Synthesis of Upconverting Hydrogel Nanocomposites Using Thiol‐Ene Click Chemistry: Template for the Formation of Dendrimer‐Like Gold Nanoparticle Assemblies

The synthesis of upconverting hydrogel nanocomposites by base‐catalyzed thiol‐ene click reaction between 10‐undecenoic acid capped Yb³⁺/Er³⁺‐doped NaYF₄ nanoparticles and pentaerythritol tetrakis(3‐mercaptopropionate) (PETMP) as tetrathiol monomer is reported. This synthetic strategy for nanocomposite gels is quite different from works where usually the preformed gels are mixed with the nanoparticles. Developing nanocomposites by surface modification of capping ligands would allow tuning and controlling of the separation of the nanoparticles inside the gel network. The hydrogel nanocomposites prepared by thiol‐ene click reaction show strong enhancement in luminescence intensity compared to 10‐undecenoic acid‐capped Yb³⁺/Er³⁺‐doped NaYF₄ nanoparticles through the upconversion process (under 980 nm laser excitation). The hydrogel nanocomposites display strong swelling characteristics in water resulting in porous structures. Interestingly, the resulting nanocomposite gels act as templates for the synthesis of dendrimer‐like Au nanostructures when HAuCl₄ is reduced in the presence of the nanocomposite gels.     

Synthesis and Characterization of Dendrimer‐Encapsulated Bimetallic Core‐Shell PdPt Nanoparticles

Using a successive method, PAMAM dendrimer‐encapsulated bimetallic PdPt nanoparticles have been successfully prepared with core‐shell structures (Pd@Pt DENs). Evidenced by UV‐vis spectra, high resolution transmission electron microscopy, and X‐ray energy dispersive spectroscopy (EDS), the obtained Pd@Pt DENs are monodispersed and located inside the cavity of dendrimers, and they show a different structure from monometallic Pt or Pd and alloy PdPt DENs. The core‐shell structure of Pd@Pt DENs is further confirmed by infrared measurements with carbon monoxide (IR‐CO) probe. In order to prepare Pd@Pt DENs, a required Pd/Pt ratio of 1:2 is determined for the Pt shell to cover the Pd core completely. Finally, a mechanism for the formation of Pd@Pt DENs is proposed.     

Dendrimer‐Tagung in Heidelberg

Unter dem Titel „Dendrimers: Platforms for Chemical Functionality”︁ fand Mitte März in Heidelberg ein zweitägiges Symposium zur Dendrimerforschung statt. 100 Teilnehmer informierten sich in zehn Plenarvorträgen und anhand von 30 Postern über aktuelle Entwicklungen und Ergebnisse. Veranstalter der Tagung waren die Deutsche Akademie der Naturforscher Leopoldina und der Heidelberger Sonderforschungsbereich 623 ‐ „Molekulare Katalyse”︁.     

Discovery of New Thioviridamide‐Like Compounds with Antitumor Activities

Thioviridamide is a structurally unique compound with potent antitumor activity. The biosynthesis of thioviridamide follows a typical pathway as ribosomally synthesized and post‐translationally modified peptides, making the genome mining‐based discovery of thioviridamide‐like compounds rational. Taking advantage of the linkage between the precursor peptide and the metabolite skeleton, we identified a new biosynthetic gene cluster in Streptomyces sp. NRRL S‐87 that could encode thioviridamide analogues. Overexpression of the whole gene cluster led to the isolation and structure elucidation of TVA‐YJ‐4 and TVA‐YJ‐5, two novel thioviridamide‐like compounds featuring N‐terminal capping groups. Chemical screening of the fermentation extracts also detected TVA‐YJ‐6, another new thioviridamide‐like compound with representative methionine sulfoxide. Detailed analysis further revealed that these structural modifications were introduced during the compound extraction process instead of through genuine enzymatic reactions. TVA‐YJ‐4 and TVA‐YJ‐5 display slightly reduced cytotoxic activities against a panel of tumor cell lines in comparison with their parental natural product, TVA‐YJ‐2. Our work will expand the membership of this rare class of compounds and promote related biosynthetic studies.     

