Jun.-Prof. Dr. rer. nat. Anzhela Galstyan

Analytical Chemistry
University of Duisburg-Essen

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  • Influence of photosensitizer concentration and polymer composition on photoinduced antimicrobial activity of PVA- and PVA-chitosan-based electrospun nanomaterials cross-linked with tailor-made silicon(IV) phthalocyanine
    Galstyan, A. and Strokov, K.
    Photochemical and Photobiological Sciences (2022)
    The ongoing effort to eradicate pathogenic bacteria and viruses is a major endeavor that requires development of new and innovative materials. Materials based on photodynamic action represent an emerging and attractive area of research, and therefore, a broad understanding of chemical design principles is required. In the present study, we investigated the antibacterial and antiviral activities of five different nanofibrous membranes composed of poly(vinyl alcohol) or poly(vinyl alcohol)-chitosan mixture cross-linked through silicon(IV)phthalocyanine derivative with the aim to identify the role of the carrier polymer and photosensitizers concentration on its efficacy. A straightforward cross-linking process was adopted to create a water-stable material with an almost uniform distribution of the fiber structure, as revealed by scanning electron microscopy. The results of the antimicrobial studies showed that the increase in the amount of chitosan in the polymer mixture, rather than the increase in the photosensitizer concentration, enhanced the activity of the material. Due to their visible light-triggered antimicrobial activity, the resulting materials provide valuable opportunities for both topical antimicrobial photodynamic therapy and the area of environmental remediation. Graphical abstract: [Figure not available: see fulltext.] © 2022, The Author(s).
    view abstract10.1007/s43630-022-00229-9
  • Regulation of photo triggered cytotoxicity in electrospun nanomaterials: role of photosensitizer binding mode and polymer identity
    Galstyan, A. and Majiya, H. and Dobrindt, U.
    Nanoscale Advances 4 (2022)
    Although electrospun nanomaterials containing photoactive dyes currently compete with the present state of art antimicrobial materials, relatively few structure-activity relationships have been established to identify the role of carrier polymer and photosensitizer binding mode on the performance of the materials. In this study scaffolds composed of poly(vinyl alcohol), polyacrylonitrile, poly(caprolactone), and tailor-made phthalocyanine-based photosensitizers are developed utilizing electrospinning as a simple, time and cost-effective method. The photoinduced activity of nanofibrous materials was characterizedin vitroagainstE. coliandB. subtilisas models for Gram-negative and Gram-positive bacteria respectively, as well as against bacteriophages phi6 and MS2 as models for enveloped and non-enveloped viruses respectively. For the first time, we show how polymer-specific properties affect antifouling and antimicrobial activity of the nanofibrous material, indicating that the most promising way to increase efficiency is likelyviamethods that focus on increasing the number of short, but strong and reversible bacteria-surface interactions. © The Royal Society of Chemistry 2021.
    view abstract10.1039/d1na00717c
  • Smartes mit Singulett-Sauerstoff
    Galstyan, A.
    Nachrichten aus der Chemie 70 (2022)
    view abstract10.1002/nadc.20224119950
  • Biodegradable supramolecular micellesviahost-guest interaction of cyclodextrin-terminated polypeptides and adamantane-terminated polycaprolactones
    Pottanam Chali, S. and Azhdari, S. and Galstyan, A. and Gröschel, A.H. and Ravoo, B.J.
    Chemical Communications 57 (2021)
    Biodegradable supramolecular micelles were prepared exploiting the host-guest interaction of cyclodextrin and adamantane. Cyclodextrin-initiated polypeptides acted as the hydrophilic corona, whereas adamantane-terminated polycaprolactones served as the hydrophobic core. © The Royal Society of Chemistry 2021.
    view abstract10.1039/d1cc03372g
  • Phthalocyanin-Synthese: vom Ursprung zu aktuellen Trends
    Galstyan, A.
    Nachrichten aus der Chemie 69 (2021)
    view abstract10.1002/nadc.20214106858
  • Some trends in sustainable catalysis development
    Galstyan, A.
    Nachrichten aus der Chemie 69 (2021)
    view abstract10.1002/nadc.20214116550
  • Turning Photons into Drugs: Phthalocyanine-Based Photosensitizers as Efficient Photoantimicrobials
    Galstyan, A.
    Chemistry - A European Journal 27 (2021)
    One of the most promising alternatives for treating bacterial infections is antimicrobial photodynamic therapy (aPDT), making the synthesis and application of new photoactive compounds called photosensitizers (PS) a dynamic research field. In this regard, phthalocyanine (Pc) derivatives offer great opportunities due to their extraordinary light-harvesting and tunable electronic properties, structural versatility, and stability. This Review, rather than focusing on synthetic strategies, intends to overview current progress in the structural design strategies for Pcs that could achieve effective photoinactivation of microorganisms. In addition, the Review provides a concise look into the recent developments and applications of nanocarrier-based Pc delivery systems. © 2020 The Authors. Published by Wiley-VCH GmbH
    view abstract10.1002/chem.202002703
  • Umbelliferone Decorated Water-soluble Zinc(II) Phthalocyanines – In Vitro Phototoxic Antimicrobial Anti-cancer Agents
    Sowa, A. and Höing, A. and Dobrindt, U. and Knauer, S.K. and Galstyan, A. and Voskuhl, J.
