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- ItemPolymer Brush-Functionalized Chitosan Hydrogels as Antifouling Implant Coatings(Columbus, Ohio : American Chemical Society, 2017) Buzzacchera, Irene; Vorobii, Mariia; Kostina, Nina Yu; de Los Santos Pereira, Andres; Riedel, Tomáš; Bruns, Michael; Ogieglo, Wojciech; Möller, Martin; Wilson, Christopher J.; Rodriguez-Emmenegger, CesarImplantable sensor devices require coatings that efficiently interface with the tissue environment to mediate biochemical analysis. In this regard, bioinspired polymer hydrogels offer an attractive and abundant source of coating materials. However, upon implantation these materials generally elicit inflammation and the foreign body reaction as a consequence of protein fouling on their surface and concomitant poor hemocompatibility. In this report we investigate a strategy to endow chitosan hydrogel coatings with antifouling properties by the grafting of polymer brushes in a "grafting-from" approach. Chitosan coatings were functionalized with polymer brushes of oligo(ethylene glycol) methyl ether methacrylate and 2-hydroxyethyl methacrylate using photoinduced single electron transfer living radical polymerization and the surfaces were thoroughly characterized by XPS, AFM, water contact angle goniometry, and in situ ellipsometry. The antifouling properties of these new bioinspired hydrogel-brush coatings were investigated by surface plasmon resonance. The influence of the modifications to the chitosan on hemocompatibility was assessed by contacting the surfaces with platelets and leukocytes. The coatings were hydrophilic and reached a thickness of up to 180 nm within 30 min of polymerization. The functionalization of the surface with polymer brushes significantly reduced the protein fouling and eliminated platelet activation and leukocyte adhesion. This methodology offers a facile route to functionalizing implantable sensor systems with antifouling coatings that improve hemocompatibility and pave the way for enhanced device integration in tissue.
- ItemExcited-state relaxation of hydrated thymine and thymidine measured by liquid-jet photoelectron spectroscopy: experiment and simulation(Washington, DC : ACS Publications, 2015) Buchner, Franziska; Nakayama, Akira; Yamazaki, Shohei; Ritze, Hans-Hermann; Lübcke, AndreaTime-resolved photoelectron spectroscopy is performed on thymine and thymidine in aqueous solution to study the excited-state relaxation dynamics of these molecules. We find two contributions with sub-ps lifetimes in line with recent excited-state QM/MM molecular dynamics simulations (J. Chem. Phys.2013, 139, 214304). The temporal evolution of ionization energies for the excited ππ* state along the QM/MM molecular dynamics trajectories were calculated and are compatible with experimental results, where the two contributions correspond to the relaxation paths in the ππ* state involving different conical intersections with the ground state. Theoretical calculations also show that ionization from the nπ* state is possible at the given photon energies, but we have not found any experimental indication for signal from the nπ* state. In contrast to currently accepted relaxation mechanisms, we suggest that the nπ* state is not involved in the relaxation process of thymine in aqueous solution.
- ItemTime-resolved photoelectron spectroscopy of adenine and adenosine in aqueous solution(London [u.a.] : Royal Society of Chemistry, 2013) Buchner, F.; Ritze, H.-H.; Lahl, J.; Lübcke, A.Time-resolved photoelectron spectroscopy is applied to study the excited state dynamics of the DNA base adenine and its ribonucleoside adenosine in aqueous solution for pump and probe photon energies in the range between 4.66 eV and 5.21 eV. We follow the evolution of the prepared excited state on the potential energy surface and retrieve lifetimes of the S1 state under different excitation conditions.
- ItemTiNb2O7 and VNB9O25 of ReO3 type in hybrid Mg−Li batteries: Electrochemical and interfacial insights(Washington, DC : American Chemical Society, 2020) Maletti, Sebastian; Herzog-Arbeitman, Abraham; Oswald, Steffen; Senyshyn, Anatoliy; Giebeler, Lars; Mikhailova, DariaAs one of the beyond-lithium battery concepts, hybrid metal-ion batteries have aroused growing interest. Here, TiNb2O7 (TNO) and VNb9O25 (VNO) materials were prepared using a high-temperature solid-state synthesis and, for the first time, comprehensively examined in hybrid Mg−Li batteries. Both materials adopt ReO3-related structures differing in the interconnection of oxygen polyhedra and the resulting guest ion diffusion paths. We show applicability of the compounds in hybrid cells providing capacities comparable to those reached in Li-ion batteries (LIBs) at room temperature (220 mAh g−1 for TNO and 150 mAh g−1 for VNO, both at 0.1 C), their operability in the temperature range between −10 and 60 °C, and even better capacity retention than in pure LIBs, rendering this hybrid technology superior for long-term application. Post mortem X-ray photoelectron spectroscopy reveals a cathode−electrolyte interface as a key ingredient for providing excellent electrochemical stability of the hybrid battery. A significant contribution of the intercalation pseudocapacitance to charge storage was observed for both materials in Li- and Mg−Li batteries. However, the pseudocapacitive part is higher for TNO than for VNO, which correlates with structural distinctions, providing better accessibility of diffusion pathways for guest cations in TNO and, as a consequence, a higher ionic transport within the crystal structure. © 2020 American Chemical Society
- ItemGrafting of functional methacrylate polymer brushes by photoinduced SET-LRP(Cambridge : RSC Publ., 2016) Vorobii, Mariia; Pop-Georgievski, Ognen; de los Santos Pereira, Andres; Kostina, Nina Yu.; Jezorek, Ryan; Sedláková, Zdeňka; Percec, Virgil; Rodriguez-Emmenegger, CesarPhotoinduced surface-initiated single electron transfer living radical polymerization (SET-LRP) is a versatile technique for the preparation of polymer brushes. The vast diversity of compatible functional groups, together with a high end-group fidelity that enables precise control of the architecture, makes this approach an effective tool for tuning the properties of surfaces. We report the application of photoinduced SET-LRP for the surface-initiated grafting of polymer brushes from a wide range of methacrylate monomers for the first time. The living character of the process was demonstrated by the linear evolution of the polymer brush thickness in time, the ability to reinitiate the polymerization for the preparation of well-defined block copolymers, and also by X-ray photoelectron spectroscopy depth profiling. The surface patterning with these brushes could be achieved simply by restricting the irradiated area. The ability of poly(methacrylate) brushes prepared in this way to prevent non-specific protein adsorption is also demonstrated, indicating the suitability of this procedure for advanced applications.
