Michael Hausmann - Academia.edu (original) (raw)

Papers by Michael Hausmann

Journal of Computational Science, 2012

Services@MediGRID MediGRID Healthgrids Grid-based tool set for genetics Grid business concepts a ... more Services@MediGRID MediGRID Healthgrids Grid-based tool set for genetics Grid business concepts a b s t r a c t

PloS one, 2015

It has been well established that the architecture of chromatin in cell nuclei is not random but ... more It has been well established that the architecture of chromatin in cell nuclei is not random but functionally correlated. Chromatin damage caused by ionizing radiation raises complex repair machineries. This is accompanied by local chromatin rearrangements and structural changes which may for instance improve the accessibility of damaged sites for repair protein complexes. Using stably transfected HeLa cells expressing either green fluorescent protein (GFP) labelled histone H2B or yellow fluorescent protein (YFP) labelled histone H2A, we investigated the positioning of individual histone proteins in cell nuclei by means of high resolution localization microscopy (Spectral Position Determination Microscopy = SPDM). The cells were exposed to ionizing radiation of different doses and aliquots were fixed after different repair times for SPDM imaging. In addition to the repair dependent histone protein pattern, the positioning of antibodies specific for heterochromatin and euchromatin wa...

A procedure was developed to provide differential fluorescent staining of metaphase chromosomes i... more A procedure was developed to provide differential fluorescent staining of metaphase chromosomes in Suspension following nucleic acid hybridization. For this purpose metaphase chromosomes were isolated from a Chinese hamster x human hybrid cell line. After hybridization with biotinylated human genomic DNA, the human chromosomes were visualized by indirect immunofluorescence using antibodies against biotin and fluoresceine-isothiocyanate-(FITC)-labeled second antibodies. This resulted in green fluorescent human chromosomes. In contrast, Chinese hamster chromosomes revealed red fluorescent staining only when counterstained with propidium iodide. Notably, interspecies chromosomal rearrangements could be easily detected. After hybridization and fluorescent staining, chromosomes still showed a well-preserved morphology under the light microscope. We suggest that this procedure may have a useful application in flow cytometry and sorting.

Science, 2007

Arrays promise to advance biology through the parallel screening for binding partners. We show th... more Arrays promise to advance biology through the parallel screening for binding partners. We show the combinatorial in situ synthesis of 40,000 peptide spots per square centimeter on a microchip. Our variant Merrifield synthesis immobilizes activated amino acids as monomers within particles, which are successively attracted by electric fields generated on each pixel electrode of the chip. With all different amino

Cytometry, 1998

Fluorescence in situ hybridization (FISH) has become a powerful tool in chromosome analysis. This... more Fluorescence in situ hybridization (FISH) has become a powerful tool in chromosome analysis. This report describes the systematic optimization of the Fast-FISH technique for centromere labeling of human metaphase chromosomes for radiobiological dosimetry purposes. For the present study, the hybridization conditions and the efficiency of two commercially available ␣-satellite DNA probes were compared (''human chromosome 1 specific'', Oncor, Gaithersburg, MD, vs. ''all-human chromosomes specific'', Boehringer-Mannheim, Germany). These probes were hybridized to human lymphocyte metaphase plates by using a hybridization buffer without formamide and without any other equivalent denaturing chemical agents. The results indicate the suitability of the method for automated image analysis on the basis of thresholding. The optimal conditions concerning hybridization time and temperature were determined by a systematic quantitative evaluation of the fluorescent labeling sites after the hybridization procedures. Under defined ''low strin-gency'' conditions, we found that the ''human chromosome 1 specific'' DNA probe labeled not only the centromere of the human chromosome 1 but also the other human centromeres in the same way as the ''all-human chromosome specific'' DNA probe. The optimized conditions to complete all centromere labeling were applied to the detection of dicentric chromosomes on irradiated human lymphocyte samples (␥-rays of 60 Co source, 0.5 Gy/min, for doses of 1, 3, and 4 Gy). The yield of dicentrics was determined after Fast-FISH and compared with results obtained after Giemsa staining. These results are very compatible and indicate that, because of its simplicity, this optimized Fast-FISH procedure would be useful for fast screening purposes in biological dosimetry after accidental overexposure. Cytometry 31:153-162, 1998. 1998 Wiley-Liss, Inc.