Chemical Synthesis of Human Insulin‐Like Peptide‐6

Human insulin‐like peptide‐6 (INSL‐6) belongs to the insulin superfamily and shares the distinctive disulfide bond configuration of human insulin. In this report we present the first chemical synthesis of INSL‐6 utilizing fluorenylmethyloxycarbonyl‐based (Fmoc) solid‐phase peptide chemistry and regioselective disulfide bond construction protocols. Due to the presence of an oxidation‐sensitive tryptophan residue, two new orthogonal synthetic methodologies were developed. The first method involved the identification of an additive to suppress the oxidation of tryptophan during iodine‐mediated S‐acetamidomethyl (Acm) deprotection and the second utilized iodine‐free, sulfoxide‐directed disulfide bond formation. The methodologies presented here offer an efficient synthetic route to INSL‐6 and will further improve synthetic access to other multiple‐disulfide‐containing peptides with oxidation‐sensitive residues.     

CuMgAlFeNO3型纳米层状复合氢氧化物的制备与表征

采用稳态共沉淀法合成了系列CuMgAlFeNO3类水滑石(CMAFNO3-HTLC), 可得到结晶良好的类水滑石材料, 并通过XRD, TG-DSC, FTIR, TEM对产物进行了表征.     

One‐Step Synthesis and Size Control of Dendrimer‐Protected Gold Nanoparticles: A Heat‐Treatment‐Based Strategy

Dendrimer‐protected gold nanoparticles have been facilely obtained by heating an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl₄ without the additional step of introducing other reducing agents. Transmission electron microscopy (TEM) and UV‐vis data indicate the size, the nucleation, and growth kinetics of gold nanoparticles thus formed, which can be tuned by changing the initial molar ratio of dendrimer to gold.

The formation of dendrimer–gold nanoparticles by the heat treatment of an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl₄.     

Pyridoxine‐Derived Organoselenium Compounds with Glutathione Peroxidase‐Like and Chain‐Breaking Antioxidant Activity

One of the vitamin B6 vitamers, pyridoxine, was modified to incorporate selenium in various oxidation states in place of the methyl group in position 2. Such compounds were conveniently accessed by treatment of bis‐4,5‐(carboethoxy)‐2‐iodo‐3‐pyridinol with disodium diselenide and LiAlH₄‐reduction. After work‐up, selone 7 was isolated in good yield as an air‐stable crystalline material. Hydrogen bonding to the neighboring hydroxyl group, as revealed by the short intramolecular Se ??? H distance in the crystal structure is likely to provide extra stabilization to the compound. Computational studies showed that selone 7 is more stable than the corresponding selenol tautomer by 12.2 kcal mol^?1. Hydrogen peroxide oxidation of the selone 7 afforded diselenide 12 , and, on further oxidation, seleninic acid 13 . Treatment of the seleninic acid with thiophenol provided an isolable selenosulfide 14 . The glutathione peroxidase‐like properties of the pyridoxine‐derived compounds were assessed by using the coupled reductase method. Seleninic acid 13 was found to be twofold more active than ebselen. The chain‐breaking capacity of the pyridoxine compounds were studied in a water/chlorobenzene membrane model containing linoleic acid as an oxidizable substrate and N‐acetylcysteine as a thiol reducing agent. Diselenide 15 could match α‐tocopherol when it comes to reactivity towards peroxyl radicals and inhibition time.     

Blue Luminescence of Dendrimer‐Encapsulated Gold Nanoclusters

Direct evidence for the blue luminescence of gold nanoclusters encapsulated inside hydroxyl‐terminated polyamidoamine (PAMAM) dendrimers was provided by spectroscopic studies as well as by theoretical calculations. Steady‐state and time‐resolved spectroscopic studies showed that the luminescence of the gold nanoclusters consisted largely of two electronic transitions. Theoretical calculations indicate that the two transitions are attributed to the different sizes of the gold nanoclusters (Au₈ and Au₁₃). The luminescence of the gold nanoclusters was clearly distinguished from that of the dendrimers.     

Large‐Scale Synthesis of Necklace‐Like Single‐Crystalline PbTiO3 Nanowires

Summary: We show in this communication that large‐scale necklace‐like single‐crystalline tetragonal perovskite PbTiO₃ nanowires can be obtained via a simple electrospinning method. The morphology and the crystal structure are investigated by SEM, XRD, and HRTEM. The length of the necklace‐like PbTiO₃ nanowires is from tens to several tens of micrometers, the wider the diameter of it is between 100 and 200 nm and the thinner the part is between 20 and 50 nm. The necklace‐like PbTiO₃ nanowires exhibit high surface photovoltage under the action of external electric field, which is probably applicable in displaying photoelectric devices of heterojunction structure.

SEM image of the electrospinning necklace‐like PbTiO₃ nanowires.     

