Bimetallic iron-copper nanozyme for determination and degradation of norfloxacin in foods.

Iron-copper nanozymes (Fe-Cu NZs) with good peroxidase activity were prepared through hydrothermal method by using copper nitrate as copper source, iron acetate as iron source and 2, 5-dihydroxyterephthalic acid as organic ligand. Upon oxidation of the colourless TMB to light blue products by Fe-Cu NZs, the addition of Norfloxacin (NOR) resulted in a colour change to dark blue. The absorbance of the system correlated linearly with NOR concentration in the range of 3.3 µM to 66 µM, and the detection limit (LOD) was 0.386 µM. A rapid colourimetric assay for the determination of NOR in food matrices was developed, with a detection time of only one minute. Additionally, the assay facilitated the simultaneous catalytic degradation of NOR via Fe-Cu NZs. The primary degradation mechanism of NOR was identified as the transformation of the quinolone ring and the cleavage of the C9 = C10 double bond, which was substantiated by high-performance liquid chromatography (HPLC).

Impact of internal metal ions in tea polysaccharides on antioxidant potential and suppression of cancer cell growth.

Four kinds of tea polysaccharides (MBTPS, MGTPS, ZBTPS, ZGTPS) were extracted from Maofeng black tea, Maofeng green tea,Ziyan black tea and Ziyan green tea, and then four tea polysaccharides (RMBTPS, RMGTPS, RZBTPS, RZGTPS) after metal removal were prepared. The physicochemical properties, antioxidant activity and inhibitory activity on cancer cell proliferation of the above polysaccharides were studied. The composition analysis shows that these tea polysaccharides were glycoproteins complexes, composed of a variety of monosaccharides, and the removal of metal ions did not lead to fundamental changes in the composition of polysaccharides. In vitro activity, after removing metal ions, the ABTS free radicals scavenging ability and reducing power of tea polysaccharides were decreased, and the inhibitory effect on proliferation of H22 cells weakened. There was a great correlation between metal elements Al and Ni and biological activity. The results showed that the metal ions in tea polysaccharides, especially Al and Ni, had positive effects on biological activity.

A dual-mode optical assay for iron(II) and gallic acid based on Fenton reaction.

The hydroxyl radicals (·OH) produced by the Fenton reaction of iron(II) and hydrogen peroxide (H2 O2 ) can oxidize the colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB (Ox-TMB), resulting in a decrease in the fluorescence intensity of the reaction system and an increase in ultraviolet absorption. Ox-TMB had a visible absorption peak at 625 nm and a fluorescence peak around 420 nm. When gallic acid (GA) was added to the system, Ox-TMB was reduced to TMB, which made the color of the system disappear and the fluorescence recover. The linear ranges for determination of iron(II) were 0.5-10 µM (fluorometric) and 0.5-20 µM (colorimetric), and the detection limits were 0.25 µM (fluorometric) and 0.28 µM (colorimetric). The linear ranges for determination of GA were 0-80 µM (fluorometric) and 0-60 µM (colorimetric), and the detection limits were 0.31 µM (fluorometric) and 0.8 µM (colorimetric). The results of anti-interference experiments shew that this dual-mode assay had very good selectivity for the determination of iron(II) and GA.

Antioxidant and hypoglycemic activity of tea polysaccharides with different degrees of fermentation.

Four polysaccharides (GTPS, OTPS, BTPS and DTPS) were extracted from green tea, oolong tea, black tea and dark tea respectively. The physical and chemical properties, antioxidant and hypoglycemic activities were studied. Structural analysis showed that these tea polysaccharides were glycoprotein complexes, and there were significant differences in microstructure, protein, total sugar and uronic acid content. They were all composed of multiple monosaccharides and different molar ratios. In terms of antioxidant activity, completely fermented BTPS and DTPS had higher activity. Regarding to hypoglycemic effects, BTPS showed higher α-glucosidase inhibitory activity in vitro. And in the treatment of type 2 diabetes mice, Oral BTPS significantly controlled the levels of blood glucose, TG, TC, LDL-C, Cr, UREA, ALT and AST in diabetic mice, and improved insulin resistance. Histopathological observation further confirmed that BTPS can alleviate liver injury caused by hyperglycemia and hyperlipidemia. Data showed that BTPS significantly improved hyperglycemia and liver function in diabetic mice.