    Chemistry - A European Journal 27 (2021)
    In this contribution we report on the synthesis, characterization and application of water-soluble zinc(II) phthalocyanines, which are decorated with four or eight umbelliferone moieties for photodynamic therapy (PDT). These compounds are linked peripherally to zinc(II) phthalocyanine by a triethylene glycol linker attached to pyridines, leading to cationic pyridinium units, able to increase the water solubility of the system. Beside their photophysical properties they were analyzed concerning their cellular distribution in human hepatocyte carcinoma (HepG2) cells as well as their phototoxicity towards HepG2 cells, Gram-positive (S. aureus strain 3150/12 and B. subtilis strain DB104) and Gram-negative bacteria (E. coli strain UTI89 and E. coli strain Nissle 1917). At low light doses and concentrations, they exhibit superb antimicrobial activity against Gram-positive bacteria as well as anti-tumor activity against HepG2. They are even capable to inactivate Gram-negative bacteria, whereas the dark toxicity remains low. These unique water-soluble compounds can be regarded as all-in-one type photosensitizers with broad applications ranges in the future. © 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH
    view abstract10.1002/chem.202102255
  • Chitosan-Silicon Phthalocyanine Conjugate as Effective Photo-Functional Hydrogel for Tracking and Killing of Bacteria
    Strokov, K. and Galstyan, A.
    European Journal of Organic Chemistry 2020 (2020)
    Hydrogels are attractive materials for many biomedical applications, including drug delivery and wound healing. A light-triggered antibacterial activity can be conferred to the material with the introduction of appropriate photosensitizers (PS). In this study, we have synthesized water-soluble silicon(IV)phthalocyanine derivative (SiPc) that contains four carboxylic groups on the periphery of the macrocycle. Obtained PS serves not only as an active chromophore but also as a cross-linking gelator, enabling simple and easy synthesis of chitosan conjugate (SiPcCh). Although UV/Vis and fluorescence spectroscopic methods showed that both free and conjugated PS are non-aggregated in water media, only SiPcCh possess remarkable antibacterial effect against Gram-positive B. subtilis and Gram-negative E. coli. © 2020 The Authors. European Journal of Organic Chemistry published by Wiley-VCH GmbH
    view abstract10.1002/ejoc.202001363
  • Dye extract of calyces of Hibiscus sabdariffa has photodynamic antibacterial activity: A prospect for sunlight-driven fresh produce sanitation
    Majiya, H. and Galstyan, A.
    Food Science and Nutrition 8 (2020)
    Photodynamic sanitation of fresh produce could help reduce spoilage and disease transmissions where conventional methods of sanitation are not available, and sunlight is available for free. In this study, we evaluated the photostability and photodynamic antibacterial activity of the dye extracts of calyces of Hibiscus sabdariffa. The dye extracts were very photostable in water but bleached in acetate-HCl buffer (pH 4.6), phosphate buffer saline (pH 7.2), and tris base-HCl buffer (pH 8.6). The photostability correlated with the photodynamic antibacterial activity of the dye extracts. Both the methanol and water dye extracts at the concentration of 0.0625 mg/ml caused complete inactivation of Bacillus subtilis (reductions of 8.5 log CFU/ml) within 2 min either with the visible light exposure at 10 mW/cm2 or in the dark without the light exposure. Reductions of 4.8 log CFU/ml and 2.2 log CFU/ml of Escherichia coli were observed when 1 mg/ml of methanol and water dye extracts were used, respectively, in water with the light exposure at 10 mW/cm2 for 20 min. Discussions are included about the ease of the dye extractions of the calyces of H. sabdariffa even in water without the need of energy for heating and the suitability of the dye extracts for the fresh produce sanitation. Dye extract of calyces of H. sabdariffa has photodynamic and nonphotodynamic antibacterial activity which could be exploited for the development of a low-tech sunlight-driven fresh produce sanitation system that is cheap, sustainable, and environmentally friendly. © 2020 The Authors. Food Science & Nutrition published by Wiley Periodicals LLC.
    view abstract10.1002/fsn3.1580
  • Exploring the Impact of Coordination-Driven Self Assembly on the Antibacterial Activity of Low-Symmetry Phthalocyanines
    Galstyan, A. and Ricker, A. and Nüsse, H. and Klingauf, J. and Dobrindt, U.
    ACS Applied Bio Materials 3 (2020)
    Understanding the action mechanisms of self-assembled photosensitizers is very important to determine the requirements that constructing monomers should fulfill to obtain nanostructures with the desired function. Here, the synthesis, supramolecular aggregation tendency, photophysical properties, and antimicrobial photodynamic activity of low-symmetry metal-free phthalocyanine are carefully examined and compared with its metalated counterpart. When exposed to the media with different pH values, striking differences in the self-assembly of these two derivatives were observed. Equilibria between active and inactive forms of this unique supramolecular system were shifted upon change of the microenvironment, influencing its biological activity against Gram-positive and Gram-negative bacteria in planktonic and biofilm states. DFT calculations helped to explain possible differences in the aggregate formation, showing that metal-ligand interaction is a key process behind the higher activity of the metalated derivative. These results point out the importance of intermolecular interactions between photosensitizers, which is essential to guide the design of self-assembled phototheranostic agents with improved performance. Copyright © 2019 American Chemical Society.
    view abstract10.1021/acsabm.9b00873
  • Facile Fabrication of Silicon(IV)Phthalocyanine-Embedded Poly(vinyl alcohol)-Based Antibacterial and Antifouling Interfaces
    Strokov, K. and Schäfer, A.H. and Dobrindt, U. and Galstyan, A.
