Microscopes are critical tools for scientific researchers and physicians, allowing them to magnify the smallest organisms. Thanks to microscopes, researchers can see what's invisible to the naked eye and study the contents of cells and tissues.
Using a microscope takes more than looking at a slide through a lens. To examine a specimen under a microscope, scientists first use microtomes. A microtome is a precision instrument that consists of three main parts: the micro-mechanism (body), the blade holder and blade, and the specimen head. The function of a microtome is to slice samples into very thin, uniform segments. Scientists can then study these thin segments under a microscope. To produce quality segments, they need to choose a suitable microtome blade. Without the proper blade, scientists risk ruining their most vital samples.
Choosing the best microtome blade mainly depends on the quality of the steel. In this microtome blade guide, we'll show you the various types of blades available and tips for making the right choice.
Microtomes are often used in histology or pathology applications. With the traditional histology technique, a scientist will place a block of paraffin-embedded tissue into a microtome's specimen head. The paraffin makes it easier to cut various tissues. The scientist will then control the microtome and move the specimen head and the tissue block against a blade to form thin ribbons of tissue. Paraffin sections typically range from 2 to 10 micrometers (µm) in thickness. The tissue segments can then be stained.
Other common microtome applications include:
Regardless of the application, you'll need a sharp, blemish-free knife to cut through the specimen.
Before choosing a microtome blade, you'll want to think about the type of materials you plan to section and how thick the segments need to be. Microtome blades come in a range of sizes, shapes, and materials designed to slice through varying levels of hardness.
Microtomes are designed for specific applications, so you'll also need to consider the type of microtome you're working with when choosing a new blade. Here are some common types of microtomes and their corresponding blades:
A rotary microtome is a general-purpose device. It features a hand-wheel which operates the knife and cutting action. Rotary microtomes are typically used to cut semi-thin to thin sections for light microscopy. You can cut larger blocks of tissue on a rotary microtome and adjust the knife angle accordingly.
You'll need a quality U.S. steel knife for this type of microtome. Most rotary microtomes can cut sections that range from 0.5 to 60 µm.
The sledge microtome was created to section much larger blocks of tissue than other machines. For example, scientists might use a sledge microtome to segment an entire brain. With this type of microtome, the tissue block sits on a steel carriage, which slides back and forth over a fixed blade.
A sledge microtome requires a large knife or one that is 24 centimeters (cm) in length. Sledge microtome blades are also typically wedge-shaped to minimize vibration and decrease the need to hone the knife.
The vibrating microtome was developed to section fresh plant or animal materials and is often used in histochemistry. The machine powers the blade with high-speed vibrations and cuts through soft materials immersed in a fluid. Sections are typically thicker than paraffin-embedded samples.
Typically, scientists use disposable, double-edged razor blades with vibrating microtomes, although specialized microtome knives are also available.
Ultramicrotomes are sophisticated devices used to cut ultrathin sections for light and electron microscopy. To produce such thin sections, an ultramicrotome uses a very sharp blade made of glass, diamond or sapphire.
You won't need a traditional knife with a laser microtome. Laser microtomes were designed to produce samples with great precision. This device uses bladeless femtosecond laser technology to slice biological tissues and a range of other materials. With a laser microtome, you can create sections with thicknesses of around 5 to 100 µm.
Saw microtomes are used to cut through tough materials such as bone, glass, ceramic and resin-embedded samples. The saw microtome cuts materials slowly using a rotating, diamond-coated saw. You can not produce very thin sections with a saw microtome, but, as long as the blade is in excellent condition, you should be able to cut sections that are 20 µm or more in thickness.
A cryostat was developed to cut thin sections of frozen tissue. A cryostat is a specially designed deep-freeze cabinet with a microtome installed. It features a glass window and a door to pass the material through. The type of blade you'd choose for a cryostat is either U.S. or German steel.
Disposable blades are often used for general microtomy and, in many cases, have replaced traditional microtome knives. With high-quality disposable blades, you can expect an extremely sharp edge and a flawless cut.
It should also be easy to find the right-sized disposable blades, as you can use universal disposable blades to fit with any microtome or get an adapted knife holder. Disposable blade edges may feature a chromium or platinum coating to increase its lifespan and strength. A Teflon coating, for example, offers minimal friction and is ideal for cryostat use. Disposable blades often come in a durable dispenser.
If you need to section extremely hard materials, such as resin blocks, it would be better to choose a fixed knife composed of glass or diamond. Keep in mind that fixed knives require frequent sharpening and honing.
Microtome blades are often described as high- or low-profile or classified by shape. It's crucial to consider the blade profile when choosing a new microtome knife because different shapes are made for certain materials. Also, some microtomes only hold high- or low-profile blades. Here's a little bit about microtome blade profiles:
High-profile blades may be the same length as low-profile blades but have a greater height. Whether you need a high- or low-profile blade largely depends on the type of microtome you use. For example, high-profile is usually used in cryostats with a various thickness 4 to 15µm. A low-profile blade works best on paraffin rotary microtomes 2 to 10µm.
Another way to think about the blade profile is to consider the shape of the blade edge. Typical blade profiles include:
Besides shape and profile, you'll also want to think about blade material. You'll need to consider the type of specimen you'll be working with and the thickness you need when choosing a blade material. Here are the common types of microtome blade materials and their applications:
Buying a microtome blade mostly comes down to choosing a knife that'll aid productivity and efficiency, produce high-quality results, and work seamlessly with the microtome you use. Keep the following tips in mind as you search for the right blade:
Histology gives physicians and researchers critical insight into the human body. Scientists need tools like microtomes to enable the microscopic study of cells and tissues. A high-quality microtome blade is an essential part of the process and something that requires careful consideration.
If you have questions about the various types of microtome blades available, we are eager to help you at Mercedes Scientific. With nearly 30 years of experience as a laboratory and medical supply and equipment distributor, we believe we are in the best position to give our customers an exceptional experience. To learn more about our microtome blades, please contact us today.