Mo3Se4 nanoparticle with ROS scavenging and multi-enzyme activity for the treatment of DSS-induced colitis in mice.

Ulcerative colitis (UC), as a most common inflammatory bowel disease (IBD), has become a global public health concern. Exploring novel method of treating UC is urgent and necessary. Recently, nanozyme with excellent antioxidant properties may be one useful therapeutic strategy. In this study, a two-dimensional transition metal chalcogenide (TMCs) nano flake and polyethylene glycol (PEG) modified Mo3Se4 nano flakes (PMNFs) was synthesized, which had multi-enzyme activity, including peroxidase, glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT). The inhibition effect of PMNFs on sodium dextran sulfate (DSS)-induced colitis was explored. UC was effectively inhibited by PMNFs in this work. PMNFs significantly reduced disease activity index (DAI) score, including weight loss, colon shorten and histopathological abnormalities. The possible mechanism of PMNFs-attenuated colitis was investigated. The results showed that PMNFs reversed DSS-induced oxidative damage, and the antioxidant pathway Nrf2-keap1 signal was activated by PMNFs. Moreover, PMNFs suppressed the expression of pro-inflammatory factors including IL-1ß, TNF-α, IFN-ß and IL-6 via the inactivation of TLR4/NF-κB pathway in DSS-induced colitis and LPS-treated macrophage. Furthermore, PMNFs treatment prevented the reduction of tight junction proteins (ZO-1, occludin, and claudin-1) and mucin-2 (MUC-2) as well as the up-regulation of epithelial apoptosis caused by DSS. These findings demonstrate that the PMNFs against DSS-induced colitis due to its prevention on oxidative damage, inflammation, and intestine barrier breakdown. Thus, PMNFs have a potential application in the treatment of various oxidative stress or inflammation-related diseases.

A colorimetric and fluorescence dual-signal determination for iron (II) and H2O2 in food based on sulfur quantum dots.

A colorimetric and fluorescence dual-signal method based on sulfur quantum dots (SQDs) was established for determination of iron (II) (Fe2+) and H2O2 in foods. Due to the complexation of Fe2+ with SQD, Fe2+ can cause fluorescence quenching of SQDs, and the color of the mixed solution changed from light yellow to deep green. By use of Fenton reaction, H2O2 can restore the quenched fluorescence of SQDs, and the color of the mixture changed from green to colorless. The concentration of Fe2+ and H2O2 has a good linear relationship with the fluorescence intensity and absorbance in the range of 2.5-55 µM and 1.25-500 µM, and the detection limits were 1.41 µM and 0.54 µM, respectively. For determination of H2O2, the linear ranges were 1.17-1.97 mM and 0.867-1.50 mM, and the detection limits were 0.03 µM and 0.06 µM, respectively.

A colorimetric and fluorescence turn-on probe for the detection of ascorbic acid in living cells and beverages.

A colorimetric and fluorescence turn-on dual-signal assay was developed for the determination of ascorbic acid (AA). Because the ultraviolet absorption of the oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) overlapped with the fluorescence emission of glutathione stabilized Au nanoclusters (AuNCs), the fluorescence of AuNCs can be quenched by oxTMB. When AA was added, the blue oxTMB was reduced to colorless TMB, and the fluorescence of AuNCs was restored simultaneously. The decrease in absorbance and increase in fluorescence signal depended on the concentration of AA. In the determination range of 0.5 to 200 µM, the detection limits (LOD) for AA were as low as 0.15 µM and 0.22 µM for fluorometric and colorimetric, respectively. The established probe was used successfully for AA detection in living cells and beverages.

Colorimetric and turn-on fluorescence determination of mercury (II) by using carbon dots and gold nanoparticles.

A colorimetric and turn-on fluorometric assay with high sensitivity and selectivity is described for the optical detection of mercury (II) ions (Hg2+), based on carbon dots with -SH (SN-CDs) and gold nanoparticles (AuNPs). On addition of Hg2+, the color of the system (SN-CDs/AuNPs) changes from red to blue. A new absorption peak appears at 700 nm, and its absorbance increases with the concentration of Hg2+, while at 530 nm, the absorbance of AuNPs decreases. Taking the ratio of absorbance at 700 and 530 nm as a signal, a colorimetric method with linear detection range of 0.5-4.0 µM was established for the determination of Hg2+. Meanwhile, citrate ions on the surface of AuNPs can reduce Hg2+ to Hg0, and through the strong affinity of Hg0 and gold, gold-mercury alloys were formed to occupy the surface of AuNPs, so that the SN-CDs were re-free and the fluorescence of SN-CDs was restored. Consequently, a fluorometric method was founded in the linear detection range from 0.5 to 15.0 µM of mercury (II). This dual-mode (colorimetric and turn-on fluorometric) method was applied successfully for determination of Hg2+ in real water samples.

