Physics of Surfaces
Physical properties of surfaces and interfaces are relevant in nearly all areas of science and engineering. The fundamental interactions between surfaces, the surrounding fluid and small objects in the fluid play an important role, for example in biology, biotechnology, mechanical engineering, or petroleum geology. The common research question can be expressed as “How does the interplay between physical surface properties, surface and interface chemistry, and fluid flow affect the entire system?”
We follow an interdisciplinary approach focusing on physical, chemical and biological properties of surfaces. The connection between surfaces and fluids is of particular interest because it is essential in many technological systems. Our research portfolio targets at a better understanding of the interplay between surface pattering (morphological and chemical) and modification with the fluid flow. Experimental methods such as microscopy, microfluidics, or spectroscopy are essential tools.
We have open positions for students and postdocs.
25. Schenderlein H., Voss A., Stark R. W., and Biesalski M. Preparation and Characterization of Light-Switchable Polymer Networks Attached to Solid Substrates.
Langmuir. 2013; 29, 14, 4525-4534.
24. Hörner S., Fabritz S., Herce H. D., Avrutina O., Dietz C., Stark R. W., Cardoso M. C. and Kolmar H. Cube-octameric silsesquioxane-mediated cargo peptide delivery into living cancer cells.
Organic & Biomolecular Chemistry. 2012; published online 06 Dec. 2012.
Cube octameric silsesquioxanes (COSS) are among the smallest nanoparticles known to date with a diameter of only 0.7 nm. We describe a COSS-based delivery system which allows for the drug targeting in human cells. It comprises a siloxane core with seven pendant aminopropyl groups and a fluorescently labeled peptidic ligand attached to one cage corner via a reversible disulfide bond to ensure its intracellular release. Bimodal amplitude-modulated atomic force microscopy (AFM) experiments revealed the formation of dendritic COSS structures by a self-assembly of single particles on negatively charged surfaces. Nuclear targeting was demonstrated in HeLa cells by selective binding of released p21Cip1/Waf1-derived cargo peptide to PCNA, a protein involved in DNA replication and repair.
23. Shimizu S., Shimizu T., Thomas H. M., Matern G., Stark R. W., Balden M., Lindig S., Watanabe Y., Jacob W., Sato N. and Morfill G. E. Synthesis of diamond fine particles on levitated seed particles in a rf CH4/H-2 plasma chamber equipped with a hot filament.
J. Appl. Phys.; 2012; 112, 7, 073303.
22. Peter D., Dalmer M., Lechner A., Gigler A. M., Stark R. W. and Bensch W. The influence of liquid media on the fracture strength of polysilicon nanostructures.
Solid State Phenomena. 2012; 187, 127-130.
21. Fabritz S., Hörner S., Könning D., Empting M., Reinwarth M., Dietz C., Glotzbach B., Frauendorf H., Kolmar H. and Avrutina O. From Pico to Nano: Biofunctionalization of Cube-octameric Silsesquioxanes by Peptides and Miniproteins.
Organic & Biomolecular Chemistry; 2012,10, 6287-6293.
Polyhedral silsesquioxanes are considered valuable conjugation scaffolds. Nevertheless, only a few examples of silsesquioxane-assembled peptide oligomers have been reported to date. We developed a new bioorthogonal cube-octameric silsesquioxane (COSS) scaffold bearing eight aminooxy coupling sites allowing for the conjugation of diverse peptides via oxime ligation. We found that the coupling efficacy depends on the ligand in view of steric hindrance and electrostatic repulsion. For the first time scaffold-based conjugation of cystine-knot miniproteins having a backbone of about thirty amino acids was successfully accomplished without loss of bioactivity. Atomic force microscopy (AFM) provided further knowledge on the size of COSS verifying them as picoscaffolds growing upon bioconjugation to nano-dimension.
20. Gigler A. M., Dietz C., Baumann M., Martinez N. F., Garcia F. and Stark R. W. Repulsive Bimodal Atomic Force Microscopy on Polymers.
Beilstein Journal of Nanotechnology; 2012, 3, 456–463.
Bimodal atomic force microscopy can provide high-resolution images of polymers. In the bimodal operation mode, two eigenmodes of the cantilever are driven simultaneously. When examining polymers, an effective mechanical contact is often required between the tip and the sample to obtain compositional contrast, so particular emphasis was placed on the repulsive regime of dynamic force microscopy. We thus investigated bimodal imaging on a polystyrene-block-polybutadiene diblock copolymer surface and on polystyrene. The attractive operation regime was only stable when the amplitude of the second eigenmode was kept small compared to the amplitude of the fundamental mode. To clarify the influence of the higher eigenmode oscillation on the image quality, the amplitude ratio of both modes was systematically varied. Fourier analysis of the time series recorded during imaging showed frequency mixing. However, these spurious signals were at least two orders of magnitude smaller than the first two fundamental eigenmodes. Thus, repulsive bimodal imaging of polymer surfaces yields a good signal quality for amplitude ratios smaller than A01/A02 = 10:1 without affecting the topography feedback.
