Diese Forschung wird vom Amt für Biologische und Umweltforschung, US Department of Energy und durch Zuschüsse aus Virginia Commonwealth Health Research Board gesponsert. Oak Ridge National Laboratory wird von UT-Battelle, LLC, für den US-Department of Energy unter Vertrag Nr. DE-AC05-00OR22725 verwaltet.

1. Mica Zubereitung: <ol><li> Schneiden Sie den Glimmer (Electron Microscopy Sciences) mit einer Schere auf die Größe notwendig, die AFM-Mikroskop (ca. 22 × 30 mm) passen. </li><li> Cleave der Glimmer auf beiden Seiten, in der Regel mit Klebeband an die äußere Schicht zu entfernen, bis nur noch glatte ungebrochene Schichten bleiben. </li></ol> 2. Herstellung von Gelatine-Lösung: <ol><li> Add 100 ml destilliertem Wasser in ein Labor Flasche. </li><li> Erhitzen Sie die Flasche in der Mikrowelle bis das Wasser zu sieden beginnt. (Wenn eine Mikrowelle nicht zur Verfügung steht, kann das Wasser in einem Becherglas auf einer Heizplatte erhitzt werden.) </li><li> Abwiegen 0,5 Gramm der Gelatine (Sigma G-6144, G-2625 oder G-2500) und fügen Sie die heiße destilliertem Wasser. </li><li> Vorsichtig schwenken die Flasche, bis die Gelatine vollständig gelöst ist. </li><li> Kühlen Sie die Gelatine-Lösung auf 60-70 ° C. </li><li> Gießen Sie ca. 15 mL in ein kleines Becherglas (20 ml), in die der Schnitt gespaltenem Glimmer getaucht werden kann. </li></ol> 3. Mica-Beschichtung: <ol><li> Tauchen Sie die Glimmer Quadrate in die erwärmte Gelatinelösung und ziehen schnell, so dass die Glimmer beschichtet ist (Abb. 1a). </li><li> Nach der Beschichtung, die Unterstützung der Glimmer sofort, am Waldrand, auf einem Papiertuch, um in der Luft trocknen lassen (Abb. 1b). Die Gelatine beschichtete Glimmer kann für mindestens 2 Wochen verwendet werden. Die überschüssige Gelatine-Lösung kann im Kühlschrank aufbewahrt werden und für rund einen Monat durch einfaches Erhitzen der Stammlösung zwischen 60-70 ° C. Es muss darauf geachtet, dass die Gelatine nicht beim Erwärmen abgekocht werden. </li></ol> 4. Montage Bakterien auf Gelatine beschichtete Glimmer: <ol><li> Pellet 1 ml einer Bakterienkultur (0,5 bis 1,0 OD bei 600 nm) bei 800 bis 4.500 rcf. Je nach Bakterien, die mindestens rcf, dass die Pellets der Zellen in ca. 5 Minuten. </li><li> Waschen des Pellets in das gleiche Volumen der gefilterten deionisiertem Wasser oder Puffer. </li><li> Sammeln Sie die Zellen wieder abzentrifugiert. </li><li> Das Pellet sofort in 500 ul der Nanopure deionisiertem Wasser oder Puffer. (Die Bakteriensuspension sollte sichtbar trüb werden, um eine ausreichende Konzentration von Zellen für die AFM haben.) </li><li> Übernehmen Sie die Zellsuspension (10-20 mL), um die Gelatine-beschichtete