Synthesis of Novel Indolo‐Spirocyclic Compounds

In the present work, we succeeded to synthesize the novel indolo‐spirocyclic compounds ( 4 , 5 , 6 , 7 and 11 ) via electrophilic condensation reactions of indoles with carbonyl compounds including different types of ketones, for example, heteroacetyl ketones (3‐acetylindole and 3‐acetylpyridine), cyclohexanone, isatin, cyclohexane‐1,4‐dione, whereas an attempt to prepare the spirocyclic 9 failed. This new idea will open a high prospective for continuous investigations related to the synthesis of novel indolo‐spirocyclic compounds.     

Synthesis of Dendrimer‐Encapsulated Silver Nanoparticles and Its Catalytic Activity on the Reduction of 4‐Nitrophenol

A new type of water soluble PEG core dendrimer having hydroxyl groups at the periphery was synthesized and used to prepare silver nanoparticles. The dendrimer and the dendrimer encapsulated nanoparticles (DENs) were characterized by spectroscopic techniques. The kinetics of catalytic activity of the prepared silver nanoparticle on the reduction of 4‐nitrophenol to 4‐aminophenol by NaBH₄ as a reductant was studied using UV‐Visible spectrophotometer.     

Regioselective Synthesis of Para‐Bromo Aromatic Compounds

Reaction of substituted benzene rings with N‐bromophthalimide, under neutral conditions, gave the corresponding bromo derivatives with a preference for the formation of the para bromo isomer over the ortho isomer. The simple work‐up procedure minimizes loss of product and the yields are good.     

PAMAM Dendrimer‐Based Nanodevices for Nuclear Medicine Applications

Nuclear medicine, involving nuclear medicine imaging and radiotherapy (RT), has become a mainstay of theranostics in the field of nanomedicine and several examples have been successfully translated into clinical practice. The combination of radionuclides with dendrimers has long been investigated in nuclear imaging, such as positron emission tomography (PET) and single‐photon emission computed tomography (SPECT), providing functional information for whole body quantitative analysis with high sensitivity due to the unique structural advantages of the dendrimer platform. Besides, radioisotopes with both therapeutic and imaging functionalities can also be combined with dendrimer platforms for theranostic applications. In this review, the recent advances in the development of radionuclide‐labeled poly(amidoamine) dendrimer‐based nanodevices for targeted PET, SPECT, SPECT/computed tomography, SPECT/magnetic resonance imaging of tumors, RT, as well as for SPECT‐imaging‐guided RT of cancer are summarized. Current restrictions hindering the clinical translation of dendrimer‐based nuclear nanodevices and future prospects are also discussed.     

Synthesis of Hierarchically Porous Sandwich‐Like Carbon Materials for High‐Performance Supercapacitors

For the first time, hierarchically porous carbon materials with a sandwich‐like structure are synthesized through a facile and efficient tri‐template approach. The hierarchically porous microstructures consist of abundant macropores and numerous micropores embedded into the crosslinked mesoporous walls. As a result, the obtained carbon material with a unique sandwich‐like structure has a relatively high specific surface (1235 m² g^?1), large pore volume (1.30 cm³ g^?1), and appropriate pore size distribution. These merits lead to a comparably high specific capacitance of 274.8 F g^?1 at 0.2 A g^?1 and satisfying rate performance (87.7 % retention from 1 to 20 A g^?1). More importantly, the symmetric supercapacitor with two identical as‐prepared carbon samples shows a superior energy density of 18.47 Wh kg^?1 at a power density of 179.9 W kg^?1. The asymmetric supercapacitor based on as‐obtained carbon sample and its composite with manganese dioxide (MnO₂) can reach up to an energy density of 25.93 Wh kg^?1 at a power density of 199.9 W kg^?1. Therefore, these unique carbon material open a promising prospect for future development and utilization in the field of energy storage.     

A Mixed Solvothermal Route to Synthesis of Dice‐Like PbS

The authors developed a simple solvothermal route to synthesis of PbS nanocrystals in the mild binary mixed solvent made of diethylenetriamine (DETA) and water. Two kinds of PbS nanostructures (dice‐like and cubic) have been successfully synthesized in the binary mixed solvothermal system at 150 °C by changing the sulfur source. The products were characterized by X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results show that the as‐prepared dice‐like PbS crystals have a hole on each of their faces. To elucidate the relationship between reaction systems and the morphologies of the final products, the authors also investigated the crystal growth by using different sulfur source. Based on the experimental results, the possible growth mechanism of the dice‐like PbS crystals was proposed.