Turn-on colorimetric detection of hydroquinone based on Au/CuO nanocomposite nanozyme.

CuO nanorods bearing Au nanoparticles (Au/CuO nanocomposites) were prepared by a solution-phase synthesis and exhibited efficient hydroquinone (HQ)-oxidase activity with good specificity. The Au/CuO nanocomposites effectively catalyzed the oxidation of colorless HQ to brown benzoquinone with an absorbance maximum at 376 nm but did not catalyze the conversions of catechol or resorcinol. Kinetic studies indicated that the Au/CuO nanocomposites exhibited a strong affinity for HQ, with a Michaelis-Menten constant of Km = 0.33 mM. Owing to the high catalytic activity and specificity, a strong color was observed at low concentrations of HQ. Quantitative measurement of HQ was performed via colorimetric analysis, which yielded a detection limit of 3 µM with a linear range of 5-200 µM. This colorimetric sensor was successfully applied to an HQ assay of real water samples with satisfactory results.

Mesoporous Core-Shell Pd@Pt Nanospheres as Oxidase Mimics with Superhigh Catalytic Efficiency at Room Temperature.

Mesoporous Pt-Pd bimetallic core-shell nanospheres (mPd@Pt NSs) with palladium-rich cores and platinum-rich shells were synthesized via a simple, two-step, wet chemical strategy mediated by nitrogen-doped carbon dots. The BET surface area of mPd@Pt NSs was found to be 210.4 m2·g-1, which is significantly higher than the currently reported unsupported Pt-based nanomaterials. Because of the large active surface area, the as-prepared mPd@Pt NSs show superhigh oxidase activity and exhibit excellent oxidase-like catalytic efficiency with a catalytic constant (Kcat) as high as 2.1 × 103 s-1 at room temperature, which is of the same order of magnitude as the natural horseradish peroxidase (HRP) (Kcat = 4.3 × 103 s-1) at 37 °C and five-fold greater than the reported Kcat values of oxidase-like nanozyme obtained at 30 °C.

SELEX tool: a novel and convenient gel-based diffusion method for monitoring of aptamer-target binding.

BACKGROUND: Aptamers, single-stranded DNAs or RNAs, can be selected from a library containing random sequences using a method called Systematic Evolution of Ligands by EXponential Enrichment (SELEX). In SELEX, monitoring the enriching statuses of aptamer candidates during the process is a key step until today. Conformational change of an aptamer caused by target-binding in gel can be used to indicate its statuses of binding. RESULTS: In this study, an easy-to-implement gel-based diffusion method (GBDM) was developed to monitor the interaction between enriched aptamer candidates and their targets. In order to prove the concept, characterization of aptamers targeting their targets including protein (thrombin) and non-protein molecules (acetamiprid, ATP, atrazine, profenofos and roxithromycin), respectively, were performed using mini gels. Our method has advantages over the common methods including easy performed with labor- and time- saving in experimental operation. The concept has been proven by monitoring enrichment of dynamic aptamer candidate libraries targeting a small molecule 2,2-bis(4-chlorophenyl) acetic acid (DDA) during SELEX process. A mini gel cassette was designed and fabricated by our laboratory to make mini agarose gels for diffusion with different directions. CONCLUSIONS: These results indicate that GBDM, in particular, chasing diffusion is suitable for monitoring the interaction between enriched aptamer candidates and their targets. These pioneering efforts are helpful for novel aptamer selection by breaking through the technical bottleneck of aptamer development and helpful for development of novel aptasensors.

High-Density Recombinant Adeno-Associated Viral Particles are Competent Vectors for In Vivo Transduction.

