BMR: Bio-Nanotechnology


Louis X. Tiefenauer, PhD	Research Highlight: Monitoring the step-by-step formation of individual hemolysin channels in free-standing POPC-bilayers which are suspended in nanopores of 200 nm diameter.

Biological cells are surrounded by lipid bilayers and proteins integrated therein control many essential life functions e.g. recognition of cells, transport of nutrients and transmission of signals induced by external ligands. In order to achieve a complete understanding of such fundamental processes, the structureand the function of isolated membrane proteins have to be investigated using adequate materials and methods. Free-standing lipid bilayers suspended in regularly arrayed nanopores are stable for days and protein-mediated ion flow across lipid bilayers is measured using electrochemical techniques.

Monitoring protein-mediated translocation of ions and uncharged molecules across free-standing lipid bilayers suspended in nanopores.

Functioanal assays for membrane proteins using nanopore array supports (MEMNA)

Lipid bilayer membranes immobilized on solid supports are stable but at the cost of a restricted fluidity whereas free standing black lipid membranes in 0.1 mm openings are fluidic but not very stable. We investigate systematically the stability of free-standing lipid bilayers in pores of nanometer dimensions using electrochemical impedance spectroscopy and fluorescence microscopy aimed at achieving both, a high stability and a high fluidity of bilayers.

We use the nanopore arrays to investigate the functionality of two biologically important membrane proteins: the ammonia channel (AmtB) and the voltage-gated sodium channel (NaChBac). Based on their known structures mutant proteins are produced aimed at understanding the transport mechanisms. The function of the reconstituted proteins is investigated using ion selective electrodes.

In the EU-Project ASMENA (http://www.asmena.ethz.ch/) a consortium consisting of 15 partners in 7 European countries is developing nano-scaled platforms as supports for stable free-standing planar lipid bilayers to be used in drug screening and for quantitative measurements of membrane proteins. In the working package 5, PSI focuses on bio-nano interfaces suitable to determine the activity rates of ion channels and transporters using electrochemical methods.

O. Azzaroni, M. Mir, L. Tiefenauer, W. Knoll: Electrochemical rectification with redox-labeled supramolecular bioconjugates: molecular building blocks for the construction of biodiodes. Langmuir, 24, 2878-2883 (2008).

X. Han, M. DiBerardino, A. Studer, H. Sehr, I. Geissbühler, F. K. Winkler, L.X. Tiefenauer: Nanopore arrays for stable and functional free-standing lipid bilayers. Advanced Materials 19, 4466-4470 (2007).

L.X. Tiefenauer: Magnetic nanoparticles as contrast agents for medical diagnosis Chapt. 29 in: “Nanotechnology in biology and medicine, methods devices, and applications”. T. Vo-Dinh (ed.), CRC Press, Taylor&Francis, p. 1-20 (2007).

J. Liu, L. Tiefenauer, S. Tian, P.E. Nielsen & W. Knoll:PNA-DNA hybridization study using labeled-streptavidin by voltammetry and surface plasmon fluorescence spectroscopy. Anal. Chem. 78, 470-476 (2006).

F. Brem, L. Tiefenauer, A. Fink, J. Dobson, A.M. Hirt: A mixture of ferritin and magnetite nanoparticles mimics magnetic properties of human brain tissue. Phys. Rev. B 73, Art. No. 224427 (2006).

L. Tiefenauer: Ethics of nanotechnology in medicine: challenges and promises. NanoBiotechnology, 2 1551-1294, (2006).

J. Liu, S. Tian, L. Tiefenauer, P.E. Nielson & W. Knoll: Simultaneously amplified electrochemical and surface plasmon resonce optical detection of DNA hybridization based on ferrocene-streptavidin conjugates. Anal. Chem. 77, 2756- 2761 (2005).

L. Tiefenauer: Nanotechnologie in der Medizin: Technologiefolgenabschätzung – Theorie und Praxis, 13. Jg.(2) 52-57 (2004).

Padeste, B. Steiger, A. Grubelnik, L. Tiefenauer: Molecular assembly of redox-conductive ferrocene-streptavidin – towards bioelectrochemical devices. Biosensors & Bioelectronics 20, 545-552 (2004).

L. Tiefenauer & K. Brander: Functional assays for membrane proteins in lipid bilayers on nanopore array supports. Patent (2004).

C. Padeste, B. Steiger, A. Grubelnik, L. Tiefenauer: Molecular assembly of redox-conductive ferrocene-streptavidin – towards bioelectrochemical devices. Biosensors & Bioelectronics 19, 239-247 (2003).

B. Steiger, C. Padeste, A. Grubelnik & L. Tiefenauer : Charge transport effects in ferrocene-streptavidin multilayers immobilized on electrode surfaces Electrochimica Acta 48, 761-769 (2003).

L. Tiefenauer & R. Ros: Biointerface analysis on a molecular level (review). Colloids & Surfaces B: Biointerfaces 23, 95-114 (2002).

H. Sorribas, C. Padeste & L. Tiefenauer: Photolithographic generation of protein micropatterns for neuron culture applications. Biomaterials 23, 893-900 (2002).

H. Sorribas, D. Braun, L. Leder, P. Sonderegger & L. Tiefenauer: Adhesion proteins for a tight neuron-electrode contrast. J. Neurosci. Methods 104, 133-141 (2001).

C. Padeste, A. Grubelnik & L. Tiefenauer: Ferrocene-avidin conjugates for bioelectrochemical applications Biosensors & Bioelectronics. 15, 431-438 (2000).

F. Schwesinger, R. Ros, T. Strunz, D. Anselmetti, H.-J. Güntherodt, A. Honegger, L. Jermutus, L. Tiefenauer and A. Plückthun: Unbinding forces of single antibody-antigen complexes correlate with their thermal dissociation rate. Proc. Natl. Acad. Sci. USA 97, 9972-9977 (2000).

R. Ros, F. Schwesinger, D. Anselmetti, M. Kubon, R. Schäfler, A. Plückthun & L. Tiefenauer: Antigen binding forces of individually addressed single-chain Fv antibody molecules. Proc. Natl. Acad. Sci. USA 95, 7402-7405 (1998).

L.X. Tiefenauer, S. Kossek, C. Padeste & P. Thiébaud: Towards amperometric immunosensor devices. Biosensors & Bioelectronics 12, 213-223 (1997).

L. Tiefenauer, A. Tschirky, G. Kühne & R.Y. Andres: In vivo evaluation of magnetic nanoparticles for use as a tumor contrast agent. Magn. Res. Imaging 14, 391-402 (1996).

L.X. Tiefenauer, G. Kühne & R.Y. Andres: Antibody-magnetite nanoparticles: In vitro characterization of a potential tumor specific contrast agent for magnetic resonance imaging. Bioconjug. Chem. 4, 347 - 352 (1993).

L.X. Tiefenauer, D.M. Bodmer, W. Frei & R.Y. Andres: Prevention of bridge binding in immunoassay: A general estradiol tracer structure. J. steroid Biochem. 32, 251-257 (1989).

Paul Scherrer Institut
Structural Biology Group
Biomolecular Research
Life Sciences Department
OFLB/007
CH-5232 Villigen PSI
Switzerland

Louis X. Tiefenauer, PhD

Research Highlight: Monitoring the step-by-step formation of individual hemolysin channels in free-standing POPC-bilayers which are suspended in nanopores of 200 nm diameter.

Research Highlight:
Monitoring the step-by-step formation of individual hemolysin channels in free-standing POPC-bilayers which are suspended in nanopores of 200 nm diameter.