2011 21st International Conference on Field Programmable Logic and Applications, 2011

Localization microscopy enhances the resolution of fluorescence light microscopy by about an orde... more Localization microscopy enhances the resolution of fluorescence light microscopy by about an order of magnitude. Single fluorescent molecules act as switchable markers. Their detected signals can be fitted with a two-dimensional Gaussian distribution and thus located with sub-pixel resolution. In this paper we propose that these fits can be done by calculating the center of mass instead of an iterative least-square fit without loosing precision. The simplification of the algorithm leads to an acceleration of more than a factor of 100 and enables an FPGA implementation with an additional performance boost by a factor of 225. Our findings allow the real-time processing of current and future image data rates in localization microscopy.

Micron (Oxford, England : 1993), 2011

Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-R... more Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-Rayleigh limit of about 200 nm laterally and 600 nm axially. So far, this progress was achieved using labelling with appropriate fluorochromes and fluorescent proteins. Here, we describe for the first time that optical resolution of cellular structures in the λ/10 range (∼50 nm) can be achieved even in label-free cells. This was obtained using Spectral Precision Distance/Position Determination Microscopy (SPDM), a method based on the general principles of localisation microscopy. Besides a substantial resolution improvement of autofluorescent structures, SPDM revealed cellular objects which are not detectable under conventional fluorescence imaging conditions.

Novel methods of visible light microscopy have overcome the limits of resolution hitherto thought... more Novel methods of visible light microscopy have overcome the limits of resolution hitherto thought to be insurmountable. The localization microscopy technique presented here based on the principles of Spectral Precision Distance Microscopy (SPDM) with conventional fluorophores under special physical conditions allows to measure the spatial distribution of single fluorescence labeled molecules in entire cells with macromolecular precision which is comparable

In order to produce a toner mass, one of 20 different Fmoc-amino acid OPfp esters (Fluka, 10% w/w... more In order to produce a toner mass, one of 20 different Fmoc-amino acid OPfp esters (Fluka, 10% w/w), a polymer, e.g. SLEC PLT 7552 (Sekisui, 84.5% w/w), pyrazolone orange (ABCR GmbH, 4.5% w/w), and Fe(naphtol) 2 complex (1% w/w) were melted, mixed and finally solidified ). The homogenized and crushed toner mass was then mixed with ~ 0,04% w/w silica particles (Degussa, Aerosil 812, hydrophobic), and slowly fed into an air jet mill where grinded particles were collected within a narrow lattice (Hosokawa alpine 50AS). The physical parameters of aminoacid-particles are described by a mean diameter of ∼10µm, a small size distribution ( ), a low tendency to aggregate, melting points of 60-80°C ( ), a Q/m value of ~ -4µC/g, and a similar toner transfer for the 20 different amino-acid-particles ( ). These parameters were measured with a Mastersizer (Malvern, type 2000), by differential scanning calorimetry (Netzsch, type DSC 204 F1 Phoenix), and a Q/m meter (Trek, type 210HS-2), respectively. Light microscopy and scanning electron microscopy (SEM) pictures to determine particle morphology ( ) were taken with an Axiovert 35 light microscope (Zeiss) and an SEM (LEO; Microscope type 1530; 10 kV electron volts). The stability of OPfp esters embedded into amino-acidparticles was analyzed by HPLC ( ). S2 2. Size distribution of amino-acid-and toner particles Figure S1. The medium diameter of magenta toner particles (Toner ref.) from the OKI color laser printer series C7400 (OKI) is ~10µm as measured by laser diffraction (Malvern Mastersizer 2000, Malvern Instruments). Milling conditions for amino-acidtoners were optimized to achieve similar size distributions.

Sensors and Actuators B: Chemical, 2010

We built high voltage complementary metal oxide semiconductor (CMOS) chips that generate electric... more We built high voltage complementary metal oxide semiconductor (CMOS) chips that generate electrical fields on their surface, such that electrically charged microparticles (diameter 10-20 m on average) can be addressed on distinct pixel electrodes according to arbitrary field patterns. Each pixel contains a memory cell in canonical low-voltage CMOS-technology controlling a high voltage (30-100 V) potential area on the top metal layer. Particle transfer with minimal contaminations in less than 10 s for a complete chip was observed for pixels of 100 m × 100 m down to 65 m × 65 m. This allows a new way to create surface modifications on top of CMOS chips without need for additional masks or stamps. Using suitable particles, a chemically modified chip surface, and compatible chemistry, this method can be utilized for self-aligned high-density biopolymer arrays, e.g., peptide arrays. Transfer of microparticles loaded with amino acids for combinatorial peptide synthesis is demonstrated. Successful synthesis of different peptides (octamers) was proven by immunostaining. Based on results obtained by a chip containing pixel areas of different characteristics, a chip for biological applications with 16,384 pixels (10,000 pixel/cm 2 ) was built. Good homogeneity of peptide synthesis over the chip area was verified by immunostaining.