Glimmer und verteilt auf der Oberfläche mit einer Pipettenspitze (Abb. 1c). Es sollte darauf geachtet werden, nicht körperlich berührt die Gelatine Oberfläche mit der Pipettenspitze während der Anwendung oder Verbreitung der bakteriellen Lösung sein. </li><li> Die Oberfläche für 10 Minuten ruhen lassen und gründlich mit einem Strom von Wasser oder Puffer (Abb. 1 cd). Während des gesamten Verfahrens darauf achten, dass die Probe nicht erlaubt ist, um zu trocknen. </li></ol> 5. Repräsentative Ergebnisse: Abbildung 2 zeigt beispielsweise Bilder von Bakterienzellen, die auf Gelatine beschichtete Glimmer wurden montiert und bebildert von AFM. In unseren Labors werden die Proben in der Regel abgebildet mit einem PicoPlus Rasterkraftmikroskop (Agilent Technologies, Tempel, AZ) mit einer 100 um Abtastkopf ausgestattet. Das Gerät ist bei 128-512 Pixel pro Zeile Scan bei einer Scan-Geschwindigkeit von 0,5-1,0 Linien / s betrieben Die Ausleger, die typischerweise verwendet werden, sind Veeco Siliziumnitrid-Sonden (MLCT-AUHW, Veeco, Santa Barbara, CA) mit nominal Federkonstanten zwischen 0,01 bis 0,1 nN / nm. <img src="/files/ftp_upload/2880/2880fig1.jpg" alt="Abbildung 1"/> Abbildung 1. Gelatine bei einer Temperatur von 60-70 ° C in einer 20 ml Becherglas gegeben. Mit einer Pinzette frisch gespaltenem Glimmer Plätze sind völlig in die Gelatine (a) zurückgezogen und aufrecht auf einem Papiertuch gelehnt einer Mikrozentrifuge Rack (b) platziert eingetaucht. Ein Tropfen einer bakteriellen Probe wird auf dem Glimmer und verbreiten mit einer Pipettenspitze in der X-und Y-Richtung (c) platziert. Nachdem man die Probe auf die Glimmer-Oberfläche für mindestens 10 Minuten inkubieren, spülen Sie die Probe in einem Strom von destilliertem Wasser. Wenn die Immobilisierung arbeitete Sie in der Lage, um ein milchiger Fleck auf dem Glimmer zu sehen, wie auf der rechten Seite von (d) gezeigt. Wenn die Immobilisierung nicht funktioniert hat man ein klares Stück Glimmer als in der linken Seite zu bekommen. Die milchiger Fleck auf der Glimmerschuppen, um die Konzentration der Bakterien in den Tropfen, die Sie auf der Gelatine behandelten Glimmer. <img src="/files/ftp_upload/2880/2880fig2.jpg" alt="Abbildung 2"/> Abbildung 2. AFM-Aufnahmen von E. coli. In Panel (a) werden die Zellen auf Gelatine-beschichteten Glimmer montiert und abgebildet in 0,005 M PBS. Zum Vergleich wird ein Bild von Bakterienzellen auf Gelatine-beschichteten Glimmer montiert und abgebildet in der Luft in Panel (b) gezeigt. Obwohl Septen sind deutlich sichtbar in Bild flüssig, höhere Auflösung, als durch die Anwesenheit von Pili (kleines Panel (b)) angegeben, sammelte sich in Luft gewonnen werden.

