.81 μM was established for H 2 O 2 determination under alkaline conditions. Notably, ammonia was found to inhibit the alkaline peroxidase-like activity of the CuO nanoparticles. Thus, a sensing platform for the determination of urea and urease was successfully constructed, with the limits of detection for urea and urease being 27 μM and 2.6 U L -1 , respectively. This platform was then applied for the detection of urea in human urine and urease in soil, which yielded satisfactory results. These results suggest that it is possible to extend the catalytic potential of peroxidase and its mimetics from acidic and neutral conditions to include activity in alkaline media as well. Furthermore, this strategy is a novel method for the analysis of urea and urease. The assay developed in this work is facile, inexpensive, convenient, and highly selective and sensitive. Therefore, it is expected that this system can serve as a template for the development of similar enzyme nano-mimics.

Nanopore structures have been successfully employed in next-generation DNA sequencing. For more complicated protein which normally contains 20 different amino acids, identifying the fluctuation of ionic current caused by different amino acids appears inadequate for protein sequencing. Therefore, it is highly desirable to develop size-controllable nanopores with optical activity that can provide additional structural information. Herein, we discovered the novel nanopore properties of the self-assembled ultramicroelectrodes originally developed by Bard and co-workers. Using a slightly modified method, the self-assembly of 7 ± 1 nm gold nanoparticles (AuNPs) can be precisely controlled to form a gold nanoporous sphere (GPS) on the tip of a glass capillary. Different dithiol linker molecules (1,3-propanedithiol, C3; 1,6-hexanedithiol, C6; and 1,9-nonanedithiol, C9) reproducibly led to rather similar nanopore sizes (5.07 ± 0.02, 5.13 ± 0.02, and 5.25 ± 0.01 nm), respectively. The GPS nanostructures were found to exhibit high ionic current rectification as well as surface-enhanced Raman scattering (SERS) activity due to the presence of nanopores and numerous "hot spots" among the cross-linked AuNPs on the surface of GPS. The rectification effect of the small nanopores was observed even under high concentration of electrolyte (290 mM), along with SERS enhancement factors well above 1 × 10 5 . The GPS nanostructures were successfully applied for SERS-based detection of glutathione from a single HeLa cell.

Intraorgan targeting of chemical drugs at tumor tissues is essential in the treatment of solid tumors that express the same target receptor as normal tissues. Here, asialoglycoprotein receptor (ASGP-R)-targeting paclitaxel-conjugated gold nanoparticles (Gal/PTX-GNPs) are fabricated as a demonstration to realize the precise treatment of liver cancer. The enhanced biological specificity and therapeutic performance of drugs loaded on nanoparticles not only rely on the ligands on carriers for receptor recognition but are also determined by the performance of gold conjugates with designed structure. The tumor cell selectivity of the designed conjugates in liver tumor (HepG2) cells is close to six times of that incubated with control conjugates without galactose modification in liver normal (L02) cells. The drug level in tumor versus liver of Gal/PTX-GNPs is 121.0% at 8 h post injection, a 15.7-fold increase in the tumor specificity compared to that of GNPs conjugated with PTX only. This intraorgan-targeting strategy results in a considerable improvement of performance in treating both Heps heterotopic and orthotopic xenograft tumor models, which is expected to be used for the enhanced antitumor efficacy and reduced hepatotoxicity in liver cancer treatment.