Sensors and Actuators A: Physical, 2011

Spatially selective deposition of electrically charged microparticles onto integrated circuits th... more Spatially selective deposition of electrically charged microparticles onto integrated circuits that generate electrical fields in programmable patterns using electrodes on their surface was previously limited to a pixel pitch of 100μm. Now, we demonstrate spatially selective deposition onto pixels of 45μm pitch in experiments on a test chip allowing arbitrary patterns, but being of limited size and of fixed characteristics,

Review of Scientific Instruments, 2010

Image processing and pattern analysis can evaluate the deposition quality of triboelectrically ch... more Image processing and pattern analysis can evaluate the deposition quality of triboelectrically charged microparticles on charged surfaces. The image processing method presented in this paper aims at controlling the quality of peptide arrays generated by particle based solid phase Merrifield combinatorial peptide synthesis. Incorrectly deposited particles are detected before the amino acids therein are coupled to the growing peptide. The calibration of the image acquisition is performed in a supervised training step in which all parameters of the quality analyzing algorithm are learnt given one representative image. Then, the correct deposition pattern is determined by a linear support vector machine. Knowing the pattern, contaminated areas can be detected by comparing the pattern with the actual deposition. Taking into account the resolution of the image acquisition system and its magnification factor, the number and size of contaminating particles can be calculated out of the number of connected foreground pixels.

Review of Scientific Instruments, 2008

We examined the high precision deposition of toner and polymer microparticles with a typical size... more We examined the high precision deposition of toner and polymer microparticles with a typical size of approximately 10 microm on electrode arrays with electrodes of 100 microm and below using custom-made microelectronic chips. Selective desorption of redundant particles was employed to obtain a given particle pattern from preadsorbed particle layers. Microparticle desorption was regulated by dielectrophoretic attracting forces generated by individual pixel electrodes, tangential detaching forces of an air flow, and adhesion forces on the microchip surface. A theoretical consideration of the acting forces showed that without pixel voltage, the tangential force applied for particle detachment exceeded the particle adhesion force. When the pixel voltage was switched on, however, the sum of attracting forces was larger than the tangential detaching force, which was crucial for desorption efficiency. In our experiments, appropriately large dielectrophoretic forces were achieved by applying high voltages of up to 100 V on the pixel electrodes. In addition, electrode geometries on the chip's surface as well as particle size influenced the desorption quality. We further demonstrated the compatibility of this procedure to complementary metal oxide semiconductor chip technology, which should allow for an easy technical implementation with respect to high-resolution microparticle deposition.

Review of Scientific Instruments, 2007

In this study examples for a noncontact procedure that allow the description of instant electric ... more In this study examples for a noncontact procedure that allow the description of instant electric charging of moving microparticles that contact dielectric surfaces, for instance, of a flow hose are presented. The described principle is based on the measurement of induced currents in grounded metal wire probes, as moving particles pass close to the probe. The feasibility of the approach was tested with laser printer toner particles of a given size for different basic particle flow and charging conditions. An analytic description for the induced currents was developed and compared to observed effects in order to interpret the results qualitatively. The implementation of the presented procedure can be applied to transparent and nontransparent particle containers and flow lines of complex geometry which can be composed from the presented basic flow stream configurations.

Micron, 2011

Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-R... more Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-Rayleigh limit of about 200 nm laterally and 600 nm axially. So far, this progress was achieved using labelling with appropriate fluorochromes and fluorescent proteins. Here, we describe for the first time that optical resolution of cellular structures in the /10 range (∼50 nm) can be achieved even in label-free cells. This was obtained using Spectral Precision Distance/Position Determination Microscopy (SPDM), a method based on the general principles of localisation microscopy. Besides a substantial resolution improvement of autofluorescent structures, SPDM revealed cellular objects which are not detectable under conventional fluorescence imaging conditions.