    ACS Applied Bio Materials 3 (2020)
    Interest in the photodynamic inactivation of bacteria as an alternative method to antibiotic treatment continues to grow. Based on this approach, light-activated anti-infective interfaces could be fabricated via incorporation of photosensitizers into the polymer-based materials. In order to combine photobactericidal and antifouling functions, the choice of the carrier polymer is of particular significance: it should enable fast and effective conjugation of photosensitizer and reduce the formation of bioburden on the artificial material in a biological environment. This study reports one-pot fabrication and characterization of two silicon(IV)phthalocyanine /poly(vinyl alcohol)-based electrospun mats. The method relies on the thermal cross-linking of components by esterification using sebacic acid as a cross-linking agent. Fabricated flexible mats showed photosensitizer-dependent antibacterial photoactivity against different Gram-positive bacteria with low cytotoxic effects on human fibroblasts and were effective against bacterial attachment, as an early step toward future biofilm formation. This work provides practical guidelines in developing photoactive materials and interfaces that can be used in nonadhesive wound dressings, food packaging, water, and air filtration. © 2020 American Chemical Society.
    view abstract10.1021/acsabm.0c00347
  • π-Extended Donor–Acceptor Porphyrins and Metalloporphyrins for Antimicrobial Photodynamic Inactivation
    Galstyan, A. and Maurya, Y.K. and Zhylitskaya, H. and Bae, Y.J. and Wu, Y.-L. and Wasielewski, M.R. and Lis, T. and Dobrindt, U. and Stępień, M.
    Chemistry - A European Journal 26 (2020)
    Free base, zinc and palladium π-extended porphyrins containing fused naphthalenediamide units were employed as photosensitizers in antimicrobial photodynamic therapy (aPDT). Their efficacy, assessed by photophysical and in vitro photobiological studies on Gram-positive bacteria, was found to depend on metal coordination, showing a dramatic enhancement of photosensitizing activity for the palladium complex. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/chem.201905372
  • Determining and unravelling origins of reduced photoinactivation efficacy of bacteria in milk
    Galstyan, A. and Dobrindt, U.
    Journal of Photochemistry and Photobiology B: Biology 197 (2019)
    Bovine mastitis is an endemic disease of dairy cattle that is considered to be one of the most frequent and costly diseases in veterinary medicine. An increase in the incidence of disease results in the increased use of antibiotics, which in turn increases the potential of bacterial resistance. This study aimed to investigate the effectiveness of antimicrobial photodynamic therapy (aPDT) in the treatment of bovine mastitis, as an alternative to systemic antibiotics. To identify the key factors affecting photoinactivation efficacy, realistic experiments in view of the end-use were conducted in milk samples using two different photosensitizers: methylene blue (MB) and silicon (IV) phthalocyanine derivative (SiPc). We explored the effects of divalent ions and fat content on the aPDT outcome and determined influence of different proteins on aPDT efficacy. Levels of bacterial sensitivity to PSs varied depending on the type of bacteria (Gram-positive vs. Gram-negative) and light exposure time. Critical interrelated factors affecting aPDT in milk were identified and an efficient combination of treatment conditions that can lead to a full photodynamic inactivation of bacteria was determined. © 2019
    view abstract10.1016/j.jphotobiol.2019.111554
  • Breaching the wall: morphological control of efficacy of phthalocyanine-based photoantimicrobials
    Galstyan, A. and Dobrindt, U.
    Journal of Materials Chemistry B 6 (2018)
    An efficient treatment of infections using antimicrobial photodynamic therapy (aPDT) anticipates that uptake of photosensitizer (PS) by bacterial cells is very fast and effective. In this work, the design, synthesis, characterization, and photodynamic activity of amphiphilic, water-soluble zinc(ii)phthalocyanine (Zn(ii)Pc) molecules bearing none, three or six thiophenyl moieties are described. We show that PSs that contain no or flexible substituents on non-peripheral positions can photoinactivate microbes at very low loading concentrations and low light doses. In contrast, a PS derivative that contains non-flexible substituents is rendered less effective, despite an increased generation of cytotoxic singlet oxygen, higher lipophilicity and a lower tendency to aggregate. Our unexpected finding emphasizes the role of the morphology of PSs in bacterial cell-molecule interactions and suggests another relevant and hitherto disregarded characteristic to improve PS design. © The Royal Society of Chemistry.
    view abstract10.1039/c8tb01357h
  • Gaining Access to Bacteria through (Reversible) Control of Lipophilicity
    Galstyan, A. and Putze, J. and Dobrindt, U.
    Chemistry - A European Journal 24 (2018)
    The development of antimicrobial photodynamic therapy (aPDT) is highly dependent on the development of suitable photosensitizers (PSs); ideally, affinity of a PS towards bacterial cells should be much higher than that towards mammalian cells. A cationic charge on a PS may lead to its selective binding to bacteria mediated through electrostatic interaction; however, the photodynamic outcome is highly dependent on the lipophilicity of the PS. Herein, we report the aPDT effect of silicon(IV) phthalocyanine derivatives bearing four positive charges and methyl, phenyl, or naphthyl substituents at the periphery of the macrocycle. We show that through modulation of lipophilicity, it is possible to find a therapeutic window in which bacteria, but not mammalian cells, are effectively killed. The photobiological activity of these PSs was significantly lower when they were deployed as host–guest complexes with cucurbit[7]uril (CB[7]). CB[7] blocks the hydrophobic part of the PS and reduces its lipophilicity, indicating that a hydrophobic interaction with the outer membrane of bacterial cells is essential for aPDT activity. The efficacies of the obtained PSs have been evaluated by using different uropathogenic E. coli isolates and human kidney epithelial carcinoma cells. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201704562
  • Oxygen-Insensitive Aggregates of Pt(II) Complexes as Phosphorescent Labels of Proteins with Luminescence Lifetime-Based Readouts
    Delcanale, P. and Galstyan, A. and Daniliuc, C.G. and Grecco, H.E. and Abbruzzetti, S. and Faust, A. and Viappiani, C. and Strassert, C.A.