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E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tension+as+a+regulator+and+integrator+of+axonal+growth.">Tension as a regulator and integrator of axonal growth.</a> Cell Motil Cytoskeleton. 17, 6-10 (1990).</li><li>Heidemann, S. R., Buxbaum, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+tension+as+a+regulator+of+axonal+development.">Mechanical tension as a regulator of axonal development.</a> Neurotoxicology. 15, 95-107 (1994).</li><li>Heidemann, S. R., Lamoureux, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytomechanics+of+axonal+development.">Cytomechanics of axonal development.</a> Cell Biochem Biophys. 27, 135-155 (1995).</li><li>Iwata, A., Browne, K. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+survival+and+outgrowth+of+mechanically+engineered+nervous+tissue+constructs+implanted+into+spinal+cord+lesions.">Long-term survival and outgrowth of mechanically engineered nervous tissue constructs implanted into spinal cord lesions.</a> Tissue Eng. 12, 101-110 (2006).</li><li>Lamoureux, P., Heidemann, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+and+elongation+within+and+along+the+axon.">Growth and elongation within and along the axon.</a> Dev Neurobiol. 70, 135-149 (2010).</li><li>Lamoureux, P., Zheng, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cytomechanical+investigation+of+neurite+growth+on+different+culture+surfaces.">A cytomechanical investigation of neurite growth on different culture surfaces.</a> J Cell Biol. 118, 655-661 (1992).</li><li>Lindqvist, N., Liu, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+glial+(Muller)+cells:+sensing+and+responding+to+tissue+stretch.">Retinal glial (Muller) cells: sensing and responding to tissue stretch.</a> Invest Ophthalmol Vis Sci. 51, 1683-1690 (2010).</li><li>Loverde, J. R., Ozoka, V. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+Imaging+of+Axon+Stretch+Growth+in+Embryonic+and+Adult+Neurons.">Live Imaging of Axon Stretch Growth in Embryonic and Adult Neurons.</a> J. Neurotrauma. , (2011).</li><li>Lu, Y. B., Franze, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viscoelastic+properties+of+individual+glial+cells+and+neurons+in+the+CNS.">Viscoelastic properties of individual glial cells and neurons in the CNS.</a> Proc Natl Acad Sci U S A. 103, 17759-17764 (2006).</li><li>O'Toole, M., Lamoureux, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+physical+model+of+axonal+elongation:+force,+viscosity,+and+adhesions+govern+the+mode+of+outgrowth.">A physical model of axonal elongation: force, viscosity, and adhesions govern the mode of outgrowth.</a> Biophys J. 94, 2610-2620 (2008).</li><li>Pfister, B. J., Bonislawski, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch-grown+axons+retain+the+ability+to+transmit+active+electrical+signals.">Stretch-grown axons retain the ability to transmit active electrical signals.</a> FEBS Lett. 580, 3525-3531 (2006).</li><li>Pfister, B. J., Gordon, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomedical+Engineering+Strategies+for+Peripheral+Nerve+Repair:+Surgical+Applications,+State+of+the+Art,+and+Future+Challenges.">Biomedical Engineering Strategies for Peripheral Nerve Repair: Surgical Applications, State of the Art, and Future Challenges.</a> Crit Rev Biomed Eng. 39, 81-124 (2011).</li><li>Pfister, B. J., Iwata, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extreme+stretch+growth+of+integrated+axons.">Extreme stretch growth of integrated axons.</a> J Neurosci. 24, 7978-7983 (2004).</li><li>Pfister, B. J., Iwata, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+transplantable+nervous+tissue+constructs+comprised+of+stretch-grown+axons.">Development of transplantable nervous tissue constructs comprised of stretch-grown axons.</a> J Neurosci Methods. 153, 95-103 (2006).</li><li>Siechen, S., Yang, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+tension+contributes+to+clustering+of+neurotransmitter+vesicles+at+presynaptic+terminals.">Mechanical tension contributes to clustering of neurotransmitter vesicles at presynaptic terminals.</a> Proc Natl Acad Sci U S A. 106, 12611-12616 (2009).</li><li>Smith, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stretch+growth+of+integrated+axon+tracts:+extremes+and+exploitations.">Stretch growth of integrated axon tracts: extremes and exploitations.</a> Prog Neurobiol. 89, 231-239 (2009).</li><li>Smith, D. H., Wolf, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+strategy+to+produce+sustained+growth+of+central+nervous+system+axons:+continuous+mechanical+tension.">A new strategy to produce sustained growth of central nervous system axons: continuous mechanical tension.</a> Tissue Eng. 7, 131-139 (2001).</li><li>Weiss, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nerve+patterns:+The+mechanics+of+nerve+growth.">Nerve patterns: The mechanics of nerve growth.</a> Growth, Third Growth Symposium. 5, 163-203 (1941).</li><li>Zheng, J., Lamoureux, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensile+regulation+of+axonal+elongation+and+initiation.">Tensile regulation of axonal elongation and initiation.</a> J Neurosci. 11, 1117-1125 (1991).</li></ol>