Journal of Proteome Research, 2007

Complementary metal oxide semiconductor (CMOS) microelectronic chips fulfill important functions ... more Complementary metal oxide semiconductor (CMOS) microelectronic chips fulfill important functions in the field of biomedical research, ranging from the generation of high complexity DNA and protein arrays to the detection of specific interactions thereupon. Nevertheless, the issue of merging pure CMOS technology with a chemically stable surface modification which further resists interfering nonspecific protein adsorption has not been addressed yet. We present a novel surface coating for CMOS microchips based on poly(ethylene glycol)methacrylate graft polymer films, which in addition provides high loadings of functional groups for the linkage of probe molecules. The coated microchips were compatible with the harshest conditions emerging in microarray generating methods, thoroughly retaining structural integrity and microelectronic functionality. Nonspecific adsorption of proteins on the chip's surface was completely obviated even with complex serum protein mixtures. We could demonstrate the background-free antibody staining of immobilized probe molecules without using any blocking agents, encouraging further integration of CMOS technology in proteome research.

Journal of Physics D: Applied Physics, 2007

We present a method based on induced currents in a cylindrical probe which allows analysis of the... more We present a method based on induced currents in a cylindrical probe which allows analysis of the micro-particle charging processes in an aerosol. The micro particles were triboelectrically charged by passing through a dielectric tube coaxially mounted into the probe. The cylindrical probe enabled the quantification of particle charging without prior calibration of the probe. An analytic model was developed

Journal of Physics D: Applied Physics, 2010

A device for the measurement of q/m-values and charge degradation of triboelectrically charged pa... more A device for the measurement of q/m-values and charge degradation of triboelectrically charged particles deposited on a surface was developed. The setup is based on the integration of currents, which are induced in a Faraday cage by insertion of a solid support covered with charged particles. The conductivity of different particle supports was taken into account. The 'blow-off' method, in

Journal of Microscopy, 2009

We present a novel technique of far-field localization nanoscopy combining spectral precision dis... more We present a novel technique of far-field localization nanoscopy combining spectral precision distance microscopy with widely used fluorochromes like the Green Fluorescent Protein (GFP) derivatives eGFP, EmGFP, Yellow Fluorescent Protein (YFP) and eYFP, synthetic dyes like Alexa 488 and Alexa 568, as well as fluoresceine derivates. Spectral precision distance microscopy allows the surpassing of conventional resolution limits in fluorescence far-field microscopy by precise object localization after the optical isolation of single signals in time. Based on the principles of this technique, our novel nanoscopic method was realized for laser optical precision localization and image reconstruction with highly enhanced optical resolution in intact cells. This allows for spatial assignment of individual fluorescent molecules with nanometre precision. The technique is based on excitation intensity dependent reversible photobleaching of the molecules used combined with fast time sequential imaging under appropriate focusing conditions. A meaningful advantage of the technique is the simple applicability as a universal tool for imaging and investigations to the major part of already available preparations according to standard protocols. Using the above mentioned fluorophores, the positions of single molecules within cellular structures were determined by visible light with an estimated localization precision down to 3 nm; hence distances in the range of 10-30 nm were resolved between individual fluorescent molecules allowing to apply different quantitative structure analysis tools.

Journal of Microscopy, 2011

The Her2/neu tyrosine kinase receptor is a member of the epidermal growth factor family. It plays... more The Her2/neu tyrosine kinase receptor is a member of the epidermal growth factor family. It plays an important role in tumour genesis of certain types of breast cancer and its overexpression correlates with distinct diagnostic and therapeutic decisions. Nevertheless, it is still under intense investigation to improve diagnostic outcome and therapy control. In this content, we applied spectral precision distance/position determination microscopy, a technique based on the general principles of localization microscopy in order to study tumour typical conformational changes of receptor clusters on cell membranes. We examined two different mamma carcinoma cell lines as well as cells of a breast biopsy of a healthy donor. The Her2/neu receptor sites were labelled by immunofluorescence using conventional fluorescent dyes (Alexa conjugated antibodies). The characterization of the Her2/neu distribution on plasma membrane sections of 176 different cells yielded a total amount of 20 637 clusters with a mean diameter of 67 nm. Statistical analysis on the single molecule level revealed differences in clustering of Her2/neu between all three different cell lines. We also showed that using spectral precision distance/position determination microscopy, a dual colour reconstruction of the 3D spatial arrangement of Her2/neu and Her3 is possible. This indicates that spectral precision distance/position determination microscopy could be used as an enhanced tool offering additional information of Her2/neu receptor status.