Single cell analysis is essential for understanding the heterogeneity, behaviors of cells, and diversity of target analyte in different subcellular regions. Nucleolin (NCL) is a multifunctional protein that is markedly overexpressed in most of the cancer cells. The variant expression levels of NCL in subcellular regions have a marked influence on cancer proliferation and treatments. However, the specificity of available methods to identify the cancer biomarkers is limited because of the high level of subcellular matrix effect. Herein, we proposed a novel technique to increase both the molecular and spectral specificity of cancer diagnosis by using aptamers affinity based portable nanopipette with distinctive surface-enhanced Raman scattering (SERS) activities. The aptamers-functionalized gold-coated nanopipette was used to capture target, while p-mercaptobenzonitrile (MBN) and complementary DNA modified Ag nanoparticles (AgNPs) worked as Raman reporter to produce SERS signal. The SERS signal of Raman nanotag was lost upon NCL capturing via modified DNA aptamers on nanoprobe, which further helped to verify the specificity of nanoprobe. For proof of concept, NCL protein was specifically extracted from different cell lines by aptamers modified SERS active nanoprobe. The nanoprobes manifested specifically good affinity for NCL with a dissociation constant K d of 36 nM and provided a 1000-fold higher specificity against other competing proteins. Furthermore, the Raman reporter moiety has a vibrational frequency in the spectroscopically silent region (1800-2300 cm -1 ) with a negligible matrix effect from cell analysis. The subcellular localization and spatial distribution of NCL were successfully achieved in various types of cells, including MCF-7A, HeLa, and MCF-10A cells. This type of probing technique for single cell analysis could lead to the development of a new perspective in cancer diagnosis and treatment at the cellular level.

Capping molecules on the surface of nanomaterials not only enhance the dispersion and stability of nanomaterials but also greatly facilitate their surface modification and biological applications. However, most capping molecules can severely block the active sites of the catalytic core, thereby decreasing the enzymatic activity of nanomaterial-based enzyme mimics. This work demonstrates the superiority of chitosan (Ch) as a capping molecule for synthesizing catalytic platinum nanoparticles (PtNPs). The experimental results show that Ch simultaneously exhibits an excellent stabilizing effect and enhances the oxidase-like activity of PtNPs. Kinetic studies indicate that Ch-PtNPs have a higher affinity for 3,3',5,5'-tetramethylbenzidine (TMB) than other kinds of oxidase mimics. Furthermore, the TMB chromogenic reaction catalyzed by Ch-PtNPs is found to be much faster in an acidic medium, thus adapting well to the optimal pH for acid phosphatase (ACP). Therefore, a novel colorimetric approach for ACP determination is developed for the first time, which is based on the Ch-PtNP-catalyzed oxidation of TMB, the inhibitory effect of ascorbic acid (AA) on the oxidase-like activity of Ch-PtNPs, and the ACP-catalyzed hydrolysis of AA 2-phosphate (AAP) into AA. The linear range for ACP is 0.25-2.5 U L -1 and the limit of detection is measured to be 0.016 U L -1 . This new colorimetric method is utilized to detect ACP in real biological samples and to screen ACP inhibitors. We believe that these new PtNPs, which exhibit high colloidal stability, excellent catalytic performance, good biocompatibility, simple preparation, and easy modification, can be promising candidates for a broad range of applications in optical sensing, environmental monitoring, clinical diagnosis, and drug discovery.

Direct photocatalysis making use of plasmonic metals has attracted significant attention due to the light-harnessing capabilities of these materials associated with localized surface plasmon resonance (LSPR) features. Thus far, most reported work has been limited to plasmon-induced chemical transformations. Herein, we demonstrate that electrochemical reactions can also be accelerated by plasmonic nanoparticles upon LSPR excitation. Using glucose electrocatalysis as a model reaction system, the direct plasmon-accelerated electrochemical reaction (PAER) on gold nanoparticles is observed. The wavelength- and solution-pH-dependent electrochemical oxidation rate and the dark-field scattering spectroscopy results confirm that the hot charge carriers generated during plasmon decay are responsible for the enhanced electrocatalysis performance. Based on the proposed PAER mechanism, a plasmon-improved glucose electrochemical sensor is constructed, demonstrating the enhanced performance of the non-enzyme sensor upon LSPR excitation. This plasmon-accelerated electrochemistry promises potential applications in (bio)electrochemical energy conversion, electroanalysis, and electrochemical devices.