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Verschiedene Faktoren können die mikrobielle Zelle Montage-und Imaging von AFM. Die Gelatine, die zur Beschichtung eingesetzt wird der Glimmer ist wichtig. Gewerbliche Gelatine wird aus einer Reihe von Wirbeltieren einschließlich Fischen, Kühen und Schweinen isoliert. Sowohl die Herkunft und das Verarbeitungsverfahren bestimmen die Gelatine die Eignung für die bakterielle Immobilisierung. Zahlreiche Quellen und Arten von Gelatine wurden auf ihre Wirksamkeit in Immobilisierung Bakterien untersucht [1]. Die beiden eff...

<table border="1"><tbody><tr><td> Name </td><td> Firma </td><td> Katalog-Nummer </td></tr><tr><td> Gelatine </td><td> Sigma, St. Louis, MO </td><td> G6144, G2625 oder G2500 </td></tr><tr><td> PicoPlus Atomic Force Microscope </td><td> Agilent Technologies, Tempe, AZ </td><td></td></tr><tr><td> AFM Cantilever </td><td> Veeco, Santa Barbara, CA </td><td> MLCT-AUHW </td></tr></tbody></table>

bacterial immobilization for imaging by atomic force microscopy

AFM ist ein hochauflösender (nm-Skala) Imaging-Tool, das mechanisch tastet eine Oberfläche. Es hat die Fähigkeit, Bilder von Zellen und Biomolekülen, in einer flüssigen Umgebung, ohne die Notwendigkeit, chemisch behandeln die Probe. Um dieses Ziel zu erreichen, muss die Probe ausreichend, um die Montagefläche haften, um die Entfernung von Kräften von der Scan-AFM Cantileverspitze ausgeübt zu verhindern. In vielen Fällen hängt die erfolgreiche Bildgebung bei der Immobilisierung der Probe auf der Montagefläche. Optimalerweise sollten Immobilisierung werden minimal-invasive, um die Probe, so dass Stoffwechselvorgänge und funktionalen Eigenschaften nicht beeinträchtigt werden. Durch die Beschichtung frisch gespaltenem Glimmer Oberflächen mit Schweinen (Schweine-) Gelatine, können negativ geladene Bakterien auf der Oberfläche immobilisiert werden und abgebildet in Flüssigkeit, die durch AFM. Immobilisierung von Bakterienzellen auf Gelatine-beschichteten Glimmer ist sehr wahrscheinlich aufgrund von elektrostatischen Wechselwirkungen zwischen der negativ geladenen Bakterien und den positiv geladenen Gelatine. Mehrere Faktoren können mit bakteriellen Immobilisierung, einschließlich der chemischen Bestandteile der Flüssigkeit, in der die Bakterien ausgesetzt, die Inkubationszeit der Bakterien auf die Gelatine beschichtete Glimmer, Oberflächeneigenschaften des Bakterienstammes und dem Medium, in dem die Bakterien sind abgebildet stören. Insgesamt ist die Verwendung von Gelatine-beschichtete Glimmer gefunden allgemein anwendbar zu sein für die Bildgebung mikrobieller Zellen.

Watch this Scientific Journal Video about Bacterial Immobilization for Imaging by Atomic Force Microscopy at JoVE.com

Bacterial Immobilization for Imaging by Atomic Force Microscopy

Live-Gram-negative und gram-positive Bakterien können auf Gelatine-beschichteten Glimmer immobilisiert werden und abgebildet in Flüssigkeit mit Atomic Force Microscopy (AFM).

Bakterielle Immobilisierung für Imaging von Atomic Force Microscopy

AFM is a high-resolution (nm scale) imaging tool that mechanically probes a surface.  It has the ability to image cells and biomolecules, in a liquid ...

bacterial-immobilization-for-imaging-by-atomic-force-microscopy

Research

JoVE Journal

Bioengineering

17.3K Aufrufe.  Oak Ridge National Laboratory. Live-Gram-negative und gram-positive Bakterien können auf Gelatine-beschichteten Glimmer immobilisiert werden und abgebildet in Flüssigkeit mit Atomic Force Microscopy (AFM).

Serie: Bacterial Immobilization for Imaging by Atomic Force Microscopy

Three-dimensional Optical-resolution Photoacoustic Microscopy

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As the mainstays of in vivo three-dimensional (3-D) optical microscopy, single-/multi-photon fluorescence microscopy and optical coherence tomography (OCT) have demonstrated their extraordinary sensitivities to fluorescence and optical scattering contrasts, respectively. However, the optical absorption contrast of biological tissues, which encodes essential physiological/pathological information, has not yet been assessable. 
The emergence of biomedical photoacoustics has led to a new branch of optical microscopy optical-resolution photoacoustic microscopy (OR-PAM)1, where the optical irradiation is focused to the diffraction limit to achieve cellular1 or even subcellular2 level lateral resolution. As a valuable complement to existing optical microscopy technologies, OR-PAM brings in at least two novelties. First and most importantly, OR-PAM detects optical absorption contrasts with extraordinary sensitivity (i.e., 100%). Combining OR-PAM with fluorescence microscopy3 or with optical-scattering-based OCT4 (or with both) provides comprehensive optical properties of biological tissues. Second, OR-PAM encodes optical absorption into acoustic waves, in contrast to the pure optical processes in fluorescence microscopy and OCT, and provides background-free detection. The acoustic detection in OR-PAM mitigates the impacts of optical scattering on signal degradation and naturally eliminates possible interferences (i.e., crosstalks) between excitation and detection, which is a common problem in fluorescence microscopy due to the overlap between the excitation and fluorescence spectra. 
Unique for optical absorption imaging, OR-PAM has demonstrated broad biomedical applications since its invention, including, but not limited to, neurology5, 6, ophthalmology7, 8, vascular biology9, and dermatology10. In this video, we teach the system configuration and alignment of OR-PAM as well as the experimental procedures for in vivo functional microvascular imaging.

Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging technology capable of imaging optical absorption contrasts in vivo with cellular resolution and sensitivity. Here, we provide a visualized instruction on the experimental protocols of OR-PAM, including system configuration, system alignment, typical in vivo experimental procedures, and functional imaging schemes.

Dreidimensionale Optische Auflösung photoakustische Mikroskopie

Optical microscopy, providing valuable insights at the cellular and organelle levels, has been widely recognized as an enabling biomedical technology. As ...

Forschung

Biotechnik

Visualization of Recombinant DNA and Protein Complexes Using Atomic Force Microscopy

Atomic force microscopy (AFM) allows for the visualizing of individual proteins, DNA molecules, protein-protein complexes, and DNA-protein complexes. On the end of the microscope's cantilever is a nano-scale probe, which traverses image areas ranging from nanometers to micrometers, measuring the elevation of macromolecules resting on the substrate surface at any given point. Electrostatic forces cause proteins, lipids, and nucleic acids to loosely attach to the substrate in random orientations and permit imaging. The generated data resemble a topographical map, where the macromolecules resolve as three-dimensional particles of discrete sizes (Figure 1) 1,2. Tapping mode AFM involves the repeated oscillation of the cantilever, which permits imaging of relatively soft biomaterials such as DNA and proteins. One of the notable benefits of AFM over other nanoscale microscopy techniques is its relative adaptability to visualize individual proteins and macromolecular complexes in aqueous buffers, including near-physiologic buffered conditions, in real-time, and without staining or coating the sample to be imaged. 
The method presented here describes the imaging of DNA and an immunoadsorbed transcription factor (i.e. the glucocorticoid receptor, GR) in buffered solution (Figure 2). Immunoadsorbed proteins and protein complexes can be separated from the immunoadsorbing antibody-bead pellet by competition with the antibody epitope and then imaged (Figure 2A). This allows for biochemical manipulation of the biomolecules of interest prior to imaging. Once purified, DNA and proteins can be mixed and the resultant interacting complex can be imaged as well. Binding of DNA to mica requires a divalent cation 3,such as Ni2+ or Mg2+, which can be added to sample buffers yet maintain protein activity. Using a similar approach, AFM has been utilized to visualize individual enzymes, including RNA polymerase 4 and a repair enzyme 5, bound to individual DNA strands. These experiments provide significant insight into the protein-protein and DNA-protein biophysical interactions taking place at the molecular level. Imaging individual macromolecular particles with AFM can be useful for determining particle homogeneity and for identifying the physical arrangement of constituent components of the imaged particles. While the present method was developed for visualization of GR-chaperone protein complexes 1,2 and DNA strands to which the GR can bind, it can be applied broadly to imaging DNA and protein samples from a variety of sources.

A tapping mode atomic force microscope (AFM) method for the visualization of plasmid DNA, cytoplasmic proteins, and DNA-protein complexes is described. The method includes alternate approaches for preparing samples for AFM imaging following biochemical manipulation. DNA containing specific protein interacting regions are observed in near-physiologic buffer conditions.

Visualisierung von rekombinanten DNA-und Protein-Komplexe mit Atomic Force Microscopy

Atomic force microscopy (AFM) allows for the visualizing of individual proteins, DNA molecules, protein-protein complexes, and DNA-protein complexes. On ...

Quantifying the Mechanical Properties of the Endothelial Glycocalyx with Atomic Force Microscopy

Our understanding of the interaction of leukocytes and the vessel wall during leukocyte capture is limited by an incomplete understanding of the mechanical properties of the endothelial surface layer. It is known that adhesion molecules on leukocytes are distributed non-uniformly relative to surface topography 3, that topography limits adhesive bond formation with other surfaces 9, and that physiological contact forces (&asymp; 5.0 &minus; 10.0 pN per microvillus) can compress the microvilli to as little as a third of their resting length, increasing the accessibility of molecules to the opposing surface 3, 7. We consider the endothelium as a two-layered structure, the relatively rigid cell body, plus the glycocalyx, a soft protective sugar coating on the luminal surface 6. It has been shown that the glycocalyx can act as a barrier to reduce adhesion of leukocytes to the endothelial surface 4. In this report we begin to address the deformability of endothelial surfaces to understand how the endothelial mechanical stiffness might affect bond formation. Endothelial cells grown in static culture do not express a robust glycocalyx, but cells grown under physiological flow conditions begin to approximate the glycocalyx observed in vivo 2. The modulus of the endothelial cell body has been measured using atomic force microscopy (AFM) to be approximately 5 to 20 kPa 5. The thickness and structure of the glycocalyx have been studied using electron microscopy 8, and the modulus of the glycocalyx has been approximated using indirect methods, but to our knowledge, there have been no published reports of a direct measurement of the glycocalyx modulus in living cells. In this study, we present indentation experiments made with a novel AFM probe on cells that have been cultured in conditions to maximize their glycocalyx expression to make direct measurements of the modulus and thickness of the endothelial glycocalyx.

