2.6
Überblick über Mikroskopietechniken
Die frühen Pioniere der Mikroskopie öffneten ein Fenster in die unsichtbare Welt der Mikroorganismen. Im Jahr 1830 entwickelte Joseph Jackson Lister e…
Die Mikroskopie ist eine Technik, bei der Mikroskope verwendet werden, um winzige zelluläre Details zu vergrößern und Gewebeeigenschaften zu untersuchen.
Basierend auf dem Prinzip der Bilderzeugung können Mikroskope verschiedener Art sein.
Die optische Mikroskopie nutzt Licht, um Proben zu visualisieren und Objekte bis zu 1000-fach zu vergrößern. Das Verbundmikroskop ist das am häufigsten verwendete optische Mikroskop.
Bei der Elektronenmikroskopie wird ein Elektronenstrahl anstelle von Licht verwendet, was eine 2- bis 50-millionenfache Vergrößerung ermöglicht.
Je nachdem, wie der Elektronenstrahl mit der Probe interagiert, gibt es zwei Haupttypen der Elektronenmikroskopie.
Mit der Transmissionselektronenmikroskopie können 2D-Bilder erzeugt werden, die Aufschluss über die innere Struktur und Zusammensetzung einer Probe geben. Die Rasterelektronenmikroskopie hingegen gibt Aufschluss über die 3D-Topographie und Oberflächenzusammensetzung von Proben wie Knochen und Haaren.
Im Gegensatz dazu wird bei der Rasterkraftmikroskopie (AFM) eine Rastersonde verwendet, die den Konturen der Probenoberfläche folgt und ein 3D-Bild der Probenoberfläche aufnehmen kann. Das Rasterkraftmikroskop kann eine bis zu 1-million-fache Vergrößerung erreichen.
View the full transcript and gain access to JoVE Core videos
Q1: What are the main types of microscopes used in diagnostic imaging?
Microscopes fall into three major categories based on their imaging principles. Optical microscopy uses light to magnify objects up to 1000 times and includes brightfield, darkfield, phase-contrast, and fluorescence microscopes. Electron microscopy uses electron beams for magnification up to 100,000 times, including transmission and scanning electron microscopes. Scanning probe microscopy uses sharp probes to achieve magnifications up to 100,000,000 times for observing individual atoms.
Q2: How does optical microscopy differ from electron microscopy?
Optical microscopy uses visible light and achieves magnification up to 1000 times, limited by light wavelengths. Electron microscopy uses short-wavelength electron beams with wavelengths of 0.005 nanometers, producing magnification up to 100,000 times with superior resolution. Electrons can resolve subcellular and some molecular structures like DNA strands, whereas light microscopes cannot achieve this level of detail.
Q3: What is the difference between transmission and scanning electron microscopy?
Transmission electron microscopy generates 2D images by passing an electron beam through the specimen, providing information about internal structure and composition. Scanning electron microscopy uses an electron beam that scans the sample surface, producing 3D topography images and surface composition data. SEM is particularly useful for examining samples like bone and hair where surface detail is important.
Q4: How does atomic force microscopy capture three-dimensional images?
Atomic force microscopy uses a scanning probe that physically follows the contours of the sample surface, directly interacting with it to gather topographical data. This probe-based approach captures detailed 3D surface images with magnification up to 1 million times. AFM can observe individual atoms and molecular structures on surfaces, making it valuable for research applications.
Q5: Why can't electron microscopy be used on living organisms?
Electron microscopy requires extensive specimen preparation methods that are incompatible with living material. The preparation process, including fixation, dehydration, and sectioning, destroys cellular viability. While electron microscopy provides exceptional magnification and resolution for studying subcellular structures, these preparation requirements limit its use to preserved or processed samples.
Q6: What advantages do light microscopes offer over electron microscopes?
Light microscopes allow observation of living cells and tissues without extensive preparation, making them ideal for diagnostic work and real-time observation. The compound microscope, the most common optical microscope, is relatively simple to use and maintain. While light microscopes achieve lower magnification than electron microscopes, their ability to visualize living material and various types of light microscopes complement each other in diagnostics and research.
Q7: What role do scanning probe microscopes play in modern microscopy?
Scanning probe microscopes, including atomic force microscopes and scanning tunneling microscopes, achieve extraordinary magnifications up to 100,000,000 times without using light or electrons. These instruments interact directly with specimen surfaces through sharp probes, enabling observation of individual atoms. While these techniques have been used primarily for research rather than diagnostics, they complement other imaging methods like computed tomography and x ray imaging in advancing visualization science.