Journal of Computational Science, 2012

Services@MediGRID MediGRID Healthgrids Grid-based tool set for genetics Grid business concepts a ... more Services@MediGRID MediGRID Healthgrids Grid-based tool set for genetics Grid business concepts a b s t r a c t

PloS one, 2015

It has been well established that the architecture of chromatin in cell nuclei is not random but ... more It has been well established that the architecture of chromatin in cell nuclei is not random but functionally correlated. Chromatin damage caused by ionizing radiation raises complex repair machineries. This is accompanied by local chromatin rearrangements and structural changes which may for instance improve the accessibility of damaged sites for repair protein complexes. Using stably transfected HeLa cells expressing either green fluorescent protein (GFP) labelled histone H2B or yellow fluorescent protein (YFP) labelled histone H2A, we investigated the positioning of individual histone proteins in cell nuclei by means of high resolution localization microscopy (Spectral Position Determination Microscopy = SPDM). The cells were exposed to ionizing radiation of different doses and aliquots were fixed after different repair times for SPDM imaging. In addition to the repair dependent histone protein pattern, the positioning of antibodies specific for heterochromatin and euchromatin wa...

A procedure was developed to provide differential fluorescent staining of metaphase chromosomes i... more A procedure was developed to provide differential fluorescent staining of metaphase chromosomes in Suspension following nucleic acid hybridization. For this purpose metaphase chromosomes were isolated from a Chinese hamster x human hybrid cell line. After hybridization with biotinylated human genomic DNA, the human chromosomes were visualized by indirect immunofluorescence using antibodies against biotin and fluoresceine-isothiocyanate-(FITC)-labeled second antibodies. This resulted in green fluorescent human chromosomes. In contrast, Chinese hamster chromosomes revealed red fluorescent staining only when counterstained with propidium iodide. Notably, interspecies chromosomal rearrangements could be easily detected. After hybridization and fluorescent staining, chromosomes still showed a well-preserved morphology under the light microscope. We suggest that this procedure may have a useful application in flow cytometry and sorting.

Science, 2007

Arrays promise to advance biology through the parallel screening for binding partners. We show th... more Arrays promise to advance biology through the parallel screening for binding partners. We show the combinatorial in situ synthesis of 40,000 peptide spots per square centimeter on a microchip. Our variant Merrifield synthesis immobilizes activated amino acids as monomers within particles, which are successively attracted by electric fields generated on each pixel electrode of the chip. With all different amino

Cytometry, 1998

Fluorescence in situ hybridization (FISH) has become a powerful tool in chromosome analysis. This... more Fluorescence in situ hybridization (FISH) has become a powerful tool in chromosome analysis. This report describes the systematic optimization of the Fast-FISH technique for centromere labeling of human metaphase chromosomes for radiobiological dosimetry purposes. For the present study, the hybridization conditions and the efficiency of two commercially available ␣-satellite DNA probes were compared (''human chromosome 1 specific'', Oncor, Gaithersburg, MD, vs. ''all-human chromosomes specific'', Boehringer-Mannheim, Germany). These probes were hybridized to human lymphocyte metaphase plates by using a hybridization buffer without formamide and without any other equivalent denaturing chemical agents. The results indicate the suitability of the method for automated image analysis on the basis of thresholding. The optimal conditions concerning hybridization time and temperature were determined by a systematic quantitative evaluation of the fluorescent labeling sites after the hybridization procedures. Under defined ''low strin-gency'' conditions, we found that the ''human chromosome 1 specific'' DNA probe labeled not only the centromere of the human chromosome 1 but also the other human centromeres in the same way as the ''all-human chromosome specific'' DNA probe. The optimized conditions to complete all centromere labeling were applied to the detection of dicentric chromosomes on irradiated human lymphocyte samples (␥-rays of 60 Co source, 0.5 Gy/min, for doses of 1, 3, and 4 Gy). The yield of dicentrics was determined after Fast-FISH and compared with results obtained after Giemsa staining. These results are very compatible and indicate that, because of its simplicity, this optimized Fast-FISH procedure would be useful for fast screening purposes in biological dosimetry after accidental overexposure. Cytometry 31:153-162, 1998. 1998 Wiley-Liss, Inc.