In this work, bimetallic Bi/Pt nanoparticles in bovine serum albumin biomolecular scaffold (BSA-Bi/PtNPs) were synthesized through a facile and green method. As compared with BSA-PtNPs, the BSA-Bi/PtNPs possess enhanced peroxidase-like catalytic activity. Moreover, the BSA-Bi/PtNPs are stable in harsh conditions such as high temperature, extreme pH environments, and high ionic strength, as well as in common biological matrixes. These prominent advantages enable the BSA-Bi/PtNPs to be applied to a wide range of fields. Bioassays, such as serum glucose detection, extracellular hydrogen peroxide (H 2 O 2 ) monitor, and cancer cells labeling, have been realized with satisfying results. The linear range of glucose determination was from 1 to 100 μM and the limit of detection (LOD) was 0.2 μM. The H 2 O 2 released from each MCF-7 cell after stimulation was calculated to be 2.66 × 10 -16  mol/s. By utilizing folic acid as a recognition element, tumor cell could be readily distinguished by BSA-Bi/PtNPs and the LOD for MCF-7 cell detection was 90 cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Enzyme mimics have been widely used as alternatives to natural enzymes. However, the catalytic performances of enzyme mimics are often decreased due to different spatial structures or absence of functional groups compared to natural enzymes. Here, we report a highly efficient enzyme-like catalytic performance of gold nanoparticles (AuNPs) by visible-light stimulation. The enzyme-like reaction is evaluated by the catalytic reaction of AuNPs oxidizing a typical chromogenic substrate 3,3',5,5'-tetramethylbenzydine (TMB) with hydrogen peroxide as an oxidant. From investigations of the wavelength-dependent reaction rate, radical capture, hole-donor addition, and dark-field scattering spectroscopy experiments, it is revealed that the strong plasmonic absorption of AuNPs facilitates generation of hot electrons, which are transfered from AuNPs to the adsorbed reactant molecule, greatly promoting the catalytic performance of the enzyme-like catalytic reaction. The present work provides a simple method for improving the performance of enzyme mimics, which is expected to find further application in the field of plasmon-enhanced biocatalysis and biosensors., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Polygoni Multiflori Radix is the dried root of Polygonum multiflorum Thunb officially recorded in the Chinese Pharmacopoeia as HeShouWu (HSW) in Chinese pinyin. The processed HSW are commonly used in TCM to treat liver disease and Chinese Pharmacopoeia has described the actions of it to tonify liver-kidney, replenish essence and blood, blacken beard and hair, strengthen sinew and bone, and resolve turbidity and lower lipid hence making it use not only as a herbal medicine in TCM but also as supplementary food in health care., Aim of the Study: Concerns about the hepatotoxicity in association with Polygoni Multiflori Radix and its processed products have been reported in some countries. In the present study, we aim to investigate the potential hepatotoxicity of HSW in rats with oral administration of 95% ethanol-extracts of Polygoni Multiflori Radix by using metabolomics method., Materials and Methods: Here, male rats with 150-180g body weight were received vehicle control or Polygoni Multiflori Radix extracts (HSW-Ex) orally at 19.2 (low dose), 192 (medium dose), or 1920mg/kg/day (high dose), respectively, for 28 consecutive days. Signs of HSW-induced toxicity were monitored by traditional toxicity assessments (e.g., clinical pathology and histopathology). Metabolomics investigation of serum was performed to identify potential endogenous metabolites which may be relevant to liver injury., Results: Rats received High and Medium dose of HSW-Ex showed greater sign of liver injury with increased levels of ASP, ALT, and AST, as well as reduced SOD activity when compared to vehicle control. In contrast, there are no significant changes relevant to liver injury observed in rats by receiving the low dose of HSW-Ex. Metabolomics analyses have identified ten potential endogenous metabolites varied significantly among the treatment groups with varying doses of HSW-Ex, of which might be related to liver injury., Conclusion: Our data has further suggested that liver damage resulting from HSW-Ex consumption is dosage dependent in rats. It is possible that disruption in amino acid and energy metabolism might lead to subsequent oxidative damage in the liver of rats. Because the clinic practice often use low dose in a short time, therefore HSW usage in TCM still keep safe currently, but we present a warning to the clinical doctors and make them has some concern about high dose of HSW usage in a long term that has potential danger to damage liver., (Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.)