- ItemFacile one-pot hydrothermal synthesis of a zinc oxide/curcumin nanocomposite with enhanced toxic activity against breast cancer cells(London : RSC Publishing, 2023) Madeo, Lorenzo Francesco; Schirmer, Christine; Cirillo, Giuseppe; Froeschke, Samuel; Hantusch, Martin; Curcio, Manuela; Nicoletta, Fiore Pasquale; Büchner, Bernd; Mertig, Michael; Hampel, SilkeZinc oxide/Curcumin (Zn(CUR)O) nanocomposites were prepared via hydrothermal treatment of Zn(NO3)2 in the presence of hexamethylenetetramine as a stabilizing agent and CUR as a bioactive element. Three ZnO : CUR ratios were investigated, namely 57 : 43 (Zn(CUR)O-A), 60 : 40 (Zn(CUR)O-B) and 81 : 19 (Zn(CUR)O-C), as assessed by thermogravimetric analyses, with an average hydrodynamic diameter of nanoaggregates in the range of 223 to 361 nm. The interaction of CUR with ZnO via hydroxyl and ketoenol groups (as proved by X-ray photoelectron spectroscopy analyses) was found to significantly modify the key properties of ZnO nanoparticles with the obtainment of a bilobed shape (as shown by scanning electron microscopy), and influenced the growth process of the composite nanoparticles as indicated by the varying particle sizes determined by powder X-ray diffraction. The efficacy of Zn(CUR)O as anticancer agents was evaluated on MCF-7 and MDA-MB-231 cancer cells, obtaining a synergistic activity with a cell viability depending on the CUR amount within the nanocomposite. Finally, the determination of reactive oxygen species production in the presence of Zn(CUR)O was used as a preliminary evaluation of the mechanism of action of the nanocomposites.
- ItemBiowaste chicken eggshell powder as a potential cure modifier for epoxy/anhydride systems: competitiveness with terpolymer-modified calcium carbonate at low loading levels(London : RSC Publishing, 2017) Saeb, Mohammad Reza; Ghaffari, Mehdi; Rastin, Hadi; Khonakdar, Hossein Ali; Simon, Frank; Najafi, Farhood; Goodarzi, Vahabodin; Vijayan P., Poornima; Puglia, Debora; Asl, Farzaneh Hassanpour; Formela, KrzysztofBiowaste chicken eggshell (ES) powder was applied as a potential cure modifier in epoxy/anhydride systems. Cure behaviour and kinetics of composites filled with very low content (0.1 wt% based on epoxy resin) of ES, calcium carbonate (CaCO3), and terpolymer-modified fillers, mES and mCaCO3, were discussed comparatively. Surface analysis was performed by X-ray photoelectron spectroscopy. Cure kinetics was investigated by differential (Friedman) and integral (Ozawa and Kissinger-Akahira-Sunose) isoconversional methods using dynamic differential scanning calorimetry (DSC) data. Overall, protein precursors naturally existing in the structure of pristine ES facilitated crosslinking of epoxy and hardener of anhydride with functional groups resulting from terpolymer attachment to CaCO3 particles. Accelerated/hindered cure was observed depending on the filler type and surface characteristics, as investigated via the autocatalytic/non-catalytic nature of reactions and comparison of activation energy values of four types of composites. An enhanced cure was identified for composites containing untreated ES, which could be inferred on account of the lower competitive cure of carboxyl groups in the terpolymer backbone with epoxy compared to peptide groups existing in microporous pristine ES. On the other hand, mCaCO3 revealed low values of activation energy compared to pristine CaCO3, but still of the same order as ground biowaste ES.