    ACS Applied Materials and Interfaces 10 (2018)
    The synthesis and photophysical properties of a tailored Pt(II) complex are presented. The phosphorescence of its monomeric species in homogeneous solutions is quenched by interaction with the solvent and therefore absent even upon deoxygenation. However, aggregation-induced shielding from the environment and suppression of rotovibrational degrees of freedom trigger a phosphorescence turn-on that is not suppressed by molecular oxygen, despite possessing an excited-state lifetime ranging in the microsecond scale. Thus, the photoinduced production of reactive oxygen species is avoided by the suppression of diffusion-controlled Dexter-type energy transfer to triplet molecular oxygen. These aggregates emit with the characteristic green luminescence profile of monomeric complexes, indicating that Pt-Pt or excimeric interactions are negligible. Herein, we show that these aggregates can be used to label a model biomolecule (bovine serum albumin) with a microsecond-range luminescence. The protein stabilizes the aggregates, acting as a carrier in aqueous environments. Despite spectral overlaps, the green phosphorescence can be separated by time-gated detection from the dominant autofluorescence of the protein arising from a covalently bound green fluorophore that emits in the nanosecond range. Interestingly, the aggregates also acted as energy donors able to sensitize the emission of a fraction of the fluorophores bound to the protein. This resulted in a microsecond-range luminescence of the fluorescent acceptors and a shortening of the excited-state lifetime of the phosphorescent aggregates. The process that can be traced by a 1000-fold increase in the acceptor's lifetime mirrors the donor's triplet character. The implications for phosphorescence lifetime imaging are discussed. © 2018 American Chemical Society.
    view abstract10.1021/acsami.8b02709
  • Boronic Acid Functionalized Photosensitizers: A Strategy To Target the Surface of Bacteria and Implement Active Agents in Polymer Coatings
    Galstyan, A. and Schiller, R. and Dobrindt, U.
    Angewandte Chemie - International Edition 56 (2017)
    Advanced methods for preventing and controlling hospital-acquired infections via eradication of free-floating bacteria and bacterial biofilms are of great interest. In this regard, the attractiveness of unconventional treatment modalities such as antimicrobial photodynamic therapy (aPDT) continues to grow. This study investigated a new and innovative strategy for targeting polysaccharides found on the bacterial cell envelope and the biofilm matrix using the boronic acid functionalized and highly effective photosensitizer (PS) silicon(IV) phthalocyanine. This strategy has been found to be successful in treating planktonic cultures and biofilms of Gram-negative E. coli. An additional advantage of boronic acid functionality is a possibility to anchor the tailor made PS to poly(vinyl alcohol) and to fabricate a self-disinfecting coating. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/anie.201703398
  • Making and breaking barriers to overcome microbial infections
    Galstyan, A. and Dobrindt, U.
    Optics InfoBase Conference Papers Part F63-OMP 2017 (2017)
    This study investigated a new and innovative strategy for targeting polysaccharides on the bacterial cell envelope and the biofilm matrix and simultaneously anchor the photosensitizer to poly(vinylalkohol) fabricating self-disinfecting coating. © 2017 OSA.
    view abstract10.1364/OMP.2017.OmW3D.4
  • A combined experimental and computational study of the substituent effect on the photodynamic efficacy of amphiphilic Zn(II)phthalocyanines
    Galstyan, A. and Riehemann, K. and Schäfers, M. and Faust, A.
    Journal of Materials Chemistry B 4 (2016)
    Zinc(ii)phthalocyanines (Zn(ii)Pc) have shown promising applications in photodynamic therapy due to their high quantum yield of singlet oxygen generation; however, optimization of their overall properties are required before their clinical application as photosensitizers (PSs). The photosensitization efficiency of photoprobes is strongly influenced by the nature of the conjugated moieties and often it can be efficiently tuned by variation in the substitution pattern. Through this study we examined how the structural design of amphiphilic carbohydrate-based Zn(ii)Pcs affects their photophysical properties, binding affinity to human serum albumin (HSA) and photodynamic activity against human cancer melanoma cells. The replacement of oxygen with sulfur at non-peripheral positions of low-symmetry Zn(ii)Pcs contributes to the bathochromic shift of maximum absorption, which is relevant for the activation of the PS in deeper tissues. Moreover, this modification also influences the overall flexibility of the macrocyclic core and results in different behaviour towards HSA. Density functional theory calculations have been carried out to substantiate the effect of the peripheral environment on the photophysical characteristics and geometry of the molecules. © The Royal Society of Chemistry 2016.
    view abstract10.1039/c6tb01341d
  • Corrigendum to: Labeling and Selective Inactivation of Gram-Positive Bacteria Employing Bimodal Photoprobes with Dual Readouts (Chem. Eur. J., 22, 2016, 10.1002/chem.201504935)
    Galstyan, A. and Block, D. and Niemann, S. and Grüner, M.C. and Abbruzzetti, S. and Oneto, M. and Daniliuc, C.G and Hermann, S. and Viappiani, C. and Schäfers, M. and Löffler, B. and Strassert, C.A. and Andreas, A.