A crack-free sub-nanometer composite structure for the study of ion transfer was constructed by in situ growth of ZIF-90 [Zn(ICA) 2 , ICA=Imidazole-2-carboxaldehyde] on the tip of a glass nanopipette. The potential-driven ion transfer through the sub-nanometer channels in ZIF-90 is strongly influenced by the pH of the solution. A rectification ratio over 500 is observed in 1 m KCl solution under alkaline conditions (pH 11.58), which is the highest value reported under such a high salt concentration. Fluorescence experiments show the super-high rectification ratio under alkaline conditions results from the strong electrostatic interaction between ions and the sub-nanometer channels of ZIF-90. In addition to providing a general pathway for further study of mass-transfer process through sub-nanometer channels, the approach enable all kinds of metal-organic frameworks (MOFs) to be used as ionic permselectivity materials in nanopore-based analysis., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Objective: Liver cancer severely threatens public health. Molecular targeted treatment is the further of cancer treatment. The functional role of Sir-related enzymes 4 (sirtuin 4) in treating liver cancer still requires further investigation. This study aimed to elucidate the effect of sirtuin 4 on aging of SMCC7721 liver cancer cell line, to underlying molecular mechanism and potential application in clinics., Materials and Methods: Adriamycin-induced aging model was established on SMCC7721 liver cancer cell line. Sirtuin 4 over-expression or siRNA plasmid was transfected. Cell aging was measured by β-galactosidase approach. Aging-related proteins P53 and P16 were quantified in Western blot, which also examined activation of Janus kinase 2 (JAK2) signal pathway. CP-690550 was used to suppress JAK2 signal pathway for measuring aging status of SMCC7721 cells., Results: In aged SMCC7721 cells, sirtuin 4 was up-regulated, whilst P53 and P16 protein levels were elevated, in accompanied with JAK2/STAT3 signal pathway. Transfection of sirtuin 4 over-expression plasmid or siRNA increased or decreased sirtuin 4 expression. Adriamycin-induced aging was enhanced or suppressed, accompanied with inhibited or potentiated JAK2 signal pathway in sirtuin 4 up-regulation or down-regulation cells, respectively. The usage of JAK2 signal inhibitor, CP-690550, enhanced Adriamycin-induced cell aging., Conclusions: Sirtuin 4 facilitates Adriamycin-induced aging of SMCC7721 liver cancer cells via inhibiting JAK2/STAT3 signal pathway, thus providing one novel anti-cancer strategy.

Objective: To assess the influence of the different exercise intervention mode, aerobic exercise training(AET), resistance training(RT) and AET RT, on blood glucose of pre-diabetes., Methods: Literatures were identified from the PubMed, EMBASE, EBSCO, CNKI and Wanfang databases. Relevant journals or conference proceedings were also searched manually. The qualities of randomized con-trolled trials that conformed to inclusion criteria were evaluated. Meta-analysis of the obtained related data was completed utilizing RevMan 5.2 statistical software. Mean difference of index related in exercise intervention groups and control group were calculated across the studies., Results: Eight original literatures enrolled in this study. Compared with control group, combined effect of different exercise interventions on fast-ing blood glucose showed no significant, consistent with different intervention subgroups analysis. RT group and AET + RT group showed a sig-nificantly reduced role on 2 h postprandial blood index ( P < 0.05). AET group showed a significantly reduced role on insulin resistance in-dex., Conclusions: To pre-diabetic, effects of exercise on postprandial 2 h blood glucose and insulin resistance index are related to modes of ex-ercise. Effects of exercise on fasting blood glucose, but still could not be determined.

