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- ItemLocal delivery to malignant brain tumors: potential biomaterial-based therapeutic/adjuvant strategies(Cambridge : RSC, 2021) Alghamdi, Majed; Gumbleton, Mark; Newland, BenGlioblastoma (GBM) is the most aggressive malignant brain tumor and is associated with a very poor prognosis. The standard treatment for newly diagnosed patients involves total tumor surgical resection (if possible), plus irradiation and adjuvant chemotherapy. Despite treatment, the prognosis is still poor, and the tumor often recurs within two centimeters of the original tumor. A promising approach to improving the efficacy of GBM therapeutics is to utilize biomaterials to deliver them locally at the tumor site. Local delivery to GBM offers several advantages over systemic administration, such as bypassing the blood-brain barrier and increasing the bioavailability of the therapeutic at the tumor site without causing systemic toxicity. Local delivery may also combat tumor recurrence by maintaining sufficient drug concentrations at and surrounding the original tumor area. Herein, we critically appraised the literature on local delivery systems based within the following categories: polymer-based implantable devices, polymeric injectable systems, and hydrogel drug delivery systems. We also discussed the negative effect of hypoxia on treatment strategies and how one might utilize local implantation of oxygen-generating biomaterials as an adjuvant to enhance current therapeutic strategies. © 2021 The Royal Society of Chemistry.
- ItemPolyoxometalates as components of supramolecular assemblies(Cambridge : RSC, 2019) Stuckart, Maria; Monakhov, Kirill Yu.The non-covalent interaction of polyoxometalates (POMs) with inorganic- or organic-based moieties affords hybrid assemblies with specific physicochemical properties that are of high interest for both fundamental and applied studies, including the discovery of conceptually new compounds and unveiling the impact of their intra-supramolecular relationships on the fields of catalysis, molecular electronics, energy storage and medicine. This minireview summarises the recent advances in the synthetic strategies towards the formation of such non-covalent POM-loaded assemblies, shedding light on their key properties and the currently investigated applications. Four main emerging categories according to the nature of the conjugate are described: (i) POMs in metal-organic frameworks, (ii) POMs merged with cationic metal complexes, (iii) architectures generated with solely POM units and (iv) POMs assembled with organic molecular networks. © 2019 The Royal Society of Chemistry.
- ItemDavydov splitting and singlet fission in excitonically coupled pentacene dimers(Cambridge : RSC, 2019) Basel, Bettina Sabine; Hetzer, Constantin; Zirzlmeier, Johannes; Thiel, Dominik; Guldi, Rebecca; Hampel, Frank; Kahnt, Axel; Clark, Timothy; Guldi, Dirk Michael; Tykwinski, Rik R.Singlet fission (SF) allows two charges to be generated from the absorption of a single photon and is, therefore, potentially transformative toward improving solar energy conversion. Key to the present study of SF is the design of pentacene dimers featuring a xanthene linker that strictly places two pentacene chromophores in a rigid arrangement and, in turn, enforces efficient, intramolecular π-overlap that mimics interactions typically found in condensed state (e.g., solids, films, etc.). Inter-chromophore communication ensures Davydov splitting, which plays an unprecedented role toward achieving SF in pentacene dimers. Transient absorption measurements document that intramolecular SF evolves upon excitation into the lower Davydov bands to form a correlated triplet pair at cryogenic temperature. At room temperature, the two spin-correlated triplets, one per pentacene moiety within the dimers, are electronically coupled to an excimer state. The presented results are transferable to a broad range of acene morphologies including aggregates, crystals, and films. © 2019 The Royal Society of Chemistry.
