Atomic Ordering Engineering of Precious Metal Alloys in Liquid Phase Synthesis.

Atomic ordering of noble metal alloys is an effective strategy for improving catalytic performance, yet the low-temperature synthesis of ordered alloys still faces significant challenges. The low-temperature liquid phase method has enormous potential for the synthesis of alloys; however, the atomic ordering mechanism of this process has not been thoroughly studied. Herein, we investigate the mechanism of the influence of metal precursors, reducing agents, solvents, and mixing modes of reactant regulating strategies on precious metal alloy ordering using this method. These regulating strategies are designed to change the coordination structure of metal complexes, affect the reduction potential of metals, and thus change the reduction order of metals and their arrangement in the alloy products. Notably, the reduction potential differences between metal complexes can be used to predict the ordering of the synthetic products (Pd-Cu, Pd-Cd, Pd-Sn, Pd-Pb, and Pt-Sn). This work provides an excellent platform for investigating atomic arrangement engineering.

Stable and Ordered Body-Centered Cubic PdCu Phase for Highly Selective Hydrogenation.

Phase engineering of nanomaterials plays a crucial role for regulating the catalytic performance. Nevertheless, great challenges still remain for elucidating the structure-selectivity correlation. Herein, this study demonstrates that the body-centered cubic phase of PdCu (bcc-PdCu) can serve as a highly active and selective catalyst for 3-nitrostyrene (NS) hydrogenation under mild conditions. In particular, bcc-PdCu displays a 3-nitro-ethylbenzene (NE) selectivity of 93.8% with a turnover frequency (TOF) value of 4573 h-1 at 30 °C in the presence of H2 . With the assistance of NH3 ∙BH3 , the selectivity of 3-amino-styrene (AS) reaches 94.5% with a TOF value of 13 719 h-1 . Detailed experimental and theoretical calculations reveal that improved NE selectivity is ascribed to the selective adsorption of the CC bond and desorption of NE on bcc-PdCu. Moreover, the presence of NH3 ∙BH3 facilitates the selective hydrogenation of NO2 due to their strong interaction and thus leads to the formation of AS. This work provides an efficient selective catalyst for NS hydrogenation under mild conditions, which may attract immediate interests in the fields of materials, chemistry, and catalysis.

Proteomic analysis reveals that ACSL4 activation during reflux esophagitis contributes to ferroptosis-mediated esophageal mucosal damage.

Ferroptosis has been shown to be involved in the pathological process of many diseases. However, the function and mechanism of ferroptosis in reflux esophagitis (RE), especially in the esophageal mucosal damage, remains unknown. The purpose of this study was to screen potential therapeutic target genes that mediate RE esophageal mucosal damage and regulate ferroptosis. RE rats were established by our previous protocol and proteomic analysis of esophageal mucosa was performed. In addition, the ferroptosis-related genes were retrieved from the FerrDb database and were cross analyzed with the differential proteins of proteomics to obtain potential therapeutic target genes Acyl-CoA synthetase long-chain family 4 (ACSL4), a key enzyme for ferroptosis. In the present study, we used the ACSL4 inhibitor rosiglitazone (ROSI) and the ferroptosis inhibitor ferrostatin-1 to intervene with RE rats, and evaluate the levels of protein, histological changes, lipid peroxidation levels, iron accumulation and morphological changes in esophageal tissue by HE staining, Western blot, related kit tests, and transmission electron microscope. The results showed that both ferrostatin-1 and ROSI treatment significantly reduced the levels of iron accumulation and lipid peroxidation, and protected against ferroptosis and esophageal tissue injury in RE rats. Through Immunohistochemical staining, 16SrDNA sequencing, Enzyme linked immunosorbent assay (ELISA), Western blot and other tests on the esophagus, gut, spleen and serum of RE rats, we further found that the changes of esophageal and intestinal microbiota and the increase of peripheral blood LPS were the key factors regulating ferroptosis in esophageal epithelial tissue. On the one hand, LPS could increase the expression of ACSL4 in esophageal tissue by up-regulating special protein 1 (Sp1). On the other hand, LPS could increase the secretion of serum ferritin in spleen and the accumulation of iron in esophageal tissue by activating Capase11/GSDMD pyroptosis pathway. Collectively, this study suggests that ACSL4 and ferroptosis are potential therapeutic targets for RE esophageal mucosal damage, and esophageal and gut microecology play a critical role in this process.