2011 21st International Conference on Field Programmable Logic and Applications, 2011

Localization microscopy enhances the resolution of fluorescence light microscopy by about an orde... more Localization microscopy enhances the resolution of fluorescence light microscopy by about an order of magnitude. Single fluorescent molecules act as switchable markers. Their detected signals can be fitted with a two-dimensional Gaussian distribution and thus located with sub-pixel resolution. In this paper we propose that these fits can be done by calculating the center of mass instead of an iterative least-square fit without loosing precision. The simplification of the algorithm leads to an acceleration of more than a factor of 100 and enables an FPGA implementation with an additional performance boost by a factor of 225. Our findings allow the real-time processing of current and future image data rates in localization microscopy.

Micron (Oxford, England : 1993), 2011

Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-R... more Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-Rayleigh limit of about 200 nm laterally and 600 nm axially. So far, this progress was achieved using labelling with appropriate fluorochromes and fluorescent proteins. Here, we describe for the first time that optical resolution of cellular structures in the λ/10 range (∼50 nm) can be achieved even in label-free cells. This was obtained using Spectral Precision Distance/Position Determination Microscopy (SPDM), a method based on the general principles of localisation microscopy. Besides a substantial resolution improvement of autofluorescent structures, SPDM revealed cellular objects which are not detectable under conventional fluorescence imaging conditions.

Novel methods of visible light microscopy have overcome the limits of resolution hitherto thought... more Novel methods of visible light microscopy have overcome the limits of resolution hitherto thought to be insurmountable. The localization microscopy technique presented here based on the principles of Spectral Precision Distance Microscopy (SPDM) with conventional fluorophores under special physical conditions allows to measure the spatial distribution of single fluorescence labeled molecules in entire cells with macromolecular precision which is comparable

In order to produce a toner mass, one of 20 different Fmoc-amino acid OPfp esters (Fluka, 10% w/w... more In order to produce a toner mass, one of 20 different Fmoc-amino acid OPfp esters (Fluka, 10% w/w), a polymer, e.g. SLEC PLT 7552 (Sekisui, 84.5% w/w), pyrazolone orange (ABCR GmbH, 4.5% w/w), and Fe(naphtol) 2 complex (1% w/w) were melted, mixed and finally solidified ). The homogenized and crushed toner mass was then mixed with ~ 0,04% w/w silica particles (Degussa, Aerosil 812, hydrophobic), and slowly fed into an air jet mill where grinded particles were collected within a narrow lattice (Hosokawa alpine 50AS). The physical parameters of aminoacid-particles are described by a mean diameter of ∼10µm, a small size distribution ( ), a low tendency to aggregate, melting points of 60-80°C ( ), a Q/m value of ~ -4µC/g, and a similar toner transfer for the 20 different amino-acid-particles ( ). These parameters were measured with a Mastersizer (Malvern, type 2000), by differential scanning calorimetry (Netzsch, type DSC 204 F1 Phoenix), and a Q/m meter (Trek, type 210HS-2), respectively. Light microscopy and scanning electron microscopy (SEM) pictures to determine particle morphology ( ) were taken with an Axiovert 35 light microscope (Zeiss) and an SEM (LEO; Microscope type 1530; 10 kV electron volts). The stability of OPfp esters embedded into amino-acidparticles was analyzed by HPLC ( ). S2 2. Size distribution of amino-acid-and toner particles Figure S1. The medium diameter of magenta toner particles (Toner ref.) from the OKI color laser printer series C7400 (OKI) is ~10µm as measured by laser diffraction (Malvern Mastersizer 2000, Malvern Instruments). Milling conditions for amino-acidtoners were optimized to achieve similar size distributions.

Sensors and Actuators B: Chemical, 2010

We built high voltage complementary metal oxide semiconductor (CMOS) chips that generate electric... more We built high voltage complementary metal oxide semiconductor (CMOS) chips that generate electrical fields on their surface, such that electrically charged microparticles (diameter 10-20 m on average) can be addressed on distinct pixel electrodes according to arbitrary field patterns. Each pixel contains a memory cell in canonical low-voltage CMOS-technology controlling a high voltage (30-100 V) potential area on the top metal layer. Particle transfer with minimal contaminations in less than 10 s for a complete chip was observed for pixels of 100 m × 100 m down to 65 m × 65 m. This allows a new way to create surface modifications on top of CMOS chips without need for additional masks or stamps. Using suitable particles, a chemically modified chip surface, and compatible chemistry, this method can be utilized for self-aligned high-density biopolymer arrays, e.g., peptide arrays. Transfer of microparticles loaded with amino acids for combinatorial peptide synthesis is demonstrated. Successful synthesis of different peptides (octamers) was proven by immunostaining. Based on results obtained by a chip containing pixel areas of different characteristics, a chip for biological applications with 16,384 pixels (10,000 pixel/cm 2 ) was built. Good homogeneity of peptide synthesis over the chip area was verified by immunostaining.

