Vapour Diffusion Sitting Drop Method to Induce Nucleation of Calcium Phosphate on Exfoliated Graphene and Graphene Oxide Flakes

The preparation of graphene/apatite and graphene oxide/apatite hybrid nanocomposites has recently attracted great attention in the biomaterial community. The sitting drop vapor diffusion technique has been assessed as a preparative method for such nanocomposites in this work. The technique has been employed to induce heterogeneous nucleation and growth of calcium phosphate in the presence of exfoliated graphene and commercial graphene oxide flakes, both labeled with L-Alanine. Exfoliated multilayered graphene flakes were produced by sonication-assisted liquid-phase exfoliation of graphite. In both composites, the apatite nanocrystals displayed similar size and shape, but different labile and B-type carbonation contributions. Graphene and graphene oxide flakes also influenced the carbonation degree of the apatite, which was almost half that measured for the apatite blank, as well as the aggregation state of their composites. In this regard, those composites with graphene oxide formed larger aggregates because of their wider size distribution, with a high-volume percentage of nanosheets (of about 4 nm length). Overall, the method is very useful to prepare small amounts of nanocomposite with high reproducibility.

Hypergolic Ignition of 1,3-Cyclodienes by Fuming Nitric Acid toward the Fast and Spontaneous Formation of Carbon Nanosheets at Ambient Conditions

A hypergolic system is a combination of organic fuel and oxidizer that ignites spontaneously upon contact without any external ignition source. Although their main usage pertains to rocket bipropellants, it is only recently that hypergolics have been established from our group as a revolutionary preparative method for the synthesis of different types of carbon nanostructures depending on the organic fuel-oxidizer pair. In an effort to further enrich this concept, the present work describes new hypergolic pairs based on 1,3-cyclohexadiene and 1,3-cyclooctadiene as the organic fuels and fuming nitric acid as the strong oxidizer. Both carbon-rich compounds (ca. 90% C) share a similar chemical structure with unsaturated cyclopentadiene that is also known to react hypergolically with fuming nitric acid. The particular pairs ignite spontaneously upon contact of the reagents at ambient conditions to produce carbon nanosheets in suitable yields and useful energy in the process. The nanosheets appear amorphous with an average thickness of ca. 2 nm and containing O and N heteroatoms in the carbon matrix. Worth noting, the carbon yield reaches the value of 25% for 1,3-cyclooctadiene, i.e., the highest reported so far from our group in this context. As far as the production of useful energy is concerned, the hot flame produced from ignition can be used for the direct thermal decomposition of ammonium dichromate into Cr2O3 (pigment and catalyst) or the expansion of expandable graphite into foam (absorbent and insulator), thus demonstrating a mini flame-pyrolysis burner at the spot.

A novel preparative method for nanoparticle albumin-bound paclitaxel with high drug loading and its evaluation both in vitro and in vivo

We developed a novel preparative method for nanoparticle albumin-bound (nab) paclitaxel with high drug loading, which was based on improved paclitaxel solubility in polyethylene glycol (PEG) and self-assembly of paclitaxel in PEG with albumin powders into nanoparticles. That is, paclitaxel and PEG were firstly dissolved in ethanol, which was subsequently evaporated under vacuum. The obtained liquid was then mixed with human serum albumin powders. Thereafter, the mixtures were added into phosphate-buffered saline and nab paclitaxel suspensions emerged after ultrasound. Nab paclitaxel was finally acquired after dialysis and freeze drying. The drug loading of about 15% (W/V) were realized in self-made nab paclitaxel, which was increased by approximately 50% compared to 10% (W/V) in Abraxane. Now this new preparative method has been authorized to obtain patent from China and Japan. The similar characteristics of self-made nab paclitaxel compared to Abraxane were observed in morphology, encapsulation efficiency, in vitro release, X-ray diffraction analysis, differential scanning calorimetry analysis, and circular dichroism spectra analysis. Consistent concentration-time curves in rats, biodistributions in mice, anti-tumor activities in mice, and histological transmutation in mice were also found between Abraxane and self-made nanoparticles. In a word, our novel preparative method for nab paclitaxel can significantly improve drug loading, obviously decrease product cost, and is considered to have potent practical value.

