Microtome Blade Buying Guide

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.

The Microtome Process

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:

• Frozen section procedure: A frozen section procedure uses Optimal Cutting Temperature compound (OCT compound) to embed tissues and a cryostat microtome to cut the frozen tissues. Frozen sections typically range from 4 to 15 µm. This type of procedure is often used for rapid diagnosis.
• Ultramicrotomy: Ultramicrotomy is the most commonly used method for transmission electron microscopy. With this method, tissues are embedded in hard material like epoxy resin. The resin block can be cut into very thin sections by a special microtome called an ultramicrotome. Sections used in transmission electron microscopy typically range from 60 to 100 nanometers (nm) in thickness.
• Botanical microtome technique: Researchers might use a sledge microtome, which features a heavy blade, to cut through tough materials such as wood and bone. Traditional botanical microtomy is not used to make very thin sections.

Regardless of the application, you'll need a sharp, blemish-free knife to cut through the specimen.

What Are Your Microtome Blade Application Requirements?

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.

The Most Popular Types of Microtome Blades

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:

1. Rotary Microtome Blade

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.

2. Sledge Microtome Blade

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.

3. Vibrating Microtome Blade

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.

4. Ultramicrotome Blade

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.

5. Laser Microtome Blade

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.

6. Saw Microtome Blade

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.

7. Cryostat Blade

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.

Fixed vs. Disposable Blades

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.

Disposable blades offer benefits such as:

• They're available with high or low profiles to cut through a variety of materials.
• They do not need to be sharpened or maintained.
• They're reliable.
• They produce quality results.
• They're easy to handle.

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.

The Different Microtome Blade Profiles

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 Microtome Blades vs. Low-Profile Microtome Blades

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.

Blade Shape

Another way to think about the blade profile is to consider the shape of the blade edge. Typical blade profiles include:

• Strongly plano-concave: A plano-concave knife has one straight side and a hollow-ground side. This type of profile is extremely sharp and suitable for cutting soft, embedded materials. You'll want to avoid cutting hard materials with a plano-concave knife, which can cause the blade to vibrate.
• Biconcave: A biconcave knife has two hollow-ground sides. Like a plano-concave knife, a biconcave blade works best against soft materials and shouldn't be used to cut hard samples.
• Plano-concave: A plano-concave knife is similar to the strongly plano-concave profile except it has a thicker back. This blade can be used to cut materials that are too hard for strongly plano-concave blades, and it can also be applied to softer materials, like tissues embedded in paraffin wax. You can find plano-concave knives with various levels of concavity.
• Wedge-shaped: Wedge-shaped knives are more rigid than concave knives and can be used to cut harder materials. However, since wedge-shaped knives have thicker tips, they cannot be ground as sharp as concave-profile blades. Nevertheless, wedge-shaped knives can be used to cut paraffin-embedded materials, frozen sections and resin-embedded samples.
• Tool-edge shaped: Tool-edge knives are more stable than the other blade profiles but are also the least sharp. Tool-edge knives are commonly used to cut hard materials, synthetic resin blocks and large wax blocks.

Various Microtome Blade Materials

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:

• Steel: Disposable steel microtome blades are made of high-quality stainless steel. When held in an appropriate knife holder, disposable blades produce superior sections. You might use steel blades to cut through plant, and animal and human tissues.
• Glass: Glass knives can be used to slice materials for light microscopy and create very thin sections for electron microscopy. Glass knives are hard and extremely sharp, but they're also breakable, so they require careful handling. Since glass knives may deteriorate with storage, they are usually produced immediately before being used in a microtome.
• Diamond: Diamond microtome knives are designed to produce very thin slices for light and electron microscopy. Diamond microtome knives are incredibly durable. You can select disposable microtome blades with an amorphous diamond coating to cut through hard tissues and decalcified bone.
• Sapphire: Sapphire microtome knives are manufactured from artificially produced sapphire. Sapphire knives have very hard cutting edges and high durability. Sapphire knives can be used with all types of materials, but they require a particular type of knife holder.
• Tungsten carbide: Tungsten carbide knives are extremely hard and resistant to wear but are also brittle and must be handled carefully. Tungsten carbide knives may be used to section hard materials, such as resin-embedded tissues.
• Non-corrosive: Non-corrosive knives are manufactured from heat-treated stainless steel and contain 12 to 15% chromium. Non-corrosive knives are used for cryostat applications.

5 Tips for Buying Microtome Blades

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:

1. Consider your budget: Blade prices vary depending on the material and the distributor. For example, a quality blade will likely cost more than a blade made of laser quality steel. You'll also want to compare prices between distributors to find the right price for your budget. If you have questions about microtome blade costs, contact us at Mercedes Scientific, where we offer competitive pricing and affordable laboratory equipment.
2. Buy from a dependable supplier: Make sure to purchase microtome blades from a trustworthy supplier. You want to be able to ask questions if you have any concerns or run into issues, so it's critical to purchase microtome equipment from a company that focuses on customer satisfaction. Ask where its made.
3. Research the brand: Whenever you buy lab equipment, it's important to investigate the brands and models you're considering. Choose brands with a history of excellence. Ask where the material is sourced from.
4. Choose quality: A microtome knife is the central component of the machine and not something you want to skimp on when it comes to quality. Make sure to prioritize quality and sharpness when you choose new microtome blades to keep productivity levels high.
5. Check the manual: You may want to refer to your microtome's manual to ensure you select a knife that will work well with the machine and the knife holder. The manual should tell you the types of knives you can use and the sizes that'll fit your microtome. Or contact your local representative at Mercedes Scientific for top recommendations.

Shop Histology Microtome Blades

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.