    Chemistry - A European Journal 22 (2016)
    In this Full Paper, a mistake was found regarding the structures of the mannose-derivatives (Scheme 1 and Schemes S3 and S6 in the Supporting Information). As correctly mentioned in the text, we have α-mannosides, whereas β-mannosides are shown in the schemes. The corrected structure for Scheme 1 is shown below and Schemes S3 and S6 have been corrected in the Supporting Information. The authors sincerely apologize for this mistake which does not affect the validity of any data or conclusions reported in the manuscript or the Supporting Information. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
    view abstract10.1002/chem.201601576
  • Labeling and Selective Inactivation of Gram-Positive Bacteria Employing Bimodal Photoprobes with Dual Readouts
    Galstyan, A. and Block, D. and Niemann, S. and Grüner, M.C. and Abbruzzetti, S. and Oneto, M. and Daniliuc, C.G. and Hermann, S. and Viappiani, C. and Schäfers, M. and Löffler, B. and Strassert, C.A. and Faust, A.
    Chemistry - A European Journal 22 (2016)
    Carbohydrate-conjugated silicon(IV) phthalocyanines with bimodal photoactivity were developed as probes with both fluorescent labeling and photosensitizing capabilities, and the concomitant fluorescent labeling and photoinduced inactivation of Gram-positive and Gram-negative models was explored. The maltohexaose-conjugated photoprobe provides a dual readout to distinguish between both groups of pathogens, as only the Gram-positive species was inactivated, even though both appeared labeled with near-infrared luminescence. Antibiotic resistance did not hinder the phototoxic effect, as even the methicillin-resistant pathogen Staphylococcus aureus (MRSA) was completely photoinactivated. Time-resolved confocal fluorescence microscopy analysis suggests that the photoprobe sticks onto the outer rim of the microorganisms, explaining the resistance of Gram-negative species on the basis of their membrane constitution. The mannose-conjugated photoprobe yields a different readout because it is able to label and to inactivate only the Gram-positive strain. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201504935
  • Radical perfluoroalkylation - Easy access to 2-perfluoroalkylindol-3-imines-via electron catalysis
    Leifert, D. and Artiukhin, D.G. and Neugebauer, J. and Galstyan, A. and Strassert, C.A. and Studer, A.
    Chemical Communications 52 (2016)
    Arylisonitriles (2 equivalents) react with alkyl and perfluoroalkyl radicals to form 2-alkylated indole-3-imines via two sequential additions to the isonitrile moiety followed by homolytic aromatic substitution. The three component reaction comprises three C-C bond formations. The endocyclic imine functionality in the products is more reactive in follow up chemistry and hydrolysis of the exocyclic imine leads to 3-oxindoles that show fluorescence properties. © The Royal Society of Chemistry 2016.
    view abstract10.1039/c6cc02284g
  • Silicon(IV) Phthalocyanine-Decorated Cyclodextrin Vesicles as a Self-Assembled Phototherapeutic Agent against MRSA
    Galstyan, A. and Kauscher, U. and Block, D. and Ravoo, B.J. and Strassert, C.A.
    ACS Applied Materials and Interfaces 8 (2016)
    The host-guest complexation of a tailored Si(IV) phthalocyanine with supramolecular β-cyclodextrin vesicles (CDV) was studied, revealing a reduced aggregation of the photoactive center upon binding to the CDV, even in aqueous environments. For this purpose, a photosensitizing unit axially decorated with one adamantyl group and one pyridinium moiety on the other side was obtained by two successive click reactions on a bis-azido-functionalized derivative of Si(IV) phthalocyanine. To evaluate its potential as a photosensitizer against antibiotic-resistant bacteria, comparative studies of the photophysical properties including absorption and emission spectroscopy, lifetimes as well as fluorescence and singlet oxygen quantum yields were determined for the Si(IV) phthalocyanine alone and upon self-assembly on the CDV surface. In vitro phototoxicity against the methicillin-resistant Staphylococcus aureus (MRSA) USA300 was evaluated, showing an almost complete inactivation. © 2016 American Chemical Society.
    view abstract10.1021/acsami.6b02132
  • Bidentate NHC pyrozolate ligands in luminescent platinum(ii) complexes
    Naziruddin, A.R. and Galstyan, A. and Iordache, A. and Daniliuc, C.G. and Strassert, C.A. and De Cola, L.
    Dalton Transactions 44 (2015)
    A bidentate C^N donor set derived from an N-heterocyclic carbene (NHC) precursor linked to a trifluoromethyl (CF3) functionalized pyrazole ring is described for the first time. The ligands have been employed to prepare four new phosphorescent complexes by the coordination of platinum(ii) centres bearing cyclometalated phenyl-pyridine/triazole-pyridine chelates. The electronic and steric environments of these complexes were tuned through the incorporation of suitable substituents in the phenyl-pyridine/triazole-pyridine ligands, wherein the position of the phenyl-ring substituent (a CF3 group) also directs the selective adoption of either a trans or a cis configuration between the CNHC and the Cphenyl donor atoms. Molecular structures obtained by X-ray diffraction for three of the complexes confirm a distorted square-planar configuration around the platinum centre, and DFT calculations show that the substituents have a significant influence on the energies of the frontier orbitals. Moreover, a platinum(ii) complex featuring the new bidentate NHC^pyrazolate ligand and a bulky adamantyl functionalized pyridine-triazole luminophore was observed to be highly emissive and exhibiting a sky-blue luminescence (λEm = 470 nm) with photoluminescence quantum yields as high as 50% in doped PMMA matrices. A complete photophysical investigation of all of the complexes in solution as well as in the solid state is herein reported. © 2015 The Royal Society of Chemistry.
    view abstract10.1039/c4dt03651d
  • Correlating the Structural and Photophysical Features of Pincer Luminophores and Monodentate Ancillary Ligands in PtII Phosphors
    Galstyan, A. and Naziruddin, A.R. and Cebrián, C. and Iordache, A. and Daniliuc, C.G. and De Cola, L. and Strassert, C.A.
