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Biological Sample Analysis

In bio application, there’re many things including nano-drugs, blood, cell, tissue till even medical devices need to be observed or analyzed. As one may know, biological samples are usually high water content with low contrast under TEM. So, a proper sample preparation for keeping the sample with original feature will be the key and the main challenge.

 


The Hitachi HT7700 is most suitable for imaging biological tissues.

 

 

MA-tek can provide the solutions for bio sample preparation, such like Native staining, CPD, unltr-microtome, cryo-treatment, and also a unique wet cell for liquid TEM.

 

  •  Negative Staining
  •  Resin Embedding
  •  Ultramicrotome
  •  Cryo-Ultramicrotome
  •  Critical Point Drying
  •  Cryo-transfer system
  •  Liquid-TEM
  •  TEM
  •  SEM

 

 

Technical Concept

Negative Staining

Many organic or biological samples are composed of light atoms (such as carbon, hydrogen, oxygen etc), thus result in low contrast in their EM images; negative staining with heavy elements (metals) could enhance the contrast for these samples; this is called “negative staining”. 

 

(Example) Biomaterial samples _ PLGA nanoparticles

(Example) Biomaterial samples _ Liposomes

 

 

Resin Embedding and Ultramicrotome

Biological samples with high water content, such as cells, bacteria, tissues, organs, as well as many synthetic biomaterials have to be undergoing the procedure of fixation, dehydration, resin embedding and ultramicrotomy; then the slices can be collected and placed on copper grid for TEM observation.

 

(Example) Biological samples – Leukocytes

(Example) Biological samples –Rat Liver

 

 

Critical Point Drying

Biological samples with high water content would need to be fixed (by glutaraldehyde), dehydrated (by ethanol), critical point dried (with carbon dioxide supercritical fluids), sputter coated with Pt or Au prior to be observed with SEM.

 

(Example) Biological Samples_ Cells are being fixed, dehydrated, and coated with Pt thin film and imaged by the SEM;gold nanoparticles of ~ 200 nm can be visualized.

 

 

 

Cryo-transfer System

Cryo-transfer holders are used in applications that require low temperature transfer and observation of frozen hydrated specimens for cryo-electron microscopy (cryo-EM).

 

With cryo TEM, solutions can be rapidly frozen and kept below sublimation temperatures to be observed under TEM. The morphology, size distribution of nano-objects can be analyzed with great resolution. The dispersiveness was also “frozen” in the process, allowing the studying of aggregation and agglomeration state much like the original liquid state.

 

(Example) Liposome, showing bi-layer structure

 

 

 

 

Application

MA-Tek provides professional and high quality services on sample preparations of different bio-samples for electron microscopic observation.

 

 

 

 

Equipment

 

 

  • TEM, Hitachi HT7700

Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it.

An image is formed from the interaction of the electrons transmitted through the specimen; the image is magnified and focused onto an imaging device, such as a fluorescent screen, and then detected by a sensor such as a CCD camera. (Rephrased from Wiki “TEM”)

 

 

  • SEM, Hitachi S8220

A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons.

The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. (Wiki “SEM”)

 

  • Ultramicrotome, Leica EM UC7 

In ultramicrotome, sample can be sliced with a diamond blade into thin sections no more than 100 nm, which is necessary for TEM observation.

Biological tissue, cells, bacteria and some medical materials can be sliced with ultramicrotome after embedding, freezing or chemical fixation.

 

  • Cryo-Ultramicrotome, Leica EM FC7 

Some materials are only suitable to be sliced at low (cryo-) temperatures, our Leica EM FC7 cryo-ultramicrotome can operate at from -15℃~-185℃, suitable for polymers, rubber and biological tissues.

 

  • Critical Point Drier, Quorum K850

Supercritical drying is a process to remove liquid from specimen without subject to surface tension, which is usually detrimental to the structure.

The liquid is first completely replaced by CO2 in liquid phase, at high pressure. Then, CO2 is brought beyond critical point and then allowed to lower pressure, converting to gas phase. The specimen is dried preserving original morphology. (wiki)