Recombinant adeno-associated viral (rAAV) vectors have recently achieved clinical successes in human gene therapy. However, the commonly observed, heavier particles found in rAAV preparations have traditionally been ignored due to their reported low in vitro transduction efficiency. In this study, the biological properties of regular and high-density rAAV serotype 8 vectors, rAAVRD and rAAVHD, were systemically compared. Results demonstrated that both rAAVRD and rAAVHD exhibited similar DNA packaging profiles, while rAAVHD capsids contained fewer VP1 and VP2 proteins, indicating that the rAAVHD particles contained a higher DNA/protein ratio than that of rAAVRD particles. Dynamic light scattering and transmission electron microscopy data revealed that the diameter of rAAVHD was smaller than that of rAAVRD. In vitro, rAAVHD was two- to fourfold less efficient in transduction compared with rAAVRD. However, the transduction performance of rAAVHD and rAAVRD was similar in vivo. No significant difference in neutralizing antibody formation against rAAVRD and rAAVHD was observed, suggesting that the surface epitopes of rAAVRD and rAAVHD are congruent. In summary, the results of this study demonstrate that rAAVRD and rAAVHD are equally competent for in vivo transduction, despite their difference in vitro. Therefore, the use of rAAVHD vectors in human gene therapy should be further evaluated.

Evaluation of anti-inflammatory and antinociceptive activities of Murraya exotica.

CONTEXT: Leaves of Murraya exotica L. (Rutaceae) are used for the treatment of various disorders such as cough, fever, and infectious wounds, as well as alleviating pains in folk medicine in southern China. OBJECTIVE: The objectives of this study were to investigate the in vivo antinociceptive and anti-inflammatory activities of ethanol (70%) extracts and isolated compounds obtained from the dried leaves of M. exotica. MATERIALS AND METHODS: The antinociceptive activities were evaluated with the methods of acetic acid-induced writhing response and hot-plate latent pain response test. Carrageenan induced hind paw edema, xylene induced ear edema, and a rat knee osteoarthritis model were employed to measure the anti-inflammatory activities. The compounds were isolated using column chromatography and thin-layer chromatography, and the structures identified by ¹H NMR, ¹³C NMR, MS, and IR. RESULTS: The ethanol (70%) extracts significantly decreased in the acetic acid-induced writhing response; increased in hot-plate latency; suppressed xylene induced ear swelling and the carrageenan-induced paw edema effectively. In the rat knee osteoarthritis model, the treatment of the ethanol (70%) extracts resulted in a significant increase in the activity of superoxide dismutase, an inhibition on inducible nitric oxide synthase activity, and a decrease in the contents of interleukin-1ß and tumor necrosis factor-α of the rat serum. Following this, we explored the components of the ethanol (70%) extracts and isolated six known coumarins, including murracarpin, which exhibited the most potential in antinociceptive and anti-inflammatory activities. DISCUSSION AND CONCLUSION: M. exotica displayed remarkable antinociceptive and anti-inflammatory activities.

An improved sensitivity non-enzymatic glucose sensor based on a CuO nanowire modified Cu electrode.

CuO nanowires have been prepared and applied for the fabrication of glucose sensors with highly enhanced sensitivity. Cu(OH)(2) nanowires were initially synthesised by a simple and fast procedure, CuO nanowires were then formed simply by removing the water through heat treatment. The structures and morphologies of Cu(OH)(2) and CuO nanowires were characterised by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The direct electrocatalytic oxidation of glucose in alkaline medium at CuO nanowire modified electrodes has been investigated in detail. Compared to a bare Cu electrode, a substantial decrease in the overvoltage of the glucose oxidation was observed at the CuO nanowire electrodes with oxidation starting at ca. 0.10 V vs. Ag/AgCl (saturated KCl). At an applied potential of 0.33 V, CuO nanowire electrodes produce high and reproducible sensitivity to glucose with 0.49 microA/micromol dm(-3). Linear responses were obtained over a concentration range from 0.40 micromol dm(-3) to 2.0 mmol dm(-3) with a detection limit of 49 nmol dm(-3) (S/N = 3). The CuO nanowire modified electrode allows highly sensitive, low working potential, stable, and fast amperometric sensing of glucose, thus is promising for the future development of non-enzymatic glucose sensors.