    European Journal of Inorganic Chemistry 2015 (2015)
    Phosphorescent PtII complexes featuring pincer luminophores of 2,6-bis(1,2,4-triazolyl)pyridine (H2L1) and 2,6-bis(pyrazolyl)pyridine (H2L3) with a bulky adamantyl or tolyl substituent (H2L4) are systematically compared, and their structural features are correlated with their photophysical properties. The combination with 4-amylpyridine (Py), triphenylphosphine (P) or benzimidazol-2-ylidene (N-heterocyclic carbene, NHC) donors as monodentate ancillary ligands gave a series of highly luminescent triplet emitters with variable aggregation properties. The molecular structures of four of these complexes, namely, Pt-L1-P, Pt-L1-NHC, Pt-L3-P, and Pt-L4-P were garnered from single-crystal X-ray diffraction analysis. The coordination complexes displayed green phosphorescence in solution and in the solid state. In doped poly(methyl methacrylate) (PMMA) matrices, most of the complexes exhibited high phosphorescence quantum yields, which reached 59 % for Pt-L3-P. A comparative analysis between the spectroscopic data and the computed parameters derived from time-dependent density functional theory (TD-DFT) calculations suggests that the emission originates from metal-perturbed ligand-centered excited triplet states (3MP-LC). The radiationless deactivation rate constants of the emissive states can be correlated with the aggregation properties derived from the substitution pattern at the tridentate luminophores and the ancillary ligands, whereas the radiative rate constants are determined by the electronic structures of the complexes. We found that PtII complexes containing pyrazolate donors showed an enhanced charge-transfer character in the excited state, whereas bulky adamantyl moieties and triphenylphosphine ancillary ligands suppress bimolecular aggregation and quenching phenomena. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/ejic.201500949
  • Sterically Hindered Luminescent PtII-Phosphite Complexes for Electroluminescent Devices
    Mydlak, M. and Yang, C.-H. and Polo, F. and Galstyan, A. and Daniliuc, C.G. and Felicetti, M. and Leonhardt, J. and Strassert, C.A. and De Cola, L.
    Chemistry - A European Journal 21 (2015)
    PtII complexes with one bulky, sterically demanding, tertiary phosphite ancillary ligand and a coordinating chromophore are herein presented. The phosphite ligand, tris(2,4-di-tert-butylphenyl) acts as a bidentate ligand coordinating the platinum ion through the central phosphorus atom and a cyclometalating carbon atom of one of the substituents. The two free phenoxy moieties lie above and below the coordination plane, leading to steric hindrance that avoids aggregation and provides solubility in organic solvents. The other two coordination sites on the central metal ion are occupied by a chromophoric ligand, which is responsible for the energy of the luminescent excited state. This separation of functions, on the two coordinated ligands, allows the use of a wider range of luminophores with good luminescent properties, maintaining the control of the intermolecular interactions with the non-chromophoric ligand. Based on this approach we were able to achieve a bright deep blue emission (λ= 444 nm, Φem=0.38) from a complex with a tailored ligand, which was then used for the fabrication of an electroluminescent device. In addition commercially available luminophores were also employed to synthesize green emitters. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/chem.201405839
  • Targeted photoinduced killing of bacterial pathogens: From chemical synthesis to photobiological application
    Galstyan, A. and Niemann, S. and Schäfers, M. and Strassert, C.A. and Faust, A.
    Optical Molecular Probes, Imaging and Drug Delivery, OMP 2015 (2015)
    This study focuses on the synthesis, photophysical characterization and examination of photodynamic efficiency of maltohexaose-conjugated silicon phthalocyanines. In this paper we present symmetrically substituted derivative showing selective killing of Gram-positive S.aureus bacteria. © OSA 2015.
    view abstract10.1364/omp.2015.om2d.4
  • Preparation of dithienylphospholes by 1,1-carboboration
    Möbus, J. and Galstyan, A. and Feldmann, A. and Daniliuc, C.G. and Fröhlich, R. and Strassert, C.A. and Kehr, G. and Erker, G.
    Chemistry - A European Journal 20 (2014)
    In this study the scope of the 1,1-carboboration reaction was extended to the preparation of mixed heterole-based conjugated π-systems. Two arylbis(alkynyl)phosphane starting materials 2 were synthesized bearing two thiophene isomers at the alkyne units and the bulky tipp-substituent (tipp=2,4,6-triisopropylphenyl) at the phosphorous atom. The bis(thienylethynyl)phosphanes 2 were converted into the corresponding 2,5-thienyl-substituted 3-borylphospholes 4 in a double 1,1-carboboration reaction sequence employing the strongly electrophilic B(C6F 5)3 reagent under mild reaction conditions. Subsequent Suzuki-Miyaura type cross-coupling yielded the corresponding 3-phenylphospholes 7 in a one-pot procedure from phosphanes 2 in high yields. Phospholes 7 were converted into the respective phosphole oxides 8. A photophysical characterization of derivatives 7 and 8 was carried out. The results presented here demonstrate the suitability of the 1,1-carboboration reaction for the preparation of phosphole-/thiophene-based, light-emitting systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201403102
  • Discrete and polymeric heteronuclear constructs derived from triangular 2,2′-bipyrazine complexes of cis-a2PtII (with a = NH3 or a2 = en)
    Galstyan, A. and Sanz Miguel, P.J. and Weise, K. and Lippert, B.
