Taking advantage of the stability and penetrability of layer-by-layer (LbL) films, we develop a novel method to fabricate a branchlike structure of Ag aggregates on the matrix of a LbL polyelectrolyte multilayer by an electrodeposition technique. The morphology of Ag aggregates can be adjusted by electrodeposition time and potential. Moreover, after further chemisorption of a self-assembled monolayer of n-dodecanethiol, the as-prepared surface becomes superhydrophobic with a contact angle as high as 154 degrees and a tilt angle lower than 3 degrees.

The influence of a basic aqueous solution on a hydrogen-bonding-directed layer-by-layer (LbL) self-assembled film, based on poly(acrylic acid) (PAA) and poly(4-vinylpyridine) (PVP), was investigated. The composition change of a multilayer film in a NaOH solution was monitored by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and UV-vis spectroscopy. The morphology variation was observed by atomic force microscopy. A two-step variation was observed: the first step is the dissolution of PAA from the film into the basic solution; the second is the gradual reconformation of PVP polymer chains remaining on the substrate, which produces a microporous film. The evidence for the reconformation of the polymer chains was further provided by single molecule force spectroscopy. Both the release of PAA and the formation of the microporous film are attributed to the properties of the LbL film based on hydrogen bonding. This interesting and novel way to fabricate microporous films is envisaged to have potential applications in areas ranging from pharmaceutics to materials science.

Electrochemical reduction of nitrate pollutants to ammonia has emerged as an attractive alternative for ammonia synthesis. Currently, many strategies have been developed for enhancing nitrate reduction to ammonia (NRA) efficiency, but the influence of the degree of structural disorder is still unexplored. Here, carbon‐supported RuO2 nanosheets with adjustable crystallinity are synthesized by a facile molten salt method. The as‐synthesized amorphous RuO2 displays high ammonia Faradaic efficiency (97.46 %) and selectivity (96.42 %), greatly outperforming the crystalline counterparts. The disordered structure with abundant oxygen vacancies is revealed to modulate the d‐band center and hydrogen affinity, thus lowering the energy of the potential‐determining step (NH2*→NH3*).

Aptamers are short single-stranded DNA or RNA oligonucleotides and can be selected from synthetic combinatorial libraries in vitro. They have a high binding affinity and specificity for their targets. Agarose gels, nitrocellulose membranes, and adsorptive microplates are often used as carriers to immobilize targets in the SELEX (systematic evolution of ligands by exponential enrichment) process, but the subsequent separation step is tedious and time-consuming. Therefore, we used magnetic nanoparticles (MNPs) as carriers to immobilize the target, hepatitis B surface antigen (HBsAg), which is convenient for fast magnetic separation. In this study, we first selected DNA aptamers against HBsAg by immobilizing HBsAg on the surface of carboxylated MNPs. The ssDNA library of each selection round was prepared by asymmetric PCR amplification for the next selection round. To obtain aptamer sequences, the final selected products were purified by gel electrophoresis, then cloned, and sequenced. DNA aptamers that specifically bind to HBsAg were successfully obtained after 13 selection rounds. The selected aptamers were used to construct a chemiluminescence aptasensor based on magnetic separation and immunoassay to detect HBsAg from pure protein or actual serum samples. There was a linear relationship between HBsAg concentration and chemiluminescent intensity in the range of 1-200 ng/mL. The aptasensor worked well even in the presence of interfering substances and was highly specific in the detection of HBsAg in serum samples, with a detection limit 0.1 ng/mL lower than the 0.5 ng/mL limit of an ELISA in use at the hospital. This aptasensor can contribute to better detection of hepatitis B virus infection.

In this communication, we report the synthesis of the three generations of Fréchet-type poly(aryl ether) dendrimers with a diselenide core that demonstrate generation-dependent glutathione peroxidase (GPx) activity with initial reduction rates as high as 2431.20 muM min-1 for the third-generation product, around 1400 times faster than Ebselen. It represents a successful example of using a dendrimer as a model for a GPx mimic.

We reported a way to fabricate microporous films by post-base treatment of hydrogen-bonding-directed multilayer films of poly(4-vinylpyridine) (PVP) and carboxyl-terminated polyether dendrimer (DEN−COOH). The PVP/DEN−COOH multilayer film was fabricated by layer-by-layer assembly of PVP and DEN−COOH from a methanol solution. UV−visible spectroscopy revealed a uniform deposition process. The interaction between PVP and DEN−COOH was identified as hydrogen bonding through Fourier transform infrared (FT-IR) spectroscopy. Meanwhile, the composition change of a PVP/DEN−COOH multilayer film in a basic solution was detected by X-ray photoelectron spectroscopy and UV−visible spectroscopy, and the morphology variation was observed by atomic force microscopy. A two-step variation was observed:  the dissolution of DEN−COOH from the multilayer into the basic solution and the gradual reconformation of PVP polymer chains remaining on the substrate, which produced a microporous film. Interestingly, compared with our previous PVP/poly(acrylic acid) (PAA) system, under the same conditions, the release of DEN−COOH from a PVP/DEN−COOH multilayer is slower than that of PAA, and the microporous morphology is also different, which indicates that the molecular structure of a building block has a remarkable influence on the variation of a hydrogen-bonding-directed film in a basic solution.

BackgroundGastric cancer is 2th most common cancer in China, and is still the second most common cause of cancer-related death in the world. Successful development of safe and effective nanoprobes for in vivo gastric cancer targeting imaging is a big challenge. This study is aimed to develop folic acid (FA)-conjugated silica coated gold nanoclusters (AuNCs) for targeted dual-modal fluorescent and X-ray computed tomography imaging (CT) of in vivo gastric cancer cells.MethodAuNCs were prepared, silica was coated on the surface of AuNCs, then folic acid was covalently anchored on the surface of AuNCs, resultant FA-conjugated AuNCs@SiO2 nanoprobes were investigated their cytotoxicity by MTT method, and their targeted ability to FR(+) MGC803 cells and FR(−) GES-1 cells. Nude mice model loaded with MGC803 cells were prepared, prepared nanoprobes were injected into nude mice via tail vein, and then were imaged by fluorescent and X-ray computed tomography (CT) imaging.ResultsFA-conjugated AuNCs@SiO2 nanoprobes exhibited good biocompatibility, and could target actively the FR(+) MGC-803 cells and in vivo gastric cancer tissues with 5 mm in diameter in nude mice models, exhibited excellent red emitting fluorescence imaging and CT imaging.ConclusionThe high-performance FA-conjugated AuNCs@SiO2 nanoprobes can target in vivo gastric cancer cells, can be used for fluorescent and CT dual-mode imaging, and may own great potential in applications such as targeted dual-mode imaging of in vivo early gastric cancer and other tumors with FR positive expression in near future.

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