A combined "AIE + ESIPT" fluorescent probe for detection of lipase activity.

Lipases are acyl hydrolases that play a key role in fat digestion and monitoring of acute pancreatitis by cleaving long-chain triglycerides into polar lipids. Due to an opposite polarity between the hydrophilic enzyme and their lipophilic substrates, lipase reaction occurs at the interface between the aqueous and the oil phases. It is quite challenging to develop a specific probe to detect lipase activity, especially in homogeneous systems. Herein we designed a blue fluorescent probe HBT-LDC for specific detection of lipase activity based on both aggregation induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) effect. The probe shows significant advantages, such as high selectivity and excellent sensitivity, no self-quenching at high concentration, large Stokes shift, low cytotoxicity, and good biocompatibility. The linear range for in vitro quantification of lipase is 0.2-1.3 mg/mL with a detection limit of 0.01 mg/mL. The probe has been successfully applied to the evaluation of commercial lipase and the in vivo bioimaging sensing exogenous lipase activity in HeLa cells. The results revealed that the probe could serve as a potential tool in lipase related drug discovery and disease diagnostics.

Centimeter-scale subwavelength photolithography using metal-coated elastomeric photomasks with modulated light intensity at the oblique sidewalls.

By coating polydimethylsiloxane (PDMS) relief structures with a layer of opaque metal such as gold, the incident light is strictly allowed to pass through the nanoscopic apertures at the sidewalls of PDMS reliefs to expose underlying photoresist at nanoscale regions, thus producing subwavelength nanopatterns covering centimeter-scale areas. It was found that the sidewalls were a little oblique, which was the key to form the nanoscale apertures. Two-sided and one-sided subwavelength apertures can be constructed by employing vertical and oblique metal evaporation directions, respectively. Consequently, two-line and one-line subwavelength nanopatterns with programmable feature shapes, sizes, and periodicities could be produced using the obtained photomasks. The smallest aperture size and line width of 80 nm were achieved. In contrast to the generation of raised positive photoresist nanopatterns in phase shifting photolithography, the recessed positive photoresist nanopatterns produced in this study provide a convenient route to transfer the resist nanopatterns to metal nanopatterns. This nanolithography methodology possesses the distinctive advantages of simplicity, low cost, high throughput, and nanoscale feature size and shape controllability, making it a potent nanofabrication technique to enable functional nanostructures for various potential applications.

Parallel near-field photolithography with metal-coated elastomeric masks.

Developing a cost-effective nanolithography strategy that enables the production of subwavelength features with various shapes over large areas is a long-standing goal in the nanotechnology community. Herein, an inexpensive nanolithographic technique that combines the wafer-scale production capability of photolithography with the subwavelength feature size controllability of near-field photolithography was developed to fabricate centimeter-scale up to wafer-scale sub-100-nm variously shaped nanopatterns on surfaces. The wafer-scale elastomeric trench-based photomasks with subwavelength apertures created at the apexes were compatible with mask aligners, allowing for the production of wafer-scale subwavelength nanopatterns with adjustable feature sizes, shapes, and periodicities. The smallest feature sizes of 50 and 80 nm were achieved on positive tone and negative tone photoresist surfaces, respectively, which could be ascribed to a near-field optical effect. The fabricated centimeter-scale nanopatterns were functionalized to study cell-matrix adhesion and migration. Compared to currently developed nanolithographic methods that approach similar functionalities, this facile nanolithographic strategy combines the merits of low cost, subwavelength feature size, high throughput, and varied feature shapes, making it an affordable approach to be used in academic research for researchers at most institutions.

Colorimetric sensing strategy for mercury(II) and melamine utilizing cysteamine-modified gold nanoparticles.

A quantitative colorimetric sensing strategy utilizing cysteamine modified gold nanoparticles (CA-AuNPs) as reporters for Hg(2+) and melamine was demonstrated. Cysteamine is a cheap and commercially available aminothiol and is also the most important chelating ligand in coordination chemistry possessing the ability to coordinate to Hg(2+) and melamine. The terminal thiol group in cysteamine is used to bind to AuNPs and another terminal amine group is used as a colorimetric probe either for Hg(2+) or melamine. By adjusting the pH, protonation of cysteamine's terminal amine groups allows for tuning of the surface charge on the cysteamine-modified gold nanoparticles. At acidic pH, the CA-AuNPs are positively charged due to the protonated amine groups, which may electrostatically bind melamine resulting in aggregation of CA-AuNPs, while at alkaline pH, the amine groups are deprotonated, and if Hg(2+) is present, they may form an N-Hg(2+)-N structure to induce the aggregation of CA-AuNPs. The detection limits (S/N = 3) of Hg(2+) and melamine were 30 nM and 80 nM respectively, which were comparable with or even lower than those of other single analyte methods. The proposed sensing mechanisms, which are based on electrostatic attraction for melamine and the N-Hg(2+)-N structure for Hg(2+), were validated by zeta potential measurements. The facile one-step surface modification strategy for AuNPs is suitable for the effective analysis of large numbers of samples, which would open new opportunities for development of miniaturized Hg(2+) and melamine sensors.