    Dalton Transactions 42 (2013)
    cis-[Pta2(H2O)2]2+ (with a = NH3 or a2 = en) and 2,2′-bipyrazine (2,2′-bpz) react in water preferentially to cyclic, triangular complexes of composition [{cis-Pta2(2,2′-bpz-N4,N4′)}3]6+ (a = NH3, 1a; a2 = en, 1b). In their C3-symmetric conformation (all bridging pyrazine rings adopt cisoid orientations with respect to the central C2-C2′ bond), 1a and 1b provide three pairs of N1,N1′ donor sites each, which are capable of chelating additional (hetero)metal ions. The latter can in turn bridge to other N1,N1′ sites in an intermolecular fashion or simply complete their coordination spheres with other ligands (water, anions). Four previously not observed structural variants of heteronuclear (PtII, CuII; PtII, Ag I; PtII, CdII) constructs have now been isolated by us and are reported here: a decanuclear Pt6Cu4 complex, [{(en)Pt(2,2′-bpz)}3]2Cu 4(H2O)6(NO3)20· 11H2O (2) with the appearance of a paddle-wheel, a dodecanuclear Pt6Cu6 capsule with a Cu2+ ion in its interior and additional Cu2+ ions in its periphery giving a total composition of [{(en)Pt(2,2′-bpz)}3]2Cu11(NO 3)34(H2O)18·3H2O (3), as well as two coordination polymers, {[{(en)Pt(2,2′-bpz)} 3]Cd2(H2O)7}(SO4) 5·{[Cd(H2O)6](SO4)} ·15H2O (4) and [{cis-(NH3)2Pt(2, 2′-bpz)}3]Ag(SiF6)3(BF 4)·7H2O (5). The structures of these four compounds are dominated by host-guest interactions between the triangular metal vases of 1a and 1b and anions, respectively, as well as hydrogen bonding involving anions and water molecules and electrostatics. In aqueous solution considerable dissociation of the heteronuclear compounds 2-5 into the triangular Pt complexes 1 and the heterometal ions takes place. Preliminary AFM (atomic force microscopy) studies reveal that the +6 cations of 1a have a strong tendency to interact with double-stranded DNA with formation of condensed DNA states. © 2013 The Royal Society of Chemistry.
    view abstract10.1039/c3dt51589c
  • Periodic mesoporous organosilica-based nanocomposite hydrogels as three-dimensional scaffolds
    Kehr, N.S. and Prasetyanto, E.A. and Benson, K. and Ergün, B. and Galstyan, A. and Galla, H.-J.
    Angewandte Chemie - International Edition 52 (2013)
    Dye-loaded periodic mesoporous organosilica particles functionalized with bioactive molecules were used for the generation of a nanocomposite alginate hydrogel. The affinity of cells was up to four times higher with the embedded particles than with simple alginate hydrogel, caused by both the nanometer-scale particle itself and its bioactive functionalization. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/anie.201206951
  • A "directed" approach toward a cationic molecular square containing four isonicotinamidate ligands and (4 + 2) (en)PtII metal entities
    Galstyan, A. and Sanz Miguel, P.J. and Lippert, B.
    Inorganica Chimica Acta 374 (2011)
    The use of 4-cyanopyridine (4-CNpy) and 3-cyanopyridine (3-CNpy) as ditopic ligands with 180° and 120° directionalities, respectively, for the construction of molecular architectures with the 90° metal fragments (en)PtII and (en)PdII in water is hampered by the ease with which these ligands undergo hydrolysis to isonicotinamide (4-C(O)NH 2py) and nicotinamide (3-C(O)NH2py). As described in this article, out of six X-ray structurally characterized complexes (1-6), only a single one (1) reveal coordination of the unchanged ligand (4-CNpy) to (en)PtII. Nevertheless also the hydrolysis products are of interest in the context of obtaining discrete metallacyclic compounds: Thus, (en)Pt II and 4-C(O)NH2py form a hexanuclear complex, [PF 6{(en)Pt}6(4-C(O)NHpy)4](NO3) 7·10H2O (2), in which the anionic isonicotinamidate ligands function as tridentate, bridging ligands to produce a hybrid between a metallasquare and a 2-floor open box. The resulting cation with a +8 charge accommodates a single hexafluorophosphate anion in its interior. Adjacent cations of 2 pack in such a way as to develop Pt4 chains as typically seen in "platinum blues" and their [PtII]4 precursors. © 2011 Elsevier B.V. All rights reserved.
    view abstract10.1016/j.ica.2011.02.041
  • Discrete Molecular Squares {[(en)M(CN)]4}4+ Derived from [(en)M(CN)2] (M = PtII, PdII)
    Galstyan, A. and Sanz Miguel, P.J. and Wolf, J. and Freisinger, E. and Lippert, B.