- ItemCovalency versus magnetic axiality in Nd molecular magnets: Nd-photoluminescence, strong ligand-field, and unprecedented nephelauxetic effect in fullerenes NdM2N@C80 (M = Sc, Lu, Y)(Cambridge : RSC, 2023) Yang, Wei; Rosenkranz, Marco; Velkos, Georgios; Ziegs, Frank; Dubrovin, Vasilii; Schiemenz, Sandra; Spree, Lukas; de Souza Barbosa, Matheus Felipe; Guillemard, Charles; Valvidares, Manuel; Büchner, Bernd; Liu, Fupin; Avdoshenko, Stanislav M.; Popov, Alexey A.Nd-based nitride clusterfullerenes NdM2N@C80 with rare-earth metals of different sizes (M = Sc, Y, Lu) were synthesized to elucidate the influence of the cluster composition, shape and internal strain on the structural and magnetic properties. Single crystal X-ray diffraction revealed a very short Nd-N bond length in NdSc2N@C80. For Lu and Y analogs, the further shortening of the Nd-N bond and pyramidalization of the NdM2N cluster are predicted by DFT calculations as a result of the increased cluster size and a strain caused by the limited size of the fullerene cage. The short distance between Nd and nitride ions leads to a very large ligand-field splitting of Nd3+ of 1100-1200 cm−1, while the variation of the NdM2N cluster composition and concomitant internal strain results in the noticeable modulation of the splitting, which could be directly assessed from the well-resolved fine structure in the Nd-based photoluminescence spectra of NdM2N@C80 clusterfullerenes. Photoluminescence measurements also revealed an unprecedentedly strong nephelauxetic effect, pointing to a high degree of covalency. The latter appears detrimental to the magnetic axiality despite the strong ligand field. As a result, the ground magnetic state has considerable transversal components of the pseudospin g-tensor, and the slow magnetic relaxation of NdSc2N@C80 could be observed by AC magnetometry only in the presence of a magnetic field. A combination of the well-resolved magneto-optical states and slow relaxation of magnetization suggests that Nd clusterfullerenes can be useful building blocks for magneto-photonic quantum technologies.
- ItemWave-shaped polycyclic hydrocarbons with controlled aromaticity(Cambridge : RSC, 2019) Ma, Ji; Zhang, Ke; Schellhammer, Karl Sebastian; Fu, Yubin; Komber, Hartmut; Xu, Chi; Popov, Alexey A.; Hennersdorf, Felix; Weigand, Jan J.; Zhou, Shengqiang; Pisula, Wojciech; Ortmann, Frank; Berger, Reinhard; Liu, Junzhi; Feng, XinliangControlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) 1 and 2 with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of 2 is unambiguously revealed by single-crystal X-ray crystallography analysis. The wave-shaped geometry is induced by steric congestion in the cove and fjord regions. Remarkably, the aromaticity of these two structural isomers can be tailored by the annulated direction of cyclopenta[b]fluorene units. Isomer 1 (Eoptg = 1.13 eV) behaves as a closed-shell compound with weakly antiaromatic feature, whereas its structural isomer 2 displays a highly stable tetraradical character (y0 = 0.23; y1 = 0.22; t1/2 = 91 days) with a narrow optical energy gap of 0.96 eV. Moreover, the curved PH 2 exhibits remarkable ambipolar charge transport in solution-processed organic thin-film transistors. Our research provides a new insight into the design and synthesis of stable functional curved aromatics with multiradical characters. © The Royal Society of Chemistry.
- ItemPalladium-catalyzed intermolecular transthioetherification of aryl halides with thioethers and thioesters(Cambridge : RSC, 2020) Li, Yahui; Bao, Gao; Wu, Xiao-FengFunctional group transfer reactions are an important synthetic tool in modern organic synthesis. Herein, we developed a new palladium-catalyzed intermolecular transthioetherification reaction of aryl halides with thioethers and thioesters. The synthetic utility and practicality of this catalytic protocol are demonstrated in a wide range of successful transformations (>70 examples). This catalytic protocol is applicable in carbonylative coupling processes as well, and the first example of carbonylative methylthioesterification of aryl halides has been achieved. Notably, this work also provides an approach to using natural products, such as methionine and selenomethionine, as the functional group sources. This journal is © The Royal Society of Chemistry.
- ItemElectrostatically PEGylated DNA enables salt-free hybridization in water(Cambridge : RSC, 2019) Chakraborty, Gurudas; Balinin, Konstantin; Portale, Giuseppe; Loznik, Mark; Polushkin, Evgeny; Weil, Tanja; Herrmann, AndreasChemically modified nucleic acids have long served as a very important class of bio-hybrid structures. In particular, the modification with PEG has advanced the scope and performance of oligonucleotides in materials science, catalysis and therapeutics. Most of the applications involving pristine or modified DNA rely on the potential of DNA to form a double-stranded structure. However, a substantial requirement for metal-cations to achieve hybridization has restricted the range of applications. To extend the applicability of DNA in salt-free or low ionic strength aqueous medium, we introduce noncovalent DNA-PEG constructs that allow canonical base-pairing between individually PEGylated complementary strands resulting in a double-stranded structure in salt-free aqueous medium. This method relies on grafting of amino-terminated PEG polymers electrostatically onto the backbone of DNA, which results in the formation of a PEG-envelope. The specific charge interaction of PEG molecules with DNA, absolute absence of metal ions within the PEGylated DNA molecules and formation of a double helix that is significantly more stable than the duplex in an ionic buffer have been unequivocally demonstrated using multiple independent characterization techniques. This journal is © The Royal Society of Chemistry.