Effect of Aurantii Fructus Immaturus Flavonoid on the Contraction of Isolated Gastric Smooth Muscle Strips in Rats.

This study was designed to investigate the effect of Aurantii fructus immaturus flavonoid (AFIF) on the contraction of isolated gastric smooth muscle in rats and explore its underlying mechanisms. Isolated antral longitudinal smooth muscle strip (ALSMS) and pyloric circular smooth muscle strip (PCSMS) of rats were suspended in tissue chambers. The responses of ALSMS and PCSMS to administration of AFIF were observed. Cyclic guanosine monophosphate (cGMP) and protein kinase G (PKG) levels of PCSMS were measured by ELISA kits. In this study, AFIF showed no significant effect on ALSMS contraction, but it dose-dependently reduced the mean contraction amplitude of PCSMS. When the concentration of AFIF reached 3000 µg/mL, 6000 µg/mL, and 10000 µg/mL, its inhibitory effect on PCSMS contraction was significant. This effect of AFIF was weakened in Ca(2+)-rich environment. And Nω-nitro-L-arginine methyl (L-NAME), the inhibitor of nitric oxide synthase (NOS), significantly inhibited AFIF's action in comparison with control (P < 0.05). After incubation with AFIF for 30 min, levels of cGMP and PKG in PCSMS were significantly increased compared with control (P < 0.05). Our results suggest that AFIF has a dose-dependent diastolic effect on PCSMS in rats, which may be related to the regulatory pathway of NO/cGMP/PKG/Ca(2+).

The enhancement of transfection efficiency of cationic liposomes by didodecyldimethylammonium bromide coated gold nanoparticles.

The development of transfection enhancement of liposomes with attributes of high stability and easy handling in gene therapy is challenging. In this study, we report didodecyldimethylammonium bromide (DDAB, a cationic lipid) coated gold nanoparticles (DDAB-AuNPs), which can enhance the transfection efficiency generated by two kinds of commercially available cationic liposomes: Lipotap and DOTAP. It showed that DDAB-AuNPs at the optimal concentrations could produce more than 2 times increase when measuring the number of cells expressed green fluorescent protein and 48-fold increase for luciferase levels after transfection, respectively. The electrophoretic mobility shift assay (EMSA) and confocal laser scanning microscopy (CLSM) experiments showed that more DNA molecules binding to the lipoplexes after adding DDAB-AuNPs. In addition, the flow cytometry (FCM) results indicated that DDAB-AuNPs increased cellular uptake efficiency of DNA molecules, which might account for the enhancement of transfection efficiency. It has also been found that the DDAB-AuNPs could decrease the cytotoxicity of liposomes to the cells.

The effect of nocodazole on the transfection efficiency of lipid-bilayer coated gold nanoparticles.

Nonviral vectors are safer than viral systems for gene therapy applications. However, the limited efficacy always prevents their being widely used in clinical practice. Aside from searching new gene nonviral vectors, many researchers focus on finding out new substances to improve the transfection efficiency of existent vectors. In this work, we found a transfection enhancer, nocodazole (NCZ), for dimethyldioctadecylammonium (DODAB, a cationic lipid) bilayer coated gold nanoparticles (AuNPs) mediated gene delivery. It was found that NCZ produces 3-fold transfection enhancement to HEK 293T cells assessed by flow cytometry (FCM). The result was further confirmed by luciferase assay, in which NCZ induced more than 5 times improvement in transfection efficiency after 48 h of transfection. The results from the inductively coupled plasma mass spectrometry (ICP-MS) and FCM showed that NCZ did not affect the internalization of DODAB-AuNPs/DNA complexes. The trafficking of the complexes by transmission electron microscopy (TEM) indicated that the interrupted transportation of the complexes to the lysosomes contributed greatly to the transfection enhancement. Therefore, NCZ can be used as a transfection enhancer in DODAB-AuNPs mediated transfection system. This work also gave an insight to improving the efficiency of lipid-mediated transfection: modifying lipid on gold nanoparticles and pre-treating cells by NCZ before the transfection.

Cationic lipid bilayer coated gold nanoparticles-mediated transfection of mammalian cells.