The mechanical characteristics of endothelial glycocalyx were measured by indentation using micron sized spheres on AFM cantilevers. Endothelial cells were cultured in a custom chamber under physiological flow conditions to induce glycocalyx expression. Data were analyzed using a thin film model to determine the glycocalyx thickness and modulus.

Die Quantifizierung der mechanischen Eigenschaften des Endothelial Glykokalyx mit Atomic Force Microscopy

Our  understanding of the interaction of leukocytes and the vessel wall during  leukocyte capture is limited by an incomplete understanding of the ...

Measuring the Mechanical Properties of Living Cells Using Atomic Force Microscopy

Mechanical properties of cells and extracellular matrix (ECM) play important roles in many biological processes including stem cell differentiation, tumor formation, and wound healing. Changes in stiffness of cells and ECM are often signs of changes in cell physiology or diseases in tissues. Hence, cell stiffness is an index to evaluate the status of cell cultures. Among the multitude of methods applied to measure the stiffness of cells and tissues, micro-indentation using an Atomic Force Microscope (AFM) provides a way to reliably measure the stiffness of living cells. This method has been widely applied to characterize the micro-scale stiffness for a variety of materials ranging from metal surfaces to soft biological tissues and cells. The basic principle of this method is to indent a cell with an AFM tip of selected geometry and measure the applied force from the bending of the AFM cantilever. Fitting the force-indentation curve to the Hertz model for the corresponding tip geometry can give quantitative measurements of material stiffness. This paper demonstrates the procedure to characterize the stiffness of living cells using AFM. Key steps including the process of AFM calibration, force-curve acquisition, and data analysis using a MATLAB routine are demonstrated. Limitations of this method are also discussed.

This paper demonstrates a protocol to characterize the mechanical properties of living cells by means of microindentation using an Atomic Force Microscope (AFM).

Messung der mechanischen Eigenschaften von lebenden Zellen mit Atomic Force Microscopy

Mechanical  properties of cells and extracellular matrix (ECM) play important roles in many  biological processes including stem cell differentiation, ...

High-resolution Spatiotemporal Analysis of Receptor Dynamics by Single-molecule Fluorescence Microscopy

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., kinetics, coexistence of different states and populations, transient interactions), which are typically hidden in ensemble measurements, such as those obtained with standard biochemical or microscopy methods. Thus, dynamic events, such as receptor-receptor interactions, can be followed in real time in a living cell with high spatiotemporal resolution. This protocol describes a method based on labeling with small and bright organic fluorophores and total internal reflection fluorescence (TIRF) microscopy to directly visualize single receptors on the surface of living cells. This approach allows one to precisely localize receptors, measure the size of receptor complexes, and capture dynamic events such as transient receptor-receptor interactions. The protocol provides a detailed description of how to perform a single-molecule experiment, including sample preparation, image acquisition and image analysis. As an example, the application of this method to analyze two G-protein-coupled receptors, i.e., &#946;2-adrenergic and &#947;-aminobutyric acid type B (GABAB) receptor, is reported. The protocol can be adapted to other membrane proteins and different cell models, transfection methods and labeling strategies.

This protocol describes how to use total internal reflection fluorescence microscopy to visualize and track single receptors on the surface of living cells and thereby analyze receptor lateral mobility, size of receptor complexes as well as to visualize transient receptor-receptor interactions. This protocol can be extended to other membrane proteins.

Hochauflösende Räumlich-zeitliche Analyse der Rezeptordynamik von Einzelmolekül-Fluoreszenzmikroskopie

Single-molecule microscopy is emerging as a powerful approach to analyze the behavior of signaling molecules, in particular concerning those aspect (e.g., ...