Recurrence of ischaemic stroke using epidemiology and neuroimaging: A retrospective study in Gansu Province.

Objectives: This retrospective study aimed to investigate the clinical and imaging recurrence of ischaemic stroke (IS), and to evaluate the risk factors for recurrence. A combined clinical and imaging diagnostic model is important for stroke prevention and management. Methods and materials: In accordance with the inclusion and exclusion criteria, we retrospectively analysed consecutively hospitalised patients with acute IS at the Affiliated Hospital of Gansu University of Chinese Medicine. Based on the epidemiological and imaging results, stroke episodes were divided into four categories: clinical first episode (CFE), clinical recurrence (CR), imaging first episode (IFE), and imaging recurrence (IR). Based on the above categories and clinical practice, a joint diagnostic system for IS was established for the first time, including the following five types: IFE, IR, CFE and IFE, CFE and IR, and CR and IR. A binomial logistic regression analysis was conducted to determine the factors which contributed to CR and IR. Results: In total, 280 patients were assessed. The CR rate was 22.9% (64/280) and the IR rate was 62.9% (176/280). The only predictor of CR was hypertension (P = 0.019, odds ratio [OR] = 3.041, 95% confidence interval [95%CI] = 1.200-7.704). The factors of hypertension (P < 0.001, OR = 3.551, 95%CI = 1.781-7.080) and age (P = 0.031, OR = 1.031, 95%CI = 1.003-1.060) were predictors of IR. Conclusion: The IR rates for IS were three times higher than the CR rates. The key to preventing IR and CR in IS was the management of blood pressure. Neuroimaging examinations were important for the early detection of IFE and IR in elderly patients with hypertension. A combined clinical imaging diagnostic model was developed for the first time.

A fishnet electrochemical Hg2+ sensing strategy based on gold nanoparticle-bioconjugate and thymine-Hg(2+)-thymine coordination chemistry.

A novel electrochemical biosensing strategy based on a three-dimensional fishnet of DNA-linked nanoparticle supramolecular structure triggered by the analyst for detection of Hg(2+) has been designed. The detection limit is 7.38 pM and the sensor's selectivity and facility have been significantly improved.

A simple and cost-effective sensing strategy of mercury (II) based on analyte-inhibited aggregation of gold nanoparticles.

A simple, cheap and ultrasensitive colorimetric Hg2+ sensing strategy has been developed in this paper. It was based on a special 'Hg2+-inhibited aggregation' mechanism, in which the pyridine-induced aggregation of unmodified gold nanoparticles (AuNPs) could be inhibited upon addition of Hg2+. Compared with the previous Hg2+-induced aggregation mechanism, the new design just employed a cheap and facile chemical reagent, pyridine, as an inducer of aggregation of AuNPs and elimination of the modifying or labeling step. The effects of pyridine concentration and size of AuNPs were investigated. The calibration curve showed that the extinction ratio value at 525 and 700 nm increased linearly over the Hg2+ concentration range of 0.15-3.00 µM with a detection limit of 55 nM. The specificity of this sensor is remarkably high over that of the other metal ions without adding any masking agent.

N-Isopropyl-3-methyl-2-nitro-benzamide.

In the title compound, C(11)H(14)N(2)O(3), the bond lengths and angles are within normal ranges. Weak inter-molecular N-H⋯O inter-actions link the mol-ecules into chains along the a axis. A non-classical intra-molecular C-H⋯O inter-action (nitro O atom and a H atom of the nearest methyl group) is found, forming a six-membered ring with a twisted conformation. This six-membered ring has a twisted conformation.

3,3'-Dimethyl-1,1'-ethyl-ene-diimidazolium dibromide.

The title compound, C(10)H(16)Br(2)N(4), was synthesized by the reaction of 1-methyl-imidazole and 1,2-dibromo-ethane in toluene. The complete dication is generated by a crystallographic inversion centre situated at the mid-point of the ethane C-C bond. In the crystal structure, weak inter-molecular C-H⋯Br inter-actions link the mol-ecules into chains along the b axis and an intramolecular C-H⋯Br close contact is also present.

1-Methyl-3-n-tetra-decyl-imidazolium bromide monohydrate.

In the title ionic liquid salt hydrate, C(18)H(35)N(2) (+)·Br(-)·H(2)O, the side chain in the cation has an extended conformation. The crystal structure is stabilized primarily by O-H⋯Br hydrogen bonds. C-H⋯O and C-H⋯Br inter-actions are also present.