Here, we demonstrated dimethyldioctadecylammonium bromide (DODAB), a cationic lipid, bilayer coated Au nanoparticles (AuNPs) could efficiently deliver two types of plasmid DNA into human embryonic kidney cells (HEK 293) in the presence of serum. The transfection efficiency of AuNPs was about five times higher than that of DODAB. The interaction of AuNPs with DNA was characterized with dye intercalation assay and agarose gel electrophoresis. The morphology of the complex of AuNPs with DNA was observed with scanning electron microscope (SEM). The intracellular trafficking of the complex was monitored with transmission electron microscope (TEM). Based on experimental results, the possible mechanism was proposed and the barriers in the process of transfection were discussed. This work demonstrates a simple way to increase the transfection efficiency of cationic lipid through changing the stability of the complex of cationic lipid with DNA. It may provide some insights into understanding and controlling the interaction of cationic lipid with DNA. It also provides a novel way to construct gold nanoparticles-based gene vectors and some insights into learning the process of nanomaterials-mediated transfection.

Coating didodecyldimethylammonium bromide onto Au nanoparticles increases the stability of its complex with DNA.

The stability of the complex of cationic lipid with nucleic acid, especially when facing serum, is crucial for the efficiency of gene delivery. Here, we demonstrated that the stability of the complex of didodecyldimethylammonium bromide (DDAB, a cationic lipid) with DNA in the presence of serum dramatically increased after coating DDAB onto the surface of the gold nanoparticles. The stability of the complex was demonstrated with dye intercalation assay, and agarose gel electrophoresis. The process of the interaction was characterized with UV-vis spectra and the morphology of the complex was observed with atomic force microscope (AFM). Cell viability assays demonstrated that the cytotoxicity of DDAB was also decreased.

Glutathione-mediated release of functional plasmid DNA from positively charged quantum dots.

DNA was efficiently bound to water-soluble positively charged CdTe quantum dots (QDs) through complementary electrostatic interaction. These QDs-DNA complexes were disrupted and DNA was released by glutathione (GSH) at intracellular concentrations. Interestingly, there was almost no detectable DNA released by extracellular concentration of GSH. The formation of QDs-DNA complexes and GSH-mediated DNA release from the complexes were confirmed by dye displacement assay, electrophoretic mobility shift assay (EMSA), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) experiments. The released DNA retained transcriptional activity and expressed enhanced green fluorescent protein (EGFP) after being transfected into HEK 293 cells. The transfection efficiency measured by flow cytometry (FCM) was comparable with the positive control. The obvious difference of GSH concentration in nature between the intra- and extracellular environments as well as the GSH concentration-dependent triggered release suggests potential applications of these positively QDs in selective unpacking of payload in living cells in a visible manner.

Effect of freeze-thawing on lipid bilayer-protected gold nanoparticles.

In this study, varieties of lipid bilayer-protected gold nanoparticles (AuNPs) were synthesized through a simple wet chemical method, and then the effect of freeze-thawing on the as-prepared AuNPs was investigated. The freeze-thawing process induced fusion or fission of lipid bilayers tethered on the AuNPs. The UV-vis spectra and transmission electron microscopy experiments revealed that the disruption of lipid bilayer structures on the nanoparticles led to the fusion or aggregation of AuNPs. The role of freeze-thawing in the evolution of lipid bilayer-protected AuNPs was studied. The addition of adequate sucrose, a well-known cryoprotectant, effectively prevented the fusion or aggregation of lipid bilayer-protected AuNPs undergoing the freeze-thawing process. The possible mechanism of sucrose preserving the integrity of the lipid bilayer-protected AuNPs was also discussed.

Room temperature ionic liquid doped DNA network immobilized horseradish peroxidase biosensor for amperometric determination of hydrogen peroxide.

A novel electrochemical H(2)O(2) biosensor was constructed by embedding horseradish peroxide (HRP) in a 1-butyl-3-methylimidazolium tetrafluoroborate doped DNA network casting on a gold electrode. The HRP entrapped in the composite system displayed good electrocatalytic response to the reduction of H(2)O(2). The composite system could provide both a biocompatible microenvironment for enzymes to keep their good bioactivity and an effective pathway of electron transfer between the redox center of enzymes, H(2)O(2) and the electrode surface. Voltammetric and time-based amperometric techniques were applied to characterize the properties of the biosensor. The effects of pH and potential on the amperometric response to H(2)O(2) were studied. The biosensor can achieve 95% of the steady-state current within 2 s response to H(2)O(2). The detection limit of the biosensor was 3.5 microM, and linear range was from 0.01 to 7.4 mM. Moreover, the biosensor exhibited good sensitivity and stability. The film can also be readily used as an immobilization matrix to entrap other enzymes to prepare other similar biosensors.