6 Publications
6.3 Collaborative work
6.3.1 Materials science
Hydrophobic gold nanoparticles were modified with dodecanethiol by ligand exchange, resulting in stable particles that could be dispersed in a polymer matrix. In the lab of our collaboration partner Dr. Gyeong-Man Kim (Halle), a PMMA solution containing the nanoparticles of about 4 nm diameter was used for electrospinning. Depending on the process parameters, the resulting polymer fibers had a diameter of 20-100 nm, by means of TEM it was found that the nanoparticles were arranged in chain-like structures that were formed during the spinning process.
[A5][5] G.-M. Kim, A. Wutzler, H.-J. Radusch, G. H. Michler, P. Simon, R. A. Sperling, W. J.
Parak: "One-Dimensional Arrangement of Gold Nanoparticles by Electrospinning", Chemistry of Materials 2005, 17, 4949-4957.
o Preparation of gold nanoparticles, surface modification by ligand exchange with dodecanethiol that is compatible with desired polymer for electrospinning.
Quantum dots were transferred to aqueous solution by means of an amphiphilic polymer that had been modified with a fluorescent dye. Due to the spectral overlap of the emission of the quantum dots and the absorption of the organic dye in the polymer shell, fluorescence energy transfer was observed, resulting in reduced QD emission and increased emission of the dye. The fluorescent dye served as a model for a calcium-sensitive dye that is intended for a future FRET-based sensor system for application inside cells.
[A6][6] M. T. Fernández-Argüelles, A. Yakovlev, R. A. Sperling, C. Luccardini, S. Gaillard, A. S.
Medel, J.-M. Mallet, J.-C. Brochon, A. Feltz, M. Oheim, W. J. Parak: "Synthesis and characterization of polymer-coated quantum dots with integrated acceptor dyes as FRET-based nanoprobes", NanoLetters 2007, 7, 2613-2617.
o Part of sample characterization
The amphiphilic polymer coating approach was extended for the transfer of hydrophobic mangan ferrite nanoparticles to aqueous solution. The polymer-coated nanoparticles were compared to other coating strategies and the influence of the surface coating on the magnetic relaxation in regard to magnetic resonance imaging was studied.
[A7][7] U. I. Tromsdorf, N. C. Bigall, M. Kaul, O. T. Bruns, M. S. Nikolic, B. Mollwitz, R. A.
Sperling, R. Reimer, H. Hohenberg, W. J. Parak, S. Förster, U. Beisiegel, G. Adam, H. Weller:
"Size and Surface Effects on the MRI Relaxivity of Manganese Ferrite Nanoparticle Contrast Agents ", Nanoletters 2007, 7, 2422-2427.
o Preparation and characterization of part of the samples
49 Yttrium oxide nanoparticles were prepared by a sol-gel method and doped with Eu3+ and Tb3+. The nanoparticles were found to be partially aggregated due to the high-temperature doping process.
The particles could be partially dispersed in organic solution by means of addtition of TOPO or other surfactants and sonication, or in aqueous solution by means of dichloroacetic acid and sonication.
TEM revealed that the particles consisted mostly of small clusters and primary particles.
[A8][8] A. Pandey, M. K. Roy, A. Pandey, M. Zanella, R. C. Sperling, W. J. Parak, H. C. Verma:
"Chloroform- and water-soluble sol-gel derived Eu+++/Y2O3 (red) and Tb+++/Y2O3 (green) nanophosphors: synthesis, characterisation and surface modification ", Nanotechnology 2007, submitted.
o Surface modification and characterization (in part)
Small gold nanoclusters were prepared by synthesis in organic solution and an additional etching step. The particles were transferred to the aqueous phase by dihydrolipoic acid (DHLA), the resulting diameter was smaller than 2 nm and nanoparticles exhibited red fluorescence emission. Though the quantum yield was considerably less than for typical semiconductor quantum dots, these very compact and cadmium-free probes are an interesting alternative in regard to biolabeling applications. The DHLA-modified nanoparticles were conjugated with single biotin moieties and used for fluorescence labeling of cells.
[A9][9] C.-A. Lin, R. A. Sperling, M. Zanella, W. Chang, J. Li, T.-Y. Yang, J.-L. Shen, H.-I. Yeh, W.