Novel Atomic Force Microscopy Based Biopanning for Isolation of Morphology Specific Reagents against TDP-43 Variants in Amyotrophic Lateral Sclerosis

Because protein variants play critical roles in many diseases including TDP-43 in Amyotrophic Lateral Sclerosis (ALS), alpha-synuclein in Parkinson&#8217;s disease and beta-amyloid and tau in Alzheimer&#8217;s disease, it is critically important to develop morphology specific reagents that can selectively target these disease-specific protein variants to study the role of these variants in disease pathology and for potential diagnostic and therapeutic applications. We have developed novel atomic force microscopy (AFM) based biopanning techniques that enable isolation of reagents that selectively recognize disease-specific protein variants. There are two key phases involved in the process, the negative and positive panning phases. During the negative panning phase, phages that are reactive to off-target antigens are eliminated through multiple rounds of subtractive panning utilizing a series of carefully selected off-target antigens. A key feature in the negative panning phase is utilizing AFM imaging to monitor the process and confirm that all undesired phage particles are removed. For the positive panning phase, the target antigen of interest is fixed on a mica surface and bound phages are eluted and screened to identify phages that selectively bind the target antigen. The target protein variant does not need to be purified providing the appropriate negative panning controls have been used. Even target protein variants that are only present at very low concentrations in complex biological material can be utilized in the positive panning step. Through application of this technology, we acquired antibodies to protein variants of TDP-43 that are selectively found in human ALS brain tissue. We expect that this protocol should be applicable to generating reagents that selectively bind protein variants present in a wide variety of different biological processes and diseases.

Using atomic force microscopy in combination with biopanning technology we created a negative and positive biopanning system to acquire antibodies against disease-specific protein variants present in any biological material, even at low concentrations. We were successful in obtaining antibodies to TDP-43 protein variants involved in Amyotrophic Lateral Sclerosis.

Novel Rasterkraftmikroskopie.Wie Biopanning für Isolierung von Morphologie Spezifische Reagenzien gegen TDP-43 Varianten in Amyotrophe Lateralsklerose

Because protein variants play critical roles in many diseases including TDP-43 in Amyotrophic Lateral Sclerosis (ALS), alpha-synuclein in ...

Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers

Atomic force microscopy (AFM) is a versatile, high-resolution imaging technique that allows visualization of biological membranes. It has sufficient magnification to examine membrane substructures and even individual molecules. AFM can act as a force probe to measure interactions and mechanical properties of membranes. Supported lipid bilayers are conventionally used as membrane models in AFM studies. In this protocol, we demonstrate how to prepare supported bilayers and characterize their structure and mechanical properties using AFM. These include bilayer thickness and breakthrough force. 
The information provided by AFM imaging and force spectroscopy help define mechanical and chemical properties of membranes. These properties play an important role in cellular processes such as maintaining cell hemostasis from environmental stress, bringing membrane proteins together, and stabilizing protein complexes.

We describe a protocol for preparation of supported lipid bilayers and its characterization using atomic force microscopy and force spectroscopy.

Rasterkraftmikroskopie und Imaging Kraftspektroskopie von unterstützten Lipiddoppelschichten

Atomic force microscopy (AFM) is a versatile, high-resolution imaging technique that allows visualization of biological membranes. It has sufficient ...

Visualizing Angiogenesis by Multiphoton Microscopy In Vivo in Genetically Modified 3D-PLGA/nHAp Scaffold for Calvarial Critical Bone Defect Repair

The reconstruction of critically sized bone defects remains a serious clinical problem because of poor angiogenesis within tissue-engineered scaffolds during repair, which gives rise to a lack of sufficient blood supply and causes necrosis of the new tissues. Rapid vascularization is a vital prerequisite for new tissue survival and integration with existing host tissue. The de novo generation of vasculature in scaffolds is one of the most important steps in making bone regeneration more efficient, allowing repairing tissue to grow into a scaffold. To tackle this problem, the genetic modification of a biomaterial scaffold is used to accelerate angiogenesis and osteogenesis. However, visualizing and tracking in vivo blood vessel formation in real-time and in three-dimensional (3D) scaffolds or new bone tissue is still an obstacle for bone tissue engineering. Multiphoton microscopy (MPM) is a novel bio-imaging modality that can acquire volumetric data from biological structures in a high-resolution and minimally-invasive manner. The objective of this study was to visualize angiogenesis with multiphoton microscopy in vivo in a genetically modified 3D-PLGA/nHAp scaffold for calvarial critical bone defect repair. PLGA/nHAp scaffolds were functionalized for the sustained delivery of a growth factor pdgf-b gene carrying lentiviral vectors (LV-pdgfb) in order to facilitate angiogenesis and to enhance bone regeneration. In a scaffold-implanted calvarial critical bone defect mouse model, the blood vessel areas (BVAs) in PHp scaffolds were significantly higher than in PH scaffolds. Additionally, the expression of pdgf-b and angiogenesis-related genes, vWF and VEGFR2, increased correspondingly. MicroCT analysis indicated that the new bone formation in the PHp group dramatically improved compared to the other groups. To our knowledge, this is the first time multiphoton microscopy was used in bone tissue-engineering to investigate angiogenesis in a 3D bio-degradable scaffold in vivo and in real-time.