Sensors and Actuators A: Physical, 2011

Spatially selective deposition of electrically charged microparticles onto integrated circuits th... more Spatially selective deposition of electrically charged microparticles onto integrated circuits that generate electrical fields in programmable patterns using electrodes on their surface was previously limited to a pixel pitch of 100μm. Now, we demonstrate spatially selective deposition onto pixels of 45μm pitch in experiments on a test chip allowing arbitrary patterns, but being of limited size and of fixed characteristics,

Review of Scientific Instruments, 2010

Image processing and pattern analysis can evaluate the deposition quality of triboelectrically ch... more Image processing and pattern analysis can evaluate the deposition quality of triboelectrically charged microparticles on charged surfaces. The image processing method presented in this paper aims at controlling the quality of peptide arrays generated by particle based solid phase Merrifield combinatorial peptide synthesis. Incorrectly deposited particles are detected before the amino acids therein are coupled to the growing peptide. The calibration of the image acquisition is performed in a supervised training step in which all parameters of the quality analyzing algorithm are learnt given one representative image. Then, the correct deposition pattern is determined by a linear support vector machine. Knowing the pattern, contaminated areas can be detected by comparing the pattern with the actual deposition. Taking into account the resolution of the image acquisition system and its magnification factor, the number and size of contaminating particles can be calculated out of the number of connected foreground pixels.

Review of Scientific Instruments, 2008

We examined the high precision deposition of toner and polymer microparticles with a typical size... more We examined the high precision deposition of toner and polymer microparticles with a typical size of approximately 10 microm on electrode arrays with electrodes of 100 microm and below using custom-made microelectronic chips. Selective desorption of redundant particles was employed to obtain a given particle pattern from preadsorbed particle layers. Microparticle desorption was regulated by dielectrophoretic attracting forces generated by individual pixel electrodes, tangential detaching forces of an air flow, and adhesion forces on the microchip surface. A theoretical consideration of the acting forces showed that without pixel voltage, the tangential force applied for particle detachment exceeded the particle adhesion force. When the pixel voltage was switched on, however, the sum of attracting forces was larger than the tangential detaching force, which was crucial for desorption efficiency. In our experiments, appropriately large dielectrophoretic forces were achieved by applying high voltages of up to 100 V on the pixel electrodes. In addition, electrode geometries on the chip's surface as well as particle size influenced the desorption quality. We further demonstrated the compatibility of this procedure to complementary metal oxide semiconductor chip technology, which should allow for an easy technical implementation with respect to high-resolution microparticle deposition.

Review of Scientific Instruments, 2007

In this study examples for a noncontact procedure that allow the description of instant electric ... more In this study examples for a noncontact procedure that allow the description of instant electric charging of moving microparticles that contact dielectric surfaces, for instance, of a flow hose are presented. The described principle is based on the measurement of induced currents in grounded metal wire probes, as moving particles pass close to the probe. The feasibility of the approach was tested with laser printer toner particles of a given size for different basic particle flow and charging conditions. An analytic description for the induced currents was developed and compared to observed effects in order to interpret the results qualitatively. The implementation of the presented procedure can be applied to transparent and nontransparent particle containers and flow lines of complex geometry which can be composed from the presented basic flow stream configurations.

Micron, 2011

Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-R... more Localisation microscopy methods allow to realize a light optical resolution far beyond the Abbe-Rayleigh limit of about 200 nm laterally and 600 nm axially. So far, this progress was achieved using labelling with appropriate fluorochromes and fluorescent proteins. Here, we describe for the first time that optical resolution of cellular structures in the /10 range (∼50 nm) can be achieved even in label-free cells. This was obtained using Spectral Precision Distance/Position Determination Microscopy (SPDM), a method based on the general principles of localisation microscopy. Besides a substantial resolution improvement of autofluorescent structures, SPDM revealed cellular objects which are not detectable under conventional fluorescence imaging conditions.

