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    General Chemistry

    Responsive exosome nano‐bioconjugates for synergistic cancer therapy

    Exosomes hold great potential in therapeutic development. However, native exosomes usually induce insufficient effects in vivo, and simply act as drug delivery vehicles. Here, we report a chemical engineering approach to construct responsive exosome nano‐bioconjugates for synergistic cancer therapy. Azide modified exosomes derived from M1 macrophages are conjugated with dibenzocyclooctynes modified antibodies of CD47 and SIRPα (aCD47 and aSIRPα) through pH‐sensitive linker. After system administration, such exosome nanobioconjugates can actively target tumors through the specific recognition between aCD47 and CD47 on tumor cell surface. In the acidic tumor microenvironment, the benzoic‐imine bonds of exosome nanobioconjugates are cleaved to release aSIRPα and aCD47 that can respectively block SIRPα on macrophages and CD47, leading to abolished “don’t eat me” signaling and improved phagocytosis of macrophages. Meanwhile, the native M1 exosomes effectively transit the macrophages from pro‐tumoral M2 to anti‐tumoral M1 owing to their abundant contents for M2 reprogram. Thus, the exosome bioconjugates exert the synergistic anticancer effect.

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    Source:: Angewandte Chemie Int. edition

          

    Bifunctional Metal Nanocrystals for Catalyzing and Reporting on Chemical Reactions

    SERS them right: Bifunctional nanocrystals with integrated plasmonic and catalytic activities hold great promise for analyzing chemical reactions by in situ surface‐enhanced Raman spectroscopy (SERS). This Minireview gives a brief introduction to the general strategies for designing such nanocrystals and there use in the elucidation of reaction mechanisms and measurement of kinetics.

    Abstract

    Bifunctional nanocrystals with integrated plasmonic and catalytic activities hold great promise for analyzing chemical reactions by in situ surface‐enhanced Raman spectroscopy. This Minireview gives a brief introduction to the general strategies for designing such nanocrystals, followed by four typical examples, including their fabrication, characterization, and potential limitation. We then use the reduction of 4‐nitrothiophenol and oxidation of 4‐aminothiophenol as two model systems to demonstrate the capabilities of these bifunctional nanocrystals to monitor chemical reactions for the elucidation of reaction mechanisms and measurement of kinetics. We conclude with perspectives on further development of these bifunctional nanocrystals into a viable platform for investigating other types of catalytic reactions.

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    Source:: Angewandte Chemie Int. edition

          

    Syntheses of Atypically Fluorinated Peptidyl Macrocycles through Sequential Vinylic Substitutions

    Synthetic peptides (red) containing combinations of Cys, Tyr, His, and Ser residues react rapidly with OFCP to afford atypically structured macrocycles through successive vinylic substitutions. YXCXXC sequences displace multiple fluorine atoms from OFCP to generate macropolycyclic compounds. This method provides facile access to a range of composite fluorinated macrocycles.

    Abstract

    Small peptides containing combinations of cysteine, tyrosine, histidine, and serine residues react with octafluorocyclopentene (OFCP) to afford atypically structured macrocycles through successive vinylic substitutions. The reactions proceed rapidly in air at 0 °C and are tolerant of spectating tryptophan, asparagine, glutamine, and threonine residues. Hexapeptides of consensus sequence YXCXXC displace four fluorine atoms from OFCP to generate fluorinated macrobicyclic compounds that display dual‐turn surfaces. The method provides facile access to a wide range of previously unknown heterocyclic structures.

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    Source:: Angewandte Chemie Int. edition

          

    Researchers design an improved pathway to carbon-neutral plastics

    Researchers from U of T Engineering and Caltech have designed a new and improved system for efficiently converting CO2, water, and renewable energy into ethylene—the precursor to a wide range of plastic products, from medical devices to synthetic fabrics—under neutral conditions. The device has the potential to offer a carbon-neutral pathway to a commonly used chemical while enhancing storage of waste carbon and excess renewable energy. …read more

    Source:: PhysOrg Chemistry

          

    The good side of carbon monoxide

    Most people think of carbon monoxide as harmful, and with good reason—the colorless, odorless gas sends 50,000 people in the U.S. to hospitals each year when their furnaces malfunction or car engines run in poorly ventilated spaces. But at low concentrations, carbon monoxide has a beneficial side that scientists are trying to harness to treat diseases, according to an article in Chemical & Engineering News (C&EN), the weekly newsmagazine of the American Chemical Society. …read more