In the work, we showed that the use of nanoemitters (tip dimension <1 μm, typically ∼100 nm) could dramatically reduce the nonspecific metal adduction to peptide or protein ions as well as improve the matrix tolerance of electrospray ionization mass spectrometry (ESI-MS). The proton-enriched smaller initial droplets are supposed to have played a significant role in suppressing the formation of metal adduct ions in nanoemitters. The proton-enrichment effect in the nanoemitters is related to both the exclusion-enrichment effect (EEE) and the ion concentration polarization effect (ICP effect), which permit the molecular ions to be regulated to protonated ones. Smaller initial charged droplets generated from nanoemitters need less fission steps to release the gas-phase ions; thus, the enrichment effect of salt was not as significant as that of microemitters (tip dimension >1 μm), resulting in the disappearing of salt cluster peaks in high mass-to-charge (m/z) region. The use of nanoemitters demonstrates a novel method for tuning the distribution of the metal-adducted ions to be in a controlled manner. This method is also characterized by ease of use and high efficiency in eliminating the formation of adduct ions, and no pretreatment such as desalting is needed even in the presence of salt at millimole concentration.

Water molecules possess discontinuous properties in confined surroundings as compared to the bulk, their transport velocity shows a step change with the increase in the radius of hydrophobic carbon nanotubes (CNTs). Here, we report that the chain of water molecules in CNTs behaves as a "spring" owing to hydrogen bonding. Thus, the transport of water molecules in confined systems proceeds as a wave motion with eigen frequencies in the terahertz region which is determined by the CNT size. Water velocities derived from molecular dynamics (MD) fit well with the ones from finite element methods (FEM) on consideration of both the no-slip and slip boundary conditions for CNT diameters less than 1 nm and more than 1 nm, respectively. The present work helps clarify the features of mass and momentum transfers in confined surroundings, and provides perspectives for mass transfer applications.

Co 2+ ions encapsulated in nitrogen doped graphene were applied as an oxygen evolution catalyst. Their redox potentials were tuned using different counter anions as liable ligands, and the redox potential related catalytic rates were explored. It was proposed that the electron density of Co 2+ ions was a general descriptor for activity.

Metal-encapsulated nitrogen-doping porous carbonaceous materials (NDPCs) prepared from metalloporphyrin-based covalent organic frameworks (MP-COFs) have become very promising candidates for highly effective oxygen reduction electrocatalysts. To enhance the ORR performance and durability of these NDPCs in novel energy conversion and storage devices, we develop a new type of metal-encapsulated NDPCs (HBY-COF-900) composed of FeN 4 active sites by introduction of metalloporphyrin into porous COFs. Comparable to the benchmark 20% Pt/C, HBY-COF-900 in acidic solutions exhibits higher oxygen reduction electrocatalytic activity, long-term durability, and good CO tolerance. These properties can be attributed to a synergistic effect of FeN 4 active sites, high graphitization, and porous structure. This work opens an avenue for the development of metal-encapsulated NDPCs from three-dimensional polyporphyrin prepared by one-step polymerization.

This paper reports a new and facile method for the synthesis of water-soluble thiolate-protected AuNCs via protein-ligand interaction. Using 3-mercaptopropionic acid (MPA) as a model ligand and bovine serum albumin (BSA) as a model protein, water-soluble AuNCs (BSA/MPA-AuNCs) with intense orange-yellow fluorescent emission (quantum yield=16%) are obtained. Results show that AuNCs produced with this method have hydrophobic interactions with BSA. The synthetic strategy is then successfully extended to produce water-soluble AuNCs protected by other thiolates. Moreover, a sensitive and eco-friendly sensing system is established for detection of the activity of inorganic pyrophosphatase (PPase), which relies on the selective coordination of Fe(3+)with BSA/MPA-AuNCs, the higher affinity between pyrophosphate (PPi) and Fe(3+), and the hydrolysis of PPi by PPase. A good linearity between the fluorescence intensity and PPase activity within the range from 0.1 to 3U/L is found, with a detection limit down to 0.07U/L. Additionally, the fluorescent assay developed here is utilized to assay the PPase activity in real biological samples and as well as to evaluate PPase inhibitor, illustrating the great potential for biological analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

