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- ItemInteraction between immobilized polyelectrolyte complex nanoparticles and human mesenchymal stromal cells(Auckland : DOVE Medical Press, 2014) Woltmann, B.; Torger, B.; Müller, M.; Hempel, U.Background: Implant loosening or deficient osseointegration is a major problem in patients with systemic bone diseases (eg, osteoporosis). For this reason, the stimulation of the regional cell population by local and sustained drug delivery at the bone/implant interface to induce the formation of a mechanical stable bone is promising. The purpose of this study was to investigate the interaction of polymer-based nanoparticles with human bone marrow-derived cells, considering nanoparticles' composition and surface net charge. Materials and methods: Polyelectrolyte complex nanoparticles (PECNPs) composed of the polycations poly(ethyleneimine) (PEI), poly(L-lysine) (PLL), or (N,N-diethylamino)ethyldextran (DEAE) in combination with the polyanions dextran sulfate (DS) or cellulose sulfate (CS) were prepared. PECNPs' physicochemical properties (size, net charge) were characterized by dynamic light scattering and particle charge detector measurements. Biocompatibility was investigated using human mesenchymal stromal cells (hMSCs) cultured on immobilized PECNP films (5-50 nmol·cm-2) by analysis for metabolic activity of hMSCs in dependence of PECNP surface concentration by MTS (3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium, inner salt) assay, as well as cell morphology (phase contrast microscopy). Results: PECNPs ranging between ~50 nm and 150 nm were prepared. By varying the ratio of polycations and polyanions, PECNPs with a slightly positive (PEC+NP) or negative (PEC-NP) net charge were obtained. The PECNP composition significantly affected cell morphology and metabolic activity, whereas the net charge had a negligible influence. Therefore, we classified PECNPs into "variant systems" featuring a significant dose dependency of metabolic activity (DEAE/CS, PEI/DS) and "invariant systems" lacking such a dependency (DEAE/DS, PEI/CS). Immunofluorescence imaging of fluorescein isothiocyanate isomer I (FITC)-labeled PECNPs suggested internalization into hMSCs remaining stable for 8 days. Conclusion: Our study demonstrated that PECNP composition affects hMSC behavior. In particular, the PEI/CS system showed biocompatibility in a wide concentration range, representing a suitable system for local drug delivery from PECNP-functionalized bone substitute materials.
- ItemThe morphology of silver nanoparticles prepared by enzyme-induced reduction(Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2012) Schneidewind, H.; Schüler, T.; Strelau, K.K.; Weber, K.; Cialla, D.; Diegel, M.; Mattheis, R.; Berger, A.; Möller, R.; Popp, J.Silver nanoparticles were synthesized by an enzyme-induced growth process on solid substrates. In order to customize the enzymatically grown nanoparticles (EGNP) for analytical applications in biomolecular research, a detailed study was carried out concerning the time evolution of the formation of the silver nanoparticles, their morphology, and their chemical composition. Therefore, silvernanoparticle films of different densities were investigated by using scanning as well as transmission electron microscopy to examine their structure. Cross sections of silver nanoparticles, prepared for analysis by transmission electron microscopy were additionally studied by energy-dispersive X-ray spectroscopy in order to probe their chemical composition. The surface coverage of substrates with silver nanoparticles and the maximum particle height were determined by Rutherford backscattering spectroscopy. Variations in the silver-nanoparticle films depending on the conditions during synthesis were observed. After an initial growth state the silver nanoparticles exhibit the so-called desert-rose or nanoflower-like structure. This complex nanoparticle structure is in clear contrast to the auto-catalytically grown spherical particles, which maintain their overall geometrical appearance while increasing their diameter. It is shown, that the desert-rose-like silver nanoparticles consist of single-crystalline plates of pure silver. The surface-enhanced Raman spectroscopic (SERS) activity of the EGNP structures is promising due to the exceptionally rough surface structure of the silver nanoparticles. SERS measurements of the vitamin riboflavin incubated on the silver nanoparticles are shown as an exemplary application for quantitative analysis.
- ItemControlling palladium morphology in electrodeposition from nanoparticles to dendrites via the use of mixed solvents(Cambridge : RSC Publ., 2020) Hussein, Haytham E. M.; Amari, Houari; Breeze, Ben G.; Beanland, Richard; Macpherson, Julie V.By changing the mole fraction of water (χwater) in the solvent acetonitrile (MeCN), we report a simple procedure to control nanostructure morphology during electrodeposition. We focus on the electrodeposition of palladium (Pd) on electron beam transparent boron-doped diamond (BDD) electrodes. Three solutions are employed, MeCN rich (90% v/v MeCN, χwater = 0.246), equal volumes (50% v/v MeCN, χwater = 0.743) and water rich (10% v/v MeCN, χwater = 0.963), with electrodeposition carried out under a constant, and high overpotential (−1.0 V), for fixed time periods (50, 150 and 300 s). Scanning transmission electron microscopy (STEM) reveals that in MeCN rich solution, Pd atoms, amorphous atom clusters and (majority) nanoparticles (NPs) result. As water content is increased, NPs are again evident but also elongated and defected nanostructures which grow in prominence with time. In the water rich environment, NPs and branched, concave and star-like Pd nanostructures are now seen, which with time translate to aggregated porous structures and ultimately dendrites. We attribute these observations to the role MeCN adsorption on Pd surfaces plays in retarding metal nucleation and growth.
- ItemStructure of Ni(OH)2 intermediates determines the efficiency of NiO-based photocathodes – a case study using novel mesoporous NiO nanostars(Cambridge : RSC, 2019) Wahyuono, Ruri Agung; Dellith, Andrea; Schmidt, Christa; Dellith, Jan; Ignaszak, Anna; Seyring, Martin; Rettenmayr, Markus; Fize, Jennifer; Artero, Vincent; Chavarot-Kerlidou, Murielle; Dietzek, BenjaminWe report the wet chemical synthesis of mesoporous NiO nanostars (NS) as photocathode material for dye-sensitized solar cells (DSSCs). The growth mechanism of NiO NS as a new morphology of NiO is assessed by TEM and spectroscopic investigations. The NiO NS are obtained upon annealing of preformed β-Ni(OH)2 into pristine NiO with low defect concentrations and favorable electronic configuration for dye sensitization. The NiO NS consist of fibers self-assembled from nanoparticles yielding a specific surface area of 44.9 m2 g-1. They possess a band gap of 3.83 eV and can be sensitized by molecular photosensitizers bearing a range of anchoring groups, e.g. carboxylic acid, phosphonic acid, and pyridine. The performance of NiO NS-based photocathodes in photoelectrochemical application is compared to that of other NiO morphologies, i.e. nanoparticles and nanoflakes, under identical conditions. Sensitization of NiO NS with the benchmark organic dye P1 leads to p-DSSCs with a high photocurrent up to 3.91 mA cm-2 whilst the photoelectrochemical activity of the NiO NS photocathode in aqueous medium in the presence of an irreversible electron acceptor is reflected by generation of a photocurrent up to 23 μA cm-2 © 2019 The Royal Society of Chemistry.