19. Janko M., Stark R. W. and Zink A. Preservation of 5300-year-old red blood cells in the Iceman.
J. R. Soc. Interface, 2012, 9, 75, 2581-2590.
Changes in elasticity and structures of red blood cells (RBCs) are important indicators of disease, and this makes them interesting for medical studies. In forensics, blood analyses rep- resent a crucial part of crime scene investigations. For these reasons, the recovery and analysis of blood cells from ancient tissues is of major interest. In this study, we show that RBCs were preserved in Iceman tissue samples for more than 5000 years. The morphological and molecular composition of the blood corpuscle is verified by atomic force microscope and Raman spectroscopy measurements. The cell size and shape approximated those of healthy, dried, recent RBCs. Raman spectra of the ancient corpuscle revealed bands that are character- istic of haemoglobin. Additional vibrational modes typical for other proteinaceous fragments, possibly fibrin, suggested the formation of a blood clot. The band intensities, however, were approximately an order of magnitude weaker than those of recent RBCs. This fact points to a decrease in the RBC-specific metalloprotein haemoglobin and, thus, to a degradation of the cells. Together, the results show the preservation of RBCs in the 5000 year old mummy tissue and give the first insights into their degradation.
18. Klein K., Gigler A. M., Aschenbrenner T., Monetti R., Bunk W., Jamitzky F., Morfill G., Stark R. W. and Schlegel J. Label-Free Live-Cell Imaging with Confocal Raman Microscopy.
Biophysical J. 2012; 102 (2), 360 – 368.
Confocal Raman spectroscopy is a noninvasive alternative to established cell imaging methods because it does not require chemical fixation, the use of fluorescent markers, or genetic engineering. In particular, single live-cell, high-resolution imaging by confocal Raman microscopy is desirable because it allows further experiments concerning the individually investi- gated cells. However, to derive meaningful images from the spectroscopic data, one must identify cell components within the dataset. Using immunofluorescence images as a reference, we derive Raman spectral signatures by means of information measures to identify cell components such as the nucleus, the endoplasmic reticulum, the Golgi apparatus, and mitochondria. The extracted signatures allow us to generate representations equivalent to conventional (immuno)fluorescence images with more than three cell components at a time, exploiting the Raman spectral information alone.
17. Shalev T., Gopin A., Bauer M., Stark R. W. and Rahimipour S. Non-leaching antimicrobial surfaces through polydopamine bio-inspired coating of quaternary ammonium salts or an ultrashort antimicrobial lipopeptide.
J. Mater. Chem. 2012; 22, 2026.
16. Davydovskaya P., Janko M., Gaertner F., Ahmad Z., Simsek Ö., Maßberg S. and Stark R.W. Blood platelet adhesion to printed von Willebrand factor.
J Biomed Mater Res Part A 2012; 100A, 335 – 341.
Von Willebrand factor (vWF), a glycoprotein in blood, mediates the adhesion of blood platelets and thus plays a crucial role in hemostasis and thrombosis. Functional coating of surfaces with vWF allows the investigation of in vitro adhesion of blood platelet. We used soft lithography to create a functional patterned substrate. vWF was printed on plasma-treated glass and mica surfaces, producing elon- gated network-like fibril structures. A minimum layer thick- ness of 3 nm was observed, corresponding to the height of a monolayer of vWF. The stability of the patterns was verifiedin a laminar fluid flow, and the bioactivity of the structures was tested with platelet adhesion experiments. Platelets adhered to and spread on printed vWF. These results indicate that printed vWF substrates are stable and functional in typi- cal perfusion experiments, and thus provide a useful tool for studying thrombus formation in vitro.
15. Gorbushina A. A., Kempe A., Rodenacker K., Jütting U., Altermann W., Stark, R. W., Heckl, W. M., Krumbein, W. E. : Quantitative 3-dimensional Image Analysis of Mineral Surface Modifications – Chemical, Mechanical and Biological.
Geomicrobiology J. 2011; 28 (2), 172 – 184.
14 Kremer B., Bauer M., Stark R. W., Gast N., Altermann W., Gursky H. J., Heckl W. M. and Kazmierczaka J. Laser-Raman and atomic force microscopy assessment of the chlorococcalean affinity of problematic microfossils.
J. Raman Spectrosc. 2012; ; 43 (1), 32 – 39.
13. Bauer M., Davydovskaya P., Janko M., Kaliwoda M., Petersen N., Gilder S. and Stark R. W. Raman spectroscopy of laser-induced oxidation of titanomagnetites.
Journal of Raman Spec 2011; 42, 1413 – 1418.
12. Peter D., Dalmer M., Lechner A., Gigler A. M., Stark R. W., Bensch W. Measurement of the mechanical stability of semiconductor line structures in drying liquids with application to pattern collapse.
J. Micromech. Microeng. 2011; 21(2):025001.
Enhanced particle removal processes in wet cleaning processes of semiconductor wafers cause significant lateral forces on the structures. These forces, however, must not exceed the mechanical stability of structures. Thus, the lateral mechanical fracture stability of polysilicon line structures was mechanically tested in process liquids. Liquid isopropanol had a stabilizing effect.
11. Wei T., Gong J., Rössle S. C., Jamitzky F., Heckl W. M., Stark R. W. A leucine-rich repeat assembly approach for homology modeling of the human TLR5-10 and mouse TLR11-13 ectodomains.
J. Mol. Model. 2011; 17(1):27-36.