    European Journal of Inorganic Chemistry (2011)
    C2h-symmetrical tetranuclear metallacycles {[M(en)(CN)] 4}(NO3)4 with M = PdII (4) and PtII (5) have been prepared upon reacting M(en)(CN)2 [M = PdII (1), PtII (2)] with [M(en)(H2O) 2](NO3)2. Replacement of the nitrate anions of 5 by terephthalate anions yields the corresponding salt 5a. The X-ray crystal structures of 1, 4, 5, and 5a have been determined. In the metallacycles 4, 5, and 5a the four metals form almost ideal squares with average M···M distances of ca. 5.05 Ã? (5, 5a) and 5.08 Ã? (4) along the sides. As shown by 1H NMR spectroscopy, the Pt square 5 is stable in aqueous solution, whereas the Pd square 4 undergoes rearrangement reactions upon aging or the presence of other Pd species such as (bpy)PdII. Preliminary studies on the possibility of non-covalent interactions of 4 and 5 with model nucleobases in water reveal that only 5 is useful in this respect. According to the concentration-dependence 1H NMR study, there is an interaction with the purine base 9-ethyladenine, molecular details of which are unclear at this stage, however. Compound 4 is substitutionally labile and is transformed into the coordination compound 8 with 1-methylcytosine. Two more side products, produced during the various reactions carried out, were characterized by X-ray crystallography: [Pt(en) 2][Pt(CN)4] (3) and [Pd(bpy)(en)](SO4) ·3H2O (7). Cationic molecular squares composed of (en)M (M = PtII, PdII) corners and cyanide bridges have been prepared and details of their formation and reactivity have been studied. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/ejic.201001216
  • Supramolecular isomerism of 2,2′-bipyrazine complexes with cis-(NH 3) 2Pt II: Ligand rotational state and sequential orientation determine the 3D shape of metallacycles
    Galstyan, A. and Shen, W.-Z. and Freisinger, E. and Alkam, H. and Hiller, W. and Sanz Miguel, P.J. and Schürmann, M. and Lippert, B.
    Chemistry - A European Journal 17 (2011)
    2,2′-Bipyrazine (2,2′-bpz) reacts with cis-(NH 3) 2Pt II in water to give a variety of products, several of which were isolated and characterized by X-ray analysis: cis-[Pt(NH 3) 2(2,2′-bpz-N4) 2](NO 3) 2·3 H 2O (1), [{cis-Pt(NH 3) 2(2,2′-bpz-N4,N4′)} 3](PF 6) 5NO 3·7 H 2O (2 a), [{cis-Pt(NH 3) 2(2,2′-bpz-N4,N4′)} 3](BF 4) 2(SiF 6) 2· 15 H 2O (2 b), and [{cis-Pt(NH 3) 2(2,2′- bpz-N4,N4′)} 4](SO 4) 4·22 H 2O (3). In 1, 2 b, and 3 the 2,2′-bpz ligands adopt approximately C 2h symmetries, hence the two pyrazine halves are in trans orientation, whereas in 2 a all three 2,2′-bpz bridges are approximately C 2v symmetric, with the pyrazine halves cis to each other. The topologies of the two triangular complexes 2 a and 2 b are consequently distinctly different, but nevertheless both cations act as hosts for anions. In 2 a a PF 6 - and a NO 3 - anion are associated simultaneously with the +6 cation, whereas in 2 b it is a BF 4 - anion and a water molecule, which are trapped in its cavity. There is no anion inclusion in case of the metallasquare 3. In principle, 3 can exist in a large number of stereoisomers, depending on the rotational states of the bridging 2,2′-bpz ligands. Isolation of a single rotamer form of 3 with C 2h symmetric 2,2′-bpz ligands and an overall meso form is proposed to be a consequence of a highly efficient self-assembly process that starts from the precursor 1 and reaction with two cis-(NH 3) 2Pt II units. This process leads to the isolated rotamer of 3 regardless of whether two cations 1 in head-head form react with two cis-(NH 3) 2Pt II, or whether the Δ enantiomer of the chiral head-tail form of 1 combines with its Λ enantiomer through two cis-(NH 3) 2Pt II entities. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    view abstract10.1002/chem.201101381
  • Electrostatics plus O-π interactions rather than "Directed" hydrogen bonding keep so42- in a triangular Pt 3Pd3-tris(2,2′-bipyrazine) host
    Galstyan, A. and Sanz Miguel, P.J. and Lippert, B.
    Chemistry - A European Journal 16 (2010)
    (Figure Presented) Not just hydrogen bonds can trap SO4 2- in a host cavity! Rather, a combination of electrostatic attraction, incomplete anion dehydration, and π interactions between the oxygen atoms and N-heterocyclic ligands of the host will do it as well (see picture). © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
    view abstract10.1002/chem.201000500
  • NO3(SO4)2: Snapshot of nitrate insertion into a cationic Pt3 metallacycle or simply a packing effect?
    Galstyan, A. and Sanz Miguel, P.J. and Lippert, B.
    Dalton Transactions 39 (2010)
    The X-ray crystal structure of [{(en)Pt(2,2′-bpz,N4,N4′)} 3](NO3)2(SO4)2· 13H2O (3) reveals a NO3- ion sandwiched between pyrazine moieties and oriented roughly perpendicular to the Pt3 plane, which is in contrast to the in-plane orientation of NO3 - when a second anion (ClO4-) is taken up by the Pt3 metallacycle simultaneously. © The Royal Society of Chemistry.
    view abstract10.1039/c0dt00463d
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