A Novel Heterogalactan from Antrodia camphorata and Anti-Angiogenic Activity of Its Sulfated Derivative.

A heterogalactan, named ACW0, was extracted from Antrodia camphorata and purified by anion exchange and gel permeation chromatography. It was composed of galactose (94.98%), traces of mannose (2.41%), and fucose (2.61%), with its molecular weight estimated to be 13.5 k Da. The polysaccharide ACW0 was shown to be a mannofucogalactan with a backbone chain of α-d-1,6-linked Gal, attached by a non-reducing terminal α-d-Man and α-l-Fuc on C-2 of nearly every six α-d-1,6-linked Gal residues. A sulfated polysaccharide, ACW0-Sul was achieved by the chlorosulfonic acid-pyridine method. Compared with the native polysaccharide, ACW0-Sul could disrupt tube formation and migration as well as cell growth of human microvascular endothelial cells (HMEC-1) dose-dependently. Further studies revealed that phosphorylation of Extracellular Regulated Protein Kinases (Erk) and Focal Adhesion Kinase (FAK) were significantly inhibited by ACW0-Sul. These results suggested that ACW0-Sul could be a potent candidate for anti-angiogenic agent development.

Synthesis of stable heterogeneous catalysts by supporting carbon-stabilized palladium nanoparticles on MOFs.

Cycling instability of catalysts is a persisting challenge in heterogeneous catalysis. In this work, we reported an effective in situ strategy for preparing ZIF-8 supported carbon-stabilized Pd nanoparticles (C@Pd/ZIF-8). The original ZIF-8 structure was well-preserved after the formation of Pd nanoparticles and amorphous carbon. Here, the Pd nanoparticles were encapsulated in the carbon matrix with a good dispersion. The as-prepared catalysts showed a better activity and cycling stability for the hydrogenation of C[double bond, length as m-dash]C containing substrates. C@Pd/ZIF-8 catalysts are reusable without significant loss of activity after 5 cycles, exhibiting higher cycling stability than those prepared from directly supported Pd nanoparticles on ZIF-8 (Pd/ZIF-8).

A plasmonic nanosensor for lipase activity based on enzyme-controlled gold nanoparticles growth in situ.

A plasmonic nanosensor for lipase activity was developed based on one-pot nanoparticle growth. Tween 80 was selected not only as the substrate for lipase recognition but also as the reducing and stabilizing agent for the sensor fabrication. The different molecular groups in Tween 80 could have different roles in the fabrication procedure; the H2O2 produced by the autoxidation of the ethylene oxide subunits in Tween 80 could reduce the AuCl4(-) ions to Au atoms, meanwhile, the lipase could hydrolyze its carboxyl ester bond, which could, in turn, control the rate of nucleation of the gold nanoparticles (AuNPs) and tailor the localized surface plasmon resonance (LSPR) of the AuNP transducers. The color changes, which depend on the absence or presence of the lipase, could be used to sense the lipase activity. A linear response ranging from 0.025 to 4 mg mL(-1) and a detection limit of the lipase as low as 3.47 µg mL(-1) were achieved. This strategy circumvents the problems encountered by general enzyme assays that require sophisticated instruments and complicated assembling steps. The methodology can benefit the assays of heterogeneous-catalyzed enzymes.

Colorimetric assay for heterogeneous-catalyzed lipase activity: enzyme-regulated gold nanoparticle aggregation.

Lipase is a neglected enzyme in the field of gold nanoparticle-based enzyme assays. This paper reports a novel colorimetric probe to rapidly visualize lipase activities by using Tween 20 functioned GNPs (Tween 20-GNPs) as a reporter. The present strategy hence could overcome the limitations caused by the heterogeneous interface in lipase assay. Catalytic hydrolytic cleavage of the ester bond in Tween 20-GNPs by lipase will trigger the rapid aggregation of GNPs at a high salt solution. The color change from red to purple could be used to sense the activity of lipase. The detection limit (3σ) is as low as 2.8 × 10-2 mg/mL. A preliminary enzyme activity screening was carried out for seven commercially purchased lipase samples. It also has been successfully applied to detecting lipase in fermentation broth of Bacillus subtilis without any pretreatment.

In situ synthesis of large-area single sub-10 nm nanoparticle arrays by polymer pen lithography.

In order to take advantage of the unique properties of nanoparticles in integrated devices, it is desirable to position monodispersed nanoparticles on substrates with controlled placement. Herein, we utilize small molecules such as ethylene glycol (EG) or glycerol to facilitate the delivery of nanoparticle precursors to the substrates in the polymer pen lithography (PPL) process. Subsequently, large-area ordered single nanoparticle arrays, including sub-10 nm Ag nanoparticle, 30 nm Au nanoparticle and 80 nm Fe2O3 nanoparticle arrays have been synthesized in situ with controllable sizes and pitches.

