CONTROL OF POLYMER PARTICLE SIZE USING POROUS GLASS MEMBRANE EMULSIFICATION A REVIEW

1.IntroductionPolymerparticleshavebeenusedinvariousfields.Besidestraditionalapplicationssuchaspaint,ink,andpaperindustries,muchattentionhasinrecentyearsbeenpaidtofineapplications,e.g.,carrierforenzyme(Omietal.,1997),separationmedia(Okubo&Hatorri,1993;Inomataetal.,1995;Ugelstadetal.,1992)forprotein,DNAandcell,andcarrierfordruginDrugDeliverySystem(DDS)(Paulettietal.,1997;Russell-Jones,2000).Controlofpolymerparticlesizeisespeciallyimportantinsuchfineapplications.Forexample,whenporouspartic…     

Cover Feature: Mechanism of Oxidative Activation of Fluorinated Aromatic Compounds by N-Bridged Diiron-Phthalocyanine: What Determines the Reactivity? (Chem. Eur. J. 63/2019)

The biodegradation of compounds with C−F bonds is challenging due to the fact that these bonds are stronger than the C−H bond in methane. In this work, results on the unprecedented reactivity of a biomimetic model complex that contains an N-bridged diiron-phthalocyanine are presented; this model complex is shown to react with perfluorinated arenes under addition of H₂O₂ effectively. To get mechanistic insight into this unusual reactivity, detailed density functional theory calculations on the mechanism of C₆F₆ activation by an iron(IV)-oxo active species of the N-bridged diiron phthalocyanine system were performed. Our studies show that the reaction proceeds through a rate-determining electrophilic C−O addition reaction followed by a 1,2-fluoride shift to give the ketone product, which can further rearrange to the phenol. A thermochemical analysis shows that the weakest C−F bond is the aliphatic C−F bond in the ketone intermediate. The oxidative defluorination of perfluoroaromatics is demonstrated to proceed through a completely different mechanism compared to that of aromatic C−H hydroxylation by iron(IV)-oxo intermediates such as cytochrome P450 Compound I.     

Intrinsic Apyrase-Like Activity of Cerium-Based Metal–Organic Frameworks (MOFs): Dephosphorylation of Adenosine Tri- and Diphosphate

Apyrase is an important family of extracellular enzymes that catalyse the hydrolysis of high-energy phosphate bonds (HEPBs) in ATP and ADP, thereby modulating many physiological processes and driving life activities. Herein, we report an unexpected discovery that cerium-based metal–organic frameworks (Ce-MOFs) of UiO-66(Ce) have intrinsic apyrase-like activity for ATP/ADP-related physiological processes. The abundant Ce^III/Ce^IV couple sites of Ce-MOFs endow them with the ability to selectively catalyse the hydrolysis of HEPBs of ATP and ADP under physiological conditions. Compared to natural enzymes, they could resist extreme pH and temperature, and present a broad range of working conditions. Based on this finding, a significant inhibitory effect on ADP-induced platelet aggregation was observed upon exposing the platelet-rich plasma (PRP) to the biomimetic UiO-66(Ce) films, prefiguring their wide application potentials in medicine and biotechnology.     

Total Syntheses of (−)‐Minovincine and (−)‐Aspidofractinine through a Sequence of Cascade Reactions

We report 8‐step syntheses of (?)‐minovincine and (?)‐aspidofractinine using easily available and inexpensive reagents and catalyst. A key element of the strategy was the utilization of a sequence of cascade reactions to rapidly construct the penta‐ and hexacyclic frameworks. These cascade transformations included organocatalytic Michael‐aldol condensation, a multistep anionic Michael‐S_N2 cascade reaction, and Mannich reaction interrupted Fischer indolization. To streamline the synthetic routes, we also investigated the deliberate use of steric effect to secure various chemo‐ and regioselective transformations.     

Hierarchical‐Structured Anatase‐Titania/Cellulose Composite Sheet with High Photocatalytic Performance and Antibacterial Activity

Bulk hierarchical anatase‐titania/cellulose composite sheets were fabricated by subjecting an ultrathin titania gel film pre‐deposited filter paper to a solvo‐co‐hydrothermal treatment by using titanium butoxide as the precursor to grow anatase‐titania nanocrystallites on the cellulose nanofiber surfaces. The titanium butoxide specie is firstly absorbed onto the nanofibers of the cellulose substance through a solvothermal process, which was thereafter hydrolyzed and crystallized upon the subsequent hydrothermal treatment, leading to the formation of fine anatase‐titania nanoparticles with sizes of 2–5 nm uniformly anchored on the cellulose nanofibers. The resulting anatase‐titania/cellulose composite sheet shows a significant photocatalytic performance towards degradation of a methylene blue dye, and introduction of silver nanoparticles into the composite sheet yields an Ag‐NP/anatase‐titania/cellulose composite material possessing excellent antibacterial activity against both Gram‐positive and Gram‐negative bacteria.     

Toward Functional Type III [Fe]‐Hydrogenase Biomimics for H2 Activation: Insights from Computation

The chemistry of [Fe]‐hydrogenase has attracted significant interest due to its ability to activate molecular hydrogen. The intriguing properties of this enzyme have prompted the synthesis of numerous small molecule mimics aimed at activating H₂. Despite considerable effort, a majority of these compounds remain nonfunctional for hydrogenation reactions. By using a recently synthesized model as an entry point, seven biomimetic complexes have been examined through DFT computations to probe the influence of ligand environment on the ability of a mimic to bind and split H₂. One mimic, featuring a bidentate diphosphine group incorporating an internal nitrogen base, was found to have particularly attractive energetics, prompting a study of the role played by the proton/hydride acceptor necessary to complete the catalytic cycle. Computations revealed an experimentally accessible energetic pathway involving a benzaldehyde proton/hydride acceptor and the most promising catalyst.     

Low‐Magnetization Magnetic Microcapsules: A Synergistic Theranostic Platform for Remote Cancer Cells Therapy and Imaging

Multifunctional magnetic microcapsules (MMCs) for the combined cancer cells hyperthermia and chemotherapy in addition to MR imaging are successfully developed. A classical layer‐by‐layer technique of oppositely charged polyelectrolytes (poly(allylamine hydrochloride) (PAH) and poly(4‐styrene sulfonate sodium) (PSS)) is used as it affords great controllability over the preparation together with enhanced loading of the chemotherapeutic drug (doxorubicin, DOX) in the microcapsules. Superparamagnetic iron oxide (SPIOs) nanoparticles are layered in the system to afford MMC1 (one SPIOs layer) and MMC2 (two SPIOs layers). Most interestingly, MMC1 and MMC2 show efficient hyperthermia cell death and controlled DOX release although their magnetic saturation value falls below 2.5 emu g^?1, which is lower than the 7–22 emu g^?1 reported to be the minimum value needed for biomedical applications. Moreover, MMCs are pH responsive where a pH 5.5 (often reported for cancer cells) combined with hyperthermia increases DOX release predictably. Both systems prove viable when used as T2 contrast agents for MR imaging in HeLa cells with high biocompatibility. Thus, MMCs hold a great promise to be used commercially as a theranostic platform as they are controllably prepared, reproducibly enhanced, and serve as drug delivery, hyperthermia, and MRI contrast agents at the same time.