    Source:: PhysOrg Chemistry

          

    Non-invasive microscopy detects activation state and distinguishes between cell types

    Most analytical methods in biology require invasive procedures to analyze samples, which leads to irreversible changes or even their destruction. Furthermore, the sensitivity of such approaches often stems from the averaging of signals generated by a large number of cells, making it impossible to study the underlying heterogeneity of responses. …read more

    Source:: PhysOrg Chemistry

          

    Theranostic Layer‐by‐Layer Nanoparticles for Simultaneous Tumor Detection and Gene Silencing

    Layer‐by‐layer nanoparticles are modular drug delivery vehicles that incorporate multiple functional materials through sequential deposition of polyelectrolytes onto charged nanoparticle cores. Here, we combined the multicomponent features and tumor targeting capabilities of layer‐by‐layer assembly with functional biosensing peptides to create a new class of nanotheranostics. These nanoparticles encapsulate a high weight percentage of siRNA while also carrying a synthetic biosensing peptide on the surface that is cleaved into a urinary reporter upon exposure to specific proteases overexpressed in the tumor microenvironment. Importantly, this biosensor reports back on molecular signatures characteristic to metastatic tumors and associated with poor prognosis – MMP9 protease overexpression. We show this nanotheranostic mediates noninvasive urinary‐based diagnostics in mouse models of three different cancers with simultaneous gene silencing in flank and metastatic mouse models of ovarian cancer. This work provides a modular nanotheranostic platform to both perturb and characterize tumors, allowing for simultaneous treatment and monitoring of disease.

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    Source:: Angewandte Chemie Int. edition

          

    ‘Self-cleaning’ concrete could keep buildings looking new

    Building materials that clean themselves could save immense time and labor in homes and businesses, as well as reduce disease risk in settings such as hospitals. Now, researchers reporting in ACS Applied Materials & Interfaces have made a new type of concrete that is strong, heat-insulating and soundproof—and best of all, liquids like milk and coffee bounce right off of it, taking dust particles with them. …read more

    Source:: PhysOrg Chemistry

          

    A benzophenone‐based photocaging strategy for the N7 position of guanosine

    The selective modification of nucleobases with photolabile caging groups provides one of the most versatile strategies to study and control the processes and interactions of nucleic acids. Numerous exocyclic and ring positions of nucleobases have been targeted, but all are formally substituting a hydrogen atom with a photo‐caging group. Nature, however, also explicitly uses ring nitrogen methylation, such as m7G and m1A, to change the electronic structure and properties of RNA and control biomolecular interactions essential for translation and turnover. We report that aryl ketones such as benzophenone and α‐hydroxyalkyl ketone are photolabile caging groups if installed at the N7 position of guanosine or the N1 position of adenosine. Common photo‐caging groups derived from the ortho‐nitrobenzyl moiety were not suitable for these positions. Both chemical and enzymatic methods for site‐specific modification of N7G in nucleosides, dinucleotides and RNA were developed, opening the door to studying the molecular interactions of m7G and m1A with spatio‐temporal control.

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    Source:: Angewandte Chemie Int. edition

          

    Phosphine‐Catalyzed [4+1] Cycloadditions of Allenes with Methyl Ketimines, Enamines, and A Primary Amine

    Unprecedented phosphine‐catalyzed [4+1] cycloadditions of allenyl imides have been discovered using various N‐based substrates including methyl ketimines, enamines, and a primary amine. These transformations provide a one‐pot access to cyclopentenoyl enamines and imines, or (chiral) γ‐lactams via two geminal C–C bond or two C–N bond formations, respectively. Several P‐based key intermediates including a 1,4‐(bis)electrophilic α,β‐unsaturated ketenyl phosphonium species have been detected by 31P NMR and HRMS analyses, which shed light on the postulated catalytic cycle. The synthetic utility of this new chemistry has been demonstrated through a gram‐scaling up of the catalytic reaction as well as regioselective hydrogenation and double condensation to form cyclopentanoyl enamines and fused pyrazole building blocks, respectively.

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    Source:: Angewandte Chemie Int. edition

          

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