Parak: "Synthesis, Characterization and Bio-conjugation of Fluorescent Gold Nanoclusters toward Biological Labeling Applications", ACS Nano 2008, submitted.
o Part of sample characterization
50 6.3.2 Biological systems
Citrate-stabilized gold nanoparticles with a diameter of 10 nm were conjugated with thiol-modified single-stranded DNA. Particles modified with strand A and particles with strand B were mixed, by addition of a linker strand with one end complementary to A and the other end to B, the nanoparticles could be cross-linked. The nanoparticle aggregates exhibited a blue-shifted optical absorption that could be used to generate DNA melting curves of which the melting temperature is decreased in case of a DNA mismatch. By employing a pulsed laser for optical heating, the melting transition could be observed in microseconds, resulting in a significant reduction of analysis time compared to temperature ramps of minutes to hours as in conventional experiments.
[A10][10] J. Stehr, C. Hrelescu, R. A. Sperling, G. Raschke, M. Wunderlich, A. Nichtl, D.
Heindl, K. Kürzinger, W. J. Parak, T. A. Klar, J. Feldmann: "Gold Nano-Stoves for Microsecond DNA Melting Analysis", Nanoletters 2008, 8, 619-623.
Patent: J. Stehr, T. Klar, J. Feldmann, C. Hrelescu, W. Parak, G. Raschke, R. Sperling, M.
Wunderlich, K. Kürzinger, D. Heindl, A. Nichtl, "Genotypisierung mittels optisch geheizter Nanopartikel-Aggregate", German patent submitted.
o Preparation of DNA-modified nanoparticles, purification and characterization.
In a short review article, the application of quantum dots for biolabeling and bioanalytics was discussed.
[A11][11] C.-A. J. Lin, T. Liedl, R. A. Sperling, M. T. Fernández-Argüelles, J. M. Costa-Fernández, R. Pereiro, A. Sanz-Medel, W. H. Chang, W. J. Parak: "Bioanalytics and Biolabeling with Semiconductor Nanoparticles (Quantum Dots)", Journal of Materials Chemistry 2007, 17, 1343-1346.
In a review article, biological applications of gold nanoparticles were summarized, including biolabeling, imaging, sensing, drug or gene delivery or hyperthermal therapy.
[A12][12] R. A. Sperling, P. R. Gil, F. Zhang, M. Zanella, W. J. Parak: "Biological Applications of Gold Nanoparticles", Chemical Society Reviews 2008, 37(9), 1896 - 1908.
In regard to the biodistribution of nanoparticles in organisms, a series of experiments in rats was carried out. Gold nanoparticles with a core diameter of 5 nm were administered via the lungs, guts or by intravenous injection. Prior to application, the nanoparticles were rendered radioactive in a neutron reactor and after incubation of 1 to 24 h, the animals were sacrificed and the organs were dissected. The analysis of radioactivity enabled the sensitive and quantitative detection of the relative particle concentration in the different organs. In this study, gold nanoparticles with sulfonated phosphine, polymer-coating and different length of poly(ethylene glycol) were compared.
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[13] W. G. Kreyling, J. Lipka, S. Takenaka, A. Wenk, R. A. Sperling, W. J. Parak, M. Semmler-Behnke: "Quantitative biokinetics of PEGylated and phosphine-coated 5 nm gold nanoparticles administered either to the lungs, circulation or gut of rats", 2008, in preparation.
o Preparation of gold nanoparticles with different surfaces, purification and characterization.
Certain leukemia cells or cells infected by a leukemia-inducing virus have been found to be affected by an antioxidant mixture consisting of vitamins, amino acids and trace elements. The proliferation and invasiveness of the cancer cells is reduced by this nutrition mixture. The effect of gold nanoparticles on this mechanism has been studied, comparing the impact of polymer-coated and PEGylated nanoparticles on different cell types.
[14] E. Baydoun, S. Sharakeh, R. A. Sperling, P. R. Gil, A. Meinhardt, W. J. Parak: "Gold nanoparticles affect the antiproliferative effect of SNS on HTLV-1 infected cells", 2008, in preparation.
o Synthesis and modification of gold nanoparticles with different surface coatings, purification and characterization of the particles.
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