- ItemCargo shuttling by electrochemical switching of core–shell microgels obtained by a facile one-shot polymerization(Cambridge : RSC, 2019) Mergel, Olga; Schneider, Sabine; Tiwari, Rahul; Kühn, Philipp T.; Keskin, Damla; Stuart, Marc C. A.; Schöttner, Sebastian; de Kanter, Martinus; Noyong, Michael; Caumanns, Tobias; Mayer, Joachim; Janzen, Christoph; Simon, Ulrich; Gallei, Markus; Wöll, Dominik; van Rijn, Patrick; Plamper, Felix A.Controlling and understanding the electrochemical properties of electroactive polymeric colloids is a highly topical but still a rather unexplored field of research. This is especially true when considering more complex particle architectures like stimuli-responsive microgels, which would entail different kinetic constraints for charge transport within one particle. We synthesize and electrochemically address dual stimuli responsive core-shell microgels, where the temperature-responsiveness modulates not only the internal structure, but also the microgel electroactivity both on an internal and on a global scale. In detail, a facile one-step precipitation polymerization results in architecturally advanced poly(N-isopropylacrylamide-co-vinylferrocene) P(NIPAM-co-VFc) microgels with a ferrocene (Fc)-enriched (collapsed/hard) core and a NIPAM-rich shell. While the remaining Fc units in the shell are electrochemically accessible, the electrochemical activity of Fc in the core is limited due to the restricted mobility of redox active sites and therefore restricted electron transfer in the compact core domain. Still, prolonged electrochemical action and/or chemical oxidation enable a reversible adjustment of the internal microgel structure from core-shell microgels with a dense core to completely oxidized microgels with a highly swollen core and a denser corona. The combination of thermo-sensitive and redox-responsive units being part of the network allows for efficient amplification of the redox response on the overall microgel dimension, which is mainly governed by the shell. Further, it allows for an electrochemical switching of polarity (hydrophilicity/hydrophobicity) of the microgel, enabling an electrochemically triggered uptake and release of active guest molecules. Hence, bactericidal drugs can be released to effectively kill bacteria. In addition, good biocompatibility of the microgels in cell tests suggests suitability of the new microgel system for future biomedical applications. © 2019 The Royal Society of Chemistry.
- ItemAzapeptide activity-based probes for the SARS-CoV-2 main protease enable visualization of inhibition in infected cells(Cambridge : RSC, 2023) Vanhoutte, Roeland; Barniol-Xicota, Marta; Chiu, Winston; Vangeel, Laura; Jochmans, Dirk; De Jonghe, Steven; Zidane, Hadeer; Barr, Haim M.; London, Nir; Neyts, Johan; Verhelst, Steven H. L.The COVID-19 pandemic has revealed the vulnerability of the modern, global society. With expected waves of future infections by SARS-CoV-2, treatment options for infected individuals will be crucial in order to decrease mortality and hospitalizations. The SARS-CoV-2 main protease is a validated drug target, for which the first inhibitor has been approved for use in patients. To facilitate future work on this drug target, we designed a solid-phase synthesis route towards azapeptide activity-based probes that are capped with a cysteine-reactive electrophile for covalent modification of the active site of Mpro. This design led to the most potent ABP for Mpro and one of the most potent inhibitors reported thus far. We demonstrate that this ABP can be used to visualize Mpro activity and target engagement by drugs in infected cells.
- ItemOn 1,3-phosphaazaallenes and their diverse reactivity(Cambridge : RSC, 2021) Fischer, Malte; Hering-Junghans, Christian1,3-Phosphaazaallenes are heteroallenes of the type RP-C-NR′ and little is known about their reactivity. In here we describe the straightforward synthesis of ArPCNR (Ar = Mes*, 2,4,6-tBu-C6H2;MesTer, 2.6-(2,4,6-Me3C6H2)-C6H3;DipTer, 2.6-(2,6-iPr2C6H2)-C6H3; R =tBu; Xyl, 2,6-Me2C6H3) starting from phospha-Wittig reagents ArPPMe3and isonitriles CNR. It is further shown that ArPCNtBu are thermally labile with respect to the loss of iso-butene and it is shown that the cyanophosphines ArP(H)CN are synthetically feasible and form the corresponding phosphanitrilium borates with B(C6F5)3, whereas deprotonation ofDipTerP(H)CN was shown to give an isolable cyanidophosphide. Lastly, the reactivity of ArPCNR towards Pier's borane was investigated, showing hydroboration of the C-N bond in Mes*PCNtBu to give a hetero-butadiene, while withDipTerPCNXyl the formation of the Lewis acid-base adduct with a B-P linkage was observed. © The Royal Society of Chemistry 2021.