An electrochemical sensor for detecting triglyceride based on biomimetic polydopamine and gold nanocomposite.

We developed a novel electrochemical sensing strategy for tributyrin detection based on a polydopamine and gold nanoparticle hybrid (GNPs@PDA) to significantly improve the performance of the sensor. The adhesive hybrid has been easily synthesized in situ via oxidative polymerization of dopamine in the presence of HAuCl4 and the lipase was then conjugated with the GNPs@PDA easily, remaining enzymatically active and catalyzing hydrolysis of tributyrin. The biomimetic material PDA here performs well both as an ideal binding agent for attaching to the sensor surface and as a good platform for grafting of the enzyme lipase. A linear response ranging from 50 to 300 mg dL-1 and a detection limit of tributyrin as low as 0.84 mg dL-1 with a fast response time (20 s) is achieved on the GNPs@PDA platform. The value of the apparent Michaelis-Menten constant (K) was obtained as 7.94 mg dL-1, which indicated high affinity of lipase to tributyrin. Furthermore, the sensor has strong anti-interference ability as well as a long shelf-life. We also use this sensor to detect triglyceride concentration in human serum samples.

Fabrication of PEDOT nanowhiskers for electrical connection of the hemoglobin active center for H2O2 electrochemical biosensing.

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowhiskers were fabricated in a [bmim][BF4] ionic liquid. The minimal size of the nanowhiskers is only 0.2 nm, and the size matches the thickness of a PEDOT single-molecular chain. They were successfully used as the electron transfer channels between the active center of hemoglobin (Hb) and an underlying electrode. The direct electron transfer process between Hb and the underlying electrode was realized without any electron mediator. Compared to that of a gold nanoparticle (AuNP)-Hb composite electrode, the catalytic current of a PEDOT nanowhiskers-AuNPs-Hb composite electrode for detecting H2O2 is increased 7 fold. A novel model of a H2O2 biosensor based on the PEDOT nanowhiskers-AuNPs-Hb composites was fabricated. The detection limit was estimated to be 0.6 µM at a signal/noise (S/N) ratio of 3, and the linear range of H2O2 concentration was from 1 µM to 1100 µM. Three constructed models of the biosensors showed a good stability, and all of them retained nearly 90% of their initial signals for 1 mM H2O2 when they were stored at 4 °C after 60 days. H2O2 concentration in contact lens nursing liquid was measured by the biosensor, and the results were in good agreement with the values provided by the supplier. It is shown that the PEDOT nanowhiskers can provide a new opportunity for the design of sensitive biosensors with long-term stability.

Fabrication of a dispersible graphene/gold nanoclusters hybrid and its potential application in electrogenerated chemiluminescence.

A dispersible graphene/gold nanoclusters hybrid in aqueous solution was fabricated in situ based on the bilayer graphene template, and its electrogenerated chemiluminescence (ECL) behavior was studied.

Direct electron transfer and electrocatalysis of hemoglobin in ZnO coated multiwalled carbon nanotubes and Nafion composite matrix.

ZnO coated multiwalled carbon nanotubes (ZnO-MWCNTs) nano-composite was synthesized by the hydrothermal method and expected to offer a promising template for biosensor fabrication due to satisfying biocompatibility and improved properties. The ZnO-MWCNTs nano-composite was mixed with Nafion solution to form a composite matrix for the fabrication of hemoglobin (Hb) biosensor. This composite matrix combined the advantages of inorganic composite (ZnO-MWCNTs) and organic polymer (Nafion) and could promote the direct electron transfer of Hb. The Hb/ZnO-MWCNTs/Nafion film exhibited a pair of well-defined, quasi-reversible redox peaks with a formal potential of -0.353V (vs. SCE), characteristic of heme redox couple (Fe(III)/Fe(II)) of Hb. Hb retained its near-native conformation in the composite film. The immobilized Hb showed fast and excellent electrocatalytic activity to H(2)O(2) with a linear range from 2x10(-7) to 1.2x10(-5)M, and the detection limit was 8.4x10(-8)M. The sensitivity and apparent Michaelis-Menten constant were 1.31A/(M x cm(2)) and 82.8microM, respectively, which indicated that Hb had a high affinity to H(2)O(2). This biosensor also showed excellent electrocatalytic activity towards trichloroacetic acid.

A novel electrochemical DNAzyme sensor for the amplified detection of Pb2+ ions.

A novel amplification strategy based on DNAzyme functionalized gold nanoparticles was employed to enhance the sensitivity of an electrochemical sensor for detection of Pb2+. The detection limit is 0.028 nM, which is much lower than for other electrochemical DNAzyme sensors.