Synthesis and Properties of Bisthiadiazoles with Ethyl and Butyl Spacers

This article is devoted to a selection of the most effective preparative method for the synthesis of bis(5-amino-1,3,4-thiadiazole-2-yl)alkanes. These compounds are binuclear diamines consisting of symmetrical 1,3,4-thiadiazole fragments connected by alkyl spacers of various lengths. The structures of the obtained compounds were determined by IR spectroscopy, mass-spectrometry and elemental analysis. The possibility of using these molecules as precursors for the synthesis of macroheterocyclic compounds with expended coordination cavity consisting of six small cycles was demonstrated. Optimal synthesis conditions of bis(5-amino-1,3,4-thiadiazole-2-yl)ethane and bis(5-amino-1,3,4-thiadiazole-2-yl)butane were found by variation of reaction time and temperature. Virtual screening of the obtained compounds was carried out in order to predict antibacterial and biological activities as well as toxic properties of the targeted products. On the basis of the known literature data on polynuclear diamines, the exhibition of the liquid crystal properties of the synthesized molecules is supposed.

Synthesis and Reactivity of Uhle’s Ketone and its Derivatives

The Uhle’s ketone and its derivatives are highly versatile intermediates for the synthesis of a variety of 3,4-fused tricyclic indole frameworks, i.e. indole alkaloids of the ergot family, that are found in various bioactive natural products and pharmaceuticals. Therefore, the development of a convenient preparative method for this structural motif as well as its opportune/useful derivatization have been the subject of longstanding interest in the fields of synthetic organic chemistry and medicinal chemistry. Herein, we summarize recent and less recent methods for the preparation of Uhle’s ketone and its derivatives as well as its main reactivity towards the synthesis of bioactive substances. Regarding the preparation, it can be roughly classified into two categories: a) using 4-unfunctionalized and 4-functionalized indole derivatives as starting materials to construct a fused six-member ring, and b) constructing the indole ring through intramolecular cycloaddition. Principally, the reactivity of the cyclic Uhle’s ketone shown here is derived from the classical electrophilicity of the carbonyl carbon or the acidity of the α-hydrogen and, though less intensively investigated, chemical reactions that induce ring expansion to form novel ring skeletons.

A novel method produces native light-harvesting complex II aggregates from the photosynthetic membrane revealing their role in nonphotochemical quenching

Nonphotochemical quenching (NPQ) is a mechanism of regulating light harvesting that protects the photosynthetic apparatus from photodamage by dissipating excess absorbed excitation energy as heat. In higher plants, the major light-harvesting antenna complex (LHCII) of photosystem (PS) II is directly involved in NPQ. The aggregation of LHCII is proposed to be involved in quenching. However, the lack of success in isolating native LHCII aggregates has limited the direct interrogation of this process. The isolation of LHCII in its native state from thylakoid membranes has been problematic because of the use of detergent, which tends to dissociate loosely bound proteins, and the abundance of pigment–protein complexes (e.g. PSI and PSII) embedded in the photosynthetic membrane, which hinders the preparation of aggregated LHCII. Here, we used a novel purification method employing detergent and amphipols to entrap LHCII in its natural states. To enrich the photosynthetic membrane with the major LHCII, we used Arabidopsis thaliana plants lacking the PSII minor antenna complexes (NoM), treated with lincomycin to inhibit the synthesis of PSI and PSII core proteins. Using sucrose density gradients, we succeeded in isolating the trimeric and aggregated forms of LHCII antenna. Violaxanthin- and zeaxanthin-enriched complexes were investigated in dark-adapted, NPQ, and dark recovery states. Zeaxanthin-enriched antenna complexes showed the greatest amount of aggregated LHCII. Notably, the amount of aggregated LHCII decreased upon relaxation of NPQ. Employing this novel preparative method, we obtained a direct evidence for the role of in vivo LHCII aggregation in NPQ.