Interdisciplinary Centre
for Bioinformatics

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Methods of functional characterisation of cells

Complementary to a comprehensive molecular cell characterisation, it is a challenge to establish detection technology platforms for the identification of stem and progenitor cells in culture, based on staining free non-invasive and highly multiplexed assays. Fundamental for a reliable characterisation of these cells are standardised culture conditions. At the Institute for Cell Techniques and Applied Stem Cell Biology (A. Bader) bioreactors are designed for different tissue specific cultivations. The inventions include methods and instructions for the GMP-adequate production of vital cell cultures, which can be successively or temporally controlled in closed mini-bioreactors in a completely new way. Cytometric analyses of cells allow to combine monitoring with system-wide exhaustive structural and functional phenotyping in a high number of cells. Application such a cytomics-technology with respect to the identification of regulatory elements governing cellular fate (e.g. lineage specification, cell kinetics) can be performed by our innovative and Europe-wide unique image cytometry system (iCys Slide Based imaging Cytometer, Compucyte, Cambridge MA) that enables for high-content and high-throughput cytometric 2D and 3D analysis of fluorescence and absorption in mixed cell population combined with high resolution confocal analysis and cell tracking. Moreover, the technology of hyperchromatic cytometry has been developed in our laboratory to measure 20 or more cell functions and phenotypes on the single cell level. The fluorescence-based analyses can be further combined with high resolution Phase sensitive Scanning Acoustic Microscopy (PSAM). At Laboratories for Solid State Optics and Acoustics (W. Grill) a variety of schemes has been developed to monitor living cells by ultrasound in such a way that beside of high lateral resolution (1µm at 1.2 GHz) and height detection (nm-resolution) by 3-dimensional phase contrast imaging, quantitative information on the mechanical properties can be derived.

Retina (Müller-Glia) cell trapped and stretched in the optical stretcher

Recently discovered cellular mechanosensitivity and mechanotransduction ask for studies on how active and passive cytoskeletal mechanics contribute to cell function (J. Käs). For this purpose the Division of Soft Matter Physics has developed a unique canon of techniques (AFM-based microrheohology, Optical Cell Stretcher, Optical Cell Guidance that characterise the viscoelastic properties of cells and of individual cytoskeletal components, measure active cellular forces, and exert well-defined mechanical or optomolecular stimuli to influence cytoskeletal activity, release of signalling molecules, and gene expression. Cell elasticity measurements have proven to be a sensitive, inherent, molecular label-free cell marker. The Optical Stretcher has been developed for microfluidic high-throughput and high-content measurements of cell elasticity and cell sorting. A commercial Optical Stretcher will be built and sold by the C.Zeiss AG. European and American patents have been awarded. A further competence (A. Robitzki) is related to miniaturisation of micro-devices, endoluminal biosensors implemented in catheters and stents and "intelligent" minimal invasive monitoring systems coupled to electronic delivery systems. This exclusive technology platform comprises a field of high technology programmes in functional bioelectronical and optical, real time imaging for living biological systems.

(A) Multielectrode array with positioned 3D in vitro retina for real time impedance measurement of cellular events e.g. proliferation, differentiation and electro-physiological stimulation and recording. (B) Photoreceptors e.g. rods and cones immunohistochemically characterised in a cryo-section of a three dimensional in vitro retina.

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Guck J, Ananthakrishnan R, Moon TJ, Cunningham CC, Kas J. Optical deformability of soft biological dielectrics. Phys Rev Lett. 2000;84(23):5451-4.
Humphrey D, Duggan C, Saha D, Smith D, Kas J. Active fluidization of polymer networks through molecular motors. Nature. 2002;416(6879):413-6.
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Mittag A, Lenz D, Gerstner AO, Tarnok A. Hyperchromatic cytometry principles for cytomics using slide based cytometry. Cytometry A. 2006 May 5; [Epub ahead of print].
Ngwa W, Wannemacher R, Grill W. Phase-sensitive acoustic microscopy of polymer thin films. Ultrasonics. 2004; 42(1-9):983-7.
Suselbeck T, ... Robitzki A, Haase KK. In vivo intravascular electric impedance spectroscopy using a new catheter with integrated microelectrodes. Basic Res Cardiol. 2005;100(1):28-34.