Green and high-yield synthesis of carbon dots for ratiometric fluorescent determination of pH and enzyme reactions.

In this work, the carbon dots (CDs) were prepared by one-pot hydrothermal method with chitosan as a carbon source and hydrogen peroxide as an oxidant, this route is a novel, simple and green. The prepared CDs has a relatively high photoluminescence (PL) quantum yield (QY) (18.9%) and good water solubility. CdTe quantum dots (CdTe QDs) possess the characteristic of responding to pH rapidly. So a ratiometric fluorescent probe for measuring pH was constructed using the prepared CDs and CdTe QDs. Under the excitation of 330 nm, the probe shows dual (blue and red) emission with peaks at 430 and 600 nm, respectively. When the pH of the solution changes, the blue fluorescence intensity of the CDs remains stable as a reference signal, while the red fluorescence intensity of CdTe QDs changes accordingly. This method has obvious pH-sensitive feature, stable fluorescence properties, and a great linear relationship with pH values in the range of pH 3.0-11.0. What is more, the method can monitor proton-producing enzyme-catalyzed reactions by acting as a ratiometric pH probe.

Ratiometric fluorescence assay for L-Cysteine based on Fe-doped carbon dot nanozymes.

In this work, a ratiometric fluorescence method based on nanozyme was fabricated to determine L-Cysteine. Taking silkworm feces as a carbon source, together with Fe3+, Fe-doped carbon dots (Fe-CDs) were synthesized through a hydrothermal method. Fe-CDs were able to oxidize the enzyme substrate o-phenylenediamine (OPD) to produce oxidized OPD (Ox-OPD) when H2O2 coexisted with them. Based on the fluorescence property of Fe-CDs and Ox-OPD, a dual-emission system was built. Since L-Cysteine contains reductive thiols that can inhibit the production of Ox-OPD, the addition of L-Cysteine caused a decrease in the fluorescence intensity of Ox-OPD. The results showed that the ratio of fluorescence intensities at 450 and 560 nm (I450/I560) varied linearly with the concentration of L-Cysteine in the range of 0.25-90 µM and the limit of detection is as low as 0.047 µM. Furthermore, using this ratiometric fluorescence system to determine L-Cysteine in serum and tap-water samples, average recoveries were evaluated to reach 98.75%-103.27% with the relative standard deviation of no more than 4.5%. Based on the fluorescence property and nanozyme-like activity, this work provides an inspiration to open a new horizon in using natural carbon source to synthesize CDs and for the application of CDs as a nanozyme.

Nitrogen-doped carbon dots from rhizobium as fluorescence probes for chlortetracycline hydrochloride.

Fluorescent nitrogen-doped carbon dots (CDs) were prepared via hydrothermal method at 190 °C for 10 h using rhizobium from soy as the carbon and nitrogen source. Their optical properties, structure, morphology, and functional groups were characterized in detail and the results showed that they possess unique excitation-dependent fluorescence behavior, with average diameter 4.5 ± 2.0 nm and good water dispersibility. Due to the overlap of the UV-vis absorbance of chlortetracycline hydrochloride (CCH) and the fluorescence excitation band of CDs, the fluorescence of the prepared CDs can be quenched by CCH selectively and sensitively. The changes of the fluorescence intensity of CDs have a good linear relationship with the concentration of CCH in a wide concentration range of 5-100 µM, with a detection limit of 0.254 µM. This present method has been successfully applied to determine the CCH in water with recovery ranging from 96.0% to 100.7%.

A ratiometric fluorometric ciprofloxacin assay based on the use of riboflavin and carbon dots.