To study the tissue distribution of galactosyl daphnoretin liposomes in rats. At the dose of 10 mg•kg⁻¹, daphnoretin solution, daphnoretin liposomes, and galactosyl daphnoretin liposomes were administered to healthy SD rats via tail vein injection. The blood and tissue of heart, liver, spleen, lung, kidney, stomach, small intestine, brain and thymus were collected at 5, 15, 30, 45, 60, 120, 240, 360 min after administration. The concentrations of daphnoretin in plasma and tissue samples were determined by HPLC. The results showed that galactosyl daphnoretin liposomes group had the highest concentration of daphnoretin in liver of unit weight at different time points; and at all of the time points, the target index DTI values of galactosyl daphnoretin liposomes to liver were greater than that of daphnoretin liposomes. Compared with daphnoretin solution, the AUC0-6 and Cmax of galactosyl daphnoretin liposomes in liver were 2.23, 5.22 times, respectively. This indicated that galactosyl daphnoretin liposomes can be concentrated at liver, with a significant liver targeting effect., Competing Interests: The authors of this article and the planning committee members and staff have no relevant financial relationships with commercial interests to disclose., (Copyright© by the Chinese Pharmaceutical Association.)

The spatial positioning of enzymes and mass transport play crucial roles in the functionality and efficiency of enzyme cascade reactions. To fully understand the mass transport regulating kinetics of enzyme cascade reactions, we investigated the contribution of convective and diffusive transports to a cascade reaction of β-galactosidase (β-Gal)/glucose oxidase (GOx) confined in a microchannel. β-Gal and GOx are assembled on two separated gold films patterned in a polydimethylsiloxane (PDMS) microchannel with a controllable distance from 50 to 100 μm. Experimental results demonstrated that the reaction yield increases with decreasing distance between two enzymes and increasing substrate flow rate. Together with the simulation results, we extracted individual reaction kinetics of the enzyme cascade reaction and found that the reaction rate catalyzed by β-Gal occurred much faster than by GOx, and thus, the β-Gal catalytic reaction showed diffusion controll, whereas the GOx catalytic reaction showed kinetic controll. Since the decrease in the enzymes distance shortens the transport length of intermediate glucose to GOx, the amount of glucose reaching GOx will be increased in the unit time, and in turn, the enzyme cascade reaction yield will be increased with decreasing the gap distance. This phenomenon is similar to the intermediates pool of tricarboxylic acid (TCA) cycle in the metabolic system. This study promotes the understanding of the metabolic/signal transduction processes and active transport in biological systems and promises to design high performance biosensors and biofuel cells systems.

Due to the complexity of biological systems and the ultralow concentration of analytes, improving the signal-to-noise ratio and lowering the limit of detection to allow highly sensitive detection is key to biomolecule analysis, especially intracellular analysis. Here, we present a method for highly sensitive imaging of mRNA in living cells by using novel invisible oriented probes to construct a turn-on signal generation mechanism from zero background. Two DNA probes (S1 and S2) are asymmetrically modified on two small gold nanoparticles (AuNPs) with a diameter of 20 nm. The hybridization of the two DNA probes with a single target mRNA leads to the formation of an AuNP dimer which shows a prominent plasmonic coupling effect. It generates a strong scattering signal from zero-background under a dark-field spectral analysis system. The unique design of the oriented assembly dimer has the ability to easily discriminate the target signal from the inherent cellular background noise in intracellular detection, thus making this approach a valuable technique for imaging single survivin mRNA and monitoring the distribution of survivin mRNA in tumor cells.

Herein, we reported for the first time that gold nanoparticles-catalyzed 3,3',5,5'-tetramethylbenzidine-H2O2 system can serve as an ultrasensitive colorimetric pH indicator. Gold nanoparticles acted as a catalyst and imitated the function of horseradish peroxidase. The absorbance at 450 nm of the yellow-color product in the catalytic reaction exhibited a linear fashion over the pH range of 6.40-6.60. On the basis of this property, we constructed a novel sensing platform for the determination of urea, urease, and urease inhibitor. The limit of detection for urea and urease was 5 μM and 1.8 U/L, respectively. The half-maximal inhibition value IC50 of acetohydroxamic acid was found to be 0.05 mM. Urea in human urine and urease in soil were detected with satisfied results., (Copyright © 2016 Elsevier B.V. All rights reserved.)