Visualizing Angiogenesis by Multiphoton Microscopy In Vivo in Genetically Modified 3D-PLGA/nHAp Scaffold for Calvarial Critical Bone Defect Repair

Here, we present a protocol to visualize blood vessel formation in vivo and in real-time in 3D scaffolds by multiphoton microscopy. Angiogenesis in genetically modified scaffolds was studied in a murine calvarial critical bone defect model. More new blood vessels were detected in the treatment group than in controls.

Visualisierung von Angiogenese durch Multiphoton Mikroskopie In Vivo in gentechnisch veränderten 3D-PLGA/nHAp Gerüst für Calvarial kritische Knochen defekt Reparatur

The reconstruction of critically sized bone defects remains a serious clinical problem because of poor angiogenesis within tissue-engineered scaffolds ...

Visualizing Adhesion Formation in Cells by Means of Advanced Spinning Disk-Total Internal Reflection Fluorescence Microscopy

In living cells, processes such as adhesion formation involve extensive structural changes in the plasma membrane and the cell interior. In order to visualize these highly dynamic events, two complementary light microscopy techniques that allow fast imaging of live samples were combined: spinning disk microscopy (SD) for fast and high-resolution volume recording and total internal reflection fluorescence (TIRF) microscopy for precise localization and visualization of the plasma membrane. A comprehensive and complete imaging protocol will be shown for guiding through sample preparation, microscope calibration, image formation and acquisition, resulting in multi-color SD-TIRF live imaging series with high spatio-temporal resolution. All necessary image post-processing steps to generate multi-dimensional live imaging datasets, i.e. registration and combination of the individual channels, are provided in a self-written macro for the open source software ImageJ. The imaging of fluorescent proteins during initiation and maturation of adhesion complexes, as well as the formation of the actin cytoskeletal network, was used as a proof of principle for this novel approach. The combination of high resolution 3D microscopy and TIRF provided a detailed description of these complex processes within the cellular environment and, at the same time, precise localization of the membrane-associated molecules detected with a high signal-to-background ratio.

An advanced microscope that permit fast and high-resolution imaging of both, the isolated plasma membrane and the surrounding intracellular volume, will be presented. The integration of spinning disk and total internal reflection fluorescence microscopy in one setup allows live imaging experiments at high acquisition rates up to 3.5 s per image stack.

Visualisierung von Adhäsion Bildung in den Zellen durch erweiterte Spinning-Disk-Total Internal Reflection-Fluoreszenz-Mikroskopie

In living cells, processes such as adhesion formation involve extensive structural changes in the plasma membrane and the cell interior. In order to ...

Traction Force Microscopy to Study B Lymphocyte Activation

Traction force microscopy (TFM) enables the measurement of forces produced by a cell on a substrate. This technique infers traction force measurements from an experimentally observed displacement field produced by a cell pulling on an elastic substrate. Here, we adapted TFM to investigate the spatial and temporal structure of the force field exerted by B cells when activated by antigen engagement of the B cell receptor. Gel rigidity, bead density, and protein functionalization must be optimized for the study of relatively small cells (~ 6 &#181;m) that interact with, and respond specifically to ligands for cell surface receptors.

Here we present a protocol used to perform traction force microscopy experiments on B cells. We describe the preparation of soft polyacrylamide gels and their functionalization, as well as data acquisition at the microscope and a summary of data analysis.

Traktionskraftmikroskopie zur Untersuchung der B-Lymphozytenaktivierung

Traction force microscopy (TFM) enables the measurement of forces produced by a cell on a substrate. This technique infers traction force measurements ...