Carbon dots (CDs) were hydrothermally synthesized from selenious yeast. They were further coupled with riboflavin to form a dually emitting probe for ciprofloxacin (CIP). Under 370 nm excitation, the probe displays dual (blue and green) emissions with peaks at 443 and 510 nm. When CIP is added, the blue fluorescence of the CDs is enhanced while the green fluorescence remains unaffected. The ratio of the relative fluorescence intensities at 443 and 510 nm increases linearly in the 0.5-200 µM CIP concentration range. The fluorescent probe is selective and has a 0.13 µM detection limit. Satisfactory recoveries (97.9-101.1%) were received when the probe was used to quantify CIP in spiked water and human serum samples. Graphical abstractBlue-emissive carbon dots were prepared from selenious yeast via a hydrothermal method, and then coupled with riboflavin as a ratiometric fluorometric probe for ciprofloxacin determination.

Rose-like Nanocomposite of Fe-Ni Phosphides/Iron Oxide as Efficient Catalyst for Oxygen Evolution Reaction.

In order to accelerate the reaction rate of water splitting, it is of immense importance to develop low-cost, stable and efficient catalysts. In this study, the facile synthesis of a novel rose-like nanocomposite catalyst (Ni2 P/Fe2 P/Fe3 O4 ) is reported. The synthesis process includes a solvothermal step and a phosphatization step to combine iron oxides and iron-nickel phosphides. Ni2 P/Fe2 P/Fe3 O4 performs well in catalyzing oxygen evolution reaction, with a very low overpotential of 365 mV to reach 10 mA cm-2 current density. The Tafel slope is as low as 59 mV dec-1 . Ni2 P/Fe2 P/Fe3 O4 has a large double-layer capacitance that contributes to a high electrochemically active area. Moreover, this catalyst is very stable for long-term use. Therefore, the Ni2 P/Fe2 P/Fe3 O4 catalyst has a high potential for use in oxygen evolution reactions.

Rosmarinic acid counteracts activation of hepatic stellate cells via inhibiting the ROS-dependent MMP-2 activity: Involvement of Nrf2 antioxidant system.

Recently, oxidative stress is involved in hepatofibrogenesis. Matrix metalloproteinase-2 (MMP-2) is required for activation of hepatic stellate cells (HSCs) in response to reactive oxygen species (ROS). This study was designed to explore the hypothesis that the inhibitory effect of rosmarinic acid (RA) on HSCs activation might mainly result from its antioxidant capability by increasing the synthesis of glutathione (GSH) involved in nuclear factor kappa B (NF-κB)-dependent inhibition of MMP-2 activity. Here, we demonstrate that RA reverses activated HSCs to quiescent cells. Concomitantly, RA inhibits MMP-2 activity. RNA interference-imposed knockdown of NF-κB abolished down-regulation of MMP-2 by RA. RA-mediated inactivation of NF-κB could be blocked by the diphenyleneiodonium chloride (DPI; a ROS inhibitor). Conversely, transfection of dominant-negative (DN) mutant of extracellular signal-regulated kinases 2 (ERK2), c-Jun N-terminal kinase 1 (JNK1), or p38α kinase had no such effect. Simultaneously, RA suppresses ROS generation and lipid peroxidation (LPO) whereas increases cellular GSH in HSC-T6 cells. Furthermore, RA significantly increased antioxidant response element (ARE)-mediated luciferase activity, nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and catalytic subunits from glutamate cysteine ligase (GCLc) expression, but not modulatory subunits from GCL (GCLm). RA-mediated up-regulation of GClc is inhibited by the shRNA-induced Nrf2 knockdown. The knocking down of Nrf2 or buthionine sulfoximine (a GCL inhibitor) abolished RA-mediated inhibition of ROS. Collectively, these results provide novel insights into the mechanisms of RA as an antifibrogenic candidate in the prevention and treatment of liver fibrosis.

[Expression of platelet-derived growth factor receptor α and its ligand PDGF- A in breast cancer].

AIM: To investigate the potential significance of platelet-derived growth factor receptor-α (PDGFR-α) and platelet-derived growth factor A (PDGF-A) expression in mammary carcinomas, and analyze its correlation with the lymph node metastasis and the expression of PDGF-A. METHODS: Used immunohistochemistry to detect the protein expression of PDGFR-α and PDGF-A in paraffinembedded breast carcinomas. RESULTS: The expression of PDGFR-α and PDGF-A were observed in 51.7% and 61.7% in the breast carcinomas, respectively and showed an association with lymph node metastasis (P < 0. 05). A correlation was also found with the expression of PDGFR-α and PDGF-A (P<0.05). CONCLUSION: PDGFR-α is expressed in invasive breast carcinomas and is associated with biological aggressiveness.