Journal of Proteome Research, 2007

Complementary metal oxide semiconductor (CMOS) microelectronic chips fulfill important functions ... more Complementary metal oxide semiconductor (CMOS) microelectronic chips fulfill important functions in the field of biomedical research, ranging from the generation of high complexity DNA and protein arrays to the detection of specific interactions thereupon. Nevertheless, the issue of merging pure CMOS technology with a chemically stable surface modification which further resists interfering nonspecific protein adsorption has not been addressed yet. We present a novel surface coating for CMOS microchips based on poly(ethylene glycol)methacrylate graft polymer films, which in addition provides high loadings of functional groups for the linkage of probe molecules. The coated microchips were compatible with the harshest conditions emerging in microarray generating methods, thoroughly retaining structural integrity and microelectronic functionality. Nonspecific adsorption of proteins on the chip's surface was completely obviated even with complex serum protein mixtures. We could demonstrate the background-free antibody staining of immobilized probe molecules without using any blocking agents, encouraging further integration of CMOS technology in proteome research.

Journal of Physics D: Applied Physics, 2007

We present a method based on induced currents in a cylindrical probe which allows analysis of the... more We present a method based on induced currents in a cylindrical probe which allows analysis of the micro-particle charging processes in an aerosol. The micro particles were triboelectrically charged by passing through a dielectric tube coaxially mounted into the probe. The cylindrical probe enabled the quantification of particle charging without prior calibration of the probe. An analytic model was developed

Journal of Physics D: Applied Physics, 2010

A device for the measurement of q/m-values and charge degradation of triboelectrically charged pa... more A device for the measurement of q/m-values and charge degradation of triboelectrically charged particles deposited on a surface was developed. The setup is based on the integration of currents, which are induced in a Faraday cage by insertion of a solid support covered with charged particles. The conductivity of different particle supports was taken into account. The 'blow-off' method, in

Journal of Microscopy, 2009

We present a novel technique of far-field localization nanoscopy combining spectral precision dis... more We present a novel technique of far-field localization nanoscopy combining spectral precision distance microscopy with widely used fluorochromes like the Green Fluorescent Protein (GFP) derivatives eGFP, EmGFP, Yellow Fluorescent Protein (YFP) and eYFP, synthetic dyes like Alexa 488 and Alexa 568, as well as fluoresceine derivates. Spectral precision distance microscopy allows the surpassing of conventional resolution limits in fluorescence far-field microscopy by precise object localization after the optical isolation of single signals in time. Based on the principles of this technique, our novel nanoscopic method was realized for laser optical precision localization and image reconstruction with highly enhanced optical resolution in intact cells. This allows for spatial assignment of individual fluorescent molecules with nanometre precision. The technique is based on excitation intensity dependent reversible photobleaching of the molecules used combined with fast time sequential imaging under appropriate focusing conditions. A meaningful advantage of the technique is the simple applicability as a universal tool for imaging and investigations to the major part of already available preparations according to standard protocols. Using the above mentioned fluorophores, the positions of single molecules within cellular structures were determined by visible light with an estimated localization precision down to 3 nm; hence distances in the range of 10-30 nm were resolved between individual fluorescent molecules allowing to apply different quantitative structure analysis tools.

Journal of Microscopy, 2011

The Her2/neu tyrosine kinase receptor is a member of the epidermal growth factor family. It plays... more The Her2/neu tyrosine kinase receptor is a member of the epidermal growth factor family. It plays an important role in tumour genesis of certain types of breast cancer and its overexpression correlates with distinct diagnostic and therapeutic decisions. Nevertheless, it is still under intense investigation to improve diagnostic outcome and therapy control. In this content, we applied spectral precision distance/position determination microscopy, a technique based on the general principles of localization microscopy in order to study tumour typical conformational changes of receptor clusters on cell membranes. We examined two different mamma carcinoma cell lines as well as cells of a breast biopsy of a healthy donor. The Her2/neu receptor sites were labelled by immunofluorescence using conventional fluorescent dyes (Alexa conjugated antibodies). The characterization of the Her2/neu distribution on plasma membrane sections of 176 different cells yielded a total amount of 20 637 clusters with a mean diameter of 67 nm. Statistical analysis on the single molecule level revealed differences in clustering of Her2/neu between all three different cell lines. We also showed that using spectral precision distance/position determination microscopy, a dual colour reconstruction of the 3D spatial arrangement of Her2/neu and Her3 is possible. This indicates that spectral precision distance/position determination microscopy could be used as an enhanced tool offering additional information of Her2/neu receptor status.